A380-800 Brake test in overweight landing situation. Dynamometer energy: 125.2 MJ Brake application speed: 90.07 m/s Stop distance: 1120 m Mean deceleration: 3.62 m/s/s Energy absorption rate: 5.04 MJ/s
DieselDucy Remember doing Elevator videos back in 2007 with Hanny/ElevatorTimes? And I would make them too from Japan. You would always show that nice little metal train in the elevator hehe Good times.
@@blockstacker5614 Nop, the economics of aviation are just changing, that's why jumbo jets like the A380 but also the 747 are being pulled out of the major airlines' fleet. The A380 was more efficient, could carry more people and was cheaper to operate that the 747.
+ozzie sheppard It goes to generate heat. A massive amount of heat. Almost exactly the same as using friction except the the system is FAR heavier and the heat is dissipated over a MUCH larger area. Not possible on an aircraft - not even close. You can't 'cancel' energy - you have to move it somewhere.
This was as much energy as an average human would output in about 10 days of normal living/working. All that energy was consumed here in only 28 seconds.
lewis johnson Where have you heard that? That's not true. Professional cyclist can generate around 500W of power for short periods of time with his legs and with this amount of power you could bring one cup of a water to its boiling point in about three minutes.
He is talking about the human bodies heat output through metabolic processes alone. You are talking about the total amount of WORK that can be accomplished by a human.
What you saw was a worst case scenario, the tire didn't burst, it would have stopped the plane in an emergency. Yes it caught fire but IMHO the test was successful.
they are allowed to in these extreme circumstances(overweigh, overspeed and max throttle of the airplane) but they are not allowed to explode in the first 5 min. and after 5 min the airport fire fighters will have wiped out the fire
Tires bursting when the plane is stopped would not be any dangerous anyway. Everything would drop a bit, but if it burst at speed it could topple the plane. So yes, very successful.
Tires bursting are very, very dangerous. Not only just from the damage that flying rubber would do, but also since these are probably split rims you could have a couple 50lb hunks of metal flying off it at high speed. There is a reason when the tires are first installed on the rims they are filled with air while locked inside a cage, to contain the shrapnel.
It's testing an overweight and overspeed landing with no thrust reversers. This is considered an emergency anyway. In this case, the brakes just have to do two things: Stop the plane before the end of the runway, and keep the fire contained long enough for the airport firefighters to respond (5 minutes). They successfully do both.
the typical landing field for an airport that supports twin-turbofan aircraft is 1.3km. which shouldnt be a surprise as this would not be an information that the engineers would just skip over in these emergency calculations
Thrust reversers don't contribute that much to braking. Same as spoilers. They are only there to disrupt the airflow over the wings and makes the braking force more efficient. Thrust reversers lessen the load on the brakes.
It's not a matter of flying overloaded, most large jets take off at a weight higher than their normal permissable landing weight, it's the nature of having to carry a lot of fuel to get somewhere. An overweight landing is needed when something goes wrong a short time into the flight and you don't have the luxury of time to spend hours burning or dumping fuel to get down to max landing weight. This a certification test to ensure the aircraft can safely stop in an emergency situation, this is not a normal landing.
The brakes did their job. The amazing aspect of it is how the tire doesnt spin over the rim. 500cc two stroke crossbike can break two heavy rim locks in high traction sitiuation, move over the rim and snap the valve. Of course these are tubeless tires and wont fail even if it spins but sure make a mess with melting rubber. There has to be some kind of lock in there or then the tire pressure is just so op it holds it with pure friction.
It is an emergency test and this configuration pass it. Yea brakes are probably destroyed, maybe whole set would nead a replacement, but this acctualy is by the book - after emergency braking whole set should be inspected and replaced in order. This would be the same if you drove your car with 2 tonnres of payload at 300kph and apply maximum brake - car would stop but brakes and tires probably would be destroyed.
BMW M5 is a super car and design to stand excesive braking. For this purpose it has a massive tires and a massive brakes. Plane's tires and brakes are acctualy wery tiny commpared to the plane's size and weight since plane can't afford extra weight. So try to commpare this configuration: small sedan with small brakes with 2 tonnes of payload pushed down the road up to 300kph and then brakes are fully applied. Do you think brakes will be ok after a stop?
b novak m5 more like luxury sport sedan. Ofc it is build for such stuff, since it can actually reach such speeds. Just saying since you hadn't specified what car were we looking at :p
A380 maximum landing weight is 430 tonnes (430,000kg) and landing speed in round 250kph (70mps). So the kinetic energy is 1/2 *m*v2= 1.05 TJ. A380 has 16 multiple wet brakes and 20 wheels. If you can immagine how much energy is 1TJ you'll get the idea. Actualy stoping a plane is done mostly by revers thrusters and spoilers+flaps, brakes are only partial applied and they are used to stop the plane when speed drops under 70 knots.
