i got a good one. What is that noise in the gear bay that is a low pitch tone followed by a higher tone beep? I think it has something to do with a systems test or resetting the FMS or something. I hear it from time to time while fueling the 737 NGs.
During a normal landing, under calm and dry conditions, typically what percentage of speed reduction can be attributed to: brakes vs spoilers vs reverse thrust ?
Exactly how bad is it to do 2 rejected landings 40 minutes apart? I was flying from Fiji to LA and apparently a fuel pump wasn't working. The pilot waited for a plane to land that was supposed to have a replacement, but it didn't, so he tried and failed to take off... Then waited for the another plane to arrive that also might have a spare pump, but the didn't, so 40 minutes after the first rejected take off, we had a second one... About 10 minutes later he said, 'Ok, lets just try that again...' Third time lucky I suppose - we got airborne! And had a completely uneventful flight to LA. Would a third rejected take off in an hour have been bad?
@@Joeybagofdonuts76 a Watt is defined as J/s, so the wattage depends on how much time it takes to convert that energy to heat. It took the 747-8 in the video about 20 seconds to stop so if we assume the A380 and 747 are similar, you're looking at 110 MW of brake power. To put this in perspective, if you could convert that to electricity, you could power about 65,000 households for those 20 seconds!
In regards to brakes being the primary well... Braking method on the aircraft that is exemplified best in the C-17. Such an enormous aircraft designed for short feild landings with huge amounts of weight on board, it uses 12 MASSIVE carbon fibre brake packs, in conjunction with spoilers covering 3/4 of the wing span to dump all of the lift, but the thing making it so much more extreme than other aircraft is that the thrust reversers direct all thrust upward, with no openings on the lower half. So all of the thrust is in effect pushing down on the brakes even harder, in effect making the aircraft even heavier to allow harder braking without locking at all. One hell of am impressive aircraft
When you were talking about failures in both braking systems, and the need to apply the brakes only once, it reminded me of the story of the B-17 bomber returning to its base in England during WWII. Its hydraulics were shot up and the pilot didn’t know if he even had one brake application. His choice was to either hope he had brakes and land back at base where their Christmas dinner would be waiting for them, or land at one of the bases with an ultra-long runway, but then spend Christmas Day in the back of a deuce and a half ton truck and miss dinner. The captain polled the crew and they all wanted Christmas dinner, so they landed at their base. Luckily, the backup system worked and they had that one application remaining.
Excellent explanation...as usual. My grandfather was an engineer at Boeing in the late 60's. He told me that he was on the development team for the 747. One of the stories he told was fascinating. The engineers had to calculate the maximum heat generated in a 747 during a rejected takeoff. To prevent the tires from bursting, they had to determine the pressure rise in the tire and then design a special plug in the wheel that will pop out (relieving pressure) just prior to the tire self-destructing. If a tire bursts, it can do severe damage to nearby components in the landing gear. A bursting tire also damages adjacent tires and can lead to a chain reaction in tire failures.
Yes! very much like wet clutches on motorbikes also which use this "pack" method to be more space efficient, i'm surprised that cars still use a single plate, large diameter clutch actually, such are the benefits of a multi-plate friction system like this
What I use to picture what 2,2 Gigajoule of energy means is: This would be sufficient energy to bring 6579 liters of water from 20° to 100° (not including evaporating it). Everyone who has been waiting in front of his noodle pod with a few liters water to finally start boiling now can imagine, that you use a lot of energy for 6579 liters.
Excellent analogy. If you can imagine a 1000 liter water tank and its mass (1 tonne) multiplied by 6.579 - that's a lot of water and mass to heat up! Interesting to know how long it would take to reach 100 deg boiling point.
MiG-21bis has brakes on the nose gear as well, with a handle on the instrument panel to enable for takeoff and landing, and disable for taxi. Its brakes are pneumatic and operate off stored pressure, which gets interesting if you use it all up.
@@cieludbjrg4706 Considering I get called Toni, Anthony, Tonio etc, no I don't mind. Not everyone speak and pronunciate in the same way. I find being such a grammar Nazi to be more offensive than calling me the N word. Seriously when someone does, this, there's vertically no reason to communicate further because instead of dealing with what's being said or conveyed, they're nic picking irrelevant crap.
In fact, the brakes are more closely related to the multi-plate clutch on a motorcycle than a car disc brake ('though the clutch default is ON and the brake OFF of course).
Great explanation. I’m amazed that steel brakes can build and retain heat over a day on short haul as each subsequent flight at minus 30-50 degrees would “suck” the heat out of them. It’s like being in a very interesting engineering class
It's been a long time ago but I can remember 727 and DC 9 occasionally arriving at the gate with very hot brakes. If it was dark outside you can actually see a glow from them and we were always told that that was burning magnesium. When we would see hot brakes we were always told to never approach the gear from the side and to the only approach from the front or the back in case it was to explode and the split Rim separated said it would blow out to the side. You definitely never wanted to throw water onto a hot break or it would explode. Usually the fire department would put fans in front and behind the landing gear to try to cool them off slowly. Having helped our mechanics replace brakes before, it's is surprising how heavy those things are.
You should never approach mains straight in. Aircraft wheels have thermal plugs that melt & deflate the tire if the brakes get too hot but you shouldn't bet on it. You really should never bet on anything an engineer designed.
Early B-727 had nosewheel brakes. Due to reliability issues, a service bulletin (SB) was issued and they were removed. Later 727's were manufactured without them.
I love these tech videos. The A-6 Intruder I was married to for fifteen years had a problematic (unreliable) anti-skid system and it was not unheard of to blow tires or have brake fires after an aggressive brake application. BTW, we disarmed the anti-skid system and increased tire pressure for aircraft carrier operations. The latter could make for an exciting arrival when flying off the boat to a shore base.
_"The antiskid system in airplanes works like that in cars..."_ Historically speaking switching that around to _"in cars it works like in airplanes"_ would even be more "correct" as when the automobile industry began to adopt that system for cars in the 1970s it was already in use for airplanes.
really as a fully electronic system like today ? In cars there were many ABS ish systems around also in the 60s and earlier but the challenge for a modern system as we know it today was that the electronic ECU is able to proccess all information and controll the actuators fast enough.. that was not possible before the invention of modern transistors, micro processsors and other hugh speed digical electronic components
@@bobl78 I studied EE in the mid 1970s and my Professor teaching "electronic circuit design" owned a company which had developed an ABS for a German car manufacturer. (ABS at that time was an "extra" you had to pay for and was typically only available for the more expensive line of models.) At that time transistors were available since more than a decade and electronic circuit designs had started to incorporate analog ICs (like simple OpAmps as the uA 741 or timers like the NE 555). Digital ICs were quickly growing out of providing just the most basic building blocks, as they had been the years before, which had given us the 7400 (4 x dual NAND) or the 7490 (4 flipflop chainable counter stage). Now we could also have ADCs and DACs, which formerly needed to be built from discrete components. While I concede car ABS then was far from the "stability control" we have today, which e.g. incorporates inputs from MEMS acceleration sensors that are processes in real time and can recognize a car starts to turning around its vertical axis. Such an advanced system as we have it today can give control back to the driver by asymmetric application of the brakes on all four wheels. A very basic ABS can be much simpler and still be effective: The key understanding is there a substantial difference between static friction and sliding friction of the tires on the asphalt. If all four wheels go from static to sliding at about the same moment in time (if the driver simply pushes the pedal as hard as he or she cab) the brakes are just less effective as they could be. Worse if the road is more slippery on one side of the car than on the other, because the asymmetry then creates a force that makes the car turn around its vertical axis, making it uncontrollable for the driver. (And when friction becomes stronger again all of a sudden the car would also be in danger to roll over "sideways".) Therefore experienced drivers at that time applied a technique called "Stotterbremse" in German, which means full force is applied intermittently only, giving you a shorter distance to a full stop as constantly applying the brake and risking the tires to block. Which explains the name ABS: It means *Anti Blocking System* and the goal is (or then was) to avoid the wheels to go into sliding friction in the first place. This actually can be achieved quite simple: the electronics would only have to determine whether a wheel still rotates and if NOT to cut the pressure in the break cylinders of that wheel until the wheel starts to turn again. Exactly that was what early ABS did in cars and you would well notice it if you e.g. pushed the brake hard on a snowy road: the rattling of the "stuttering breaks" could be easily heard (and felt too).
