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Lufthansa B747 crash in Nairobi 40 years ago

40 years ago today, a Lufthansa Boeing 747 crashed soon after takeoff from Nairobi Airport. This was the first fatal accident involving a Boeing 747, a new model back then.

Officers of the Kenya Police at the wreckage of Flight 540 in Nairobi, 20th November 1974.

Officers of the Kenya Police at the wreckage of Flight 540 in Nairobi, 20th November 1974.

The crash of Lufthansa Flight LH 540 has all but faded from memory. Four years after the accident, Nairobi Airport moved into a brand new terminal building and was renamed the Jomo Kenyatta International Airport (JKIA). Most – if not all – the people who witnessed the accident are no longer working at the airport.

LH 540 is significant in several ways. It was the first fatal accident involving the Boeing 747, a model that began commercial service four years prior to the accident. The Nairobi crash forced Boeing to enhance B747 flight deck warning systems which, until the crash, were considered inadequate.

The crash of flight LH 540 was perhaps the deadliest plane crash to occur in Kenya. Out of 157 passengers and crew, 59 people died while 98 were injured. Amazingly, the pilots, crew and some of the passengers walked away with little injury.

Why exactly did flight LH 540 crash?

According to the accident report from the East African Community which had jurisdiction at the time, the crash was caused by a combination of pilot error and inadequate warning systems in the cockpit.

Flight LH 540 stopped over in Nairobi on the way from Frankfurt to Johannesburg. On 20th November 1974, the flight was being performed by a Boeing 747-100, registered D-ABYB. The particular aircraft was slightly over four years old and was one of Lufthansa’s first 747s.

D-ABYB, the ill-fated aircraft, seen here in 1970.

D-ABYB, the ill-fated aircraft, seen here in 1970.

According to SkyNet Special Reports, the aircraft’s engines were started at 07.42 hrs local time. In the cockpit were Commander Captain Christian Krack, Co-pilot Joachim Schacke and Flight Engineer Rudi Hahn. There were 157 people aboard including the crew, giving a total estimated take-off weight, including baggage and freight, of 254,576kg. The co-pilot was designated the handling pilot for the first sector of flight.

Excerpts of conversations with Nairobi tower show the pilots chose to take off on runway 24. During takeoff, the crew felt vibration or buffeting and suspected engine trouble. The Commander thought it was an imbalance of the landing gear, and proceeded to raised it.

The co-pilot, who was handling the aircraft, noticed a complete lack of acceleration and lowered the nose in an attempt to maintain airspeed. The aircraft lost altitude and the rear fuselage made contact with the ground approximately 1,120 metres beyond the departure end of runway 24. Parts of the aircraft struck an elevated road 114 metres further on and it started to break up.

The main portion of the aircraft skidded an additional 340 metres during which time it turned to the left through approximately 180 degrees. The aircraft was destroyed by impact and subsequent fire.

Actual cause of the crash

A report by the East African Community and quoted by the Federal Aviation Administration (FAA) says that LH 540 stalled on taking off. Leading edge slats were in a retracted position and had not been extended because the pneumatic system which operated them was off. Trailing edge flaps were deployed, but without leading edge slats being in an extended position, the aircraft’s stall speed was higher and the maximum angle of attack was lower. The stall explains the buffeting the pilots heard while taking off.

Additionally, because of the elevation of Nairobi Airport (5,327 feet above sea level) and the high ambient temperature, the thinner air was responsible for reduced aerodynamic performance. The elevation and temperature at the airport were within the capability of the 747, but only with both leading and trailing edge flaps extended.

However, there is more to the story than pilot error. It seems that Boeing had not installed adequate aural systems in the cockpit to warn pilots when leading edge slats were not extended. After the crash of LH 540, Boeing added the necessary aural warning systems.

Another factor that may have contributed to the crash was the Captain’s decision to raise the landing gear when he thought it was responsible for vibrations felt when taking off. In reality, there is a transient increase in drag when the landing gear is raised as the main gear doors lower into the airstream prior to the entire undercarriage retracting. This increase in drag may have been critical in slowing down the aircraft and worsening the stall.

All in all, the flight crew failed to observe standard operating procedures. They did not properly adhere to the checklist and failed to notice that leading edge slats were still retracted.

For a transcript of conversation between the pilots and Nairobi Tower, please click here.

For additional analysis, click here (PDF).

It’s worth noting that Lufthansa is using the old D-ABY* registration series on their new Boeing 747-800s. However, D-ABYB has been skipped due to flight LH 540.

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