The accident investigation revealed that the captain entered a left bank as his attitude director indicator (ADI) froze and showed no roll moment. He continued the bank as the copilot's ADI and the standby ADI both showed he was now banking excessively. The airplane's comparator warning system sounded to alert all concerned that there was a problem with at least one of the ADI's. Throughout all this the first officer said nothing. The flight engineer did call out the problem, but the captain ignored his warnings as well as those from the airplane. Less than 60 seconds from takeoff, they all died.
— James Albright
HL 7451, from Aviation Safety Network
The failure in Crew Resource Management and the failure of both pilots to recognize an Unusual Attitude killed them both and their two crew mates. But why? The British Accident Investigation Board hints at a few answers:
- The captain flew single-seat fighters for the Korean Air Force and retired as a colonel. Korean culture forbid that he be hired as anything but a captain, less he lose face. Though he had never commanded an air crew in the military, that is precisely what he did from day one with Korean Air.
- The first officer was of much lower social status, having never been a retired Air Force colonel, and was in a position that he knew would mean certain dismissal if the captain was somehow displeased. As was said in the T.V. documentary, May Day - Bad Attitude, the first officer would have rather died than risk the captain's displeasure.
- The captain had been reprimanded months before for tardy performance. During this flight a delayed flight clearance put the crew behind schedule and the captain became irritated. No one on the crew dared increase that irritation.
- Simulator tests proved that the aircraft was recoverable well into the flight, but no recovery attempt was made by either pilot.
There is another factor not mentioned in the accident report. Older aircraft the captain may have been familiar with would have self contained ADI's. That is, these ADI's were units unto themselves, not connected with any other equipment. If an ADI malfunctioned, the fault was more than likely to be in the ADI itself. Newer ADI's, such as the one installed on this Boeing 747, often get their attitude information from Inertial Reference Units (INUs). Pilots can easily cross train from one aircraft to another and not have a firm grasp of this idea. Had this captain understood that a little better, he might have properly diagnosed the problem.
Sitting in the left seat brings with it several responsibilities, among which is the need to stay sharp and avoid complacency. The best way to do that is to stay in the books and invite critique from others on the flight deck; but if you shut them down that opportunity is lost.
- Date: 22 DEC 1999
- Time: 18:38 UTC
- Type: Boeing 747-2B5F (SCD)
- Operator: Korean Air
- Registration: HL7451
- Crew: Fatalities: 4 / Occupants: 4
- Passengers: Fatalities: 0 / Occupants: 0
- Total: Fatalities: 4 / Occupants: 4
- Airplane fate: Written off (damaged beyond repair)
- Location: near Great Hallingbury (United Kingdom)
- Phase: Initial climb (ICL)
- Nature: Cargo
- Departure airport: London-Stansted Airport (STN/EGSS), United Kingdom
- Destination airport: Milano-Malpensa Airport (MXP/LIMC), Italy
[On the previous flight] The commander was the handling pilot and at 1,000 feet, after a full power takeoff, the commander commenced a right turn. He reported that his ADI operated normally until the aircraft reached an angle of bank of between 10° and 15°. As the angle of bank increased further the attitude comparator warning activated (both aural and visual warnings). The commander reported that he compared his ADI indication with the standby horizon and the first officer's ADI, and with peripheral outside visual cues realised that, although his ADI was showing the correct pitch attitude, it was not showing the correct angle of bank. He handed over control of the aircraft to the first officer who continued to fly the departure and the crew cancelled the aural warnings.
Source: United Kingdom Aircraft Accident Report 3/2003, §1
This was a textbook response as would have been called for in the aircraft flight manual and by standard unusual attitude recovery procedures.
More about this: Unusual Attitudes.
The aircraft arrived at Stansted Airport at 1505 hrs on 22 Dec 1999, after the 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.
[Ground technicians removed the ADI and] noticed that Socket No. 2 on the smaller plug (ie the half of one connector forming part of the aircraft wiring) had been pushed back and he seemed to indicate that he felt this was significant. . . . [a second ground technician arrived with the necessary tools] and performed the task, hearing the distinctive 'click' as the socket was relocated in position. . . . He then pressed the 'Test' button on the captain's ADI and saw the correct instrument response, which also activated the 'Comparator' warning.
Source: United Kingdom Aircraft Accident Report 3/2003, §1
The investigators point out the pushed back pin was likely to have occurred during installation and since the ADI had been working normally until the previous flight, it was unlikely to be the cause of the problem.
- During the turnaround, some cargo was offloaded and other cargo . . . was loaded. . . . The loading was almost complete when the outbound crew arrived.
- The outbound crew:
- The commander was 57 years old, had 13,490 total flying hours, 8,495 in type, was previously an Air Force Colonel in F5As and A37s.
- The first officer was 33 years old, had 1,406 total flying hours, 195 hours in type, had previously flown the F100.
- The flight engineer was 38 years old, had 8,301 total flying hours, 4,511 in type.
- At 1727 hrs, the crew called 'Stansted Delivery' on frequency 125.55 MHz for their flight clearance; however this frequency is only manned when a high number of airport movements are planned. At 1729 hrs after two unsuccessful attempts to contact ATC on 'Delivery' frequency, the crew contacted 'Stansted Ground' on frequency 121.72 MHz to request start and push back clearance from their position at Stand Alpha 6. They were informed that ATC had no details for their flight and so were requested to standby. Then at 1733 hrs, the crew were informed that no flight plan had been received and they should contact their handling agents. The agents submitted the flight plan and at 1742 hrs the crew of HL-7451, call sign KAL 8509, were advised that their clearance to Malpensa (Milan) on a Dover 6R Standard Instrument Departure (SID) with a transponder setting of 2230; the crew read back their clearance correctly.