@@mittelwelle_531_khz very interesting, thank you. The first german electronic ABS I know of was introduced in the Mercedes W116 around 1978 or so .. most like a 2 or 3 cannel sytem... So what was the challenge to bring an electronic ABS into a car ? I started drivin in the 90`s and remember that back then the systems were great compared to non ABS cars but compared totoday´s systems react and pulse much faster and contain many many more functions .BTW is a modern ABS system able to adapt the way it works to speed and ground / friction levels? Does it work different on snow than on dry road ? I remember when my dad got his first W126 in 1982 with ABS as a super expensive option ...
That's just some absolutely fantastic material. It's great to get into so much technical detail without boring the audience one second. I'm only experiencing aviation via flight sims and after watching this video I kinda feel content that in sims brakes work 100% of the time in maximum efficiency.
I’m impressed that as well as being a pilot you know the physics and engineering very well. I hadn’t appreciated the brake cool time was even an issue before
727 actually did have nose wheel brakes as an option, I believe for unimproved runways. Pretty sure some did exist but most 727s did not have the option added.
Dear Petter, I love your channel. MentourPilot, BlancoLirio and VASAviation (all with a Spanish connection!) are my go-to sites for all things aviation. But I do have one BIG criticism to make: Your programs, barring those to do with sad events, are not the same without your adorable pooches, they never fail to bring a smile to my face!
If doing multiple short legs on a busy day, would pilots ever go gear-down early on approach to cool the brakes more if ground cooling fans arent available? Obviously the pilot would have enough temp 'reserve' to land if they were good for a take-off, but to prevent delays on the next departure? Would that be a company procedural thing? I.e. bean-counters determined that the increased fuel-burn was cheaper than 10-20 minute delay waiting on brakes for whatever reason, so gear down x miles further out from touchdown then they normally would be?
Back in the 70s and 80s I worked for PSA in San Diego maintenance on the B-727. All our 727s had nose brakes which were only activated during heavy braking. They were required to operate out of airports with shorter runways to assure stopping during a rejected take-off at higher weights. More passengers were carried with operative nose brakes. We were required to remove the brakes after so many months because they were never used and send them out for overhaul basically to remove the rust.
I remember having seen the brakes of my parents car glowing red hot (had to stop on the side of the road) going down a mountain when I was a kit. Also, when you turn off your car, you don't have hydraulic assistance anymore. If you need to brake, you also have to brake with one push on the pedal. Otherwise you will loose any braking assistance, like Peter explained for the plane.
The brakes on a car will still work even with no engine power, the pedal just gets very hard and you have to apply a lot of pressure. If you ever driven a old car or a race car, same story with them. 🤷🏼♂️
On most cars you have pneumatic brake boost. The brakes work with hydraulic fluid and work if the car is on or off and are divided in 2 seperate circles if one fails.
I experienced something like that once. I was driving down the Rockies traveling west from Denver. Anyone who's driven there knows the freeway has steep descents for miles. I decided to put it in neutral and see how fast it would go just coasting. (My engine was choking in that high altitude, so I didn't do it just to see what would happen.) Well it ended up exceeding my car's speed limiter at 109 mph. I figured that would do nothing while the car was in neutral, but no, it still cut ignition and the engine just died. I lost power brakes and power steering while descending a hill and going around a curve. Then I had to slow the car down to get it to start up again. Losing power assist wasn't as bad as regaining it and having the steering suddenly become soft. I ended up rolling down the mountain and dying. It was a bad day.
A guy stole a car and proceeded to flee from the police on my town a little while back. The car was abandoned in the street in front of my alley, and my surveillance system caught the whole thing. The guy didn't even bother putting it in park it looked like. Those brakes were glowing so hot in the footage you couldn't see the tire rim any more. It was just white hot on the screen. Absolutely nuts.
The DeHavilland DHC-7 "Dash 7" had an option to have brakes fitted on the nose wheel as well. However, very few aircraft got that option as it turned out the benefit, even in a STOL market as it was made for, the difference in stopping distance was minimal, but maintenance complexity was increased.
I think it's fair to say that in most airliner operations, required takeoff field length is greater than for landing? Perhaps another reason why a bit less stopping distance wasn't worth it.
After a long taxi on a hot day we could see the brake temps climb. It was a good idea then (at most airports) to leave the gear down for a few minutes after takeoff. Hot gear in a tight well might cause problems.
Love the technical videos! It was fun trying out a rejected takeoff with the brakes set to RTO in my sim. I normally set them to RTO but I had no idea how it would actually feel rejecting the takeoff after 80kts.
I’ve read that Concorde was one of the first airliners to make use of Carbon Ceramic brakes, not only for the weight savings, but also because of the higher takeoff and landing speeds she had compared to her subsonic counterparts. She also had brake cooling fans to help keep the brake temperatures in check during taxi and after landing.
We commissioned an induction heater for company which makes carbon brake discs. One of many stages is to cook them in an induction heater for hours. Process is quite interesting but messy (everything is covered with a fine graphite dust). Advantage of using induction for any conductive material is that heat generates in the workpiece so it does not need to conduct to it from hotter heater. in short terms indction heater is a transformer with shorted secondary winding (workpiece).
Great technical video, thanks. I've only been through a rejected takeoff once, as a passenger of course since I'm not a pilot just always interested in how things happen with aircraft. It was in a Shorts turbo prop (or fan, don't recall) on a short runway at a relatively small airport (SBA). Passengers experienced that situation of hanging on our seatbelts during maximum braking but nobody panicked and we were at full stop with room to spare remaining ahead on the runway. I recall it turned out to be a false warning indicator that caused the rejected TO. It was tested, resolved and we proceeded back out to takeoff with nothing further of note. After initial concern, it became an interesting diversion from normal operation, at least for myself. Cheers and stay safe.
Petter, any semi truck driver who deals with long down hill runs know this. That's why they gear down and use engine (jake) brakes rather than rely on friction brakes. Brake fade is a thing, and if a trucker overheats their brakes - well that's what runaway lanes are for. I can't imagine anything more terrifying than having a brake failure as a pilot, trucker or, in my case, in my POS car.
My understanding is that some early model variants of the 727 200 had nosewheel brakes to supplement the main brakes. However, I believe they were ultimately removed due to ineffectiveness and relibility issues.
I would never even think of a fact that brake discs actually don't have the time to cool down during A WHOLE FLIGHT, although a short one. Amazing as always, thank you!
@@pilotavery Whatever OFC denotes I had a girl friend whom held an MBA and obtained work at ( major carrier ) I can assure you is is no joke to them: If some person in that position reads this they might just do the calc's ~ the person expressed wonderment at how 2 major airframe had reported being under 1 mile separation - all the computing power we have nowadays can be brought to bear saving 0.000051 / seat-mile → Many do not realize the commercial carriers operate on thin margins
I used to work for a company who manufactured wheel speed sensors for a number of aircraft, it's actually really interesting how the anti-skid system works. Depending on the aircraft, they can be a single or dual channel system, and there's a system in place to detect a broken wire even if the brakes are not being used.
That is a good story about breaking. During all the flights I took,, on landing there was a regular descelerating movement. Just grab your seat bars and everything was fine. On one landing in Washington DC. from Europe the plane was descelerating so heavily I was pushed forward strongly, I had to grab the backseat in front of me so not to get slammed against it.
I once got to experience max braking while standing up (in the cockpit, behind the captain during an accelerate/stop test). I was hanging on for dear life to the column of a temporary equipment rack behind me. Even back in my lean/40-pushups days, it was all I could do to stay out of the captain's lap.
Whenever I read or see a video on brakes or braking, I remember Swiss Air 306. The Caravelle crashed because of overheated brakes stowed after takeoff resulting in fire and destruction of hydraulic systems. 80 lives perished. Morbid, I know.
The c141 had anti skid system . We had to change 8 wheels after hard landing. They all blew out. A person approaching the plane from the side got hit with the wheel rim in the chest and died. The wheels can be very hot and dangerous. They are rather heavy.
Just to add to what you said about the rejected take-off test, when they do this, the test is done with the brakes degraded to the point where an airline would normally be required to replace them. Once they stop the plane, the plane has to sit for five minutes without catching on fire to simulate the time it would take the fire crew to get there. As far as nose wheel brakes, the Boeing 727 had added in at some point, but they were later removed after it was determined that they didn't really have much of an effect when it came to stopping the plane.
@@gabrielsimon7944 I hope so! It’s been a dying itch to understand this! Especially between short flights. For example, San Diego CA - Las Vegas NV. Only a 45 minute flight but seems like it could be shorter if they would just fly straight!
GOL airlines, in BR, upgraded some of their 737 brakes to carbon to comply with higher performance requiriments for the (somewhat) short SAO PAULO city airport runway. With the upgrade they were able to operate with full (passenger) capacity. Those restrictions were latter lifted.
