Investigation Summary
The accident occurred during a scheduled stopover in Nairobi. The high elevation of Embakasi Airport (5,327 feet) already reduced the aerodynamic performance of the aircraft, making proper wing configuration vital. During the pre-takeoff phase, the flight engineer failed to open the bleed air valves that powered the pneumatic system for the leading-edge slats. Although the pilots moved the flap lever to the 10-degree position, only the trailing-edge flaps deployed. The leading-edge slats remained retracted. Because the 747's takeoff configuration warning system at the time only monitored the position of the flap lever and the trailing-edge flaps, no alarm sounded. Upon rotation, the aircraft lacked the necessary lift to climb effectively. The crew felt a heavy buffeting vibration, which the captain mistakenly attributed to a wheel imbalance or bird strike. Suspecting a landing gear issue, he retracted the gear, further deteriorating the aircraft's aerodynamic state. The 747 reached a maximum height of only 100 feet before sinking back to the ground.
Final Conclusions
The primary cause was the crew's failure to ensure the leading-edge slats were extended for takeoff, compounded by a failure to follow the checklist correctly. A significant contributory factor was a design deficiency in the Boeing 747's warning systems, which did not provide a distinct alert if the leading-edge slats failed to deploy despite the flap lever being in the correct position. The crash resulted in 59 deaths, primarily due to the post-impact fire and explosions in the left wing.
Photographic Evidence (1)
Video Analysis
Lufthansa Flight 540: The 747 Crash That Changed Aviation — A detailed look at the first fatal Boeing 747 crash, exploring how a simple pneumatic valve oversight led to a tragedy in Nairobi and forced a redesign of cockpit warning systems.
If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Leading-edge Slats
Aerodynamic surfaces on the front of the wing that increase lift at low speeds; they failed to deploy because the pneumatic system was not activated.
Takeoff Configuration Warning
A system designed to alert pilots if the plane is not configured for flight; in 1974, it did not monitor the actual position of the leading-edge slats.
Pneumatic Bleed Air System
The system that provides compressed air from the engines to power various components, including the actuators for the leading-edge slats.
Interesting Facts
- 01This was the first fatal accident involving a Boeing 747 since the type entered service in 1970.
- 02The aircraft, named 'Hessen', was only four years old and had logged 16,781 flying hours.
- 03The cockpit crew survived the crash because the nose section remained relatively intact after breaking away.
- 04Nairobi's high altitude (over 5,300 feet) meant the aircraft had a much lower margin for error during takeoff due to thinner air.
- 05The crash remains the deadliest aviation accident in Kenyan history.
Safety Actions & Advisories
Warning System Redesign
Boeing modified the takeoff configuration warning system to ensure an alarm sounds if the leading-edge slats are not extended, regardless of the flap lever position.
Checklist Procedures
Lufthansa and other 747 operators revised pre-flight checklists to include a specific verification that the pneumatic valves for the slats are open.