- Subsequently, at 1836 hrs, KAL 8509 was cleared to take off with a reported surface wind of 190°/18 kt. After rotation the first officer confirmed a positive rate of climb and the commander called for "GEAR UP". Shortly after the first officer called "PASSING NINE HUNDRED FEET", the commander confirmed with him that they should turn at 1.5 DME and then said that his DME was not working. There was then a short exchange between the two pilots, confirming the departure heading after the 1.5 DME turn as 158°, following which the flight engineer called "BANK, BANK".
- The Tower controller considered that the takeoff was normal and, at 1836 hrs, as the aircraft indicated altitude passed 1,400 feet, transferred KAL 8509 to 'London Control' on frequency 118.82 MHz. Shortly after the first officer had acknowledged the change of frequency, the commander asked him to obtain radar vectors. The flight engineer then made a further, more urgent, call of "BANK".
- No radio calls were heard from the aircraft subsequent to the frequency transfer from 'Stansted Tower'. ATC personnel in the Tower then saw an explosion to the south of the airport and realised that KAL 8509 had crashed and immediately implemented their emergency procedures.
Source: United Kingdom Aircraft Accident Report 3/2003, §1
- [The previous crew] The time of day and weather conditions were conducive to the crew achieving a successful outcome in that a clear external horizon was visible, the sun was low above the horizon, to assist them in responding to the fault and retaining control of the aircraft.
- However, the rectification action employed did not clear the fault and, on the subsequent departure from Stansted, the outbound crew lost control of the aircraft.
- Maintenance records indicate that the captain's ADI was fitted some five months prior to the accident, at which time it is likely that the No 2 socket on the J1 connectors became displaced. The lack of any attitude instrument malfunctions or comparator warnings over this period, with the exception of the roll attitude warnings on both the accident and preceding flights, indicates that pin and socket No 2 in connector J1 were in contact. Therefore, the displaced socket was not associated with the failure of the captain's ADI to indicate the correct roll attitude of the aircraft after takeoff from Tashkent.
- The selection of 'ALT' on the captain's altitude and compass stabilisation selection switch cancelled the comparator trigger for the warning systems and resulted in the captain's ADI indicating correctly. As this selection changed the attitude data source for the captain's ADI from INU No 1 to INU No 3 it confirmed that the fault was not with the ADI or its connections but was a fault with data supplied by INU No 1.
- The flight crew had arrived at the aircraft with sufficient time to enable them to achieve their departure time. The first minor problem occurred when they could not contact 'Stansted Delivery' at 1727 hrs; however, within two minutes, they had made contact with ATC on 'Stansted Ground'. Unfortunately, ATC had no details for the flight and the crew were advised to contact their handling agents. The agents had not submitted the flight plan and it was not until 1742 hrs that ATC had received the flight plan and advised the crew of their clearance. The next distraction was a delay in providing a vehicle to push-back HL-7451 and clearance to push-back was not received until 1813 hrs. Then, during push-back, it became apparent that the vehicle was having problems and it was necessary for a marshalling vehicle to position and for the aircraft to be marshalled onto the taxiway centreline. Clearance to taxi was given at 1825 hrs, some 58 minutes after the crew initially attempted to contact ATC. It is not unusual for crews to be subjected to some delays or distractions during clearance and ground movements at airports but the delay experienced by the crew of HL-7451 was greater than normal and would have resulted in an understandable degree of frustration in the commander. Content of the CVR indicated that the commander was showing signs of frustration. After personally handling the ATC communication a number of times prior to and during engine start (KAL standard procedure is for the first officer to handle ATC radio calls), he suddenly reprimanded the first officer for not responding to a radio call. On the taxi call, he faulted the first officer for not advising him to taxi to the centreline, then on receiving the line-up clearance told the first officer that a "Roger' alone was sufficient. By making these comments, it is considered that the commander contributed to setting a tone which discouraged further input from the other crew members, especially the first officer.
- There is no evidence to explain the commander's lack of response to a number of significant cues. The aircraft was apparently failing to respond to a control wheel roll demand such that the roll command was maintained for an abnormal period with a pitch attitude displayed that he will have never experienced before in a large civilian aircraft.
- At no time did the first officer respond audibly to the comparator or flight engineer's warnings or comment to the commander about the extreme aircraft attitude, which was developing. It remains a matter of conjecture as to whether he was so distracted by other duties that his instrument scan broke down, to the extent that he was unaware of the aircraft attitude and did not appreciate the significance of the comparator warnings, or he felt inhibited in bringing the situation to the attention of the commander.
- [The flight engineer] appears to have noticed a problem with bank angle indication and repeatedly indicated concern over the aircraft bank angle.
Source: United Kingdom Aircraft Accident Report 3/2003, §2
- 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.
- 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.
- 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.
Source: United Kingdom Aircraft Accident Report 3/2003, §3
May Day: Bad Attitude, Cineflix, Episode 79, Season 11, 20 January 2012 (Korean Air 8509)
United Kingdom Air Accidents Investigation Branch, Aircraft Accident Report 3/2003, Report on the accident to Boeing 747-2B5F, HL-7451, near London Stansted Airport on 22 December 1999