Partly. You arm the spoilers to deploy automatically by (1) selecting RTO on the Autobrakes dial as Mentour showed and (2) move the spoiler handle to the "ARMED" position. Moving the spoiler handle to the ARMED detent will also cause the ground spoilers to automatically deploy during not only a rejected takeoff but during landing as well.
It always shocked me when I remember that all airliners don’t have brakes on the nose-wheel. The way the nose suspension bounces up and down when they arrive at the gate braking to a stop makes it look like the braking is coming from the nose
If you think airliner braking is a complicated issue, you should try operating smaller turboprops with no anti-skid and perhaps badly designed brakes. They can be a nightmare! Some of those aircraft (Cessnas C406 & C441 and the DHC-6 Twin Otter) have nicely designed no-antiskid systems where the brake pedal force directly translates to brake effect, just like an ancient car with no ABS. There was one aircraft I have flown that has astonishingly difficult brakes, the Do228 Dornier. after landing, you applied brake pedal and nothing happened. Then you carefully applied some more pedal pressure and very little happened. THEN, if you had to, you applied just a little more pedal pressure and the wheels would lock up! A flat spot on the main tires SERIOUSLY damages them, an expensive occurrence. Fortunately the Do228 has a touchdown speed well below 100 knots and being a Garret-powered high-wing aircraft has MAGNIFICENT reverse capabilities. Wheel braking was rarely needed for anything more than taxying.
Anti-lock braking first appeared in planes, but the system that cars use is different. Planes have huge wheels compared to cars, so their system is to have a gear inside the inner wheel rim like a cog which detects that it's not turning anymore (the wheel is not turning) and backs off the hydraulic pressure on the brakes. On-off-on-off many times a second until maximum braking is attained just prior to the known brake lock point. It's purely mechanical. Cars use a 2 ot 3 channel electronic system.
Hi. This is interesting. As introduction, it'll be interesting to mention that airplane breaking is constitute by: aero brakes, tires brakes, and thrust reverse. Thank you.
This is incredibly interesting....whenever I have flown I always hear the jet engines "spool" upon landing, which I thought was the major braking force (i.e. reverse jet power), however, it is fascinating to know that the aircraft's brakes are the primary stopping force...
That loud acceleration sound you hear is tje air rushing through and against the thrust reversers not engine revving up. I sit nest the wing almost every flight and constantly watch and hear the music of landing.
Thank you for a new highly detailed video! Quite a lot new things to know. The question on the autobrake (especially on the RTO braking). As i understand the manual brake application disengage the autobrake system. But, as i understand the captain are mandated to manually apply near full manual braking at the rejected takeoff above 80 knots, so RTO just saves about a second or so and serves as failsafe for human error basically? Is that correct?
I would like to note that anti skid systems are actually very different from the traditional ABS systems in cars, The ABS system is like the anti lock systems where anti skid systems are "adapting" to surface condition thus, anable amazing tire efficacy (up to 98%), this enables to operate the tires very close to the slip point
I guess there was a version of a B727 that had nose wheel brakes in an attempt to reduce even more landing distances, but it was abandoned due to weight and not achieve the desired objective.
A brake is basically just a type of clutch, that happens to connect the wheels to the frame. These brakes are actually quite similar to a multi plate clutch. That being said, there are few things faster and heavier, than a landing airplane, lots and lots of heat.
Exactly what I was thinking: they reminds me a lot my motorcycle clutch, just working the other way around (not to transfer motion to the wheel but to stop the wheel to spin, a bit like shifting down).
Railway trains can be much heavier and have far less grip - steel wheel on steel rail is what makes them efficient, but also means they are unable to stop hard. Of course, failure to strap down the self-loading cargo is also a limiting factor. Ships are vastly heavier, although much slower, but again - very limited grip so emergency stops are not a thing in naval architecture.
There are different kinds of brakes though. You are talking about friction brakes but there are induction and regenerative brakes, too, that are used on high-speed trains.
@@unvergebeneid They are still limited to the grip of the wheel on its running surface. The only exceptions are those used on a few mountain railways and tramways which grip the rail itself, but they are limited in usefulness due to the inability to deal seamlessly with points and crossings. Regenerative braking is also used on EVs.
There are also brake fans that are supposed to cool brakes after landing. At least in some airbus a320 family. Funny thing about those is that you have to make sure no one is standing next to main landing gear when those fans are applied because it blows out carbon fibre dust which can be extremely harmfull to your lungs.
Wow, excellent video! @Mentour Pilot, back in June of 1993, I was on a red eye flight with Southwest Airlines and in a Boeing 737, from Las Vegas, Nevada to San Diego, California. As we were flying, something happened that caused the airplane to lose all power, including both engines, exterior and interior lighting and then the plane immediately went into a very steep nose dive that literally felt like we were going straight down. Now obviously, we were in a dark airplane, somewhere over the desert, where there is virtually no light pollution and it was very late at night. I’m guessing that it was somewhere around midnight to 1:00am in the morning. And so as a result of that, I didn’t really have anyway of actually referencing how steep of a nose dive that we were actually in. I do remember being pinned into me seat and unable to move. One of the flight attendants was getting ready to start serving drinks and peanuts but when everything happened she caught air and ended up getting pinned to the ceiling of the aircraft. I was sitting right on the center of the wing and she was a few rows behind me, in the isle of the aircraft. It’s weird, because still to this day, I can still very vividly remember hearing both of the engines start spooling down and can still recall in full detail everything that ended up happening. I don’t know how long we were actually in a nosedive for but my guess is probably around 30 seconds to maybe 45 seconds max but it seemed like an eternity, that’s for sure. The pilots eventually got power restored to everything and the engines started again. They then put the plane into a very steep climb that felt about twice as steep as a normal take off. But again, it was sometime in the middle of the night and over the desert so I had no reference points to say for sure how steep everything actually was? When the plane started climbing the flight attendant then fell, hit her head on the back of one of the isle seats and was then pinned to the floor while the plane was climbing. From Las Vegas, Nevada to San Diego, California it only a 6 hour drive or around 350 miles or so. The flights aren’t very long either. They are only about 50 minutes to maybe an hour max. As a result of that, the plane only flys to an altitude of I think somewhere between 20,000 feet to maybe 25,000 feet max. Because of this and there being several mountain ranges all throughout that desert, I am only assuming and guessing that the pilot put the plane into such a steep climb because he was probably trying to gain much needed altitude to clear an obstacle. If that is indeed what happened, I’m going to guess and assume that the obstacle or obstacles needing to be cleared was one of those mountains or mountain ranges in the desert. Once the plane leveled off again, maybe after climbing for only around a minute or 2, 3 to 5 minutes maximum, 1 of the other flight attendants helped the injured flight attendant to the back of the plane to try and help her out. The rest of the flight it seemed like the pilot was fighting the plane the entire time. Of course that may have also been caused or due in part to there being turbulence but it lasted all the way to San Diego, up until we landed. And when we landed, it was a very hard touchdown that literally caused the plane to briefly become totally airborne again, for a few seconds. Also, right before we touched down, it seemed like we were at a little bit higher of an altitude and then we just dropped and slammed onto the runway before bouncing up off of it for a second or 2. Before we taxied to our gate, air traffic control had us park the plane just off of the runway so the 1 flight attendant that got injured during the flight could be taken off of the plane to an already awaiting Paramedic and/or EMT ambulance crew. After the injured flight attendant was taken off the plane, we were then able to taxi to our assigned gate. After we got off of the plane, I then had to explain to 1 of my Dads church friends that had picked me up from the airport, why my shirt and pants were all wet and covered in alcohol and I smelled like it, due to the guy who was sitting in the seat in front of me somehow bringing alcohol onto the flight and then spilling it all over me when the plane went into its dive. With everything that I described, in your opinion, what could have caused the plane to do what it did? Every pilot or knowledgeable aviation person that I have ever talked to about this incident has said that either they did not know or it could have been a number of things. If possible, can you please offer up suggestions or advice as to what you think may have caused everything to happen? In asking this question, I’m not wanting or trying to criticize or blame the pilots or Southwest Airlines. In fact, it’s quite the opposite actually. The pilots and entire flight crew should have been given an award for everything that they did to not only save the plane but keep everyone as calm as possible and as informed as possible as well. Since then, I have only flown twice. In August of 99’, I flew from San Diego, California to Dallas, Texas to see a good friend while I was on vacation. After visiting him and his girlfriend, I then flew back home and have never flown again since then. I used to love flying and was never afraid of doing so. But after that flight, I have now become afraid of flying. This is why I watch your channel and others like it, so I can learn as much as possible about flying. And then maybe one day, sometime in the near future, hopefully I will be able to face my fears, get on an airplane and then fly to some place nice and no longer be worried that the plane might crash. From the bottom of my heart. Thank you Mentour Pilot, for all that you do! I truly have learned a tremendous amount from all of your videos and best of all, they are building up my confidence to consider trying to fly again someday.