+Jia Chun Lim one of the problems is, if they douse water or anything cold onto those burning white hot ceramic/metal brake disks or systems- they will probably explode due to the extreme thermal shock.
Jia Chun Lim Yes, which is why there is a safety mechanism. If it's too hot, it usually means the brake was successful. The whole brake system is usually replaced. At the same time, the safety mechanism is that there is a metallic item, the thermal capacity of which is known to a high degree of accuracy, which is designed to melt and cause a safe and non-explosive depressurization of the tires in case the threshold temperature is reached.
5 MJ/s ! that is pretty crazy. It looks 394000 kg A380 with landing speed of 155 knots (290 km/h = 80 m/s), have total kinetic energy of 2.5 GJ. So it takes 22 wheels and breaks like in these Break test video (each doing 1/8 GJ), to stop it. It happens that A380-800 have 22 wheels... I am a bit concerned now :) Shouldn't it have more? But well, it have 90 m/s here, and it makes a quiet a big difference to 80 m/s. Also 394000 kg is maximal allowed landing weight, most often it would be a bit less than that. (~350000 kg). And often it will land with speed of below 200 km/h. But still. In this demo I am more amazed by the tire itself, and the rubber, how well it transfer energy to the breaks. Wow.
Hey you need to realize it's not just the disc brakes doing all the work, the air brakes, spoilers and thrust reversers contribute significantly more to stopping the plane than the brakes do.
yifuj Good point, indeed, I forgot about air drag, and additional air breaks, and possibility of using thrust reversal (are they used in normal conditions, or just in emergrencies?). Thanks! I will sleep now better, knowing breaks can handled all that easily :)
movax20h Thrust reversers are used in almost every landing involving a turbofan engine. For turboprops or piston driven aircraft, pitch reversers are used.
Yep, a high bypass one at that, which is essentially 90% propeller plane, and 10% jet. Turbojets are reserved for fighter jets of the past, most modern day fighters use low bypass turbofans, which are more efficient, although they are slower than turbojets. Pulsejets will never be used on commercial aircraft (too noisy and inefficient), ramjets are efficient only at Mach 3 and up, so they have no commercial applications, and scramjets are still under development.
The only reason why the wheel caught on fire was because that would simulate breaking the plane without reverse thrusting and deploying the air brakes. The purpose of this test is to make sure the plane can properly brake without the two other means of slowing down.
It was to push the limits of the breaks. This was to test how the breaks would react with a overspeed landing no reverse thruster and with a overweight landing as well as simulating a wet surface (Just testing the scenario where everything goes wrong and all the environmental conditions are at its worst). As long as the braking is smooth and the tires don't explode after a certain amount of time it passes.
Please. "Airbrakes" are called SPOILERS. And what they actually do is to spoil the airflow over the wing and the pressure difference on top and under the wing causing it to lose lift and therefore putting weight in the wheels.
I only just realised, not only is this an overweight test with no other forms of braking, they are also, it looks like, spraying water on the tire - if you look when the tire first makes contact with the dynamometer, the pipe above and between them begins spraying stuff at the tire, so it's also a weather based test
Brain dump: Formula 1 car brakes also reach red hot temperatures but they must not go up in flames. They need to last a number of laps not just one "landing". Sure this was a corner case of overload anyway. 125.2 MJ are 34.78 kWh (in house heating terms that does not seem a lot at first, thinking of 35 x 1kW hairdryers running for one hour .. or in other words this is 29,903.51 kcal or approx. 10 days of food supply at 3000 kcal/day . This equals the energy of 60 bars of 100g chocolate or 120 bars of snickers or 18 slices of Chocolate Tower Truffle Cake from CPK. The wheel withstands approx 30.865 metric tons of weight (so ball park weight of the plane is how much with 22 total wheels => 660 t ? Wiki says A380 weighs up to 650 t. Well that all plays along. Very impressive video !
RU-vid recommended Belike: 2007: No 2008: No 2009: no 2010: no 2011: no 2012: no 2013: no 2014: No 2016: no 2016: no 2017: no 2018: No 2019: no 2020: YES OFCOURSE YES
Thanks for the recommendation RU-vid, that's insane. Now I know what happened on the brakes with QF32 in Singapore. The Pilot's book on the situation said that the brakes were BEYOND white hot because the plane had no autobrakes or Reverse thrust, so he had to plant the manual brakes to the floor. 4 Kilometer runway, he ended up with less than 100m left.
after watching this a few times I'm thinking that the hose spraying the tire is actually spraying sand to increase traction between the tire and dyno, rubber on smooth metal has less tractive force then rubber on high strength concrete.
I might be late on this, but I think that what they were spraying was water. They're basically simulating a landing on a wet runway, which would make sense since they are testing for the worst possible scenario
They are testing the brakes, not the effectiveness of the tire traction on the landing surface. They want ALL of the force to go into the brakes, not to be wasted as tire slippage on the metal dyno surface. There are water tests, but this wasn't a water test.
