In this Video we will understand how the leading edge devices on the wings work. The aircraft has 14 slats, 12 outboard and two inboard. Slats cannot be installed between the engine pylons and the inboard slats as their movement will be obstructed by the engine cowlings. Therefore, two Krueger flaps are installed to assist the slats. The slats are fly-by-wire controlled with three modes of operation: the flap lever is used to select the three available slat positions: up, sealed, and gapped.

Let's put the slats to the sealed position. When the flap lever is selected to 1, the position change signal is sent to the flap/slat electronics unit. The computer first engages the primary mode for slat control, then it sends a signal to the slat hydraulic valve. The center hydraulic system of the aircraft is used to operate the slats. The valve opens to run the hydraulic motor, which drives the slat power drive unit gearbox. Connected to the gearbox are the torque tubes. Angle gearboxes help route the torque tubes to the right wing.

Now let's see how the torque tube rotation results in slat extension. Offset gearbox uses the torque tube rotation to drive a rotary actuator. The actuator rotates the slat pinion gear. There are two gear connections for each slat. The gears extend the slat to the sealed position with the help of tracks. The Krueger flap has two positions: retracted or fully extended, and instead of gears and tracks, uses a pushrod connection. Just like the inboard slats, the outboard slats extend with the help of gears and tracks.

Position sensors on the offset gearbox measure the torque tube rotation and send the signal to the flap/slat computer. This allows the computer to determine the slat position and control them with precision. Flap lever position 5, 15, and 20 controls the trailing edge flaps. The slats remain in the sealed position. Changing the lever position from 20 to 25 results in both the flap and slat movement, but they will not extend simultaneously. The computer will follow a sequence: first, it will command the slat power drive unit and move the slats to the gapped position. After slats extend, the flaps are moved to 25. Flaps 30 will move the trailing edge flap to its maximum extension.

Now let's look at the retraction sequence. First, the flaps retract to 20. Next, the slats are commanded to the sealed position. If the hydraulic components fail during a slat command, the computer will automatically switch to the secondary mode. In secondary mode, signal is sent to the electric motor to operate the power drive unit. The torque tubes are driven in the opposite direction and the slats retract to the sealed position. Next step in the sequence, the computer retracts the flaps up. Finally, the slats are moved to the retracted position.

If the computer malfunctions, the flaps and slats can be controlled using the alternate mode. Arming the system will disengage the current mode and prevent the computer from controlling the flaps and slats. Let's extend the slats in alternate mode. The switch directly sends a signal to the electric motor to run. Since the computer has been bypassed, there will be no sequencing. The slats and flaps will extend simultaneously in the alternate mode. The slats can only be extended to the sealed position and flaps to maximum 20.

As we have covered all the flight control surfaces, in our next part of the series we will understand their function in flight.

Today we're working on how an airplane creates lift. As pilots, it's really important for us to know how an airplane uses relative winds and the shape of its wings in order to create lift. If you remember from lesson one, lift is that upward force that opposes weight. So how does the airplane create lift? It does it by using Bernoulli's principle. Let's take a closer look. Bernoulli's principle states that as the velocity of a moving fluid increases, the pressure within that fluid decreases. Narrow areas like this, which are often called a Venturi, force the fluid to increase its speed. And with that increase in speed, we get a decrease in pressure. Just like in a Venturi, the curved surface of the upper wing forces the air on top of the wing to travel more quickly than the air on the bottom of the wing. This forces an area of lower pressure on the upper surface of the wing.

So, what happens if there's lower pressure on the upper surface of the wing and higher pressure on the bottom surface of the wing? You get an upward force, and that upward force is known as lift.

In this video, we will be looking at what is a VOR, the operation of a VOR, how the VOR information is presented in an aircraft, and its uses. What is a VOR? VOR stands for VHF Omnidirectional Range. A VOR is a short-range navigational aid which has been in use since 1960. The VOR can be used during the day or during the night. The VOR may be paired with a DME, which will provide the range and the bearing information for an aircraft.

How does the VOR function? The VOR produces 360 radials at one-degree spacing. These radials are aligned to the magnetic north at the VOR location. The VOR transmits two signals: one signal is the reference signal which is frequency modulated, the other signal is a directional signal which is amplitude modulated. The directional signal will have a phase difference with the reference signal depending on the radial. Let's understand this with a few examples: if an aircraft is north of the VOR transmitter, then it is at the zero-degree radial. The phase difference between the reference signal and the directional signal will be 0 degrees. If the aircraft is east of the VOR, then it is at the 90-degree radial, the phase difference between the reference signal and the directional signal will be 90 degrees. Similarly, if the aircraft is south or west of the VOR, the radials will be 180 and 270 degrees. The phase difference between the signals will be 180 and 270 degrees. So the phase difference between the reference signal and the directional signal will be the same as the corresponding radial. The VOR transmits 360 radials, each at a spacing of 1 degree, so the phase difference will also vary accordingly.

But if we consider an aircraft at a particular radial, let's say 170, how will the aircraft know whether it is flying towards or away from that VOR? To understand this, let's look at how the VOR information is presented in the cockpit. The VOR information is presented on an instrument known as the coarse deviation indicator. To know whether an aircraft is flying towards or away from a VOR, a "To" or a "From" flag will appear on this indicator. "To" means the aircraft is flying towards the VOR, "From" means the aircraft is flying away from the VOR.

Let's look at some other indications and the function of this knob on this instrument. Once a particular VOR frequency is tuned on the navigation radio, the knob is used to select a particular bearing or radial. This knob is called the Omni Bearing Selector. The selected bearing will be shown on the instrument. Depending on the position of the needle, the aircraft may need to fly towards the right or towards the left. If the needle is towards the right, the aircraft has to fly towards the right. If the needle is towards the left, the aircraft has to fly towards the left to capture the selected bearing.

What are the factors that affect the VOR transmission? Since the VOR transmits in the VHF band, it operates in the line-of-sight range. The transmitter power has a direct impact on the range of VOR signals. The terrain around the VOR will also have an impact on the transmission. What is the cone of ambiguity? When flying towards a VOR, the radials will converge, which means the course deviation indicator will become inaccurate. The needle will oscillate rapidly, and an "off" flag may appear for some time. After crossing this cone, the "front" flag will appear and the needle will become steady.

How to identify a VOR? VORs can be identified by three-letter codes which are transmitted by that specific VOR. These signals are transmitted along with the reference signal. A monitoring system at the VOR transmitter location will continuously monitor the identifier signal, the navigation signals, the signal strength, and the status of the monitoring system itself. Nowadays, GPS is the primary navaid that is used in most of the modern aircraft, but VOR is also available as backup or for marking certain airways, for approach procedures, or as a holding point.

Your drone may be small but it can create a big hazard. That's why aviation rules say drones must not fly anywhere near aircraft taking off or landing. That means staying at least 4 kilometers away from any airport or aerodrome, including helipads at hospitals or those used for sightseeing operations.

But what's known as controlled airspace can go well beyond those four K's around airports so before you launch your drone check the area you're planning to fly in. The map on airshare.co.nz shows the controlled airspace within New Zealand. If your backyard is inside that controlled airspace these rules apply there too. You may be able to fly a drone in controlled airspace if you log your intended flight details on airshare.co.nz and ask air traffic control for clearance but there is a way you can fly your drone safely without that clearance. It's by doing what's called a shielded operation.

That means you fly your drone near and below the height of an object that shields your drone from other aircraft. The shielding object could be a building, a tree, or even your house. You must only fly your drone within a hundred metre zone around that object and never above the object's height. That way your drone is less likely to get in the way of another aircraft.

If you're flying a shielded operation within 4 kilometres of an airport or aerodrome, so where there are likely to be quite a few aircraft, you must also have a physical barrier between your drone and the airport. Whatever the barrier is it must be solid enough to stop your drone straying into the path of other aircraft, should you lose control. Keep your drone below the height of the barrier and the shielding object so there's no danger of the drone getting in an aircraft's way.

Doing a shielded operation also means you can safely fly your drone at night - something that's not usually allowed. Another thing to think about before you do a shielded operation is to turn off any obstacle avoidance features as these might make your drone automatically fly up and over your barrier. You can get training to fly a shielded operation safely. Go to the drones page on the CAA website for info.

Finally, wherever and whenever you're flying if you see another aircraft always get your drone out of the way and land immediately. If you need any more information or even just want to check something we're here to help. Get in touch - visit flyyourdrone.nz for more safety tips or follow Fly Your Drone on Facebook. Consider others, be responsible. That's how you fly the right way.

The job of being a pilot can be demanding. Whether it's dealing with long and unpredictable hours, average accommodation, or simply trying to find a decent meal, it's all a challenge. Add to this a full day of flying, including planning, demanding routes, dirt strips, refuelling, baggage handling, and not to mention passengers, it's a full-time gig. We haven't even included home-life pressures - bills, crying babies or second jobs - all adding their weight to a pilot's wellbeing. PILOT: Finally.

WOMAN: Sorry, I got stuck in traffic. MAN: And this makes high workloads, stress, lack of sleep and struggling to stay healthy real issues. They can be a simple daily challenge or an overwhelming problem. It just depends on how they're managed. IAN HOSEGOOD: Helping people help themselves can sometimes be challenging. We're not all as good at planning for our health and wellbeing as we might be, for example, planning for our finances. We think it's of mutual benefit for us to invest in people's wellness, and the things that they can do to feel well today and this year and this month, and there are things that they can do to make sure that they're still well in 5, 10, 20 years from now. So it's about investing in your future but also doing good health and wellbeing measures on any given day as well.

MICHAEL DRANE: Diet, I think, is... It's an interesting conundrum of the 21st century, because there are any number of programs for what you must eat. My mum, who is a nutritionist, said, "Moderation in all things. " And there's probably some sense in that. What we do know is that there are a whole range of illnesses associated with overweight and overeating, and Australia is unfortunately a world leader in that respect. And eating vast amounts of refined carbohydrate sugar is clearly not good for us. We're in the middle of an epidemic of diabetes. And so the common-sense advice to moderate the amount of sugar that we eat, to moderate the amount of unrefined carbohydrate, is sensible.

DARRELL BONETTI: Well, for pilots regarding nutrition, they really just need to focus on eating real food, focusing on eating real food, which is not being modified too much, which is difficult to achieve these days, but eating real food versus eating packet, processed food. Getting as close to nature as possible with your eating pattern. And that can be very, very broad. Making sure that an individual can eat fruit, vegetables, healthy meats, fish, nuts, eggs, dairy if that's appropriate for them - that is real food, and I think everyone can achieve that.

GLENN SINGLEMAN: The interesting thing about health and wellbeing is that the evidence is there. It's been there for 20 years. If you look after yourself, you stay fit, then you're going to live longer and live a better quality life. But people don't take this on board. I mean, the population exercise rate in Australia has actually declined over the last 20 years, instead of increased. And yet we've come to know that exercise is, you know, is really beneficial for our health and wellbeing. But we're not taking that information on board, because there are so many other priorities nipping at our heels, those societal priorities.

One of the benefits of being a doctor is, not only do I understand this research and what it means, I've been able to incorporate that into my life. I prioritise my health, so that I go running. I prioritise my diet, so I don't eat fatty foods. I'm actually a vegan, because it's the diet with the best evidence in terms of mortality and morbidity. Everybody knows this stuff. When you're sitting for hours in a seat, that's not a very healthy thing to do. It's not a natural thing to do. Our bodies were designed to move.

It's a well recognised risk factor that more than 48 hours' immobility per month dramatically increases your risk of getting a deep vein thrombosis. Pilots really do, and all their crew, need to spend a bit of time having health and their own health and safety and personal safety as a priority. And that, to me, is about exercise and diet.

