Accident summary | |
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Date | April 4, 1979 |
Type | Unknown |
Site | Detroit, Michigan |
Passengers | 82 |
Crew | 7 |
Injuries | 8 |
Fatalities | 0 |
Survivors | 89 (all) |
Aircraft type | Boeing 727-31 |
Operator | TWA |
Tail number | N840TW |
On April 4, 1979, a Boeing 727-31 (tail number N840TW) operating as TWA Flight 841 took off from John F. Kennedy International Airport, New York City, en route to Minneapolis-Saint Paul International Airport in Minneapolis, Minnesota. Over Saginaw, Michigan, while the plane was cruising at 39,000 feet (11,887 m) and Mach 0.816, it began a sharp roll to the right. The roll continued despite the corrective measures taken by the autopilot and the human pilot. The aircraft went into a spiral dive, losing about 34,000 feet (10,363 m) in 63 seconds. During the course of the dive, the plane rolled through 360 degrees twice, and crossed the Mach limit for the 727 airframe. Control was regained at about 5,000 feet (1,524 m) after the captain decided to extend the landing gear in an attempt to slow the aircraft[1], and following the loss of the #7 slat from right wing. The plane suffered substantial structural damage, but made an emergency landing at Detroit Metropolitan Airport, Michigan, without further trouble. No fatalities occurred among the 82 passengers and seven crew members. Eight passengers reported minor injuries relating to high G forces.[2]
The National Transportation Safety Board investigated the accident and established after eliminating all individual and combined sources of mechanical failure, that the extension of the slats was due to the flight crew manipulating the flap/slat controls in an inappropriate manner.
The crew, Capt. Harvey "Hoot" Gibson, first officer Jess Kennedy, and flight engineer Garry Banks, denied that their actions had been the cause.
At no time prior to the incident did I take any action within the cockpit either intentionally or inadvertently, that would have caused the extension of the leading edge slats or trailing edge flaps. Nor did I observe any other crew member take any action within the cockpit, either intentional or inadvertent, which would have caused the extension.—Capt. Gibson, April 12, 1979
The crew suggested instead that an actuator on the #7 slat had failed, causing its inadvertent deployment. The NTSB rejected this as improbable and attributed the extension of the flaps to the deliberate actions of the crew. The crew claimed that such failures had happened on other 727s prior and subsequent to this incident. The NTSB report notes seven such cases.[2]
Despite the sworn testimony of the crew that they had not engaged the flaps, the NTSB argued that they probably were attempting to use 2 degrees of flaps at cruising speed.
When retraction of the flaps was ordered, the Number 7 leading edge slat failed to retract, causing the uncommanded roll to the right.
Captain Gibson appealed the NTSB's findings, first to the NTSB itself, and then to the U.S. Ninth Circuit Court of Appeals. Both petitions were rejected: the former for lack of new evidence, and the latter for lack of jurisdiction.
The aircraft was repaired and returned to service in May 1979.
Stewart, Stanley (2002) [1989]. Emergency: Crisis on the Flight Deck (2nd edition ed.). Airlife Publishing. pp. 150–176. ISBN 1-84037-393-8.
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