Loss of control Accident Boeing 727-31 N840TW, Wednesday 4 April 1979
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Date:Wednesday 4 April 1979
Time:21:48
Type:Silhouette image of generic B721 model; specific model in this crash may look slightly different    
Boeing 727-31
Owner/operator:Trans World Airlines - TWA
Registration: N840TW
MSN: 18905/160
Year of manufacture:1965
Total airframe hrs:35412 hours
Engine model:Pratt & Whitney JT8D-7B
Fatalities:Fatalities: 0 / Occupants: 89
Other fatalities:0
Aircraft damage: Substantial, repaired
Category:Accident
Location:near Saginaw, MI -   United States of America
Phase: En route
Nature:Passenger - Scheduled
Departure airport:New York-John F. Kennedy International Airport, NY (JFK/KJFK)
Destination airport:Minneapolis-St. Paul International Airport, MN (MSP/KMSP)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
TWA Flight 841 entered an uncontrolled maneuver at FL390. The aircraft descended to about 5,000 feet in about 63 seconds before the flightcrew regained control. About 22:31, the flightcrew made an emergency landing at Detroit.
The flight was cruising in visual flight conditions at night at FL390 when the uncontrolled maneuver began; there was no turbulence. There was a cloud layer near FL200 and, at 21:55, the reported weather at Saginaw was 500-foot overcast with 3 miles visibility in light snow; small breaks were reported in the overcast. Analysis of the evidence indicated that the uncontrolled maneuver began about 2147:47 with isolation of the aircraft's No. 7 leading edge slat (on its right wing) in the extended or partially extended position. During the preceding 14 seconds, the aircraft had rolled slowly to the right to about 35° of right bank and was returned to near wings level flight. Thereafter, the aircraft rolled again to about 35° of right bank in about 4 seconds. About 2147:51, the right roll was stopped near 35° 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 descending spiral. During the following 33 seconds, the aircraft completed 360° of roll while descending to about 21,000 feet. The aircraft entered a second roll to the right during which the No. 7 slat was torn from the aircraft. Control of the aircraft was regained about 21:48:58 at an altitude of about 8,000 feet.

PROBABLE CAUSE: "The 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 captain's untimely flight control inputs, to counter the roll resulting from the slat asymmetry. Contributing to the cause was a pre-existing misalignment of the No. 7 slat which, when combined with the cruise condition airloads, precluded retraction of that slat. After eliminating all probable individual or combined mechanical failures or malfunctions 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 captain's untimely use of the flight controls was distraction due probably to his efforts to rectify the source of the control problem."
A.o. the ALPA did not agree with the NTSB findings. A complex interaction that involved the tightly coupled response of lateral and directional flight controls on the B727-100 aircraft was claimed to have caused the accident.

Accident investigation:
  
Investigating agency: NTSB
Report number: DCA79AA016
Status: Investigation completed
Duration: 1 year and 5 months
Download report: Final report

Sources:

Flight International 1-7 February 1995(25)

History of this aircraft

Other occurrences involving this aircraft

23 May 1983 N840TW Trans World Airlines, Inc. 0 Colorado Spring, CO min

Revision history:

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