Yeah, Qantas is very lucky to have an in-house medical department, and we do have a health and wellbeing program. Some smaller organisations may not have those sorts of resources to hand. But certainly, CASA itself has some really good health and wellbeing materials on its website. And then also what we tend to suggest is that these smaller organisations go to the peak bodies - The Heart Foundation for cardiac health, Diabetes Australia for good diabetes advice. So we look to those peak bodies, and they've got some fantastic resources that organisations just pick up and run with. When we look at creating a healthy culture, one of the risks to a healthy culture for us in particular is people being overseas on layovers in particular. And some of the risks that are there is that people can be quite isolated.

Not everybody is a social person, and we can see that isolation can be a risk factor. We've also got risk factors around people sometimes on layovers, you know, tending to drink too much alcohol, not get enough exercise and perhaps not eat so well either. So what we're doing is encouraging people through education and training and tools and resources that we provide to them about how to be connected, how to conduct activities like exercise and cycling and social connectedness, and finding out what's available in those locations,

rather than being in their hotel room and perhaps being isolated and otherwise perhaps just using alcohol as a way of dealing with the boredom when they're on a layover. (MACHINE BEEPS) (EXTENDED BEEP) KIRK CAMPBELL: At Seair, we've got a breathalyser in the office, and all our flight crew, all our engineering, anyone who is involved in the aviation sensitive activity is required to do a breathalyser in the morning.

That's a good result. PETER GASH: No alcohol detected. Smiley face for Kirk. The alcohol testing is great, 'cause it's just a part of the culture. They know the person sitting next to them is definitely a zero, that the guy in the workshop's definitely a zero. I'm also proud to say that in the 10 or 11 years, or whatever it is, maybe 12 years since we installed it - and we're onto its second one, we wore the first one out 'cause everyone blows in it every day - we've never had anyone blow over.

This is a part of my responsibility, my commitment to myself, my team, and I'm gonna do it right. - Post-alcohol impairment is really also known as a hangover, essentially, and how much of a hangover people get is affected by quite a few different factors. First of all, it might be affected by their tolerance, and that really relates to how much they regularly drink.

It also clearly obviously relates to how much they've drunk in that particular sitting. And some of the effects are obvious - things like being dehydrated, having a headache, feeling tired, concentration difficulty - those are all flight safety relevant issues. But some of them are a little less obvious, and, for example, what happens with alcohol is it actually gets into our semi-circular canals, which is our balance organ in our inner ear, and it makes the fluid in those inner ears far more sloshy or liquid,

and that means that our balance is actually put off. So those sorts of subtle performance impairments can last quite a long time after an alcohol session, so it's really important for people not just to consider if they don't have a headache anymore and they're feeling generally OK, that there may not be some impairment. There will be some impairment.

So it's really important that people understand that and they drink responsibly when they're in proximity to a flight operation. PILOT: Welcome aboard. PASSENGER: Thank you. - (LAUGHS) WOMAN: How you feeling? - Yeah, haven't been better. - (CHUCKLES) - Where pilots' mental health and wellbeing is concerned, one of the biggest difficulties is the lack of communication.

Who can you tell? The average alpha male finds it very difficult to say "help". And there's been a lot of effort put into developing pathways for people to say just that - "Help, things aren't going right." In the larger airlines, we know that they have put a lot of emphasis upon building peer support and channels for reporting of concerns.

We think peer support is the single most effective intervention that can be done for pilots with mental health issues and alcohol and other drug issues. It means that people are far more likely to seek help early and get referred in to the appropriate mechanisms. MELANIE TODD: A lot of young pilots are going, you know, moving a long way from home, they're without a basic peer support group in some remote locations.

They'll have other pilots, but if something happens or they're ostracised from that group or there's something about that group that doesn't click, then they don't have a support base. MAZ SALVATI: One thing that I've brought up with the team lately is mental health, you know... You know, you might see someone having a bit of a laugh at dinnertime, but they may have had a strenuous day and they may be stressed, so I think it's important to talk about it and not to hide, you know?

I always make sure that I'm asking people, "Are you OK? Are you stressed? "If so, why are you stressed?" - So being mindful of some of the signs in people that they're under additional stress. So, their personality can change in terms of how they respond to you. So somebody who is normally outgoing might become quiet.

Somebody who is normally quiet might snap more easily or be more vocal about not caring about anything anymore, you know? So, watching out for these general signs and saying, "OK, is something going on here?" and then actually having an intervention with that person to say, "Look, are you OK? This is not like you.

" - Sometimes we find ourselves in stressful situations, and it is what it is, you know? You can't help that. We're only humans. Humans get stressed and you'll never be able to beat that or fight that. But I think it's very important to just slow down, take a breath, and say, "Hey, look, listen, what's actually going on?" Because all it can take is one misjudged fuel calculation and you might find yourself in quite a fair bit of trouble.

There's some pretty basic things that you can do. First of all there's some attitudes that are very helpful in terms of wellbeing. So the attitudes that we look for is optimism. We try and make sure that people are looking at things in an optimistic way. There's gratitude, making sure that you feel grateful for what you've got.

And that really has been evidence-based shown to improve people's wellbeing. Mindfulness is a really good evidence-based skill that pilots and others can do to make sure that their mental wellbeing and resilience is strong. Also encouraging people to have social connectedness as well. Within Australia, we're very lucky to have an entire set-up, including CASA, which is aimed towards returning people to flying, not towards excluding people from flying.

Of course absolutely they need to be safe to return to the cockpit, but everybody's working towards making sure that we have that ability to do that. And people can come back in a limited capacity - they might need some supervision or some surveillance initially. As soon as they are safely able to return to the flight deck, they are.

TODD MICKLESON: Fatigue is a difficult one to manage, because fatigue affects everybody differently. It depends on a lot of things, you know, the hours that you work - some people are better working early mornings, late at night. Some people just are more robust at working longer hours than others. If you've got a duty where you're flying all night, you don't want to be up early in the morning and awake all day.

We've got to try and manage that, you know, try and get a sleep in the afternoon. (UPBEAT MUSIC) MATT FOX: Yeah, even at home, like, before I start night shift, um, it's helpful that my daughter's two, and she likes an afternoon sleep for a couple of hours, 'cause I sleep before night shift for two hours.

'Cause there are those nights, they don't happen often, but you can be out flying all night. And it is fatiguing between 2:00 and 6:00 in the morning, like, you do notice in the morning when the sun comes up, "Ooh, I've been flying all night." You do need those good rest hours. - Sleep is absolutely tantamount to wellbeing.

It has a significant impact on both physical health and mental health, and of course with the risk of fatigue within aviation operations, getting good sleep is really, really important. And the other thing we encourage within the sleep bucket is to make sure that people consider whether they may even have a sleep disorder.

So it's a pretty significantly common issue, particularly within the pilot community, to have sleep apnoea, for example. And sleep apnoea can affect not only your ability to deal with a difficult and challenging roster from an aviation perspective, but also can affect your health quite significantly as well, in terms of risk of heart disease and dementia and other health issues.

ROBERT FOSTERLEE: But fatigue is a multidimensional factor. I mean, there is loads of elements to fatigue. But sleep is at the base. You need to get reasonable amounts of sleep. And, you know, we have these kind of algorithms and rules of how many hours someone should get, but the one thing in life we don't learn is, what's your sleep? You might be a seven-hour sleeper.

I could be an eight-hour sleeper. And if I don't get my eight, I'm going to be fatigued. And so, we have to understand that sometimes when we look at these algorithms or these methods of kind of scheduling, what they're doing is, they're scheduling to the average. They're not scheduling to the individual.

And that can be, again, a bit dangerous, especially for those who might need more sleep than average. 'Cause there's...there are a few nine-hour sleepers out there too. And so by saying, "Oh, well, you got eight, you should be fine," that, again, can lead to someone developing fatigue. CARMEL HARRINGTON: Sleep is really essential, and if we don't sleep well, we're going to have cognitive deficits, so we're not going to be able to think and learn as well.

We're going to have health problems. We're more likely to develop cardiovascular or a chronic disease such as metabolic syndrome or type 2 diabetes. And on top of that, we're also not gonna feel very happy. So, we know lack of sleep affects our mental health as well. It's highly associated with the formation of... development of depression.

But if you're fatigued, you don't quite have the resources for it, and you become a bit short. You're irritable. Some people are susceptible to maybe anxiety or nervousness. Other people are more susceptible to maybe feeling negative mood states, we'd call it depression. So again, everybody's different, and they show that fatigue differently.

But the one thing that we can say is that it changes a person, their ability to kind of react. And so when I talk about the psychosocial, that means, oh, teamwork. It means communication. It means CRM. All of those things in the workplace get impacted from those elements of fatigue. "So, were you tired on the day?" "No, I wasn't tired, I was stressed.

" But isn't it a form of fatigue? I mean, it's not just about sleep. Oftentimes if you're emotionally upset, you don't sleep so well. Or sometimes you're not sleeping so well, and that leads again to that susceptibility to become more emotionally upset, and it's a bit of a spiral. I think sometimes if we focus too much on just getting sleep, we're missing out on the big picture and all of the other factors that kind of combine to facilitate performance.

PILOT: What the hell is going on in your head? CO-PILOT: I'm sorry, I'm just... - It's just not good enough! This is your incident! You deal with it! DREW DAWSON: Fatigue is always a shared responsibility. Both ours and many other people's research will show you that when somebody is fatigued in the workplace, it's about as likely to be a result of non-work-related factors as it is to be a result of work-related factors.

And as a result, the company or the organisation can only be really accountable for work-related fatigue. On the other hand, the individual needs to be responsible for non-work-related causes of fatigue. What we've seen in a number of the transport industry initiatives in the last few years is a tendency to realise that family are often the drivers of fatigue, and therefore families need to be part of the educational milieu in which that training and education occurs.

I think it's really important that we begin to understand, because it's fine if you decide, "I don't want to sleep tonight, "I'm gonna go and party or I'm gonna do whatever," provided you're not the driver of my child's school bus. It's a community issue, and we have to start judging people by what damage are you going to do by not sleeping? Are you gonna be my doctor? Are you gonna be my train driver? Are you gonna be my pilot? 'Cause maybe I've got a whole different interest in how you sleep if you're one of those people.

At present, BrahMos is the fastest and only supersonic cruise missile on the planet. During its cruise, it breaks the sound barrier by traveling three times faster than a sound wave, and no known weapon system can intercept it due to its speed. In the first stage, solid boosters power this missile, and the second stage features the ramjet engines. We'll learn more about these intriguing engines in this video. We thank brilliant.org for supporting this video. More about less.ex brilliant collaboration towards the end of this video.

To understand ramjet technology, we first need to understand the concept of shock waves. Everybody is familiar with the ripples that are created in water when an object is thrown into it; these ripples travel uniformly. Right now, take a look at this interesting scenario: suppose a boy is pulling a tennis ball towards him. The movement of the source produces ripples that are not concentric. Isn't that interesting? The same effect can happen with sound waves during aircraft movement. Here, the sound waves are taking the place of the water ripples, and the aircraft is taking the place of the tennis ball. In this scenario, the sound ripples will obviously travel at the speed of sound. But here's a brain teaser for you: what will happen if the aircraft moves at the speed of sound? Obviously, the sound waves won't be able to move forward, so if you move along with the aircraft, it will look as if the sound waves are stuck at the front, forming a sound barrier.

During World War II, the sound barrier was assumed to be an invisible wall due to the aircraft experiencing high drag. However, what if the aircraft moves faster than the sound waves? The concentrated waves at the front of the aircraft will suddenly form a distributed ripple pattern as shown. The aircraft needs to apply more thrust during this transition. The distributed pattern has a conical shape. The interesting thing is that a very narrow volume with a thickness of 200 nanometers and high temperature and pressure is formed on this conical shape. The pressure in this narrow region is almost 29 times that of the atmospheric pressure. This region is known as a shock wave.

