How Good Are Your Brakes?

[Wylde1]

Can your brakes take the heat?

http://bangshift.com/blog/watch-the...-test-on-earth-incredible-forces-at-work.html

We saw lots of hot brakes and clamping forces at work during the 2012 Run to the Shore, but even the big binders on the pro touring cars have nothing on the stoppers air liners use. Hauling all that weight down to a stop in the amount of time you have before running off the end of a runway is not the job of weak suck parts. Due to the fact that airplanes that run off of runways and injure people don’t help sales for their manufacturers, the companies building these massive planes go through extreme measures to test them. This video shows one of those tests and it is pretty amazing.

The brakes being tested are for an Airbus A380-800, which weighs in at more than one million pounds. The object of the test was to have the plane stop itself at landing speed in about 1200 meters (roughly 3600 feet). Using a massive flywheel and a tire and brake setup, the test requires the brakes to do the job exactly as they would have to on the ground.

When the huge flywheel comes into contact with the tire to simulate touchdown note the distortion from the force and then pay close attention to the brake caliper and rotor because they really start working their asses off and quickly heat up to something akin to the surface of the sun.

This is bad *** engineering at work!

[ame="http://www.youtube.com/watch?v=m1dv_y_3EK0"]Airbus A380-800 Brake test - YouTube[/ame]



Wylde1.

 

[67Dart273]

PBS, awhile back, did a documentary of one of the then-new Boeings, 777? Don't remember.

There is some test, I believe it's to simulate power failure on takeoff. They get the thing up to flying speed, and then the thing MUST stop on it's own using the brakes. Tires are allowed to blow (they did!!) but the brakes must be "free to move" after the stop, I guess so the runway can be cleared. It was an IMPRESSIVE sight!!


777:

[ame="http://www.youtube.com/watch?v=f4LFErD-yls&feature=related"]Boeing 777 Rejected Takeoff Test (RTO) - YouTube[/ame]

Couple'a screenshots from that video

747-8F

[ame="http://www.youtube.com/watch?v=am392XmYBps"]Boeing 747-8F Performs Ultimate Rejected Take-off - YouTube[/ame]

 

[memike]

WOW!!!! I never even thought about or ever considered all the testing they do on these giants.......... Thank you for sharing this testing on the brake system Wylde1 and 67Dart273 :thumblef:
I sure would like to see the wheel bearings under these plains before and after a test like that

 

[godfatherofchry]

good videos,but hell my wife's car looks like that just about every time she comes home.ops:...........Artie lmao!!!

 

[OneOfMany]

I wonder if Midas still offers a redo for $100 with a lifetime warranty on pads

Cool video

Grant

 

[67Dart273]

WOW!!!! I never even thought about or ever considered all the testing they do on these giants.........
I sure would like to see the wheel bearings under these plains before and after a test like that

Someone said on the 777 vid how much money this cost in new tires and parts, seemed to me it was the better part of a million bucks.

Just imagine, you are on some horridly short runway with a cliff or the water at the end, and at V the engines collectively pretty much quit. Will it stop? Will you PLEAUSZE stop!!!!??

 

[FISHBREATH]

Cool videos. The V1 speed is the decision time to determine whether you fly or stay on the runway. V1 speed is determined after weight and balance are calculated for each flight. This is not critical on small general aviation aircraft because their wieght and balance do not change as much as cargo and commercial passenger aircraft. Air density is also figured into the calculation because an airplane can take off in considerably less distance at sea level on a cold dry day than on a mountain top on a hot humid day.

The brakes on big aircraft must convert a huge amount of momentum into heat via the brakes.

Mass = kilograms (kg)
Distance = meters (m)
Time = seconds (s)

Momentum (kg m/s) = mass (kg) x velocity (m/s); also, Force = mass x acceleration.

Kinetic energy (joules) = 1/2 x mass (kg) x velocity (m/s) squared.

Joule = kg x m (squared) / s (squared)

1 BTU = 1055 joules
1 BTU = 778 to 782 lb.ft. force
1 BTU = 1.054 to 1.060 kJ (kilo Joules)
1 BTU = .293071 Wh (Watt hours)

So, you can see that a tremendous amout of kinetic energy is developed by an airliner by the time V1 speed is achieved. That energy is changed to heat energy via the brakes and, to a much lesser degree, air friction. The same holds true on landing. Fuel tanks are filled to the minimum necessary for a flight plus required reserve for reaching alternate destinations. The reason for dumping fuel during unscheduled early landings is to bring down aircraft weight (and, therefore, momentum) so the aircraft can land on a specific length of runway.

Physics is phun.

 

[rp23g7]

777 and 747 brakes are pretty impressive, been working Functional Test on the 787 for about 8 months. The 787 uses completely different systems.

Its really a flying computer/electrical power plant. One of the reasons its late, troubleshooting systems when they have a issue. No bleed air systems, the reason why the engines get better fuel economy.

It has 4 Electric Motor Pumps, generating 5000 PSI for the hydraulics, these are driven by 3 generators, making 480 Killiwatts apiece, enough to run a few houses for a while.

The brakes on the 787 are electric too, working off of 280 Volts 3 phase DC, we killed the power supply to the aircraft external power systems for the whole building once by trying to run the EMP's and the brake test at the same time.

But wanna see something really cool aircraft wise??? google or YouTube videos of crosswind landings, or aircraft landing at Princess Julianna airport in St Maarten