| Delta Air Lines Flight 1080 | |
| Image Upright: | 1.15 |
| Occurrence Type: | Incident |
| 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 |
| Operator: | Delta Air Lines |
| Aircraft Type: | Lockheed L-1011 Tristar |
| Tail Number: | N707DA |
| Origin: | San Diego International Airport |
| Stopover0: | Los Angeles International Airport |
| Stopover1: | 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 |
| Injuries: | 0 |
| Fatalities: | 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.[1] 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.[2] 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.[3] [4] The entire incident lasted 55 minutes.
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 _ flight hours. The captain was 56 year old Jack McMahan, who had __ flight hours, of which __ were in the L-1011. The first officer, __ year old Wilbur Radford, had _ flight hours, and __ were on the L-1011, and 30 year old flight engineer Steven Heidt having __ out of his __ total flight hours on the L-1011. There were 8 flight attendants on board the aircraft.[5]
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.
When the aircraft suddenly pitched up, it was found to be slightly controllable although captain McMahan did push the column fully down 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 place seemed to return to a normal flight condition. at 400 ft, the aircraft began pitching up again, from 15° to 18°.
The investigation found that the pressurization and depressurization of the L-1011 during flight cycles had caused water to be pushed inside a bearing, 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.[6]
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.[7] For his skill in landing the crippled aircraft, the captain, Jack McMahan, was awarded the FAA's Distinguished Service Award.[8] 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.[9]