Why is the shock wave formed when the airplane moves at a speed greater than the speed of sound? This result is because in fluid, the information travels at the speed of sound. When the airplane travels faster than sound, the air volume shaded in red color has absolutely no information about the disturbance the moving object is making. However, inside the green region, the disturbance in the fluid happened with prior information. When the disturbed fluids suddenly interact with fluid particles in the red region, which has no information about what is going on, a shock gets formed in the boundary.

Shock waves can cause harm to a human body. However, even though these high pressure waves are disastrous, opportunity lies in the middle of difficulty. Using the concept of the shock wave, let's understand how a ramjet engine works. Ramjet engines have a very simple geometry. They have only three main stationary parts: a diffuser region at the entrance, a combustion chamber in the middle, and a nozzle at the exit. The duty of the diffuser is to increase pressure and temperature of the air. The ramjet engines will work only in supersonic conditions. Since the flow is supersonic, the scientists tweaked the shock wave concept to increase the diffuser pressure. Let's see how.

The shock waves get generated from many points of this cylindrical object. Remember, in a shock wave, the high pressure and temperature are there only in a narrow region. However, when many such shock waves club together, something interesting happens. You can see at the inlet a conical region is formed with no effective shock wave at all; this will be a low-pressure region. It is also clear a high-pressure conical wall is getting generated at the inlet region. What about the remaining volume? To understand the remaining volume condition, let's take a cross-section of the cones at different lengths. You can see a flower-like shape. If you increase the number of cones, this flower will fill the entire area. Remember, the number of shock cones getting generated from a circle edge is infinite. This area filling is true for any length, which means after the initial void cone, a thick volume of high pressure and temperature air is formed inside the cylinder. In short, it forms automatic compression action with the help of shock waves. This is the ram effect.

This high pressure and high temperature air can create effective combustion in the combustion chamber. Hydrogen is commonly used as fuel for ramjet engines. The combustion chamber further increases the gas temperature and also the fluid velocity. According to Newton's third law, the greater the exhaust jet speed, the more thrust the rocket derives. To increase the speed of the jet further, a converging-diverging nozzle is also added at the exit.

Even though this simple diffuser arrangement achieves a very high-pressure boost, if the combustion pressure exceeds limits, the shock front will be blown out, resulting in compressed air spilling out around the front of the tube. This spill limits the speed of the ramjet to 1.2 Mach. Scientists didn't stop here; they further improved the ram effect with the help of an aerodynamically designed inner body. In this new geometry, you can see that the area allocated for the air is actually decreasing along with the flow. For supersonic flow, when the area decreases, the pressure increases. In ramjets, the majority of the pressure rise happens due to the shock effect and because of a concept called oblique shock wave. When air hits the nose of the inner body, it deflects with some angle, forming an oblique shock wave. This oblique shock wave hits the outer tube, deflects multiple times, and is finally terminated by a normal shock wave. In this method, the air spillout does not happen, and scientists were able to achieve a high Mach number for the ramjet engine.

Now let's learn a little more about the combustion chamber design of ramjet engines. The airflow speed through the ramjet is so high that the mixing of fuel completes within two to five milliseconds. For complete mixing of fuel and air, a flame holder is used, which helps to maintain continuous combustion. It also stops the flame from blowing out by sheltering it. Ramjets are the most efficient in the speed range of Mach 3 to Mach 6. When traveling at low speed, the thrust isn't sufficient to overcome the drag. As a result, the stand-alone ramjet engine is not feasible; it needs the solid booster to propel the missile towards supersonic speeds. The ramjet does not contain any moving parts, unlike jet engines.

Before you leave, please make use of brilliant.org lesix collaboration and get a discount of 20 percent. Brilliant has recently upped the interactivity on their platform to a new level. Check out this interactive lesson on the center of mass, for example. This is an example of Brilliant's newly updated scientific thinking course. Follow the link given below and be a brilliant and creative engineer. We hope you enjoyed the amazing technology of the ramjet engines.

In this lesson from Free Pilot Training, we'll be discussing the pitot-static instruments and we'll explain how those work. In the last few lessons, we've been discussing the gyroscopic instruments, but today we're going to talk about three of those primary flight instruments that use air pressure to give us information. These are the airspeed indicator, the altimeter, and the vertical speed indicator. These instruments are provided air pressure from the pitot tube and the static port, and they turn it into information that's really important for pilots in flight.

There are three types of air pressure that come into play when we talk about these instruments: static air pressure, dynamic air pressure, and total air pressure. Static pressure, which is also called ambient air pressure, is pressure that's caused by our atmosphere. This is always present, whether the airplane is stopped or moving, and although it might seem unnoticeable to you, these air molecules push on everything in our atmosphere. The closer you are to the center of the Earth, the more tightly these air molecules are packed, and because they're packed so tightly at lower elevations, the lower your altitude, the higher your static air pressure is. Our airplanes use static ports to sense this type of air pressure. These are usually placed on the side so they're not affected by relative wind. Static air pressure is measured in inches of mercury. On a normal standard day at sea level, the average air pressure is 29.92 inches of mercury. Now, the air pressure isn't always 29.92 inches of mercury there, but this is about the average, so this is what we call standard air pressure. Then every thousand feet above sea level, the pressure reduces by one inch of mercury.

In the next lesson, we're going to go into a lot more detail about this and how the altimeter works, so if you haven't already subscribed, please consider doing so now. Anytime an object like an airplane moves through the air, it's impacted by the air molecules that it is traveling through, and this creates a certain amount of pressure on the object that's equal and opposite to the airplane's direction of travel, and this is called dynamic air pressure. In order to understand how the pitot-static system works, you have to understand that this pressure is directly related to the speed at which the aircraft is flying.

Next, we have the total air pressure, and this is a combination of dynamic and static air pressure. While this may seem obvious at first, you'll see why we talk about this here in just a minute. Now, the altimeter uses a static port to sense the static pressure outside the aircraft, and because the static pressure changes one inch of mercury every thousand feet, the altimeter is able to give us an altitude reading because it senses that pressure. As I mentioned before, static ports are placed on the side of aircraft, and this keeps the instruments from being affected by dynamic air pressure, and this keeps the readings as accurate as possible.

The other instrument that uses a static port is the vertical speed indicator. This instrument allows air to escape or come in through a small hole, which is vented through the static port. By allowing air to come in or go out, this instrument senses the pressure differences as we climb or descend, then it gives us a reading in feet per minute. The airspeed indicator is a little bit different animal. It also receives air from the static port but not for reasons you might think. The airspeed indicator measures the ram air that comes from relative wind through the pitot tube, but this doesn't give us an accurate measurement because static air actually makes its way into the pitot tube as well, and this is that total air pressure we were talking about earlier. And by taking static air from the static port, the airspeed indicator is able to offset any static air that might come in through the pitot tube to keep the airspeed indicator as accurate as possible.

The people who designed your airplane usually put the pitot tube in a spot where it won't be affected by the prop wash, but there is something that can affect your airspeed indicator, and that's the angle of the pitot tube in relation to the relative wind. High angles of attack and different airplane configurations can affect the accuracy of your airspeed indicator, and that's because weird angles can make it difficult for the ram air to enter the pitot tube. Every airplane is different, but every airplane has some kind of error caused by this, and the manufacturers account for this by putting a chart in the POH. This is what we call calibrated airspeed. Once you make these corrections, something else you could run into that would cause these instruments to get errors is if the pitot tube or the static port got clogged up, and there's a lot of different things that could clog up these things—anything from bugs, mud, ice, and that's just to name a few.

One thing that shouldn't clog up your pitot tube, though, is water. That's because of this little drain hole here on the back, I call this the weeping hole. This is there so if water enters the front of your pitot tube, it'll just slide right out the back here. But if the water freezes in or on the pitot tube, then it can start clogging it up again, but that's what these little heating elements are for. You just turn the pitot heat on in your cockpit, and it should heat these up enough to melt that ice. So what happens if these things get clogged? Well, if the pitot tube gets clogged, the only instrument that's going to be affected is your airspeed indicator, and if you remember, that's because this is the only instrument that uses dynamic air pressure to give us a reading.

For the airspeed indicator, three possible problems could happen. The first would be if the hole in the front of the pitot tube for the ram air got clogged. As long as your drain hole doesn't get clogged, what will happen is your airspeed will drop to zero, and that's because the pitot tube is no longer taking in ram air but the static port and the drain hole are still both taking in static air which allow them to offset each other. The second possibility is if the front of the pitot tube and the drain hole get clogged. If this happens, any air pressure in the pitot system will be trapped, and your airspeed indicator is frozen at the last indication it was giving you. From here, if the static port is also plugged, you won't see any change, but if the static port is clear, then the airspeed indicator will make minor changes with altitude. I like to tell students that your airspeed indicator just turned into an altimeter at this point.

The third thing that could possibly happen is only the static port gets clogged. If this happens, the pitot tube is still taking in the dynamic and the static pressure from the front of the pitot tube, but the static port is unable to offset that static air that's also coming in the front. This means that your airspeed indicator is going to give you faster airspeeds than what you're actually going. Now, because the altimeter and the vertical speed indicator both use a static port to get their information, if this gets clogged, it's going to affect both of those too. For the altimeter, if the static port gets clogged, it's going to freeze at the last altitude that it was indicating. But the vertical speed indicator will only display 0 because it can no longer sense a climb or a descent. If you're lucky enough to have a clogged static port, I do have some good news for you, though.

On most newer training airplanes, they have something called an alternate static source. Typically, this is an alternate static port that's on the inside of your cockpit, and you can select this alternate static port by flipping a switch labeled "alternate static" on most airplanes. Just keep in mind when you use this alternate static source, it's not quite as accurate as the one on the outside of the airplane, and that's because the pressure difference on the inside of the cab is slightly different than outside. Now, if you don't have an alternate static source, one thing you can do is you can break the glass on any of the static instruments. If you do this, I recommend breaking the glass on the vertical speed indicator, and that's because it's by far the least important of the instruments.

Once again, if you do this, this is nowhere nearly as accurate as a static port on the outside of the airplane, but something is better than nothing, and in an emergency, this could save your life. I hope you enjoyed today's video. If you did, would you click that like button for me? Also, if you're really enjoying this training from the Free Pilot Training channel, be sure to check out our t-shirt store in the description below, then watch this video right here. You know you want to.

Developed over the course of decades, GPS has become far more ubiquitous than most people realize. Not just for navigation, its extreme accuracy in timekeeping (+/- 10 billionths of a second) has been used by countless businesses the world over for everything from aiding in power grid management to helping manage stock market and other banking transactions. The GPS system essentially allows for companies to have near atomic clock-level precision in their systems, including easy time synchronization across the globe, without actually needing to have an atomic clock or come up with their own systems for global synchronization.

The problem is that, owing to a quirk of the original specifications, on April 6, 2019, many GPS receivers are about to stop working correctly unless the firmware for them is updated promptly. So what’s going on here, how exactly does the GPS system work, and who first got the idea for such a system? On October 4, 1957, the Soviet Union launched Sputnik. As you might imagine, this tiny satellite, along with subsequent satellites in the line, were closely monitored by scientists the world over. Most pertinent to the topic at hand today were two physicists at Johns Hopkins University named William Guier and George Weiffenbach. As they studied the orbits and signals coming from the Sputnik satellites the pair realized that, thanks to how fast the satellites were going and the nature of their broadcasts, they could use the Doppler shift of the signal to very accurately determine the satellite’s position.

