Re: A 777 with four engines.

Date:         06 Aug 98 11:26:30 
From:         andyweir <andyweir@compuserve.com>
References:   1 2 3 4 5 6 7 8
Followups:    1
Next article
View raw article
  or MIME structure


>> Does anybody know of a case where a plane was controlled successfully
>> using asymmetric control of the engines?

>AA DC-10 over Windsor, Ontario, in the early 1980s? The basic problem was
>similar to that of the THY DC-10 just a little later: ie loss of the aft
>cargo door and damage to the cabin floor and, as a consequence, to the
>controls. The pilots used asymmetric thrust in getting the plane down (at
>Detroit, if memory serves) without further damage. But I don't recall how
>severe the damage was, and whether there was in fact total loss of
>hydraulics. Anyone?

Had occasion to talk a couple of years ago to Bryce McCormick, captain
during said Windsor AA DC-10 incident (in June 1972, BTW. He did land at
Detroit). His ability to control the aircraft with differential thrust had
been due, at least in part, to his conservatism when converting to the
DC-10 from B707. He told me that at the time he instinctively distrusted
exclusively hydraulically-operated controls. What if, he asked his
instructor, you lose hydraulics? Can't happen, he was told. No way.
Nonetheless, he asked and was allowed to experiment in the sim with
differential thrust until he got the hang of it. I believe that in his
incident McCormick had lost the tail engine but retained limited control of
the elevators and the ailerons. Not a total hydraulic loss, I think, but
enough to make differential thrust pretty important. Captain Denny Fitch's
knowledge of this incident had contributed to his ability to control UAL
232 when he was invited into the Al Haynes cockpit to operate the throttles
in the famous flight which ended at Sioux City July 1989.
It became McCormick's party trick. He told me how he astounded some FAA
inspectors along with him on a test flight for an air generator by landing
the plane (don't know from how far out)  without touching the control
column. He flared by slightly pulling back on the tail engine and pushing
forward on the other two. "It just squeaked in", he said. In 1995 NASA, I
think it was, demonstrated a propulsion control software package called PCA
that took the guesswork out of differential thrust. It simply plugged into
the FMC or FADEC of an MD-11. Don't know the current situation, but I
believe NASA expressed disappointment in the lack of interest in the
package from airlines. Presumably, the software's principles are
universally applicable and could be adapted for any big jet with FMC and/or
FADEC. I wonder what became of it?