Terror at 41,000 feet... follow up

From:         jebright@magnus.acs.ohio-state.edu (James R Ebright)
Organization: The Ohio State University
Date:         04 Apr 93 15:01:07 PDT
References:   1
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Several months ago we had a thread on a 727 almost falling out of the
sky (39,000 to 5,000 ft in 63 seconds). As I remember it, no one was
able to identify the acutal incident.  It took me about 20 minutes on
Nexis to find it... but I did!   It seems to fit into the discussion
of the ongoing 727 slats thread :)

Aviation Week, April 16, 1979; October 5, 1979 and The Washington Post,
May 13, 1979...

April 4, 1979 TWA 841, a Boeing 727-100 (N840TW) left JFK for Minneapolis.
At about 21:48 EST while at 39,000 ft near Saginaw, MI the aircraft
"entered an uncontrolled maneuver".  

To quote from AvWeek's NTSB report ... "the uncontrolled maneuver began
about 21:47:47 with isolation of the aircraft's No 7 leading edge slat (on
it's right wing) in the extended or partially extended position.  During
the preceding 14 sec. the aircraft had rolled slowly to the right to about
35 deg. of right bank and was returned to near wings level flight.
Thereafter, the aircraft rolled again to about 35 deg. of right bank in
about 4 sec.  About 21:47:51, the right roll was stopped near 35 deg. of
bank for a few seconds.  At that time, the aircraft reached a condition
wherein Mach number, angle of attack, and sideslip combined to reduce the
aircraft's lateral control margin to zero or less, and the aircraft
continued to roll to the right in a decending spiral.  During the
following 33 sec. the aircraft completed 360 deg. of roll while decending
to about 21,000 ft.  The aircraft enter a second roll to the right during
which the No 7 slat was torn from the aricraft.  Control of the aircraft
was regained about 21:48:55 at an altitude of about 8,000 ft.

"The safety board [NTSB] determines that the probable cause of this 
accident was isolation of the No 7 leading edge slat in the fully or 
partially extended position after an extension of the Nos. 2,3,6, and 7 
leading edge slats and the subsequent retraction of the Nos. 2,3, and 6 
slats, and the captian's untimely flight control inputs to counter the 
roll resulting from the slat asymmetry.

"Contributing to the cause was a preexisting misalignment of the No. 7 slat
which, when combined with the cruse condition airloads, precluded 
retraction of that slat.  Ater eliminating all probable individual or 
combined mechanical failures, or malfuncitions which could lead to slat 
extension, the safety board determined that the extension of the slats was 
the result of the flightcrew's manipulation of the flap/slat controls.  
Contributing to the captian's untimely use of the flight controls was 
distraction due probably to his efforts to rectify the source of the 
control problem."

The aircraft landed at Detroit Metro with only 3 of the 89 pax injured.

The aircraft exceed 500kts and experienced 4-5gs during pullout. (PHEW!)

To regain control of the aircraft during the nose down dive, the captain
had to lower the landing gear to create sufficient drag to slow the

The investigation was hampered by the erasure of the cockpit voice recorder
by the captain (Harvey G. Gibson) upon landing in Detroit.  The captian
was given 4 days of training review by TWA.  The co-pilot and flight
officer were given 1 day each.  All returned to regular service when no
evidence could be found to indicate "the flightcrew's maniupulation of the
flap/slat controls" was a deliberate act as some of the rumors posted in
the original thread in sci.aeronautics.airliners indicated. (??!?)

"Just the facts, mam, just the facts." -- Sgt. Joe Friday


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