Not long after, one Frank McClure, also of Johns Hopkins University, asked the pair to study whether it would be possible to do this the other way around. They soon found that, indeed, using the satellite’s known orbit and studying the signal from it as it moved, the observer on the ground could in a relatively short time span determine their own location. This got the wheels turning. Various systems were proposed and, in some cases, developed. Most notable to the eventual evolution of GPS was the Navy’s Navigation Satellite System (also known as the Navy Transit Program), which was up and running fully by 1964. This system could, in theory, tell a submarine or ship crew where they were within about 25 meters, though location could only be updated about once per hour and took about 10-15 minutes to acquire.

Further, if the ship was moving, the precision would be off by about one nautical mile per 5 knots of speed. Another critical system to the ultimate development of GPS was known as Timation, which initially used quartz clocks synchronized on the ground and on the satellites as a key component of how the system determined where the ground observer was located. However, with such relatively imprecise clocks, the first tests resulted in an accuracy of only about 0.3 nautical miles and took about 15 minutes of receiving data to nail down that location. Subsequent advancements in Timation improved things, even testing using an atomic clock for increased accuracy. But Timation was about to go the way of the Dodo.

By the early 1970s, the Navigation System Using Timing and Ranging (Navstar, eventually Navstar-GPS) was proposed, essentially combining elements from systems like Transit, Timation, and a few other similar systems in an attempt to make a better system from what was learned in those projects. Fast-forward to 1983 and while the U.S. didn’t yet have a fully operational GPS system, the first prototype satellites were up and the system was being slowly tested and implemented. It was at this point that Korean Air Lines Flight 007, which originally departed from New York, refueled and took off from Anchorage, Alaska, bound for Seoul, South Korea. What does this have to do with ubiquitous GPS as we know it today? On its way, the pilots had an unnoticed autopilot issue, resulting in them unknowingly straying into Soviet airspace.

Convinced the passenger plane was actually a spy plane, the Soviets launched Su-15 jets to intercept the (apparently) most poorly crafted spy plane in history- the old “It’s so overt, it’s covert” approach to spying. Warning shots were fired, though the pilot who did it stated in a later interview, “I fired four bursts, more than 200 rounds. For all the good it did. After all, I was loaded with armor-piercing shells, not incendiary shells. It’s doubtful whether anyone could see them.” Not long after, the pilots of Korean Air 007 called Tokyo Area Control Center, requesting to climb to Flight Level 350 (35,000 feet) from Flight Level 330 (33,000 feet).

This resulted in the aircraft slowing below the speed the tracking high-speed interceptors normally operated at, and thus, them blowing right by the plane. This was interpreted as an evasive maneuver, even though it was actually just done for fuel economy reasons. A heated debate among the Soviet brass ensued over whether more time should be taken to identify the plane in case it was simply a passenger airliner as it appeared. But as it was about to fly into international waters, and may in fact already have been at that point, the decision was made to shoot first and ask questions later. The attacking pilot described what happened next: “Destroy the target…!” That was easy to say. But how? With shells? I had already expended 243 rounds. Ram it? I had always thought of that as poor taste. Ramming is the last resort. Just in case, I had already completed my turn and was coming down on top of him. Then, I had an idea. I dropped below him about two thousand meters… afterburners. Switched on the missiles and brought the nose up sharply. Success! I have a lock on. Two missiles were fired and exploded near the Boeing plane causing significant damage, though in a testament to how safe commercial airplanes typically are, the pilots were able to regain control over the aircraft, even for a time able to maintain level and stable flight. However, they eventually found themselves in a slow spiral which ended in a crash killing all 269 aboard.

As a direct result of this tragedy, President Ronald Reagan announced on September 16, 1983, that the GPS system that had previously been intended for U.S. military use only would now be made available for everyone to use, with the initial idea being the numerous safety benefits such a system would have in civil aviation over using then available navigation tools. This brings us to how exactly the GPS system works in the first place. Amazingly complex on some levels, the actual nuts and bolts of the system are relatively straightforward to understand. To begin with, consider what happens if you’re standing in an unknown location and you ask someone where you are. They reply simply- “You are 212 miles from Seattle, Washington.” You now can draw a circle on a map with a radius of 212 miles from Seattle. Assuming the person giving you that information is correct, you know you’re somewhere along that circular line. Not super helpful at this point by itself, you then ask someone else, and they say, “You are 150 miles from Vancouver BC.” Now you’re getting somewhere. When you draw that circle on the map, you’ll see it intersects at two points. You are standing on one of those two points. Noticing that you are not, in fact, floating in the ocean, you could at this point deduce which point you are on, but work with us here people. Instead of making such an assumption, you decide your senses are never to be trusted and, after all, Jesus stood on water, so why not you? Thus, you ask a third person- they say, “You are 500 miles from Boise, Idaho.” That circle drawn, you now know exactly where you are in two-dimensional space. Near Kamloops, Canada, as it turns out. This is more or less what’s happening with GPS, except in the case of GPS you need to think in terms of 3D spheres instead of 2D circles. Further, how the system tells you your exact distance from a reference point, in this case each of the satellites, is via transmitting the satellites’ exact locations in orbit and a timestamp of the exact time when said transmission was sent. This time is synchronized across the various satellites in the GPS constellation. The receiver then subtracts the current known time upon receiving the data from that transmission time to determine the time it took for that signal to be transmitted from the satellites to its location. Combining that with the known satellite locations and the known speed of light with which the radio signal was propagated, it can then crunch the numbers to determine with remarkable accuracy its location, with margins of error owing to things like the ionosphere interfering with the propagation of the signal, and various other real-world factors such as this potentially throwing things off a little. Even with these potential issues, however, the latest generation of the GPS system can, in theory, pinpoint your location within about a foot or about 30 centimeters. You may have spotted a problem here, however. While the GPS satellites are using extremely precise and synchronized atomic clocks, the GPS system in your car, for example, has no such synchronized atomic clock. So how does it accurately determine how long it took for the signal to get from the satellite to itself? It simply uses at least four, instead of three, satellites, giving it the extra data point it needs to solve the necessary equations to get the appropriate missing time variable. In a nutshell, there is only one point in time that will match the edge of all four spheres intersecting in one point in space on Earth. Thus, once the variables are solved for, the receiver can adjust its own timekeeping appropriately to be almost perfectly synchronized, at least momentarily, with the much more precise GPS atomic clocks. In some sense, this makes GPS something of a 4D system, in that, with it, you can know your precise point in not only space, but time. By continually updating its own internal clock in this way, the receiver on the ground ends up being nearly as accurate as an atomic clock and is a timekeeping device that is then almost perfectly synchronized with other such receivers across the globe, all for almost no cost at all to the end-users because the U.S. government is footing the bill for all the expensive bits of the system and maintaining it. Speaking of that maintenance, another problem you may have spotted is that various factors can, and do, continually move the GPS satellites off their original orbits. So how is this accounted for? Tracking stations on Earth continually monitor the exact orbits of the various GPS satellites, with this information, along with any needed time corrections to account for things like relativity, frequently updated in the GPS almanac and ephemeris. These two data sets are used for holding satellite status and positional information and are regularly broadcast to receivers, which is how said receivers know the exact positions of the satellites in the first place. The satellites themselves can also have their orbits adjusted if necessary, with this process simply being to mark the satellite as “unhealthy” so receivers will ignore it, then move it to its new position, track that orbit, and once that is accurately known, update the almanac and ephemeris and mark the satellite as “healthy” again. So that’s more or less how GPS came to be and how it works at a high level. What about the part where we said many GPS devices may potentially stop working very soon if not updated? Near the turn of the century something happened that had never happened before in the GPS world- dubbed a “dress rehearsal for the Y2K bug”. You see, as a part of the time stamp sent by the GPS satellites, there is something known as the Week Number- literally just the number of weeks that have passed since an epoch, originally set to January 6, 1980. Along with this Week Number, the number of seconds since midnight on the previous Saturday evening is sent, thus allowing the GPS receiver to calculate the exact date. So what’s the problem with this? It turns out every 1024 weeks (about every 19 years and 8 months) from the epoch, the number rolls back to 0 owing to this integer information being in 10-bit format. Thus, when this happens, any GPS receiver that doesn’t account for the Week Number Rollover will likely stop functioning correctly, though the nature of the malfunction varies from vendor to vendor and device, depending on how said vendor implemented their system. For some, the bug might manifest as a simple benign date reporting error. For others, such a date reporting error might mean everything from incorrect positioning to even a full system crash. If you’ve done the math, you’ve probably deduced that this issue first popped up in August of 1999, only about four years after the GPS system itself was fully operational. At this point, of course, GPS wasn’t something that was so ubiquitously depended on as it is today, with only 10-15 million GPS receivers in use worldwide in 1999 according to a 1999 report by the United States Department of Commerce’s Office of Telecommunications. Today, of course, that number is in the billions of devices. Thankfully, when the next Week Number Rollover event happens on April 6, 2019, it would seem most companies that rely on GPS for critical systems, like airlines, banking institutions, cell networks, power grids, etc., have already taken the necessary steps to account for the problem. The more realistic problems with this second Week Number Rollover event will probably mostly occur at the consumer level, as most people simply are not aware of the issue at all. Thankfully, if you’ve updated your firmware on your GPS device recently or simply own a GPS device purchased in the last few years, you’re probably going to be fine here. However, should you own a GPS device that is several years old, that may not be the case and you’ll most definitely want to go to the manufacturer’s website and download any relevant updates before the second GPS epoch. That public service announcement out of the way, if you’re now wondering why somebody doesn’t just change the specification altogether to stop using a 10-bit Week Number, well, you’re not the first to think of this. Under the latest GPS interface specifications, a 13-bit Week Number is now used, meaning in newer devices that support this, the issue won’t come up again for about a century and a half. As the machines are bound to rise up and enslave humanity long before that occurs, that’s really their issue to solve at that point.

In this video, we'll be talking about spins. According to the FAA, a spin is an aggravated stall where yaw is introduced, which causes a downward torque screw path. Just as we discussed in lesson three, when an airfoil exceeds its critical angle of attack, it will stall. When an aircraft stalls, it is possible for one wing to stall more than the other wing; this is called an aggravated stall.

This can happen when an airplane stalls in uncoordinated flight. Uncoordinated flight is what happens anytime the vertical axis of the aircraft is not aligned with the direction of travel; this is also known as a side slip. You can eliminate side slip conditions by using your inclinometer and rudder pedals. In a turn, you'll hear your instructor refer to these as slips or skids. An easy way to remember which pedal to use is to step on the ball. If the airplane does get into a side slip or yawed condition, then it stalls, whichever wing has stalled more will drop faster than the other one. One wing dropping more quickly than the other; the airplane will begin to rotate and then it will follow the corkscrew path.

Be sure to look at your aircraft's specific POH in order to know your aircraft's specific spin recovery procedures, but most instructors will use the acronym PARE: Power idle, Ailerons and elevator neutral, Rudder opposite until the spinning stops, then Elevator up to recover to level flight. You'll want to memorize these procedures when you start your flight training.

But for the FAA written exam, the most important thing to remember today is that in a spin, both wings are stalled. Thanks for joining me for today's lesson on spins. Please click that like button if you're getting value out of this training and don't forget to subscribe so you know when there's a new video on Free Pilot Training. Aircraft calling, safe position.

Airplanes generate thrust to overcome drag. Drag is the air resistance that opposes flight; it acts parallel and in the same direction as the relative airflow and is a relentless force that deserves a thorough Flight Club treatment and your full attention. Total drag consists of drag forces that are linked to lift production, known as induced drag, and those that are not linked to lift production, known as parasite drag.

