Friday, May 13, 2011

The Ultimate Brake Test

It's been a standard feature of automobile commercials for years: to emphasize the safety of their products, car makers like to stage "sudden stop" sequences, showing their products braking to a swift halt with a minimum of swaying and skidding.

Stopping a 2,000-pound car (traveling 60 miles an hour), in minimal distance, is one thing. Now, imagine the same feet with a wide-body jetliner.

To demonstrate the capabilities of its new 747-8 aircraft (and help secure its safety certification), Boeing devised a rather impressive braking test. As it approached rotation speed, the crew of the 747-8 would abort their takeoff, as pilots sometimes must do. Nothing really unusual about that.

But the engineers at Boeing decided to make their test a little more challenging. The jetliner's brakes (made by B.F. Goodrich) were replaced with a duplicate set that was completely worn out. But the Boeing team still wasn't finished. The 747-8 would abort the takeoff at near-maximum takeoff weight (just under one million pounds), at a speed of 200 mph. Thrust reversers could not be used in the test, meaning the pilots could only rely on the bad brakes--and their skill. And, to simulate the chaos that often ensues during airport emergencies, fire fighters would not be allowed to hose down the brakes for a full five minutes after the aircraft came to a halt.

The results can be see via this link, from cnet. Despite its worn-out brakes, the 747-8 stopped in a shorter distance that predicted by test engineers. Amazingly, the brakes didn't catch fire, despite their inherent deficiencies. Not a bad advertisement for Goodrich aircraft brakes--or the Boeing 747-8.
ADDENDUM: Safety certification for the 747-8 has not been without controversy. Rival Airbus insisted that the 747-8 was a new design, and should meet all requirements for aircraft moving from the drawing board to operational service. Boeing argued for a less-stringent test program, noting that the "new" aircraft is actually a derivative of the 747-400, which has already met (and surpassed) all required safety criteria. Events like the brake test are clearly aimed at silencing critics, while highlighting the safety features of the "stretch" jumbo jet.

1 comment:

F said...

I don't have time to search for it now, but I saw a similar test performed on the Airbus 300. The brakes DID catch fire, though, and eventually ignited the aircraft, which was entirely lost. I think the Boeing design is much better.