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22 December 1999 - Korean Air 8509

Boeing 747-2B5F, with registration HL-7451, arrived at Stansted at 15.05 after a flight from Tashkent. Prior to leaving the aircraft, the flight engineer made an entry in the Technical Log stating "Captain's ADI [Attitude Director Indicator] unreliable in roll' he also verbally passed the details to the operator's ground engineer who met the aircraft on arrival. During turnover repair works on the ADI were carried out.

Some cargo was offloaded and other cargo loaded for the flight to Milan-Malpensa (take-off weight was 548,352 lb including 68,300 lb of fuel) and a new crew boarded the aircraft. After a delay of an hour, because ATC had not received the flight plan, Flight 8509 was cleared to depart Stand Alpha 6 and taxi to runway 23 holding point at 18.25. Subsequently, at 1836 hrs KAL 8509 was cleared to take-off with a reported surface wind of 190deg/18 kt. The Dover 6R Standard Instrument Departure called for a climb ahead to 1.5 miles DME, then a left turn onto the 158 inbound radial to the Detling VOR. Climbing through 900 feet, the ADI 'Comparator' buzzer sounded three times. Shortly afterwards, the warning sounded a further two times, coincident with the captain expressing concerns over his DME indication. Climbing through 1400ft, ATC instructed the crew to contact 'London Control'. And as the captain initiated the procedure turn to the left, the 'Comparator' warning sounded again some 9 times. The maximum altitude reached was 2,532 feet amsl. The aircraft then banked left progressively and entered a descent until it struck the ground in an approx. 40deg nose down pitch and 90deg bank to the left; the speed was high in the region of 250 to 300 kt.

CAUSAL FACTORS: The following causal factors were identified:
1 The pilots did not respond appropriately to the comparator warnings during the climb after takeoff from Stansted despite prompts from the flight engineer.
2 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.
3 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.
4 The maintenance activity at Stansted was misdirected, despite the fault having been correctly reported using the Fault Reporting Manual. Consequently the aircraft was presented for service with the same fault experienced on the previous sector; the No 1 INU roll signal driving the captain's ADI was erroneous.
5 The agreement for local engineering support of the Operator's engineering personnel, was unclear on the division of responsibility, resulting in erroneous defect identification, and misdirected maintenance action.

Download the full AAIB report

Transcript of the Cockpit Voice Recorder (CVR)

Legenda CPT= Voice identified as Captain FO= Voice identified as First Officer FE = Voice identified as EngineerRDO-2 = Radio transmission from First OfficerT WR= Stansted Tower italics= translation from Korean

time until crash source content
02:03.5 TWR Korean Air eight five zero nine surface wind one nine zero one eight knots clear takeoff runway two three
01:57.5 RDO-2 Clear to takeoff runway two three Korean Air eight five zero nine
  CPT it is strange the surface looks damp but is slippery
  FO Clear for takeoff
  CPT CHA GULO GAB NI DA Now rolling
  CPT Body gear steering
  FE Body gear steering
  FE Compass cross check
01:29.9 FE Time check three seven
  FE Before takeoff check list complete
  FE Stabilized
  CPT Set takeoff thrust
  FE Set
  FE (reduced) thrust
01:17.9 FE Check
01:12.4 FO Eighty knots
  CPT Roger
01:04.9 FO V one rotate
00:58.5 FO V two
00:58.1   [sound of trim movement]
00:54.5 FO Positive climb
  CPT Gear up
  FO Gear up
00:46.4 CPT Oh
  CPT IL JEOM one decimal
  CPT I didn't expect this
00:41.9 FO Passing nine hundred feet
00:39.8   [Warning chime begins]
00:38.2   [Warning chime ends after sounding three times]
00:36.4 CPT We should turn at one point five DME
00:33.5 FO Yes sir
00:30.7   [Warning chime begins]
00:30.7 CPT DME not working
00:29.8   [Warning chime ends after sounding two times]
00:29.5 FO One five eight
  CPT Ah?
00:28.1 FO Heading standby sir
00:28.1 FO Heading one five eight
00:23.9   [Warning chime begins]
00:21.5 TWR Korean Air eight five zero nine contact London one one eight decimal eight two good night
00:20.8 FE Bank is not working
00:17.9   [Warning chime ends as 10th chime begins]
00:16.9 FE Bank bank
00:15.5 RDO-2 one one eight eight two Korean Air eight five zero nine
00:11.5 CPT YA (eh you)
00:10.2 FE Standby indicator also not working
00:06.9 CPT Request radar vector
00:04.9 CPT YA (eh you)
00:01.5 FE OY Bank
00:00.0   [end of recording]
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