Lufthansa Flight 540

Lufthansa Flight 540

Accident summary
Date	20 November 1974
Type	Design flaw, flight crew error
Site	Kenyatta International Airport, Nairobi, Kenya
Passengers	140
Crew	17
Fatalities	59
Survivors	98
Aircraft type	Boeing 747-130
Aircraft name	Hessen
Operator	Lufthansa
Tail number	D-ABYB
Flight origin	Frankfurt
Stopover	Jomo Kenyatta International Airport, Nairobi
Destination	Jan Smuts International Airport, Johannesburg

Lufthansa Flight 540 was a scheduled commercial flight for Lufthansa operated with a Boeing 747-130, 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 ever crash and third hull loss of a Boeing 747.

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 ascent 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 3,700 feet (1,100 m) 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. Of the 157 people aboard, 59 perished (55 passengers and 4 crew members).

Efforts by crew members saved a number of lives. Thomas C. Scott, a commercial pilot working the flight as a cabin crew member, was credited with saving the lives of a dozen passengers before the fuselage exploded by carrying the injured and escorting the dazed.

The cause of the crash was determined to be a stall caused by the leading edge flaps having been left in retracted position. Without leading edge flaps deployed, the aircraft's stalling angle of attack was much lower, especially at a hot and high airport like Nairobi's with its airport elevation of 5,327 feet (1,624 m). The thinner air at higher altitudes generates less lift and further degrades the aircraft's ability to handle high angles of attack, as well as reducing the thrust provided by the 747's four turbofan engines.

The elevation and temperature at the airport were within the capability of the 747, but only with leading and trailing edge flaps extended. With the leading edge flaps retracted, the aircraft lacked sufficient lift and thrust to continue climbing once out of the ground effect found near the surface. The flight engineer was found to have failed to open the engine bleed air valves as required on the pre-flight checklist. This prevented bleed air from flowing to the 747's pneumatic system and since the leading edge flaps on the 747 are pneumatically driven, kept it from deploying the leading edge flaps for takeoff.

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. 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 such conditions existed prior to takeoff.

Bibliography

Moorhouse, Earl : Wake Up, It's a Crash! The story of the first ever 747-Jet disaster. A survivor's account. London Corgi 1982 ISBN 0552119326

External links

• Accident description at the Aviation Safety Network
• Photos of the crashed airliner from AirDisaster.com
• Pre-crash photos of the airliner at airliners.net