Re: Braking

Date:         23 May 97 09:03:30 
From:         faurecm@halcyon.com (C. Marin Faure)
Organization: Northwest Nexus Inc.
References:   1 2 3
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In article <airliners.1997.1122@ohare.Chicago.COM>, Matthew Willshee
<96mjw@eng.cam.ac.uk> wrote:

> On 9 May 1997, dzul wrote:
>
> ><snip air v. wheel brakes arguments>
> >
> > if the wheel brakes gets too hot (if u do not use the reverse thrust),
u need
> > a lot of time to cool them off.
>
> UK Channel Four television screened "21st Century Aircraft", a series
> which followed the certification of the 777 late last summer.  I should
> think something similar was shown in most other places.
>
> One bit I found especially interesting was a part of the flight test
> programme that involved braking from V1 (I think) to a standstill using
> wheel brakes with the engines at full power.  There was a minimum time
> limit that the plane then had to stand (the brakes glowing red hot)
> without the undercarriage catching fire.

Not quite correct, but close.  The RTO test (Refused Take Off) consists of
accelerating the airplane to takeoff speed (in this case 210 mph) and then
closing the throttles and stopping the plane using the wheel brakes
alone.  The engines are not producing any power once they spool down.
John Cashman, the chief pilot on the 777 program, told me that initially
it seems as though the plane will never slow because at first, even though
the power levers are pulled to idle, the engines are still producing
thrust against the brakes.  Then once the engines spool down, the brakes
begin to take effect with the result you saw on the television show.  The
flames you saw was lubricating grease that caught fire- none of the brake
components themeselves caught fire.

C. Marin Faure
  author, Flying A Floatplane