Let's have a look at induced drag. At high angles of attack, the high-pressure air below the wing likes to swirl around the wingtip towards the low-pressure air above the wing. A twisting vortex of air forms behind the wing, deflecting the airflow downwards. An inclined local airflow is created, which is the average of relative airflow and the deflected airflow, resulting in the lift vector tilting backwards and contributing to total drag.

Now for parasite drag, which consists of form drag, skin friction drag, and interference drag. Form drag is caused by disturbed airflow that separated from the surface and spawned into turbulent wake. The more streamlined an object is, the less form drag it creates, so any obstruction to smooth airflow, such as dangling wheels, will produce form drag. If we flatten a spherical object completely, the only drag we get now is the skin friction. As the name suggests, skin friction depends on the quality of the skin surface the airflow passes over. A laminar flow results when the airflow passes over smooth surfaces, so drag is small. But introduce wing ice or exposed rivets, and a turbulent boundary layer forms, resulting in more skin friction drag.

The airflow around the wing may flow faster than the airflow around the fuselage, so where these different airflows meet, interference drag is born because they clash within the space they share. These graphs represent induced and parasite drag against airspeed. Induced drag is most significant at low airspeeds and high angles of attack, where the pressure differential between the top and bottom of the wing is the greatest. On the other hand, an increase in airspeed increases parasite drag by a factor of the square of airspeed. So, if you double the airspeed, for example, you get four times the parasite drag.

Explore how temperature differences and air pressure variations shape the movement of winds from the poles to the equator. Learn about the roles of high and low pressure areas, the impact of the Coriolis effect, and see how trade winds, westerlies, and easterlies influence our climate. Perfect for pilot students and flight instructors.

On December 17th, 1903, the history of aviation was changed forever when the Wright brothers made the world's first successful flight. You might think that their design was so simple. The propellers move the aircraft forward, the wings produce the lift and the aircraft stays in the air. But when you examine it closely, you will be amazed by the numerous ingenious technologies these high school dropouts developed 100 years ago.

Their design was so complete that even the current modern aircraft use the same principles of flight. First thing's first, to make an aircraft fly you have to first overcome the pull of gravity, or in other words, you have to produce a lift force. The Wright brothers borrowed the idea of lift generation from their own earlier experience on gliders. They knew that when air flowed over a curved surface, it generated a lift force. The higher the speed, the more would be the lift force. An increase in angle of attack also increases the lift force. How is this lift generated? That's a topic for another video.

To make the aircraft move forward, two propeller blades were used. They produced thrust force, again, from the same airfoil principle. The thin propeller blades were a clever design choice. Until then, the common belief was that an aircraft propeller should be something like that of a ship's propeller. However, the Wright brothers proved that to work efficiently in air, a high-speed narrow blade was the ideal choice.

Moreover, you will notice that the blades were rotating in opposite directions. This was another crucial design decision. Without this, control of the aircraft would not have been possible. We will learn about that at the end of the video. The blades were driven by an engine which sat on the wing. To fly an aircraft, you have to obey the following force equations of flight. To come up with an aircraft design which satisfies these equations, the Wright brothers developed their own lift data by abandoning all the wrong lift data that was available at that time.

The Wright brothers' wing had a top point near the leading edge. This design produced more lift than the top at center design used at that time. With an optimized wing design alone, this aircraft would not lift from the ground. The Wright brothers realized that the existing heavy automobile engines being used were the main villains. They had to make the engine lighter without compromising its power output. Only a powerful engine could give the aircraft a good speed. As explained earlier, the more the speed the more the lift.

Unable to find any such engine, with the help of their mechanic, the Wright brothers designed and built their own engine. A lightweight, 12 horsepower petrol engine. Even before the new engine development, the Wright brothers had calculated that they needed an engine of less than 200 pounds in weight, with at least eight horsepower to meet the equations of flight. To reduce weight, they even cast the crankcase with aluminum, a first at that time. They painted the crankcase black so that their competitors would not know about the construction material. You can see the details of the chain and sprocket mechanism used to transfer power from the engine to the propeller blades.

With this design, at proper airplane speed, the lift force would overtake the gravitational pull, and they would have take-off. Did you notice a rail track in this visual? That was another clever design decision from the Wright brothers. They knew that it was impossible to get a good airplane speed in the sandy terrain, so they used a 60-foot-long rail track arrangement for a smooth take-off.

The Wright brothers' main innovation was the development of successful flight controls. Aircraft crashes were a common issue in those days, and nobody knew how to control them. To have a successfully flight, the Wrights had to control their plane in three axes: Pitch, roll, and yaw. They again relied on the principles of the airfoil to accomplish this task. To pitch the airplane, the Wright Flyer had an elevator arrangement at the front. You can see that by moving this lever, a rope mechanism changes the angle of the elevator. If the elevator's rotated up, there would be an upward lift force as per the airflow principle. The torque produced by this lift force could push the whole aircraft up as shown. To push the aircraft nose down, they just did the reverse. In modern airplanes, the elevators are fitted at the back.

To roll the aircraft, Wilbur Wright had a great idea: wing warping. It was clear that by twisting the wing along its length at one end, the angle of attack would be positive and at the other end, it would be negative. This would obviously create a lift differential, and the airplane would roll. To understand how the Wright brothers practically achieved wing warping, let's have a look at this animation. The pilot controls a cradle, using his hip, which in turn controls two separate cables attached to it. The cable movement makes the wing warp through a clever mechanism.

This is a brilliant mechanism. We need a separate, dedicated video to understand the details of it. In modern aircraft, ailerons are used to generate the lift differential. However, when the Wright brothers tried to roll the aircraft using wing warping, the result was disastrous. They noticed that along with the rolling, the airplane took an unintended turn as shown. They called it a "steering reversal problem." This phenomenon is now called, "adverse yaw." The physics behind the adverse yaw are now well understood. The airflow above the high angle wing region produces high drag. On the other tip, the drag force is low. The difference in the drag force makes the airplane yaw as shown.

The Wright brothers overcame this issue with the help of a rudder arrangement. If the aircraft was yawing in this way, they turn the rudder as shown, in such a way that the torque produced by the rudder would exactly cancel the adverse yaw torque. Here the Wright brothers made another smart move. Since the rudder had to be operated whenever there was wing warping, they connected the rudder and wing warping controls together. Both these motions were simultaneously operated from the hip control. By using these controls effectively, the Wright brothers were able to give the aircraft the stability needed. Pitch the aircraft to climb up or climb down, and make a smooth turn by banking the aircraft.

Now back to the interesting question posed in the middle of the video. Why did the Wright brothers use opposite directions of rotation for the blades? This was to cancel the gyroscope effect of a rotating wheel. Any rotating object has an angular momentum. Assume the Wright brothers designed the aircraft with the blade spinning in the same direction. Now the pilot decides to pitch the aircraft by lowering the elevator. The lowering of the elevators would obviously produce a torque as shown. However, the airplane would not pitch upwards as expected due to the angular momentum of the blades. Instead, it would take an unexpected side turn as shown. This unexpected phenomenon is known as gyroscopic procession. Gyroscopic procession conforms perfectly with Newton's Second Law of Motion. You can see that the direction of change in angular momentum is the same as that of the torque applied. The only way to overcome such unexpected behavior is by eliminating the very cause of it: the angular momentum of the spinning blades. That is exactly what the Wright brothers did with two blades spinning in opposite directions.

It is astonishing to discover that the Wright brothers thought about such detailed engineering points, despite their limited formal education. Did you notice that the pilot's position was not in the middle of the aircraft? Please support us by clicking the help button if you are astonished by the marvelous engineering feats that the Wright brothers accomplished.

Reduced Vertical Separation Minima or RVSM requires aircraft flying in the same airspace to be separated by 1000 feet. Precision altimeters and ground-based secondary surveillance radars have made it possible to fly aircraft in such close proximity safely. However, as increasing demand continues to congest the airspace, the risk of mid-air collision has never been greater. A simple miscommunication or a lapse in concentration is enough to send two aircraft on a collision course. To avert the calamity, one of the most advanced systems is installed on the aircraft: the Traffic Collision Avoidance System (TCAS).

The TCAS system has a computer in the aircraft avionics compartment and two antennas. The top antenna scans the area above the aircraft, and the bottom antenna scans the area below. The TCAS computer collects several data from the aircraft systems and creates a three-dimensional area of protected airspace around the aircraft. The system has a wide scanning range and can detect several aircraft in the vicinity, but only gives warning alerts when a traffic is a potential collision threat.

Let's see how the system determines that. The onboard TCAS computer sends an interrogation signal to the traffic aircraft. The TCAS computer of the traffic aircraft responds with an identification code and altitude. The onboard TCAS computer locates the position of the traffic aircraft by tracking the direction of the response signal and calculating the distance from the traffic by measuring the time taken between interrogation and response. Change in altitude and position of the traffic over time helps the TCAS computer to calculate the airspeed, vertical speed, and heading of the traffic aircraft.

Using data of both aircraft, the TCAS computer solves three important questions: Number one, what is the closest point of approach (CPA)? CPA is the point where the two aircraft will meet having the minimum distance between them. Number two, is the traffic an intruder? That is, will the traffic aircraft path interfere with the protected airspace at the time of CPA? If yes, then the most important question: How much time is left to meet at the closest point if both aircraft continue on the same flight path?

With 45 seconds to go, the TCAS issues a Traffic Advisory: "Traffic, traffic," and the traffic is displayed on the navigation display. An amber dot indicates the aircraft, and the "+05" indicates the traffic is 500 feet above. In Traffic Advisory, there are no maneuvering instructions; it just draws the attention of the flight crew to an incoming aircraft. With 25 seconds to go, TCAS warning changes to Resolution Advisory. The amber indications turn red. Instruction is given in the cockpit to maneuver the aircraft. Red lines on the flight display indicate the areas to avoid flying. The TCAS computer on the traffic aircraft is coordinated to give an opposite direction command, "Clear up, conflict."

When it comes to possible mid-air collision, TCAS may be the last line of defense, but a very effective one.

Welcome to the Boeing 7 auxiliary power unit series. The APU is a small gas turbine engine in the aircraft's tail cone. The auxiliary engine supplies electric and pneumatic power to operate the aircraft independently on the ground, start the main engines, and provide backup power during flight emergencies. In this extensive series, we will understand the functioning of the APU engine and its critical role in successful aircraft operations. Let's begin by starting the APU with no engines running and no external power connected.

The only available power sources are the two aircraft batteries. The main battery supplies DC power to the electrical load management system. Selecting the main battery switch closes the contactors inside the panel and energises the DC battery bus. Now we can select the APU switch. The load management system activates multiple components when the switch is moved to the on position. A signal is sent to the APU fuel pump to run, and the APU fuel feed valve is commanded to open. The APU controller is powered on, and the APU air inlet door is operated. The air inlet system has an electric actuator that moves the door to the open position.

The APU controller controls and monitors the start procedure. When the start signal is given through the APU switch, the controller selects the available crank option. Since the aircraft's pneumatic power is unavailable, the controller will switch to an electric start. The APU electric start system has a dedicated battery. The battery is connected to the APU power distribution panel. The controller closes the contractors inside the panel and operates the electric starter. The electric starter is a DC motor installed on the front side of the APU. The battery power operates the starter, which is connected to a ratchet wheel. The ratchet drives a paw clutch mechanism. The clutch transmits the torque to the drive gear. The driver turns the accessory gearbox connected to the gearbox is the engine shaft. Mounted on the shaft are the two-stage centrifugal compressors. The compressor's rotation creates suction and draws air through the inlet duct.