Could have potentially been a microburst, this would have also had to cause something like a compressor stall to get one or both engines to stall out also causing lack of power, but this is entirely a guess
funny thing. calculation (model of cooling) is used in industry too - Aluminium billets heating is an example - when billet is rejected [press unable to accept it because of any hold-ups] billet is delivered to reject and PLC models cooling process to take it back to heating after press recovers. it must cool down by ca 200 degrees C for re-heat because Al must be heated with taper (front warmer and back cooler - ratio is up to 100deg/m). Taper is to prevent ready extruded profile from overheating - Al extrusion is slow and heat generated by press can travel back. too high extruded profile temperature could destroy its mechanical proporties.
I wouldn't say quickly, it would be quicker than if you didn't use anti-skid, but the wear rate is according to design. The issue with this is that you wear down and destroy the tires when the wheels lock up.
@Jim Mork Friction coefficient (with A/S) is around 0.75 for airliner tires on dry pavement (varies a bit with speed). A wet runway knocks that down to more like 0.4 depending on the particulars, and then ice or hydroplaning closer to 0.1 or less. So reversers don't typically matter much for average stops on a dry runway, but are crucial when runway friction is severely degraded.
@Jim Mork In my answers I like to throw in numbers perhaps not readily available on the internet, for whomever might be curious, but the bottom line is antiskid systems work on contaminated runways as well. What changes as surface friction degrades is how the plot of brake pressure vs time looks. On a dry runway, the antiskid-enabled brake pressure is a flat-ish line with just small ripples from the antiskid's pressure dumps. The lower the runway friction, the deeper and wider those pressure drops get.
@@Leminge42 Was at Farnborough many years ago with a Saab pilot showing off the nosewheel brake whilst spooling up the engine. Then off he went! They don't let you that close now.
Great video, Petter! Super interesting. I'm an auto, and "just about everything else" mechanic. Never knew brakes on large aircraft were set up like a giant motorcycle clutch with multiple friction discs. Great footage of those glowing brakes, too - that was great!! 👍😎
They don't, a big burly wizard stands at the end of the runway and screams at the plane "THOU SHALT NOT PASS" and then the plane fills it's underpants and comes to a stand still. All jokes asside love the content Peter, wishing you a happy new year!
The 737’s wheels are exposed to the elements during cruise, so wouldn’t the freezing temperatures and winds/apparent winds up there cool the brakes down pretty fast?
Probably not that fast. Obviously the landing gear is designed to reduce drag as much as possible when it is retracted. Thus the air circulation through the wheels is probably limited. In fact, a quick image search shows that 737s probably have wheel covers (hubcaps if you will). These would would help keep the brakes nice an snug in their wheel wells when retracted. 😀
I always enjoy your videos. I am a competent physicist so I have no difficulty with the principles but the videos alert me to things that I may not have thought about. Which is always interesting. Of course I am waiting for the video on the "mid air parking brake" that can hold a plane stationary in the air in the event of a system failure. It might be quite a few years before they get that one perfected.
Just by the way: if you try to drive a truck for the first time, fasten your seatbelt properly :-) A truck has brakes controlled by an air pressure. There is no feedback in the pedal and there is a little delay. So let me explain one second when you try to brake: Stepping a little bit - no feedback, no reaction, so increasing pressure to the pedal and still nothing hapening! Finally stepping very hard and sudenly kaboom! :-D All breaking force is applied!
In case anyone is wondering, carbon brake discs are actually made of graphite, with a near perfect crystalline structure. They can work at up to 2000°C.
i love watching your video's from the United states very intresting and great information and entertaining hope all is well with you and the family thank you
These videos are awesome! Keep them coming. Personally I'd like to see one on pilot:ATC communication. What are the standards, what can go wrong, examples during emergency, why calls are made and when. If that sounds too dull for everyone :), then what about the air France that went off end of the runway at YYZ? I remember that because I was on the 401 (highway next to 24L) when it happened. I think it was and A340. Thanks!!
BTW: GJ is the order of magnitude of energy stored in large superconducting magnets. The energy must be removed within small part of a second in these cases.
Get 20% discount on the yearly subscription of Brilliant by using this code 👉🏻 brilliant.org/Mentourpilot/
Hej!
i got a good one. What is that noise in the gear bay that is a low pitch tone followed by a higher tone beep? I think it has something to do with a systems test or resetting the FMS or something. I hear it from time to time while fueling the 737 NGs.
During a normal landing, under calm and dry conditions, typically what percentage of speed reduction can be attributed to: brakes vs spoilers vs reverse thrust ?
Exactly how bad is it to do 2 rejected landings 40 minutes apart? I was flying from Fiji to LA and apparently a fuel pump wasn't working. The pilot waited for a plane to land that was supposed to have a replacement, but it didn't, so he tried and failed to take off... Then waited for the another plane to arrive that also might have a spare pump, but the didn't, so 40 minutes after the first rejected take off, we had a second one... About 10 minutes later he said, 'Ok, lets just try that again...' Third time lucky I suppose - we got airborne! And had a completely uneventful flight to LA. Would a third rejected take off in an hour have been bad?
Mentour Pilot ( Wow !!!) SHEIKH MD. SHADDAT HOSSAIN .
For those who wasn't struck by lightning: 2.2 GJ is approximately the explosive energy of half a ton of TNT.
Who does that equal to a gigawatt?
@@Joeybagofdonuts76 it's 0.61 megawatt-hour, if anyone is interested.
@@Joeybagofdonuts76 If you release 2.2GJ in ~1.8s you get 1.21GW
@@maxsz91 thanks
@@Joeybagofdonuts76 a Watt is defined as J/s, so the wattage depends on how much time it takes to convert that energy to heat. It took the 747-8 in the video about 20 seconds to stop so if we assume the A380 and 747 are similar, you're looking at 110 MW of brake power. To put this in perspective, if you could convert that to electricity, you could power about 65,000 households for those 20 seconds!
In regards to brakes being the primary well... Braking method on the aircraft that is exemplified best in the C-17. Such an enormous aircraft designed for short feild landings with huge amounts of weight on board, it uses 12 MASSIVE carbon fibre brake packs, in conjunction with spoilers covering 3/4 of the wing span to dump all of the lift, but the thing making it so much more extreme than other aircraft is that the thrust reversers direct all thrust upward, with no openings on the lower half. So all of the thrust is in effect pushing down on the brakes even harder, in effect making the aircraft even heavier to allow harder braking without locking at all. One hell of am impressive aircraft
Good ol' Moose!
@@roriquevernonii8439 she's definitely a beast 😁
@@yukionna1649 Don't know if it's just JBER, but she's called a moose up here.
@@roriquevernonii8439 i think we've all always known her as the moose. She's got the call after all 😁
@@yukionna1649 love that sound!
When you were talking about failures in both braking systems, and the need to apply the brakes only once, it reminded me of the story of the B-17 bomber returning to its base in England during WWII. Its hydraulics were shot up and the pilot didn’t know if he even had one brake application. His choice was to either hope he had brakes and land back at base where their Christmas dinner would be waiting for them, or land at one of the bases with an ultra-long runway, but then spend Christmas Day in the back of a deuce and a half ton truck and miss dinner. The captain polled the crew and they all wanted Christmas dinner, so they landed at their base. Luckily, the backup system worked and they had that one application remaining.
Excellent explanation...as usual. My grandfather was an engineer at Boeing in the late 60's. He told me that he was on the development team for the 747. One of the stories he told was fascinating. The engineers had to calculate the maximum heat generated in a 747 during a rejected takeoff. To prevent the tires from bursting, they had to determine the pressure rise in the tire and then design a special plug in the wheel that will pop out (relieving pressure) just prior to the tire self-destructing. If a tire bursts, it can do severe damage to nearby components in the landing gear. A bursting tire also damages adjacent tires and can lead to a chain reaction in tire failures.
Between you, captain joe, and 74 gear, I get all the different types of aviation content I need!
Interesting, I'm expecting ground staff with leaf blowers like in F1 next time I fly 😀
I woundet how it work in like middle east where the runway can be really hot
Yeah, and others packing the inner wheels with dry ice.
