9th of March 1992
30 years ago today a Lockheed L1011-385-3 Tristar (series 500) was scheduled to operate a flight between Frankfurt (Germany) and Saint Lucia (Saint Lucia). The aircraft had one defect that it was allowed to operate with, in accordance with the Configuration Deviation List (CDL), A thrust reverse blocker door on the #1 (left-hand) engine was removed.
13 crew and 173 passengers were on board the aircraft when it took off from Frankfurt Airport at 14.35 UTC.
The Rolls Royce RB211-524B4-02 after landing with the translating cowl missing (© AAIB)
The take-off and initial climb were uneventful and the aircraft continued to climb to the initial cruise flight level. While climbing through FL100 a thud was heard, the aircraft shuddered, and there appeared to be an engine stall. The pilot flying (first officer) Called "engine failure #1 engine". The captain observed the engine had not failed completely the Fan rpm (N1) was recovering to a normal level, however, the Engine Pressure Ration (EPR) was low 1.20, compared to 1.55 to 1.66 on the other engines. A light vibration was noticeable through the aircraft and a report from the cabin reached the flight deck that a passenger had seen something come off the #1 engine.
~4 minutes after the onset of the engine issue, the #1 engine was shut down. With a heavy load of fuel for the long flight, the aircraft was well above its maximum landing weight and needed to dump ~106.000 lbs (~41.000 kg) of fuel to reach its maximum landing weight. This would take approximately 30 minutes, it was decided to fly to London Heathrow in the meantime as this was the airline's principal maintenance base. The aircraft had levelled off at FL140 for the flight west, towards London.
The flight engineer and the captain had checked the engine from the cabin and both concluded that the thrust reverser translating cowl had separated from the #1 engine.
At 15.20 UTC London ATC was contacted with the request to dump fuel, and approximately 30 minutes would be required to carry out the fuel dump while flying at 10.000 feet (3000 meters), This was approved by ATC, they asked the flight if they wanted to declare emergency due to the engine being shut down. The reply from the captain was "No I don't think so, we'll be alright" (the CVR recording later revealed that this decision was motivated by the inconvenience it would cause the crew once landed)
The recovered translating cowl (© AAIB)
During the fuel dump, the crew was informed by a passenger that the left horizontal stabiliser was damaged, and the damage appeared to be worsening. (as a fuel pump had failed dumping was taken a lot longer than anticipated) This information made the captain abandon the fuel dump and initiate an overweight landing at London Heathrow. ATC was informed and the approach to Heathrow was initiated. (DUe to potential disruption due to the emergency the Airport Authorities requested that the aircraft would defer to London Stansted, but this was rejected by the crew. On the approach, the nose gear failed to lock down initially. But after application of the required Emergency Checklist, the nose gear locked down successfully after using the Manual Landing Gear Uplock Release handle. In the meantime, fuel dumping had continued and ATC warned the aircraft they were still dumping fuel. On receiving this info the captain ordered the flight engineer to stop the dump (who had just initiated that) The airport had gone to full emergency and all emergency services were awaiting the arrival of the aircraft. On touch down the auto-spoilers failed and spoilers were selected manually. While turning off the runway the "C" hydraulic system had to be switched off due to a drop in quantity.
FDR Data showing the moment of failure (orange arrow) & #1 engine shutdown (© AAIB)
The aircraft taxied under its own power to a parking stand. Damage to the aircraft was extensive;
#1 engine translating sleeve had separated from the engine
Damage to wing lower skin
Damage to the wing leading edge
Left Stabiliser was damaged (Large ragged hole)
The incident was investigated by the Air Accident Investigation Branch (AAIB), their report is available by clicking here. The following probable causes are summarised from the report;
The ground engineer took actions that were not supported by his knowledge of the aircraft and, unrealised by him, were not mandated by the Master Minimum Equipment List.
The ground engineer's supervisors failed to identify that an incorrect procedure had been followed although he had communicated his actions clearly to them
The damage became evident which was probably an indication of progressive cowl failure but it was not recognised as such."