Re: Undercarriage retraction on the ground

From:         falke@pweh.com ( 0 Falke_Charlie phone dist )
Date:         11 Oct 96 19:44:55 
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roygbvgw@aol.com (RoyGbvgw) wrote:
      Peter Coe expressed amazement at a report that a 747 at
   BA Cardiff had its undercarriage retracted while on the ground.
      Years ago when I read Nevil Shute's "No Highway", I was
   skeptical when the hero retracted an airliner's undercart while
   on the ground to disable the craft.

Roy,
  As I remember it, a technician explains in passing to the good boffin Honey
that he (the technician) has just disabled the squat switch mechanism for
some reason, and explains the hazard.   This will only protect against
actively raising the gear, not it's folding up by itself.
  As another submitter correctly pointed out, even light airplanes
are equipped with weight on wheels switches to inhibit accidental gear
retraction.
At flight test, they put locking pins in the retraction mechanism after
landing and before towing.  Nobody I've asked so far knows how likely it
would be to fold up if the pins weren't there, but it's invariant SOP to put
them in. (And to hold them up for the flight crew to see after the pins are
pulled. before engine start and taxi.)

--
Charlie Falke                 Pratt & Whitney
System Test Team Leader       C/O Boeing Comm AP grp.