A single-stage compressor consists of an impeller and a diffuser. The impeller accelerates the airflow radially. The diffuser increases the pressure and directs the airflow into the next stage. The airflow enters the second-stage compressor, which further increases the pressure. The compressed airflow then heads for combustion. The APU feed line supplies fuel from the wing tank to the fuel cluster on the accessory gearbox. The fuel cluster comprises a mechanical pump, valves, filter, and distribution manifold. When the engine reaches 7% RPM, the controller commands the fuel shutoff valve to open. The fuel travels through the primary manifold and into the 14 fuel nozzles across the combustion chamber. As the fuel nozzles atomise and inject the fuel into the combustor, compressed airflow enters through the swirlers. The swirlers twist the airflow, which results in a thorough fuel-air mixture and ensures efficient combustion.

At 7% engine RPM, the controller also activates the ignition system. It sends 28-volt DC power to the ignition unit. The unit converts the power into high voltage pulses and transfers it through the ignition lead to the two igniter plugs. The high voltage pulse generates a spark in the igniter plugs. The spark ignites the fuel-air mixture and sets off the combustion. The APU engine has a reverse flow annular combustion chamber. The peak temperature inside the section can reach 2000° C. Therefore, a significant portion of the compressor's airflow is used to cool the combustor. The combustion chamber is intricately designed with holes throughout the casing that allow airflow injection. The additional flow protects the combustor liner, improves combustion efficiency, stabilizes the flame, and reduces the temperature of the gas before it hits the turbine blades.

The combustion gas then flows into the turbine section. The engine has a three-stage axial flow turbine. A single stage consists of a stator and a rotor. The stator directs the flow towards the rotor blades. The rotor harnesses the kinetic energy of the combustion gas and drives up the engine speed. The flow then passes through the exhaust duct and exits the aircraft from the left side of the tail cone. The combustion inside the chamber, once ignited, is self-sustaining. To prevent flameout and uncontrolled shutdown during the start process, the ignition system remains active until the engine reaches half its rated speed. The controller then switches off the ignition unit at 50% RPM. The controller opens the contactors in the power panel and breaks the supply to the electric starter. As the motor rotation stops, the paw clutch disengages from the ratchet, and the starter is isolated from the gearbox rotation.

The fuel pressure in the pump increases with the increase in engine speed. Around 50% RPM, the pressure causes an internal flow divider valve to open. Additional fuel travels through the secondary fuel manifold, and the fuel flow into the combustion chamber increases. The engine accelerates to reach the rated speed. When the engine is close to 100% RPM, the APU's electric and pneumatic power are available for selection. In the next part of the series, we will operate the aircraft systems and start the main engines using the APU power. Thanks for watching.

Welcome to the free pilot training channel, this is Private Pilot Ground Lesson 12. In this episode, we're going to be explaining V speeds and the airspeed indicator. You don't want to miss out on any part of this lesson since you might see questions relating to this on your check ride or on your written exam. Just a couple quick notes before we get started with this lesson. First, is that the letter 'V' in these V speeds stands for velocity; it's not just some made-up letter to confuse you. Second, is that when we discuss V-speeds, we're specifically talking about indicated airspeed. This is the airspeed that your airspeed indicator shows that you're going.

Just be aware there are other types of airspeed. Let's take a really quick look at those. We'll discuss exactly how the airspeed indicator works in a future lesson, but just know that the indicated airspeed you're seeing may not be the actual airspeed that you're traveling at. Different airspeeds and flap configurations there can be some installation and instrument error. Manufacturers account for this by putting a chart in the POH. This adjusted airspeed is called calibrated airspeed. True airspeed is calibrated airspeed that's adjusted for altitude and temperature. At colder temperatures and higher altitudes, there's less pressure. This affects our airspeed indicator because it uses pressure to tell us how fast we're going. The most accurate way to get your true airspeed is to use a flight computer, but a quick way is to add two percent to your calibrated airspeed for every thousand feet of altitude.

The next one is ground speed. This is simply how fast your airplane is flying over the ground. For example, if you have a headwind, you're traveling over the ground slower than your airspeed indicator tells you that you are. All right, enough of that, let's go back to talking about V-speeds. These are simply indicated airspeeds you need to know to operate your airplane safely. First, let's look at two airspeeds we might want to climb at: these are Vx and Vy. Now we always want to climb away from the ground with max power, but if we pitch for Vx, this gives us the best angle of climb. That means we get the most altitude in the shortest amount of distance. This is the airspeed we want to pitch for any time we're trying to climb over an obstacle. I remember this by thinking Vx, I'm dead if I hit that tree.

Next is Vy. This is the best rate of climb. Vy gives you the most altitude in the shortest amount of time. Unless you need to clear an obstacle, we typically climb out at Vy. I'm sorry I don't have a memory aid for this one. If you do, post it in the comments below so you can help someone else out. Now let's discuss maneuvering speed, this is Va. We talked about maneuvering speed a little bit in our lesson on load factor. Maneuvering speed is the fastest airspeed you can fly without causing structural damage if you make a sudden input to one of the control surfaces or you run into turbulence. At maneuvering speed and below, if you put too much of a load on the airplane, you will stall before structural damage can happen. Just remember, above Va or maneuvering speed, if you put too much of a load or G's on the airplane, you can cause structural damage or structural failure, and an airplane without wings can be kind of tricky to fly.

Let's take a look at our V speeds on the airspeed indicator. You'll find that most of your speed limitations are actually color-coded. First, I want to point out something that's not a V speed: zero airspeed marker. This may seem kind of obvious, but it should read zero when we're not moving. I usually check this during the run-up, then on the takeoff roll, I check it again to make sure it's moving away from zero. That's how we check to make sure it works properly. Now let's take a look at the wide arc. The wide arc is our flap operating speed. At the bottom of the white arc, we have power-off stall speed. This is the stall speed in the landing configuration, meaning that the gear and flaps are extended. This V-speed is Vs0. You can remember this by "stall with stuff out."

At the upper limit of the wide arc, we have the maximum speed with the flaps extended. On this particular airplane, that airspeed is 105 knots. This V-speed is Vfe, for flaps extended. If you fly above this airspeed with the flaps extended, you could damage the flaps. Now let's take a look at the green arc, which is our normal operating range. On the bottom or the lower limit of the green arc, we have stall speed with the gear and flaps retracted. This V-speed is Vs1. You can remember this by "stall with stuff in." On the upper limit of the green arc, we have Vno. This is our maximum structural cruising speed. This is the fastest we want to fly in smooth air. For this one, remember "normally operate at this speed."

Now let's take a look at the yellow arc, also known as the caution ring. Only fly in this range in smooth air, then proceed with caution. The lower limit of the yellow arc is also Vno. Remember, this is our normal operating speed, and more importantly, remember that we only fly in the yellow arc in smooth air. On the upper limit of the yellow arc, we have this little red line. This line indicates Vne, which means never exceed. Operating above Vne, even in smooth air, can result in structural damage or even structural failure of your airplane. Let's look at a couple more that have to do with retractable landing gear, since as a private pilot, you could get an endorsement to fly an airplane with retractable gear. First is Vlo. This is the maximum speed for actually extending or retracting the gear. Remember this one by remembering "landing gear lowered." Next is Vle. This is the maximum speed you can fly around after you have lowered the gear. Remember "landing gear extended.

Well, it's all to do with the jet stream, as is often the case. The jet stream at the moment is a topic of discussion, and its position has become more commonplace in weather broadcasts. It is often blamed for why we get the weather we do, but why are we so interested in it, and how does it influence our weather? A jet stream is another name for fast-flowing currents of air which encircle the globe at high altitudes. The major jet streams are the polar front and subtropical jets. They can reach speeds over 200 miles per hour, but this speed is not constant throughout the length of the jet stream.

Embedded within the wave-like pattern of the jet stream are localized areas of even faster winds. Even though these areas are relatively small-scale features within the larger jet stream, they are important as they provide a focus for modifications to surface pressure patterns. Their position within the trough-ridge pattern of the larger jet stream influences the resultant shape and can affect the development of weather at the surface. A stronger jet on the left or rearward side of a trough will cause that feature to sharpen or extend. A sharper trough can cause deeper low-pressure systems at the surface, giving stormier weather. For a ridge, this same position of the stronger jet will cause the feature to amplify.

An amplified ridge can block the normal west-east progression of weather systems and bring more prolonged periods of settled weather. On the other hand, a stronger jet on the right or forward side of a trough will cause that feature to relax. For a ridge, this same position of the stronger jet will cause that feature to decline. Both circumstances have less impact on the development of surface weather systems.

Jet streams affect the weather by generating regions where air ascends or descends, which can lead to areas of falling and rising pressure at the surface. Certain regions of jet streams are more favorable for rising or sinking air. To explore this, let's take a journey through a simplified jet stream in the northern hemisphere. Two isobars, lines of constant pressure, are shown on a horizontal surface. High pressure lies in the warmer air to the south, and lower pressure lies in the colder air to the north. The isobar spacing is closer together at the center, showing the region of the strongest pressure gradient and stronger winds.

Before air moves into the stronger jet entrance, it is subject to a balance of forces known as geostrophic balance. This is a balance between the pressure gradient force, which acts from high to low pressure, and the Coriolis force, an apparent force that is the result of the Earth's rotation. As the air enters this region, it accelerates because of the increased pressure gradient. To maintain the balance, the Coriolis force would also have to increase, but its response is not immediate.

This means that while the overall movement of the air through the jet stream is still eastward, there is now a component towards the north. This northwards component is the ageostrophic wind, which results from the imbalanced forces in the entrance region of the stronger jets. This component causes the transfer of air from the right side of the jet entrance to the left side. This removal of air from the right entrance creates an area of upper-level divergence, while air piling up in the left entrance region of the jet creates an area of upper-level convergence.

These areas of divergence and convergence have a significant influence on surface pressure and the weather we experience. Diverging air at high levels means that the air in the column is being depleted. To fill this depletion, air from below rises. If this region of diverging winds is stronger than the corresponding converging surface winds, there is an overall loss of air from the vertical column. As pressure is the weight of air in a vertical column, if the amount of air decreases, the surface pressure must fall.

This would cause an underlying surface low-pressure system to deepen, bringing increasing wind speeds and heavier rain. For an underlying area of high pressure, this situation would cause surface pressure to lower, lessening its blocking effect and allowing the eastward progression of weather systems. For the left entrance region, where air is piling up, there is an overall increase in the mass of air in the vertical column, and so surface pressure must rise. This would cause an underlying surface low-pressure system to fill and weaken, bringing decreasing wind speeds and less unsettled weather.

Pressure in an underlying area of surface high pressure would get even higher, continuing the settled conditions but also increasing the risk of visibility problems caused by haze, mist, or fog. Our journey now takes us to the core of the stronger winds where the Coriolis force has caught up with the increased pressure gradient and geostrophic balance is restored. However, this balance is short-lived as air starts to decelerate in the widening pressure gradient in the exit region. Again, the Coriolis force is slow to respond, creating an imbalance, but this time the Coriolis force is larger than the pressure gradient force.

This now creates a southward component of a geostrophic wind. This southwards component now causes the transfer of air from the left side of the jet exit to the right side. So air is now piling up in the right exit region, creating an area of upper-level convergence, sinking air, and surface pressure increases. And air is leaving the left exit region, creating an area of upper-level divergence, rising air, and surface pressure falls. When focusing on the regions of jet streams that are most likely to cause a larger impact in the weather that we experience, meteorologists look for the right entrance and left exit regions.

When these upper-level development regions coincide with favorable surface features such as low-level temperature or humidity gradients, we experience the three-dimensional nature and interdependencies of our complex and interesting weather.

