1. Aircraft and crew
     Aircraft    Crew  

2. Accident

3. Cause

4. Aftermath

5. See also

6. Bibliography

7. References

8. External links

Lufthansa Flight 540 was a scheduled commercial flight for Lufthansa operated with a Boeing 747-100, carrying 157 people (140 passengers and 17 crew members). The flight was operating the final segment of its Frankfurt–Nairobi–Johannesburg route. On 20 November 1974 it crashed and caught fire shortly past the runway on takeoff. This was the first fatal accident and third hull loss of a Boeing 747. This was also the third fatal accident involving a wide-body aircraft, after Eastern Air Lines Flight 401 in 1972 and the crash of Turkish Airlines Flight 981 earlier in 1974. To date, it is also the deadliest plane crash to occur on Kenyan soil as well as the deadliest plane crash in Lufthansa's history.

Aircraft and crew

Aircraft

The aircraft involved was a Boeing 747-130 registered as D-ABYB and was named Hessen. It was the second 747 to be delivered to Lufthansa. It made its first flight on 30 March 1970 and was delivered to Lufthansa on 13 April the same year. The aircraft was powered by four Pratt and Whitney JT9D-7 turbofan engines. The aircraft had 16,781 flying hours at the time of the accident.

Crew

The flight crew consisted of 53-year-old captain Christian Krack (who had more than 10,000 flying hours, with 1,619 hours in the Boeing 747), 35-year-old first officer Joachim Schacke (flying experience unknown) and 51-year-old flight engineer Rudi Hahn (flying experience unknown).^[1]

Accident

As the aircraft was making its takeoff from runway 24 at the Jomo Kenyatta International Airport in Nairobi, the pilots felt a buffeting vibration. The captain continued the climb and retracted the landing gear. However, as this was being done, the aircraft started to descend and the stall warning system light came on. The aircraft continued to descend and approximately {{convert|3700|ft|m|-2}} from the end of the runway, the 747 grazed bushes and grass. It then struck an elevated access road and broke up. The left wing exploded and fire spread to the fuselage. 55 of the 140 passengers and 4 of the 17 crew members were killed.

Cause

The cause of the crash was determined to be a stall caused by the leading edge slats (strictly speaking, Krueger flaps) having been left in the retracted position. Even though the trailing edge flaps were deployed, without the slats being extended the aircraft's stall speed was higher and the maximum angle of attack was lower. As a result, the aircraft was unable to climb out of ground effect. The flight engineer was found to have failed to open the slat system bleed air valves as required on the pre-flight checklist. This prevented bleed air from flowing to the 747's pneumatic slat system and, since the leading edge slats on the 747 are pneumatically driven, kept it from deploying the leading edge slats for takeoff. The take-off warning system that would have sounded an alarm due to the flaps not being lowered did not have a separate warning that the slats' pneumatic valve had not been opened by the flight engineer.

The faulty state of the slats should by design have been indicated by yellow warning lights: one for the pilot, and eight for the flight engineer. However, both crew members stated in court that these lights had been green. Three possible explanations have since been offered for this inconsistency: that the morning sun was blinding the cockpit crew and thus hampered color perception, that a construction error could have caused green lights despite the retracted slats, and that the crew lied. None of these possibilities could be conclusively proven.^[2][3] The flight crew was blamed for not performing a satisfactory pre-take-off checklist, but the accident report also faulted the lack of adequate warning systems which could have alerted the crew to the problem.^[4] Two previous occurrences of this error had been reported, but in those cases the pilots had been able to recover the aircraft in time. After this third, deadly incident, Boeing added systems to warn pilots if the slat valve had not been opened prior to takeoff.

Captain Krack and flight engineer Hahn were dismissed from Lufthansa shortly after, but their dismissals were overturned by a labor court, as there was no investigation report available to rule out the chances of a technical defect.^[4]

Flight engineer Hahn was charged with criminal negligence, but was acquitted in 1981.^[5]

Aftermath

Lufthansa gave the name Hessen to a Boeing 747-400 that was delivered in 1998.^[6] The registration of the aircraft involved, D-ABYB, has not been issued since.^[7]

See also

• British European Airways Flight 548
• Northwest Airlines Flight 255
• LAPA Flight 3142
• Spanair Flight 5022
• Delta Air Lines Flight 1141
• Mandala Airlines Flight 091

Bibliography

• {{cite book|last=Moorhouse|first=Earl|title=Wake Up, It's a Crash! The story of the first ever 747-Jet disaster. A survivor's account|publisher=Corgi|location=London|year=1982|isbn=0-552-11932-6|ref={{harvid|Moorhouse|1982}}}}

The final report is this work:

• "Report on Accident to Boeing 747 Registered D-ABYB which occurred on 20th November 1974 at Nairobi Airport, Kenya." East African Community Accident Investigation Branch (Nairobi), 1976. Worldcat entry.

References

External links

• {{ASN accident |id=19741120-0}}
• [https://web.archive.org/web/20091202045601/http://www.airdisaster.com/photos/lh540/photo.shtml Photos of the crashed airliner from AirDisaster.com]
• Pre-crash photos of the airliner at airliners.net
• Cockpit Voice Recorder transcript and accident summary

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