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Delta Air Lines Flight 1080

N754DL, an aircraft similar to the one involved
Incident
Date	April 12, 1977 (1977-04-12)
Summary	Loss of pitch control due to mechanical failure and jamming of the elevator and elevator tab control system
Site	Los Angeles International Airport, Los Angeles, California, United States
Aircraft
Aircraft type	Lockheed L-1011 Tristar
Operator	Delta Air Lines
Registration	N707DA
Flight origin	San Diego International Airport
1st stopover	Los Angeles International Airport
2nd stopover	Dallas/Fort Worth International Airport
Last stopover	Louis Armstrong New Orleans International Airport
Destination	Hartsfield–Jackson Atlanta International Airport
Occupants	52
Passengers	41
Crew	11
Fatalities	0
Injuries	0
Survivors	52

Delta Air Lines Flight 1080 was a scheduled flight from San Diego, California to Atlanta, Georgia, notable for the incident that occurred on April 12, 1977 during the San Diego to Los Angeles leg of the flight. Unknown to the crew, the Lockheed L-1011's left elevator had become stuck in a fully upwards position. This led to the aircraft pitching up aggressively and causing the aircraft to lose speed and nearly stall. The pitching force, unable to be overcome by fully pushing the control column down, was counteracted by reducing the thrust on the L-1011's wing engines but not the tail engine. The differential thrust, along with moving all the passengers as far forwards as possible in the cabin, pitched down the nose of the airliner and allowed the pilots to land the aircraft.The entire incident lasted 55 minutes.

Aircraft and Crew

The aircraft was a 2 year old Lockheed L-1011-385 Tristar (Serial number 193C-1077) and was delivered to Delta on 24 May 1974 (registered as N707DA), at the time of the accident, had 5,000 flight hours. The captain was 56 year old Jack McMahan, who had 23,000 flight hours, of which 2,000 were in the L-1011. The first officer, 34 year old Wilbur Radford, had 10,000 flight hours, and 1,500 were on the L-1011, and 30 year old flight engineer Steven Heidt having 500 out of his 5,000 total flight hours on the L-1011. There were 8 flight attendants also on board the aircraft.

Incident Timeline

Takeoff

At 23:53 PDT (19:53 UTC), the conditions were reported as 800 ft of overcast, visibility 5 miles, temperature 58°F, winds 260° at 8 knots. while taxing to runway 27, the crew preformed a flight control check, and during this is what caused the bearing to break, jamming the stabilizer upwards. When the aircraft rolled down the runway, the takeoff was described as 'normal' until at 126 knots (Vr speed), the nose rotated off the ground with little to no pull on the column.

Initial Problems

When the aircraft suddenly pitched up, it was found to be slightly controllable, although McMahan did push the column fully down on the control column with little response. The captain then checked the stabilizer trim setting; it was set at the correct 3.5° nose up. The aircraft seemed to stop pitching up at 15°, the gear was retracted and the plane seemed to return to a normal flight condition. at 400 ft, the aircraft began pitching up again, from 15° to 18°. The crew kept trying to use the thumbwheel trim after the movement of the thumbwheel stopped. The controls were described to be very sluggish, with little response from them. The back-up system, which overrides the electric trim, was used, but it didn't result in a change in controllability. The SPI instrument indicated that the stabilizer was already 'zeroed out', and so the pilots were still puzzled on why the aircraft kept pitching upwards. Heidt, at the request of McMahan, looked over and checked the hydraulic systems, as McMahan believed that one of the hydraulic systems had failed. While Radford conducted an area test, McMahan unlatched and latched any switches associated with trim, and Heidt double checked the hydraulics, and check for any popped circuit breakers, and by the time the aircraft reached 3,000 ft, all procedures for jammed controls, trim, axis jam, and hydraulic malfunctions had been performed with no change in control.

Declaring an Emergency

The crew informed San Diego Departure Control that they were experiencing a pitch issue, and instead of switching frequencies, they requested to stay with departure control.

Investigation

The investigation found that the pressurization and depressurization of the L-1011 during multiple flight cycles had caused water to be pushed inside the left elevator aft drive quadrant (also referred to as the bell crank), heavily corroding it and causing it to become jammed during a routine control surfaces check prior to takeoff. The FAA issued an emergency airworthiness directive instructing airlines to do a check of the bearing. This verification, however, was not sufficient to prevent takeoff with a jammed elevator; and a similar incident followed two months later. The FAA then made it mandatory for crews to inspect the elevators before each takeoff.

Aftermath

As a result of the incident, Lockheed redesigned the elevator systems to be redundant upon failure of the bearings, as well as adding a seal to the bearing and a deflector to reduce the amount of water contacting the part. Lockheed also modified the pilot's manual to improve the Pitch Axis Control Assist Procedures. The FAA further made it mandatory for pilots to be informed of these changes.

For his skill in landing the crippled aircraft, the captain, Jack McMahan, was awarded the FAA's Distinguished Service Award. The aircraft was repaired and continued to fly for Delta until 1985, when it was subsequently sold to American Trans Air, where it was registered with the tail number "N187AT". The aircraft was scrapped at Victorville, California in 2002.

See also

• Alaska Airlines Flight 261, a MD-82 that suffered a failure of the jackscrew in the stabilizer, leading to the deaths of 88 people.
• Aeroflot Flight 8641, a Yakovlev Yak-42 that suffered a jackscrew failure due to metal fatigue and a design flaw resulting in 132 deaths.

References

1. ^ "The Saving Of Flight 1080". The Washington Post. 1978-10-08. ISSN 0190-8286. Retrieved 2018-05-19.
2. ^ "Flight 1080" (PDF). Tristar500.net. Retrieved 27 August 2018.
3. "Delta's L1011 Routes - Airliners.net". www.airliners.net. Retrieved 2023-07-27.
4. "NTSB ID: LAX77IA037". www.ntsb.gov. Archived from the original on 9 June 2020. Retrieved 2020-06-09.
5. "NASA Technical Paper : Development and Flight Evaluation of an Emergency Digital Flight Control System Using Only Engine Thrust on an F-15 Airplane" (PDF). Nasa.gov. Archived from the original (PDF) on 15 August 2020. Retrieved 27 August 2018.
6. ^ Wilson, Robert (2021-02-04). "Midnight special | Flight Safety Australia". Retrieved 2024-11-17.
7. ^ "Airworthiness directives: Lockheed-California Company Model, L-1011-385 Series Airplanes" (PDF). Federal Register. 42 (176): 45631–45632. 1977-09-12.
8. Montoya, Howell, Bundick, Ostroff, Hueschen, Belcastro, R. J., W. E., W. T., A. J., R. M., Christine (August 1983). "Restructurable Controls" (PDF). 19830025625.pdf. Retrieved 16 November 2024.{{cite web}}: CS1 maint: multiple names: authors list (link) CS1 maint: url-status (link)
9. "American Trans Air N187AT (Lockheed L-1011 TriStar - MSN 1077) (Ex N707DA ) | Airfleets aviation". www.airfleets.net. Retrieved 2020-02-08.

External links

• Portrait of N707DA the accident aircraft taking off
• Video explaining the incident

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