Operator Korean Air
|Aircraft type Boeing 747-2B5F|
Date 22 December 1999
Fatalities 4 (all)
Crew count 4
|Summary Instrument malfunction, pilot error, spatial disorientation|
Site Great Hallingbury, England, United Kingdom
1st stopover Tashkent International Airport, Tashkent, Uzbekistan
Flight origins Gimpo International Airport, Seoul
Similar Korean Air Flight 801, Nigeria Airways Flight 2120, Continental Express Flight 2574, Northwest Airlines Flight 85, West Caribbean Airways F
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Korean Air Cargo Flight 8509 was a Boeing 747-2B5F, registered HL7451 and bound for Milano-Malpensa Airport, that crashed due to instrument malfunction and pilot error on 22 December 1999 shortly after take-off from London Stansted Airport. The aircraft crashed into Hatfield Forest near the village of Great Hallingbury, close to but clear of some houses. All four crew on board were killed.
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- The aircraft
- INU failure and failed repair
- Flight crew
- In popular culture
Mayday air crash investigation s11e07 bad attitude korean air cargo flight 8509
The aircraft involved was a Boeing 747-200F freighter registered HL7451. Built on 4 April 1980, the aircraft had completed 15,451 flights with a total flight time of 83,011 hours before its fatal flight on 22 December 1999.
INU failure and failed repair
Following the plane's departure from Tashkent on the previous flight segment, one of its inertial navigation units (INUs) had partially failed, providing erroneous roll data to the captain's attitude director indicator (ADI or artificial horizon). The first officer's ADI and a backup ADI were correct, a comparator alarm called attention to the discrepancy, and in daylight the erroneous indication was easily identified. The ADI's input selector was switched to the other INU and the correct indications returned.
At Stansted, the engineers who attempted to repair the ADI did not have the correct Fault Isolation Manual available and did not think of replacing the INU. One of them identified and repaired a damaged connecting plug on the ADI. When the ADI responded correctly to its "Test" button, they believed the fault had been corrected, although this button only tested the ADI and not the INU. The ADI's input selector was left in the normal position.
The flight crew consisted of 57-year-old Captain Park Duk-kyu (Hangul: 박득규, Hanja: 朴得圭, RR: Bak Deuk-gyu, M-R: Pak Tŭkkyu), 33-year-old First Officer Yoon Ki-sik (Hangul: 윤기식, Hanja: 尹基植, RR: Yun Gi-sik, M-R: Yun Kishik), 38-year-old Flight Engineer Park Hoon-kyu (Hangul: 박훈규, Hanja: 朴薰圭, RR: Bak Hun-gyu, M-R: Pak Hun'gyu), and 45-year-old maintenance mechanic Kim Il-suk (Hangul: 김일석, Hanja: 金日奭, RR: Gim Il-seok, M-R: Kim Ilsŏk). The captain was a former Colonel (Korean: Daeryeong) and pilot in the Republic of Korea Air Force and a highly experienced airman, with a total of 13,490 flying hours – 8,495 of which were accumulated flying Boeing 747s. The first officer, in contrast, was relatively inexperienced with just 195 hours of flying experience on the 747 and a total of 1,406 flight hours. The flight engineer, like the captain, had a lot of experience flying 747s – 4,511 out of his 8,301 total flight hours were accrued in them.
It was dark when the plane took off from London Stansted Airport, with the captain flying. When the captain tried to bank the plane to turn left, his ADI showed it not banking and the comparator alarm sounded repeatedly. The first officer, whose instrument would have shown the true angle of bank, said nothing, although the flight engineer called out "bank". The captain made no response and continued banking farther and farther left. At 18:38, 55 seconds after take-off, Flight 8509's wing dragged along the ground, then the aircraft plunged into the ground at a speed of between 250 and 300 knots, in a 40° pitch down and 90° left bank attitude. The aircraft exploded on impact.
After the investigation, the United Kingdom's Air Accidents Investigation Branch issued recommendations to Korean Air to revise its training program and company culture, to promote a more free atmosphere between the captain and the first officer. Korean Air has not had a single fatal crash since this accident in 1999.