The earth's climate system is driven by two things. The way energy from the sun moves in and out of the atmosphere and the way heat moves around the atmosphere and the oceans. Energy from the sun is the main driver for our climate system. When the energy from the sun reaches the atmosphere, some is absorbed and some is reflected, mainly from clouds. Most of the remaining energy heats the Earth's surface, although again a tiny fraction is reflected.

The earth's surface then loses its heat again through rising air currents, radiation, and the evaporation of water. Some of this heat passes straight through the atmosphere and back to space, but some is absorbed by greenhouse gases like carbon dioxide, water vapor, methane, and ozone. Most of the air, nitrogen and oxygen, doesn't do this.

The atmosphere re-emits the absorbed heat. Some escapes to space but some heats the earth's surface again. Eventually, all the heat escapes into space but not before the temperature of the earth has been raised enough to allow us to survive. If the greenhouse gases didn't absorb and re-emit heat, we wouldn't be able to live on earth.

If nothing else happened in the earth's climate system, weather and climate wouldn't change across the globe. However, the sun's energy is distributed unevenly across the globe. Because the earth tilts, the sun's intensity changes at different latitudes and in different seasons. Generally, there is more heat in the equator than there is at the poles.

In this example, the variation is shown during the northern hemisphere winter. To balance this inequality, the climate system moves heat from the equator to the poles through the atmosphere and the oceans. In the tropics, near the equator, thunder clouds develop, forcing warm air to rise and then drift towards the poles at high levels.

Cooler air flows in the opposite direction at the earth's surface, setting up cells. Similar cells develop in other areas as you move towards the poles. At the boundaries between these cells, air is either rising from the earth's surface or falling down towards it. Where the air is rising, you will get low pressure, often with rain or snow.

Where it's coming down, you will get high pressure and fine weather. That's how heat is moved around the atmosphere. Now let's see how it moves around the oceans. Changes in sea temperatures and saltiness create ocean currents. For example, the Gulf Stream is one of the strongest currents in the world.

Surface water in the North Atlantic is cooled by winds from the Arctic. Cold, dense, salty water sinks and travels towards the equator deep in the ocean. In turn, the Gulf Stream moves warm water from the Gulf of Mexico northeastwards at the surface to replace it. This brings warmth to northwest Europe making the climate milder than any other place at the same latitude.

It is these interactions between the sun's energy and how the atmosphere and the oceans move heat around the earth which produce different climates in different parts of the world and set up variations in our day-to-day weather. A warming world caused by increases in greenhouse gases could upset the delicate balance of our climate system and have an impact on our long-term climate.

This is an airplane in flight, so what makes it stay up in the air? To understand the basic physics of flight, let's have a look at the properties of air, in particular, air pressure. Air is made up of many small molecules. Air molecules are made up of many tiny atoms. Air may appear invisible, but air has mass; therefore, it has weight. In the Earth's atmosphere, there are a multitude of air molecules. You can think of air as water, as it behaves like a fluid. Each time an air molecule comes in contact with an object, it puts pressure on it.

Let's have a look at this scenario again and discuss two types of air pressure. In the case of an object that is stationary, air exerts static air pressure on the object. For instance, how is it possible that an inflated balloon does not get squashed by the static air pressure? It's because the air inside the balloon balances the pressure outside. However, should the static air pressure outside decrease, the balloon will expand to fill in the space. Oops! If you force an object onto air, it's the object's energy that causes air pressure.

In this case, the object experiences dynamic air pressure. For instance, when you stick your head out of a moving bus, the wind resistance you feel on your face is dynamic air pressure. So, static air pressure plus dynamic air pressure make up total air pressure. What this formula suggests is that for a constant value of total air pressure, if dynamic air pressure goes up, static air pressure must go down, and vice versa.

If you observe air flowing through a tunnel like this, you will notice that static air pressure is applied to the walls of the tunnel, as represented here by the red arrows. For a straight and even tunnel, the static air pressure is equal throughout. But if you reduce the width of the tunnel and observe the airflow, something interesting happens. Inside the thinner section of the tunnel, the speed of the air increases. Consequently, the dynamic air pressure in this section increases. However, static air pressure decreases, represented here by the small red arrows.

So, in simple terms, the surface area where the faster airflow is has less static air pressure. Perhaps now you can see what we are getting at. The shape of the surface in the tunnel where the lower static air pressure looks similar to the top surface of an airplane wing. In part, this is how lift is created that allows the aircraft to fly, by reduced air pressure above the wing compared to the higher air pressure below the wing, as long as the plane is moving fast enough through the air.

An aircraft is a well-balanced machine. In straight and level flight, all forces are in equilibrium. To understand this concept, let's have a look at the moments of force. This is a balanced seesaw; however, with different weights on each end, it becomes imbalanced. A child's weight is essentially a force of gravity. If one child weighs ten kilograms and the other weighs five kilograms, and they are exactly the same distance away from the center, how can the seesaw balance again? Since the lighter child is half the weight of the heavier child, you must put her twice as far from the center to attain the perfect equilibrium.

Archimedes once said, "Give me a stick long enough and a pivot, and I shall move the world." What all this means is that little force can achieve bigger results given a long enough arm to create the moment of force that is needed. Mathematically, a moment is defined as force multiplied by the arm. Going back to our seesaw analogy, we can prove that the lighter child is able to balance the heavier child by using a longer arm to achieve the same moment of force.

These arrows represent the four main forces acting on an airplane in flight. For demonstration purposes, these forces are often shown to act from a single spot, but in reality, that's not the case. On a typical light aircraft, the average of weight is slightly forward of lift; thrust is above drag. Combining the moments of these forces together suggests then in this configuration, the airplane has a natural tendency to pitch down.

So how is this fixed? The stability takes care of it by generating an opposing downward force. This downward force does not need to be great, since the arm is long, which helps to create a moment of force that is strong enough for the airplane to remain in equilibrium.

Pressure and density altitude play a big role in performance calculations on the test and it's a consistent weak area so let's have a look at it here. In low pressure air, air molecules are spread out, there isn't as much air in a given space when the pressure is low. When the air pressure is high, those air molecules become more tightly packed and the air is denser. Aircraft performance depends on this density, the propeller is more effective when it's pushing more air molecules to produce thrust, the wing generates more lift when it's pushing more air molecules downwards, and the engine produces more power when it has more air molecules going into the cylinders to combust.

The pressure of the air changes as we move up in the atmosphere. At lower altitudes, aircraft experience higher pressure due to the compacting force of all of the air molecules above it pressing down. At higher altitudes, there isn't as much of this air pressing down, and so the molecules are more spread out, and the pressure is lower. Aircraft performance is poorer at higher altitudes. Heating in air mass causes its molecules to move faster and spread out, higher temperatures create lower pressure air, aircraft performance is poorer in hotter temperatures. Changes in weather conditions give rise to high and low pressure air systems on different days, aircraft performance is poorer on days with low pressure. Water vapor present in the atmosphere on humid days reduces the density of air, bigger water molecules push or crowd out air molecules out of a space of air, aircraft performance is poorer on days with high humidity.

If we look at all these factors that are at play on a particular flight and say something about how well the aircraft will perform, we're going to be using pressure and density altitude to say it. In other words, after looking at things like altitude, pressure, and temperature, we can say that the aircraft will perform the way it would at a certain altitude under standard conditions or under conditions where temperature and pressure are held to a constant. First of all, if the aircraft climbs, it'll perform worse, so the true altitude of the aircraft is a determining factor of performance. Here it is at 8,000 feet. Now, if the pressure falls or is lower than the standard 29.92 inches of mercury at sea level, the aircraft will perform not as though it were at 8,000 feet but as if it were at, say, 11,000 feet under that standard model in fantasyland where pressure and temperature held constant. This aircraft would behave as if it were at 11,000 feet. This is its pressure altitude.

Similarly, if the temperature rises and air molecules spread out, the aircraft will behave as if it is even higher. So, raising the temps causes the aircraft to perform not as if it were at its pressure altitude of 11,000 feet but at what's called its density altitude of 12,000 feet. The definitions are pressure altitude is true altitude corrected for non-standard pressure or the altitude indicated when the altimeter is set to 29.92. Density altitude is pressure altitude corrected for non-standard temperature, so it's a multi-step process to get to density altitude.

So just to review, an increase in altitude causes an increase in density altitude, a decrease in pressure causes an increase in density altitude, and an increase in temperature causes an increase in density altitude. On the test, a chart like this one will be used to determine pressure altitude and density altitude. Pressure altitude is found by taking the altimeter setting and finding the conversion factor, and adding it to the field elevation.

So if the altimeter is 29.92, it's pretty simple, you find that the conversion factor is zero and add that to the field elevation of, say, 1,000 feet. This means pressure altitude also equals 1,000 feet. What about if you have an altimeter setting of 28.90? You find that conversion factor, which is 957, add it to the field elevation, and get the pressure altitude of 1,957. Let's try a full example like we'd see on the test.

They give us field elevation, temperature, and altimeter setting, we have to find pressure and density altitude. First, we'll start by finding the conversion factor for the altimeter. There's not a line for our altimeter setting of 30.35, so we'll have to interpolate between the two closest ones. This means we'll take the conversion factors for 30.30 and 30.40 and average them, or divide their sum by 2, to get our conversion factor of negative 394. Now if we apply that to the field elevation, subtract 394 from 3,894, we get our pressure altitude of 3,500.

Next, to find density altitude, we use the chart on the left. We find the temperature of 20 degrees Fahrenheit at the bottom and move up until we get to the pressure altitude of three thousand five hundred. This is halfway between the lines for three and four thousand. From there, move to the left and read the density altitude of 2,000 feet. Now these charts can be very difficult to read, even using the straight edge you'll have with you on test day, so it might be helpful to remember that a 15-degree Fahrenheit increase will lead to about a 1,000-foot increase in density altitude. This is helpful if you're like me and have trouble reading exact figures off these charts.

The center of gravity position affects the stall speed. Does a forward center of gravity increase or decrease the stall speed? You may wish to view our videos on stalling and moments of force for some background information on this subject.

A forward center of gravity causes the aircraft to develop a pitching down tendency. Equilibrium is regained with help from the elevator, which creates a counterbalancing downward-facing force. Unfortunately, this downward-facing force increases the aircraft's apparent weight, which means that more lift needs to be generated to keep the forces balanced.

According to the lift formula, once the critical angle of attack has been reached, more apparent weight requires more lift, causing the only other variable, stall speed, to increase as well. Remember the two Fs: forward center of gravity equals faster stall speed.

The pitot static system is an essential part of an aircraft, intimately connected to critical flight instruments like the altimeter, airspeed indicator, and vertical speed indicator. These devices provide pilots with vital information about their altitude, speed, and climb or descent rate, utilizing atmospheric pressure measurements to deliver accurate data.

To grasp the significance of the pitot static system, one must first understand the atmosphere's structure. Air molecules near the Earth's surface are densely packed due to gravity, which compresses them, creating higher pressure at sea level compared to higher altitudes. This variation in atmospheric pressure is what the pitot static system measures to calculate altitude and speed.

The system collects pressure data through two components: the pitot tube and static ports. The pitot tube measures the pressure of moving air as the aircraft flies, typically mounted under the wing to avoid interference. Some aircraft feature a pitot mast instead, but its function remains unchanged. To prevent blockages from water or ice, the tube includes a drain hole and can be heated.

The static port's location varies across different aircraft designs, positioned to accurately measure the static air pressure unaffected by the plane's movement. For example, on the Cessna 172, it's found on the forward fuselage's left side. Both the pitot tube and static port feed pressure data into the pitot static instruments, aligning their internal pressure with the external atmosphere.