Some airliners do have brake fans that the pilots can turn on to cool the brakes down after they get hot
I thought of F1 when he talked about pump braking (aka cadence braking)...
I have seen videos of aircraft brakes being hosed off on some island hopper routes.
Interestingly, the brakes are very similar to "race" clutches in a car, or clutch packs in an automatic transmission.
Yes! very much like wet clutches on motorbikes also which use this "pack" method to be more space efficient, i'm surprised that cars still use a single plate, large diameter clutch actually, such are the benefits of a multi-plate friction system like this
My dad used to build autobrake/anti-skid control modules for the 737 back in the 1990s. Great video as always, Petter!
What I use to picture what 2,2 Gigajoule of energy means is: This would be sufficient energy to bring 6579 liters of water from 20° to 100° (not including evaporating it). Everyone who has been waiting in front of his noodle pod with a few liters water to finally start boiling now can imagine, that you use a lot of energy for 6579 liters.
Excellent analogy. If you can imagine a 1000 liter water tank and its mass (1 tonne) multiplied by 6.579 - that's a lot of water and mass to heat up! Interesting to know how long it would take to reach 100 deg boiling point.
Release this energy in less than ~1.8s and you have enough power to power the flux capacitor and jump back to the future
@@maxsz91 As long as your speed is 88mph = 76.5kn.
The Flux Capacitor is very reliable.
@@rainscratch Minimum speed requirement goes without saying - it's basic knowledge
@@maxsz91 Only genius mad scientists can design the system though.
MiG-21bis has brakes on the nose gear as well, with a handle on the instrument panel to enable for takeoff and landing, and disable for taxi. Its brakes are pneumatic and operate off stored pressure, which gets interesting if you use it all up.
Ah yes but the beloved Frog Foot?
This is the kind of content that makes me glad I found this channel. Thank you Peter for producing great content:-)
So glad you like it my friend! Feel free to share it around
FYI, his name is Petter not Peter.
@@richardbutler9466 Really!?! Are you that bothered by one single letter?
@@AntonioCunningham Would you be happy if your name got written Antoni? Cuningham? His name is PeTTer, not PeTer. It matters to us Scandinavians! :)
@@cieludbjrg4706 Considering I get called Toni, Anthony, Tonio etc, no I don't mind. Not everyone speak and pronunciate in the same way.
I find being such a grammar Nazi to be more offensive than calling me the N word. Seriously when someone does, this, there's vertically no reason to communicate further because instead of dealing with what's being said or conveyed, they're nic picking irrelevant crap.
In fact, the brakes are more closely related to the multi-plate clutch on a motorcycle than a car disc brake ('though the clutch default is ON and the brake OFF of course).
Great explanation. I’m amazed that steel brakes can build and retain heat over a day on short haul as each subsequent flight at minus 30-50 degrees would “suck” the heat out of them. It’s like being in a very interesting engineering class
Just goes to show the myriad of physics, aerodynamics, electrical, aircraft systems, and engineering topics pilots have to be familiar with.
It's been a long time ago but I can remember 727 and DC 9 occasionally arriving at the gate with very hot brakes. If it was dark outside you can actually see a glow from them and we were always told that that was burning magnesium. When we would see hot brakes we were always told to never approach the gear from the side and to the only approach from the front or the back in case it was to explode and the split Rim separated said it would blow out to the side. You definitely never wanted to throw water onto a hot break or it would explode. Usually the fire department would put fans in front and behind the landing gear to try to cool them off slowly.
Having helped our mechanics replace brakes before, it's is surprising how heavy those things are.
You should never approach mains straight in. Aircraft wheels have thermal plugs that melt & deflate the tire if the brakes get too hot but you shouldn't bet on it. You really should never bet on anything an engineer designed.
Early B-727 had nosewheel brakes. Due to reliability issues, a service bulletin (SB) was issued and they were removed. Later 727's were manufactured without them.
I love these tech videos. The A-6 Intruder I was married to for fifteen years had a problematic (unreliable) anti-skid system and it was not unheard of to blow tires or have brake fires after an aggressive brake application. BTW, we disarmed the anti-skid system and increased tire pressure
for aircraft carrier operations. The latter could make for an exciting arrival when flying off the boat to a shore base.
_"The antiskid system in airplanes works like that in cars..."_
Historically speaking switching that around to _"in cars it works like in airplanes"_ would even be more "correct" as when the automobile industry began to adopt that system for cars in the 1970s it was already in use for airplanes.
One more “what has NASA done to improve our lives here on Earth?” example.
Dunlop Maxaret, eh?
really as a fully electronic system like today ? In cars there were many ABS ish systems around also in the 60s and earlier but the challenge for a modern system as we know it today was that the electronic ECU is able to proccess all information and controll the actuators fast enough.. that was not possible before the invention of modern transistors, micro processsors and other hugh speed digical electronic components
@@bobl78 I studied EE in the mid 1970s and my Professor teaching "electronic circuit design" owned a company which had developed an ABS for a German car manufacturer. (ABS at that time was an "extra" you had to pay for and was typically only available for the more expensive line of models.)
At that time transistors were available since more than a decade and electronic circuit designs had started to incorporate analog ICs (like simple OpAmps as the uA 741 or timers like the NE 555). Digital ICs were quickly growing out of providing just the most basic building blocks, as they had been the years before, which had given us the 7400 (4 x dual NAND) or the 7490 (4 flipflop chainable counter stage). Now we could also have ADCs and DACs, which formerly needed to be built from discrete components.
While I concede car ABS then was far from the "stability control" we have today, which e.g. incorporates inputs from MEMS acceleration sensors that are processes in real time and can recognize a car starts to turning around its vertical axis. Such an advanced system as we have it today can give control back to the driver by asymmetric application of the brakes on all four wheels.
A very basic ABS can be much simpler and still be effective: The key understanding is there a substantial difference between static friction and sliding friction of the tires on the asphalt.
If all four wheels go from static to sliding at about the same moment in time (if the driver simply pushes the pedal as hard as he or she cab) the brakes are just less effective as they could be.
Worse if the road is more slippery on one side of the car than on the other, because the asymmetry then creates a force that makes the car turn around its vertical axis, making it uncontrollable for the driver. (And when friction becomes stronger again all of a sudden the car would also be in danger to roll over "sideways".)
Therefore experienced drivers at that time applied a technique called "Stotterbremse" in German, which means full force is applied intermittently only, giving you a shorter distance to a full stop as constantly applying the brake and risking the tires to block.
Which explains the name ABS: It means *Anti Blocking System* and the goal is (or then was) to avoid the wheels to go into sliding friction in the first place.
This actually can be achieved quite simple: the electronics would only have to determine whether a wheel still rotates and if NOT to cut the pressure in the break cylinders of that wheel until the wheel starts to turn again.
Exactly that was what early ABS did in cars and you would well notice it if you e.g. pushed the brake hard on a snowy road: the rattling of the "stuttering breaks" could be easily heard (and felt too).
@@mittelwelle_531_khz very interesting, thank you. The first german electronic ABS I know of was introduced in the Mercedes W116 around 1978 or so .. most like a 2 or 3 cannel sytem... So what was the challenge to bring an electronic ABS into a car ? I started drivin in the 90`s and remember that back then the systems were great compared to non ABS cars but compared totoday´s systems react and pulse much faster and contain many many more functions .BTW is a modern ABS system able to adapt the way it works to speed and ground / friction levels? Does it work different on snow than on dry road ? I remember when my dad got his first W126 in 1982 with ABS as a super expensive option ...
That's just some absolutely fantastic material. It's great to get into so much technical detail without boring the audience one second. I'm only experiencing aviation via flight sims and after watching this video I kinda feel content that in sims brakes work 100% of the time in maximum efficiency.
I’m impressed that as well as being a pilot you know the physics and engineering very well. I hadn’t appreciated the brake cool time was even an issue before
727 actually did have nose wheel brakes as an option, I believe for unimproved runways. Pretty sure some did exist but most 727s did not have the option added.
Those were air brakes
I'd love to see an animation showing how the stator and rotor plates all get pushed together.
Dear Petter, I love your channel. MentourPilot, BlancoLirio and VASAviation (all with a Spanish connection!) are my go-to sites for all things aviation. But I do have one BIG criticism to make: Your programs, barring those to do with sad events, are not the same without your adorable pooches, they never fail to bring a smile to my face!
They will be back. Molly has just given birth and Patxi is keeping my mother-in-law company after she lost her little dog.
