Investigation Summary
The incident was triggered by a design vulnerability in the L-1011's tail section. Investigation revealed that moisture from rain and fog had collected on a structure in the tail and dripped onto a bearing in the elevator control system. The repeated pressurization and depressurization cycles of the aircraft acted as a pump, forcing water into the bearing housing. This led to severe internal corrosion. During the pre-flight control check, the bearing failed, causing the left elevator to jam at its maximum upward deflection. The crew's innovative use of the #2 (tail) engine's thrust to create a nose-down pitching moment was critical, as the primary flight controls were insufficient to overcome the jammed surface.
Final Conclusions
The NTSB and Lockheed determined the cause was a jammed elevator and elevator tab control system resulting from a corroded bearing. The corrosion was accelerated by moisture ingress driven by cabin pressure cycles. The successful outcome was attributed to the captain's exceptional airmanship and the crew's creative use of non-standard control methods, including differential thrust and passenger relocation.
Video Analysis
Delta Air Lines Flight 1080: The Jammed Elevator Incident — A Lockheed L-1011 experienced a severe pitch-up after a bearing failure jammed the left elevator. The crew used differential thrust and passenger relocation to land safely at Los Angeles.
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Airframe & Maintenance
Crew Experience
Captain
Jack McMahan, age 54
First Officer
Wilbur Radford, age 34
Flight Engineer
Steven Heidt, age 30
Systems & Failure Modes
Elevator / Stabilizer
The primary pitch control surface which jammed in a full trailing-edge-up position.
Differential Thrust
The technique of using varying power settings between the wing engines and the tail engine to control the aircraft's pitch.
Stabilizer Trim
The crew attempted to use both electric and manual backup trim systems, but neither could overcome the jammed elevator.
Interesting Facts
- 01The aircraft had only 5,000 flight hours at the time of the incident.
- 02The captain used the tail-mounted engine (Engine 2) to maintain pitch control while idling the wing engines.
- 03A British Airways L-1011 (G-BEBE) experienced a similar elevator control issue on June 28, 1977, shortly after this incident.
- 04The jammed elevator was caused by a bearing that had been corroded by water forced inside by pressure changes.
Safety Actions & Advisories
FAA Emergency Airworthiness Directive
Source ↗The FAA issued a mandatory directive requiring immediate inspection of elevator bearings on all L-1011 aircraft in the United States.
Lockheed Design Modification
Lockheed developed a deflector shield to drain water away from the elevator bearings to prevent moisture accumulation and corrosion.
Pre-flight Visual Checks
The FAA briefly mandated a visual inspection of the elevator movement before every L-1011 takeoff following a second incident in Spain.