Each pitot static instrument operates uniquely. The altimeter, for instance, displays altitude using aneroid wafers that expand or contract with pressure changes. This mechanical action, translated through gears and levers, rotates the instrument's hands to indicate the aircraft's altitude. Pilots can adjust the altimeter for current atmospheric pressure to ensure accuracy.

The vertical speed indicator (VSI) measures the aircraft's climb or descent rate by comparing the current and past atmospheric pressures. A calibrated leak allows for a controlled change in case pressure, creating a pressure difference that moves the needle on the instrument's face to indicate vertical speed. However, this instrument may experience a slight lag in reading changes.

Lastly, the airspeed indicator is the only instrument connected to both the static port and pitot tube. It measures the ram pressure, which increases with the aircraft's speed, and uses this data to expand a diaphragm inside the instrument. By subtracting the static air pressure, it provides an accurate speed reading that adjusts for altitude changes.

The airspeed indicator's face features color-coded speed ranges to guide pilots in maintaining safe flight speeds under various conditions. These ranges indicate normal operating speeds, flap extension limits, and the maximum speed for smooth air only, helping pilots avoid exceeding the aircraft's limitations.

In summary, the pitot static system is a fundamental aspect of aviation, enabling pilots to navigate and operate aircraft safely by providing critical information on altitude, speed, and vertical movement. Its accurate readings, essential for flight safety, depend on the sophisticated interplay between atmospheric pressure measurements and mechanical linkages within the system's instruments.

Dive into the harrowing tale of survival and aviation safety with 'A Mid-Air Explosion Leaves a 737 Passenger Cabin Exposed: Air Disasters.'

This dramatic video recounts the chilling experience aboard Aloha Flight 243 when, at 24,000 feet over the Pacific, passengers found themselves exposed to the elements after an explosive decompression. The story unfolds with gripping detail, exploring the April 28, 1988 incident that left a Boeing 737 with no walls or roof mid-flight. Discover how this catastrophic event reshaped airline regulations and safety protocols, brought to you by the insightful storytelling of Air Disasters. Watch now to understand the full impact of this historic aviation crisis.

Tower, Delta 191 heavy, out here in the rain, feels good. 191 heavy, we're not getting any bad warnings from the weather or from other pilots, which we rely on as they come through it. As the pilots of Delta 191 prepare for landing, the rain begins to fall harder. At the foot of the runway, one of the most ferocious types of storm clouds stands in their way. Before landing check, landing gear down, three green.

At the time, the type of storm the Delta crew is approaching barely has a name. John McCarthy is one of the world's leading experts on these storms. It is a tiny thing, meteorologically speaking, compared to a big storm or snowstorm or a hurricane. It's just like a needle in a haystack. The needle is a microburst, one of the deadliest and at the time, most poorly understood weather phenomena. They've taken down airliners before, but as Delta 191 makes its approach, there are no warning systems that can effectively alert the pilots of the danger they're in.

Prior to 1985, the radars on board the aircraft were built to detect thunderstorms, essentially heavy areas of precipitation. They were not effective; they were not even designed to detect the Micro Burst. If you're at the kitchen sink and you turn on the water and it goes straight down and it splashes out in all directions, that's kind of what a microburst is, except that it is extremely bad news if you're an airplane flying through it. When a plane hits a microburst, it encounters a complex and powerful set of conditions. Downdrafts and tailwinds batter a plane; it's a deadly combination.

Just short of the runway, Delta 191 flies into the microburst. "You're going to lose it, all of a sudden, there it is. Push it up, push it way up, way up, way up, way up, hang on to the son of..." The pilots of Delta Flight 191 did their very best to recover from this situation, and it didn't work out. "I must have caught sight of him just at the last millisecond, and he cartwheeled into the tank." In just an instant, and then, of course, there was fire, not a ball of fire, but a wall of fire.

Just 27 people survived the crash of Delta 191, 137 people are killed. After the crash of Delta 191, the Federal Aviation Administration races to develop technology that can prevent microbursts from killing again. If there is one crash that we can look back on now and say this made things safer because we learned from it, it was Delta 191.

Weather patterns are a fundamental aspect of our planet's atmospheric behavior, intricately linked to the complex interplay of temperature and pressure differences. At the heart of these patterns lies the dynamic movement of air, primarily driven by temperature disparities within the atmosphere. These differences lead to variations in pressure, which, when combined with the Earth's rotation, orchestrate the global movement of air. This movement is what we experience as wind, a common but vital component of the Earth's weather systems.

Among the most powerful and influential wind systems are the jet streams. These are not just any winds; they are very strong winds located in the high part of the atmosphere, typically between 5 to 7 miles above the Earth's surface. The speed of these streams can astonishingly exceed 200 miles per hour, making them a formidable force in the atmospheric dynamics. Jet streams are characterized by their extensive size, often stretching for thousands of miles in length and spanning hundreds of miles in width. In the Northern Hemisphere, their direction is generally from west to east, following broad, meandering paths that shift northward or southward depending on the season.

The intensity and behavior of the jet stream are greatly influenced by the seasonal temperature contrasts, particularly between the cold polar air and the warm tropical air. It is during the wintertime that these contrasts are most pronounced, resulting in the jet stream reaching its peak strength. This period is also when weather fronts tend to develop along these boundaries, where the jet stream acts as a guiding force for the movement and formation of weather systems.

A fascinating aspect of the jet stream is its role in weather development, especially in terms of low-pressure systems. These systems can be likened to giant funnels of wind, spiraling inwards and upwards, drawing warmish air towards their center before causing it to rise. As this moist air ascends, it cools and condenses, forming clouds and, subsequently, weather phenomena. Over the North Atlantic, for instance, the jet stream typically directs depressions from west to east, with a stationary jet stream pattern leading to frequent depressions affecting the same region.

However, the jet stream's path is not always stable or predictable. There are instances when warm air moves further north than usual, or cold polar air ventures further south. Such deviations can disrupt the prevailing west to east jet stream pattern, causing the stream to buckle. This buckling effect can lead to depressions being steered towards different regions or even block their movement entirely. The implications of these changes are profound, as they can have a significant impact on our weather, influencing everything from precipitation patterns to temperature fluctuations.

In conclusion, jet streams play a pivotal role in determining our weather, acting as the high-altitude currents that guide and influence weather systems across the globe. Their strength, direction, and behavior are critical factors in the development of weather fronts and the overall dynamics of the Earth's atmosphere. Understanding the mechanisms and effects of jet streams is crucial for predicting weather patterns and preparing for their impacts on our environment and daily lives.

Airliners are marvels of modern engineering, with each component meticulously designed for both efficiency and safety. Among these, the flying tail stands out as an unusual yet fascinating feature. It is essentially a stabilator surface that integrates with a geared elevator. This innovative arrangement allows for a synchronised movement: when the pilot adjusts the control column, both the stabilator and the elevator respond in harmony.

The result is a seamless motion where, if the stabilator pitches up, the elevator does too, augmenting the overall camber of the control surface. This increases the effectiveness of the aircraft's pitch control, offering pilots finer command over the plane's movement in the sky. The flying tail isn't common in commercial airliners, but when implemented, it represents a remarkable synergy of design and functionality. Though not many airliners feature this system, those that do, often exemplify advanced aerodynamic capabilities and exceptional handling characteristics.

Witness the harrowing account of Aloha Flight 243, where passengers faced the unimaginable—surviving a mid-air explosion that tore away the cabin's walls and roof at 24,000 feet. This video delves into the chilling events of April 28, 1988, and the lessons learned from one of aviation's most dramatic air disasters.

The Boeing 777, a marvel of modern aviation, incorporates three fuel tanks: two main tanks located in the wings and a central tank. During refuelling, the wing tanks are filled first, followed by the center tank, which may not always be fully utilised depending on the flight's requirements. This aircraft, with a hefty weight capacity, demonstrates a sophisticated balance between structure and function. The fuel in the wing tanks, apart from providing energy, plays a critical role in counteracting the stress on the aircraft's wings, thus contributing to structural integrity during flight.

However, the central fuel tank presents a unique challenge. Historical events, such as the tragic explosion of TWA Flight 800, have highlighted the dangers posed by certain conditions within the fuel tank, including the presence of oxygen, fuel vaporisation, and potential ignition sources. The investigation into such incidents revealed the vulnerability of commercial aircraft to fuel tank explosions due to these conditions, leading to significant advancements in safety protocols and the introduction of the Nitrogen Generation System (NGS).

The NGS is a groundbreaking safety feature that leverages the principle that air consists of approximately 78% nitrogen. By using bleed air from the engines, the system cools and separates this air to enrich and transfer nitrogen into the center fuel tank, effectively reducing the oxygen levels to below 12%. This critical threshold ensures that even if fuel vaporises and electrical sparking occurs, combustion is not supported, thus mitigating the risk of an explosion.

This technology not only exemplifies the ongoing commitment to aviation safety but also represents a significant engineering achievement in minimising the risk associated with fuel tank explosions. By understanding and addressing the complex interplay of factors that can lead to such catastrophic events, the aviation industry continues to improve the safety and reliability of air travel for passengers around the world.

Have you ever wondered why some regions of the world experience warmer climates than others, despite being equidistant from the equator? A prime example of this phenomenon can be observed when comparing the mild January temperatures of the Scilly Isles, located off Cornwall's southwest coast in England, with the harsh winter conditions in St. John's, Newfoundland, Canada. Despite their similar latitudinal positioning, the Scilly Isles enjoy average daytime temperatures of around 10°C and nighttime temperatures of about 5°C, with frosts and snow being rare occurrences. Contrastingly, St. John's battles with an average of 18 days of snow cover in January and chilling nighttime temperatures averaging -9°C.

This striking 14-degree difference can largely be attributed to the Gulf Stream, a warm Atlantic Ocean current, and its offshoot, the North Atlantic Drift, which specifically impacts the Scilly Isles by maintaining sea surface temperatures at a winter average of 11°C. Meanwhile, the sea around St. John's lingers at a frigid 0.5°C. The Gulf Stream's influence, driven by oceanic water circulation and wind patterns, exemplifies the complex interplay between the Earth's climate, ocean currents, and global atmospheric circulation.

Moreover, the Earth's Global Circulation Model sheds light on how atmospheric circulation, powered by solar energy, dictates heating and cooling patterns worldwide. Solar radiation, absorbed and converted by the Earth's surface, heats the surrounding air, affecting local climates. Factors such as the intensity of solar radiation—which is most potent over the equator and least effective at the poles due to the angle of sunlight—play a crucial role. Additionally, geographical location significantly impacts temperature; for instance, the Sahara Desert can see temperatures soaring above 50°C during its hottest months.

This interconnected system, where the distribution of solar heat, ocean currents, and wind patterns converge, ultimately dictates our diverse global climate. From the intense heat of Central Australia and the heavy rains in the Amazon rainforests to the stormy North Atlantic and the reflective polar ice caps, each element contributes to the vast climatic variety we observe on our planet.

An aircraft is an amazing machine, capable of flying in any direction by rotating about in three dimensions. These are called axes of movement.

The average location of an aircraft's mass is a point that is called the center of gravity. So if you suspend an aircraft from the center of gravity by a line like this, The aircraft remains perfectly balanced. Each of the three axes moves about the center of gravity. The aircraft's principal axes are normal axis, drawn from top to bottom, lateral axis, drawn parallel to the wings, and longitudinal axis, drawn from tail to nose.

Each axis is perpendicular to the other two axes. Let's look at each individually. The rotation about lateral axis is called pitch. This movement changes the vertical direction of the aircraft's nose. The rotation about normal axis is called your, this is the movement of the nose of the aircraft from side to side.

The rotation about the longitudinal axis is called roll. This is the movement of the aircraft's wings. One wing goes up, the opposite wing goes down. So in summary, these are the three principal axes of movement.