If doing multiple short legs on a busy day, would pilots ever go gear-down early on approach to cool the brakes more if ground cooling fans arent available? Obviously the pilot would have enough temp 'reserve' to land if they were good for a take-off, but to prevent delays on the next departure? Would that be a company procedural thing? I.e. bean-counters determined that the increased fuel-burn was cheaper than 10-20 minute delay waiting on brakes for whatever reason, so gear down x miles further out from touchdown then they normally would be?
They would delay landing gear retraction on take offs ...
Back in the 70s and 80s I worked for PSA in San Diego maintenance on the B-727. All our 727s had nose brakes which were only activated during heavy braking. They were required to operate out of airports with shorter runways to assure stopping during a rejected take-off at higher weights. More passengers were carried with operative nose brakes. We were required to remove the brakes after so many months because they were never used and send them out for overhaul basically to remove the rust.
I remember having seen the brakes of my parents car glowing red hot (had to stop on the side of the road) going down a mountain when I was a kit.
Also, when you turn off your car, you don't have hydraulic assistance anymore. If you need to brake, you also have to brake with one push on the pedal. Otherwise you will loose any braking assistance, like Peter explained for the plane.
The brakes on a car will still work even with no engine power, the pedal just gets very hard and you have to apply a lot of pressure. If you ever driven a old car or a race car, same story with them. 🤷🏼♂️
On most cars you have pneumatic brake boost. The brakes work with hydraulic fluid and work if the car is on or off and are divided in 2 seperate circles if one fails.
The pnuematic boost will work ONCE after the engine is turned off. . . until vacuum is lost.
I experienced something like that once. I was driving down the Rockies traveling west from Denver. Anyone who's driven there knows the freeway has steep descents for miles. I decided to put it in neutral and see how fast it would go just coasting. (My engine was choking in that high altitude, so I didn't do it just to see what would happen.) Well it ended up exceeding my car's speed limiter at 109 mph. I figured that would do nothing while the car was in neutral, but no, it still cut ignition and the engine just died. I lost power brakes and power steering while descending a hill and going around a curve. Then I had to slow the car down to get it to start up again. Losing power assist wasn't as bad as regaining it and having the steering suddenly become soft. I ended up rolling down the mountain and dying. It was a bad day.
A guy stole a car and proceeded to flee from the police on my town a little while back. The car was abandoned in the street in front of my alley, and my surveillance system caught the whole thing. The guy didn't even bother putting it in park it looked like.
Those brakes were glowing so hot in the footage you couldn't see the tire rim any more. It was just white hot on the screen. Absolutely nuts.
The DeHavilland DHC-7 "Dash 7" had an option to have brakes fitted on the nose wheel as well.
However, very few aircraft got that option as it turned out the benefit, even in a STOL market as it was made for, the difference in stopping distance was minimal, but maintenance complexity was increased.
I think it's fair to say that in most airliner operations, required takeoff field length is greater than for landing? Perhaps another reason why a bit less stopping distance wasn't worth it.
I want 22" rims with low profile tiers on my 737
22" rims would actually be pretty small on the main wheels. 😉
With spinners.
I’ll loan you the 22’s on my vehicle. Don’t trash them because I’ll need them back!!! 🤣🤣🤣
American: Tires. British: Tyres. Definitely not Tiers.
After a long taxi on a hot day we could see the brake temps climb. It was a good idea then (at most airports) to leave the gear down for a few minutes after takeoff. Hot gear in a tight well might cause problems.
huh, interesting. I didn't figure the brakes would be a clutch-pack, makes a lot of sense
I thought: "Brakes? What's there to talk about?" Boy, was I wrong!! Thanks for a very interesting video.
Ditto that!
It send chills down my spine when I see that Helios livery 😔
Love the technical videos! It was fun trying out a rejected takeoff with the brakes set to RTO in my sim. I normally set them to RTO but I had no idea how it would actually feel rejecting the takeoff after 80kts.
I’ve read that Concorde was one of the first airliners to make use of Carbon Ceramic brakes, not only for the weight savings, but also because of the higher takeoff and landing speeds she had compared to her subsonic counterparts. She also had brake cooling fans to help keep the brake temperatures in check during taxi and after landing.
We commissioned an induction heater for company which makes carbon brake discs. One of many stages is to cook them in an induction heater for hours. Process is quite interesting but messy (everything is covered with a fine graphite dust). Advantage of using induction for any conductive material is that heat generates in the workpiece so it does not need to conduct to it from hotter heater. in short terms indction heater is a transformer with shorted secondary winding (workpiece).
Love the two pictures behind you. Someone has great taste! Oh yeah, love watching you, I learn a lot from your clips.
The link to the artist is in the description. Check him out! instagram.com/plakaty_lotnicze?igshid=yltik8pqq8mt
Hey! New house?
Great technical video, thanks. I've only been through a rejected takeoff once, as a passenger of course since I'm not a pilot just always interested in how things happen with aircraft. It was in a Shorts turbo prop (or fan, don't recall) on a short runway at a relatively small airport (SBA). Passengers experienced that situation of hanging on our seatbelts during maximum braking but nobody panicked and we were at full stop with room to spare remaining ahead on the runway. I recall it turned out to be a false warning indicator that caused the rejected TO. It was tested, resolved and we proceeded back out to takeoff with nothing further of note. After initial concern, it became an interesting diversion from normal operation, at least for myself. Cheers and stay safe.
I’ve heard of some of the 727s having the nose wheel breaks but got removed
Years later, sadly, the 727s got removed. ;^)
Petter, any semi truck driver who deals with long down hill runs know this. That's why they gear down and use engine (jake) brakes rather than rely on friction brakes. Brake fade is a thing, and if a trucker overheats their brakes - well that's what runaway lanes are for. I can't imagine anything more terrifying than having a brake failure as a pilot, trucker or, in my case, in my POS car.
That is really a case for hybrid trucks
My understanding is that some early model variants of the 727 200 had nosewheel brakes to supplement the main brakes. However, I believe they were ultimately removed due to ineffectiveness and relibility issues.
I would never even think of a fact that brake discs actually don't have the time to cool down during A WHOLE FLIGHT, although a short one. Amazing as always, thank you!
Drop the landing gear for a few seconds at a couple thousand feet altitude to cool it off
Haha I thought the same thing. Wouldn't that be a drag? 😆
@@lordw9609 Well the extra fuel might be less than the extra revenue from reduced loading times. It's a cost-benefit.
This is a joke OFC
I'm sure there is a procedure to do this.
@@froggymicb Yes; Look it up in the manual *before* attempting the approach!
@@pilotavery
Whatever OFC denotes I had a girl friend whom held an MBA and obtained work at ( major carrier ) I can assure you is is no joke to them: If some person in that position reads this they might just do the calc's ~ the person expressed wonderment at how 2 major airframe had reported being under 1 mile separation - all the computing power we have nowadays can be brought to bear saving 0.000051 / seat-mile → Many do not realize the commercial carriers operate on thin margins
I used to work for a company who manufactured wheel speed sensors for a number of aircraft, it's actually really interesting how the anti-skid system works. Depending on the aircraft, they can be a single or dual channel system, and there's a system in place to detect a broken wire even if the brakes are not being used.
Fascinating, especially the physics of the kinetic energy calculation.
Thank you so much! I really enjoyed this, I love systems videos, really interesting!
That is a good story about breaking. During all the flights I took,, on landing there was a regular descelerating movement. Just grab your seat bars and everything was fine.
On one landing in Washington DC. from Europe the plane was descelerating so heavily I was pushed forward strongly, I had to grab the backseat in front of me so not to get slammed against it.
I once got to experience max braking while standing up (in the cockpit, behind the captain during an accelerate/stop test). I was hanging on for dear life to the column of a temporary equipment rack behind me. Even back in my lean/40-pushups days, it was all I could do to stay out of the captain's lap.
Damn. I always thought that reverse thrust was the best way to stop (or at least brake) an airplane. Now I've learned something! 😄
Concorde had breaks on the nose wheel, but only to stop the wheel spinning when it was being retracted
Concorde had wheel brake fans in its rear bogies.
Whenever I read or see a video on brakes or braking, I remember Swiss Air 306. The Caravelle crashed because of overheated brakes stowed after takeoff resulting in fire and destruction of hydraulic systems. 80 lives perished.
Morbid, I know.
Love the animations! These technical videos are the best!
The c141 had anti skid system . We had to change 8 wheels after hard landing. They all blew out. A person approaching the plane from the side got hit with the wheel rim in the chest and died. The wheels can be very hot and dangerous. They are rather heavy.
