Re: O'Hare Accident

Date:         09 Aug 97 02:28:28 
From:         kls@ohare.Chicago.NOSPAM.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
References:   1 2 3
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>Things I've read in the past suggest that had they lowered the nose, the
>stall could have been prevented. That would have then given them time to
>deal with the asymmetrical flap situation.

The NTSB report doesn't quite say that:

   ... the stall speed for the left wing increased to 159 KIAS [knots
   indicated air speed].

   ... the first officer continued to comply with carrier procedures
   and maintained the commanded pitch attitude; the flight director
   command bars dictated pitch attitudes which decelerated the
   aircraft toward V2, and at V2+6, 159 KIAS, the roll to the left
   began.

   ...

   Since the roll to the left began at V2+6 and since the pilots were
   aware that V2 was well above the aircraft's stall speed, they
   probably did not suspect that the roll to the left indicated a
   stall.

   ...

   The simulator tests showed that the aircraft could have been flown
   successfully above 159 KIAS, or if the roll onset was recognized as
   a stall, the nose could have been lowered, and the aircraft
   accelerated out of the stall regime.

They talk about lowering the nose as a part of stall recovery, not as
a means of preventing the stall in the first place.

> I believe this scenario had been sucessfully flown in simulators
> using that technique.

Continuing from the NTSB report:

   However, the stall warning system, which provided a warning based
   on the 159 KIAS stall speed, was funcitoning on the successful
   simulator flights.  Although several pilots were able to recover
   control of the aircraft after the roll began, these pilots were
   all aware of the circumstances of the accident.  All participating
   pilots agreed that based upon the accident circumstances and the
   lack of available warning systems, it was not reasonable to expect
   the pilots of Flight 191 either to have recognized the beginning of
   the roll as a stall or to recover from the roll.  The safety board
   concurs.

Recovery, not prevention, and that only if they had the stall warning,
which lacked redundancy in the design of the DC-10 and which was
disabled by loss of the #1 engine.

--
Karl Swartz	|Home	kls@chicago.com
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