On 22 December 1999, a KAL Boeing 747 freighter crashed shortly after take-off from Stansted UK, following an ADI malfunction.
The following is an extract taken from the Synopsis from the AAIB Accident Report:
"…The aircraft arrived at Stansted Airport after a flight from Tashkent, Uzbekistan. Prior to leaving the aircraft, the flight engineer made an entry in the Technical Log to the effect that the captain's Attitude Director Indicator (ADI) was "unreliable in roll"; he also verbally passed the details to the operator's ground engineer who met the aircraft on arrival. This fault had been detected after takeoff from Tashkent. The inbound flight crew then left the aircraft without meeting the outbound crew who were due to operate…later that day.
…[The aircraft departed Stansted at 1836 hrs, bound for Milan] The Tower controller considered that the takeoff was normal and the aircraft disappeared from sight as it entered the cloud base at about 400 ft agl. At 1838 hrs, as the aircraft indicated altitude passed 1,400 ft, [the aircraft] was transferred to "London Control" on frequency 118.82 MHz. The crew had been cleared for a departure procedure, which required a left turn at 1.5 nm from the Stansted DME…No radio calls were heard from the aircraft subsequent to the frequency transfer instruction…
Investigations revealed that, throughout the accident flight, the captain's ADI indicated the correct pitch attitude but that the roll attitude remained at wings level indication. Radar and Flight Data Recorder data showed that the aircraft commenced a turn to the left but that this turn was continuous until impact with the ground. At impact, the aircraft was assessed to be pitched approximately 40° nose down, banked close to 90° to the left and with a speed in the region of 250 kt to 300 kt.
The investigation identified the following causal factors [including]:
- The pilots did not respond appropriately to the comparator warnings during the climb after takeoff from Stansted despite prompts from the flight engineer.
- The commander, as the handling pilot, maintained a left roll control input, rolling the aircraft to approximately 90° of left bank and there was no control input to correct the pitch attitude throughout the turn.
- The first officer either did not monitor the aircraft attitude during the climbing turn or, having done so, did not alert the commander to the extreme unsafe attitude that developed…."