Just to add to what you said about the rejected take-off test, when they do this, the test is done with the brakes degraded to the point where an airline would normally be required to replace them. Once they stop the plane, the plane has to sit for five minutes without catching on fire to simulate the time it would take the fire crew to get there. As far as nose wheel brakes, the Boeing 727 had added in at some point, but they were later removed after it was determined that they didn't really have much of an effect when it came to stopping the plane.
"1.21 Jigawatts!!! (Gigawatts)" -Doc Brown
If the A380 stopped in about 2 seconds, than yes :-)
@@zapfanzapfan That call a crash, my friend
It's as much as lightning strike!
Thanks again for videos like this. Love the technical videos. Every video i learn just how amazing aviation is.
Can you do a video on why airplanes don’t fly in a straight line even to short destinations?
Ahhh you got a heart I think that might mean a video is coming ...
I’d like know that,,too. Great suggestion!
@@gabrielsimon7944 I hope so! It’s been a dying itch to understand this! Especially between short flights. For example, San Diego CA - Las Vegas NV. Only a 45 minute flight but seems like it could be shorter if they would just fly straight!
my guess is the world is round...
Usually it's because of airways.
GOL airlines, in BR, upgraded some of their 737 brakes to carbon to comply with higher performance requiriments for the (somewhat) short SAO PAULO city airport runway.
With the upgrade they were able to operate with full (passenger) capacity.
Those restrictions were latter lifted.
Does RTO also arm spoilers for rejected takeoff ?
Yes, but it’s a different system that activates it
Partly. You arm the spoilers to deploy automatically by (1) selecting RTO on the Autobrakes dial as Mentour showed and (2) move the spoiler handle to the "ARMED" position. Moving the spoiler handle to the ARMED detent will also cause the ground spoilers to automatically deploy during not only a rejected takeoff but during landing as well.
It always shocked me when I remember that all airliners don’t have brakes on the nose-wheel. The way the nose suspension bounces up and down when they arrive at the gate braking to a stop makes it look like the braking is coming from the nose
If you think airliner braking is a complicated issue, you should try operating smaller turboprops with no anti-skid and perhaps badly designed brakes. They can be a nightmare! Some of those aircraft (Cessnas C406 & C441 and the DHC-6 Twin Otter) have nicely designed no-antiskid systems where the brake pedal force directly translates to brake effect, just like an ancient car with no ABS. There was one aircraft I have flown that has astonishingly difficult brakes, the Do228 Dornier. after landing, you applied brake pedal and nothing happened. Then you carefully applied some more pedal pressure and very little happened. THEN, if you had to, you applied just a little more pedal pressure and the wheels would lock up! A flat spot on the main tires SERIOUSLY damages them, an expensive occurrence. Fortunately the Do228 has a touchdown speed well below 100 knots and being a Garret-powered high-wing aircraft has MAGNIFICENT reverse capabilities. Wheel braking was rarely needed for anything more than taxying.
Anti-lock braking first appeared in planes, but the system that cars use is different. Planes have huge wheels compared to cars, so their system is to have a gear inside the inner wheel rim like a cog which detects that it's not turning anymore (the wheel is not turning) and backs off the hydraulic pressure on the brakes. On-off-on-off many times a second until maximum braking is attained just prior to the known brake lock point. It's purely mechanical. Cars use a 2 ot 3 channel electronic system.
Hi. This is interesting. As introduction, it'll be interesting to mention that airplane breaking is constitute by: aero brakes, tires brakes, and thrust reverse. Thank you.
This is incredibly interesting....whenever I have flown I always hear the jet engines "spool" upon landing, which I thought was the major braking force (i.e. reverse jet power), however, it is fascinating to know that the aircraft's brakes are the primary stopping force...
That loud acceleration sound you hear is tje air rushing through and against the thrust reversers not engine revving up. I sit nest the wing almost every flight and constantly watch and hear the music of landing.
Thank you for a new highly detailed video! Quite a lot new things to know.
The question on the autobrake (especially on the RTO braking).
As i understand the manual brake application disengage the autobrake system. But, as i understand the captain are mandated to manually apply near full manual braking at the rejected takeoff above 80 knots, so RTO just saves about a second or so and serves as failsafe for human error basically? Is that correct?
I enjoy your very informative videos, your are not only a pilot, but
your are a very good teacher
Small point, but I recall Boeing once offered nose wheel brakes as an option on its high gross 727-200 ADV’s.
Thank you for using Helios LIvery in the video!
Fascinating info Petter, I love these technical videos!
I would like to note that anti skid systems are actually very different from the traditional ABS systems in cars,
The ABS system is like the anti lock systems where anti skid systems are "adapting" to surface condition thus, anable amazing tire efficacy (up to 98%), this enables to operate the tires very close to the slip point
I guess there was a version of a B727 that had nose wheel brakes in an attempt to reduce even more landing distances, but it was abandoned due to weight and not achieve the desired objective.
Excellent teaching about aircraft braking. Thank you for your wonderful videos.
Well, that was a lot more interesting than I thought it would be.
These always are
Hey Mentour, I hope you're doing absolutely fantastic. ❤
Hey mentour pilot love your videos:) would love to see a video about aircraft maintenance and what goes around in the hangers.
2:45 - You left out the part that the brakes are certified to be able to stop an MTOW aircraft WITHOUT the use of thrust reversers.
Your animated 737 is spookily like Helios to look at.
It is from the Helios video so...🤭
@@speedbird9313 Oh right, I should have had my glasses on. LOL. Thanks for that.
A brake is basically just a type of clutch, that happens to connect the wheels to the frame.
These brakes are actually quite similar to a multi plate clutch.
That being said, there are few things faster and heavier, than a landing airplane, lots and lots of heat.
Exactly what I was thinking: they reminds me a lot my motorcycle clutch, just working the other way around (not to transfer motion to the wheel but to stop the wheel to spin, a bit like shifting down).
Railway trains can be much heavier and have far less grip - steel wheel on steel rail is what makes them efficient, but also means they are unable to stop hard. Of course, failure to strap down the self-loading cargo is also a limiting factor.
Ships are vastly heavier, although much slower, but again - very limited grip so emergency stops are not a thing in naval architecture.
There are different kinds of brakes though. You are talking about friction brakes but there are induction and regenerative brakes, too, that are used on high-speed trains.
@@unvergebeneid They are still limited to the grip of the wheel on its running surface. The only exceptions are those used on a few mountain railways and tramways which grip the rail itself, but they are limited in usefulness due to the inability to deal seamlessly with points and crossings. Regenerative braking is also used on EVs.
There are also brake fans that are supposed to cool brakes after landing. At least in some airbus a320 family. Funny thing about those is that you have to make sure no one is standing next to main landing gear when those fans are applied because it blows out carbon fibre dust which can be extremely harmfull to your lungs.
Wow, excellent video!
@Mentour Pilot, back in June of 1993, I was on a red eye flight with Southwest Airlines and in a Boeing 737, from Las Vegas, Nevada to San Diego, California.
As we were flying, something happened that caused the airplane to lose all power, including both engines, exterior and interior lighting and then the plane immediately went into a very steep nose dive that literally felt like we were going straight down.
Now obviously, we were in a dark airplane, somewhere over the desert, where there is virtually no light pollution and it was very late at night. I’m guessing that it was somewhere around midnight to 1:00am in the morning. And so as a result of that, I didn’t really have anyway of actually referencing how steep of a nose dive that we were actually in. I do remember being pinned into me seat and unable to move.
One of the flight attendants was getting ready to start serving drinks and peanuts but when everything happened she caught air and ended up getting pinned to the ceiling of the aircraft. I was sitting right on the center of the wing and she was a few rows behind me, in the isle of the aircraft. It’s weird, because still to this day, I can still very vividly remember hearing both of the engines start spooling down and can still recall in full detail everything that ended up happening.
I don’t know how long we were actually in a nosedive for but my guess is probably around 30 seconds to maybe 45 seconds max but it seemed like an eternity, that’s for sure.
The pilots eventually got power restored to everything and the engines started again. They then put the plane into a very steep climb that felt about twice as steep as a normal take off. But again, it was sometime in the middle of the night and over the desert so I had no reference points to say for sure how steep everything actually was?
When the plane started climbing the flight attendant then fell, hit her head on the back of one of the isle seats and was then pinned to the floor while the plane was climbing.
From Las Vegas, Nevada to San Diego, California it only a 6 hour drive or around 350 miles or so. The flights aren’t very long either. They are only about 50 minutes to maybe an hour max. As a result of that, the plane only flys to an altitude of I think somewhere between 20,000 feet to maybe 25,000 feet max.
