Re: aborted takeoff and brake damage

Date:         17 Sep 97 02:49:22 
From:         shafer@ferhino.dfrc.nasa.gov (Mary Shafer)
Organization: NASA Dryden Flight Research Center, Edwards CA
References:   1 2 3
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On 11 Sep 97 03:35:30 , khowie8@gte.net (Keith Howie) said:

K> Chris may be referring to the footage of the "refused takeoff" test
K> conducted during the 777 certification program. I believe this is
K> contained in the PBS documentary "21st Century Jet". This test is
K> arguably the most severe in any certification program. For the 777,
K> the test plane was loaded to its MTOW, then accelerated to V1, the
K> last point where a takeoff can be aborted. The takeoff WAS aborted,
K> and the airplane had to be brought to a stop using only the brakes
K> (i.e., no thrust reversers) within a specified distance (I forget
K> the exact length). To top it off, the aircraft was then required to
K> sit on the runway unattended for several minutes to simulate the
K> time it would typically take to get fire equipment to the plane.

However, the airplane was not really unattended.  The entire Edwards
flightline fire department was out there watching intently, nozzles
aimed at the gear and crew at the ready.  This is a test, true, but
the penalty for failing it is not a burnt-out shell.  Rather, if
there's a real fire before the waiting period ends, the fire
department will go ahead and put it out.  The company just has to get
it right eventually.

K> The film footage is spectacular. As Chris says, the brakes are
K> glowing red from the friction. The tires are all blown out, and God
K> only knows what other damage resulted.

I don't think there was much other damage.  The tires don't actually
blow out, even.  They have relief plugs that blow first, mostly to
avoid launching hot chunks of rubber at the underside of the wet wing.
There are fuse links in the brakes and undercarriages, too, to reduce
damage.

K> The important thing,
K> however, was that the damage was contained, nobody was injured, and
K> the aircraft could be refurbished.

I'd say "refurbished" is too strong a word.  They just replaced the
tires and brakes, and perhaps some minor bits of the gear.  I'm pretty
sure I saw the plane right after this test.  They brought it back to
our ramp with a tug and the crew spent a day or two working on the
gear and then they got back to flying.

My favorite takeoff/landing test is the minimum takeoff length test.
They put a big oak skid on the underside of the tail cone and go out
and drag it down the runway, having really rotated a lot at a pretty
low speed.  There's so much heat and friction that the wooden skid
will sometimes burst into flames, in fact.  It just amazes me how
little runway they use when they're doing this test.  Airliners can
really jump off the ground if they need to.

We're lucky here at Edwards to get to watch so many airliners do their
runway certification work.  The AFFTC is set up with all the
instrumentation and support needed to do it right and the
manufacturers are glad to use the place.  They save money by not
having to have their own setup, which they'd use only infrequently,
and AFFTC makes money renting out the excess capacity of equipment
they already have in place.  The 777 was based here at Dryden during
the testing since Boeing doesn't have a facility of their own here.
We were convenient for them and, again, economical, since we have
everything necessary to support a plane like that and we didn't charge
them a lot to use it.

--
Mary Shafer               NASA Dryden Flight Research Center, Edwards, CA
SR-71 Flying Qualities Lead Engineer     Of course I don't speak for NASA
shafer@ferhino.dfrc.nasa.gov                               DoD #362 KotFR
URL http://www.dfrc.nasa.gov/People/Shafer/mary.html
For personal messages, please use shafer@ursa-major.spdcc.com