Re: B747 technical questions

Date:         04 Aug 97 21:28:52 
From: (C. Marin Faure)
Organization: Northwest Nexus Inc.
References:   1 2 3 4 5 6 7
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In article <airliners.1997.1662@ohare.Chicago.COM>, wrote:
> In the PBS TV series and book "Twentieth-Century Jet" (about the 777
> development program), there is a segment (photo in the book) about test
> flights.  One test involved ballasting the aircraft to MTOW,
> accelerating to V1, then doing a maximum-performance stop.  IIRC, this
> dissipated approximately 1.5 billion foot-pounds into the braking
> system.  On the TV segment, the brake disks are glow orange-hot, and the
> tires start to burn.  The aircraft then had to remain in place for 5
> minutes (simulated crash crew response time) before any attempt to
> extinguish the fire was made.  The idea was to demonstrate that the fire
> would not spread.

I just completed producing a video for Boeing on flight testing the 777,
during which I extensively interviewed John Cashman, the chief pilot of
the 777 program.  While the footage of the 777 max gross weight RTO
(refused takeoff) test looks quite dramatic, in fact the flames are not
the tires but simply the lubricating grease in the hubs that liquified and
caught fire.  The tires themselves were virtually undamaged by fire,
although they all went flat when the fuse plugs melted out as they were
supposed to once the plane cleared the runway.  Also, the plane does not
have to remain in place for 5 minutes.  The only requirement is that it
come to a complete stop before moving again.  Cashman stopped the plane,
let it rock forward and back once to prove to the FAA observer it had
stopped, and then immediately applied power to taxi clear of the runway.
If the plane had remained where it stopped, the tires would have deflated
and the Edwards runway would have been closed for four or five hours while
the wheels and tires were changed.  SSo one of the goals of the test was
to taxi the 777 clear of the runway before the tires began to deflate.
However, the fire crews cannot approach the plane and begin hosing down
the brakes for five minutes.  You are correct in that the five minute wait
is to ensure that any fires that might start will not endanger the
passengers, as well as simulate the time it would normally take an airport
fire crew to reach the scene.

C. Marin Faure
  author, Flying A Floatplane