Because of this and there being several mountain ranges all throughout that desert, I am only assuming and guessing that the pilot put the plane into such a steep climb because he was probably trying to gain much needed altitude to clear an obstacle. If that is indeed what happened, I’m going to guess and assume that the obstacle or obstacles needing to be cleared was one of those mountains or mountain ranges in the desert.
Once the plane leveled off again, maybe after climbing for only around a minute or 2, 3 to 5 minutes maximum, 1 of the other flight attendants helped the injured flight attendant to the back of the plane to try and help her out.
The rest of the flight it seemed like the pilot was fighting the plane the entire time. Of course that may have also been caused or due in part to there being turbulence but it lasted all the way to San Diego, up until we landed. And when we landed, it was a very hard touchdown that literally caused the plane to briefly become totally airborne again, for a few seconds. Also, right before we touched down, it seemed like we were at a little bit higher of an altitude and then we just dropped and slammed onto the runway before bouncing up off of it for a second or 2.
Before we taxied to our gate, air traffic control had us park the plane just off of the runway so the 1 flight attendant that got injured during the flight could be taken off of the plane to an already awaiting Paramedic and/or EMT ambulance crew. After the injured flight attendant was taken off the plane, we were then able to taxi to our assigned gate.
After we got off of the plane, I then had to explain to 1 of my Dads church friends that had picked me up from the airport, why my shirt and pants were all wet and covered in alcohol and I smelled like it, due to the guy who was sitting in the seat in front of me somehow bringing alcohol onto the flight and then spilling it all over me when the plane went into its dive.
With everything that I described, in your opinion, what could have caused the plane to do what it did? Every pilot or knowledgeable aviation person that I have ever talked to about this incident has said that either they did not know or it could have been a number of things.
If possible, can you please offer up suggestions or advice as to what you think may have caused everything to happen? In asking this question, I’m not wanting or trying to criticize or blame the pilots or Southwest Airlines. In fact, it’s quite the opposite actually. The pilots and entire flight crew should have been given an award for everything that they did to not only save the plane but keep everyone as calm as possible and as informed as possible as well.
Since then, I have only flown twice. In August of 99’, I flew from San Diego, California to Dallas, Texas to see a good friend while I was on vacation. After visiting him and his girlfriend, I then flew back home and have never flown again since then.
I used to love flying and was never afraid of doing so. But after that flight, I have now become afraid of flying. This is why I watch your channel and others like it, so I can learn as much as possible about flying. And then maybe one day, sometime in the near future, hopefully I will be able to face my fears, get on an airplane and then fly to some place nice and no longer be worried that the plane might crash.
From the bottom of my heart. Thank you Mentour Pilot, for all that you do! I truly have learned a tremendous amount from all of your videos and best of all, they are building up my confidence to consider trying to fly again someday.
Could have potentially been a microburst, this would have also had to cause something like a compressor stall to get one or both engines to stall out also causing lack of power, but this is entirely a guess
The third brake is the wall of the airport:))
The “brake pad” would be the cockpit and crew.
funny thing. calculation (model of cooling) is used in industry too - Aluminium billets heating is an example - when billet is rejected [press unable to accept it because of any hold-ups] billet is delivered to reject and PLC models cooling process to take it back to heating after press recovers. it must cool down by ca 200 degrees C for re-heat because Al must be heated with taper (front warmer and back cooler - ratio is up to 100deg/m). Taper is to prevent ready extruded profile from overheating - Al extrusion is slow and heat generated by press can travel back. too high extruded profile temperature could destroy its mechanical proporties.
I have a question: can frequent use of the anti-skid system wear off carbon brakes quickly?
I wouldn't say quickly, it would be quicker than if you didn't use anti-skid, but the wear rate is according to design. The issue with this is that you wear down and destroy the tires when the wheels lock up.
@Jim Mork Friction coefficient (with A/S) is around 0.75 for airliner tires on dry pavement (varies a bit with speed). A wet runway knocks that down to more like 0.4 depending on the particulars, and then ice or hydroplaning closer to 0.1 or less. So reversers don't typically matter much for average stops on a dry runway, but are crucial when runway friction is severely degraded.
@Jim Mork In my answers I like to throw in numbers perhaps not readily available on the internet, for whomever might be curious, but the bottom line is antiskid systems work on contaminated runways as well. What changes as surface friction degrades is how the plot of brake pressure vs time looks. On a dry runway, the antiskid-enabled brake pressure is a flat-ish line with just small ripples from the antiskid's pressure dumps. The lower the runway friction, the deeper and wider those pressure drops get.
Loved the video, great explanation and good demos. I hope to see more of these!!
the early 727s had an option for nose brakes.
The saab gripen has also nosebreaks. They really nake a diffenerce in combination with the canards pushing down
@@Leminge42 Was at Farnborough many years ago with a Saab pilot showing off the nosewheel brake whilst spooling up the engine. Then off he went! They don't let you that close now.
Great video, Petter! Super interesting. I'm an auto, and "just about everything else" mechanic. Never knew brakes on large aircraft were set up like a giant motorcycle clutch with multiple friction discs. Great footage of those glowing brakes, too - that was great!! 👍😎
They don't, a big burly wizard stands at the end of the runway and screams at the plane "THOU SHALT NOT PASS" and then the plane fills it's underpants and comes to a stand still.
All jokes asside love the content Peter, wishing you a happy new year!
Wow, that was interesting. I would have thought that the temperatures at cruise altitudes would have cooled the brakes off more.
The 737’s wheels are exposed to the elements during cruise, so wouldn’t the freezing temperatures and winds/apparent winds up there cool the brakes down pretty fast?
Probably not that fast. Obviously the landing gear is designed to reduce drag as much as possible when it is retracted. Thus the air circulation through the wheels is probably limited. In fact, a quick image search shows that 737s probably have wheel covers (hubcaps if you will). These would would help keep the brakes nice an snug in their wheel wells when retracted. 😀
@@andrewsnow7386 yup, the "hubcaps' and the rubber seals around the wheels when retracted will prevent airflow in the wheelwells.
The brakes are applied on landing hardest. The air is not enough. The brakes get very hot when applied. It just takes time to cool brakes down.
I always enjoy your videos. I am a competent physicist so I have no difficulty with the principles but the videos alert me to things that I may not have thought about. Which is always interesting. Of course I am waiting for the video on the "mid air parking brake" that can hold a plane stationary in the air in the event of a system failure. It might be quite a few years before they get that one perfected.
Is there any feedback in the pedals? In other words, does the pressure required to move the brake pedal change as the pedal travels?
That’s a great question.
In a way yes, the "feedback" you get on the pedals when braking on the 737 is very similar to when you brake in a car (or even a GA aircraft).
Artificial feedback, just a simple spring really, making it harder to push the further you apply them
@@yukionna1649 probably is an FBW servo thus just won't do it for me
Just by the way: if you try to drive a truck for the first time, fasten your seatbelt properly :-)
A truck has brakes controlled by an air pressure. There is no feedback in the pedal and there is a little delay. So let me explain one second when you try to brake:
Stepping a little bit - no feedback, no reaction, so increasing pressure to the pedal and still nothing hapening! Finally stepping very hard and sudenly kaboom! :-D All breaking force is applied!
In case anyone is wondering, carbon brake discs are actually made of graphite, with a near perfect crystalline structure. They can work at up to 2000°C.
i love watching your video's from the United states very intresting and great information and entertaining hope all is well with you and the family thank you
Great to hear that
Very interesting video. I do enjoy the more technical aspects of aircraft design. Thanks!
Great explanation. A very felt THANK YOU! Happy new year, Mentour Pilot ..
These videos are awesome! Keep them coming. Personally I'd like to see one on pilot:ATC communication. What are the standards, what can go wrong, examples during emergency, why calls are made and when. If that sounds too dull for everyone :), then what about the air France that went off end of the runway at YYZ? I remember that because I was on the 401 (highway next to 24L) when it happened. I think it was and A340. Thanks!!
You can use the heat energy to warm up your coffee system.
Petter/Mentour - fantastic video thank you!
God bless
Paul (in MA USA)
BTW: GJ is the order of magnitude of energy stored in large superconducting magnets. The energy must be removed within small part of a second in these cases.
Yes, that is why MRI scanners use liquid nitrogen to cool them.
A typical nuclear power station produces 1GJ of electric power per second (1GW), that is a lot of energy in a small space...
@@gordonrichardson2972 Air-cooled, at that.
As a Aussie very chuffed to see the big Qantas baby in you video. More than that love these technical videos. Well don from Down under!
You good mentour,,, your vedios are just good,🤗
14:13 I actually jumped a bit when I heard the sound. Natural reflex-- thought there might be a plane crash near my desk.
Love your content😄🤗