Lufthansa Flight 2904
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| Summary | |
|---|---|
| Date | September 14, 1993 |
| Type | Overshot runway, Pilot Error |
| Site | Warsaw, Poland |
| Passengers | 64 |
| Crew | 6 |
| Injuries | 68 |
| Fatalities | 2 |
| Survivors | 68 |
| Aircraft type | Airbus A320-200 |
| Operator | Lufthansa |
| Tail number | D-AIPN |
Lufthansa Flight 2904 was an Airbus A320-200 which overran the runway, in Okęcie International Airport on September 14, 1993. It was a flight from Frankfurt, Germany to Warsaw, Poland.
Contents |
[edit] Description of the incident
Lufthansa Flight 2904 was cleared to land on Okęcie International Airport and was told of the existence of wind shear on the approach. To compensate for the windshear, the pilots attempted to touch down with the aircraft banked slightly to the right. Additionally they landed with a speed about 20 knots (37 km/h) faster than usual. According to the manual, this was the correct procedure for the reported weather conditions. But the weather report was not up to date. At the moment of touch down, the assumed crosswind turned out to be a tailwind. Due to the tailwind of approximately 20 knots (37 km/h) and the increased speed the airplane hit the ground at approximately 170 knots (310 km/h) and far beyond the normal touch down point. The aircraft's right gear touched down 770 m from the runway 11 threshold. The left gear touched down 9 seconds later, 1525 m from the threshold. Only when the left gear touched the runway did the ground spoilers and engine thrust reversers deploy, these automatic systems depending on oleo strut (shock absorber) compression. The wheel brakes, triggered by wheel rotation being equal to or greater than 72 knots (133 km/h) began to operate after about 4 seconds. Seeing the approaching end of the runway and the obstacle behind it, the pilot steered the aircraft off the runway to the right. The aircraft departed the runway at a speed of 72 knots (133 km/h) and rolled 90 m before it hit the embankment and an LLZ aerial with the left wing. A fire started in the left wing area and penetrated into the passenger cabin. Only two of 70 occupants died in this accident, the co-pilot who died on impact and one passenger who was unable to escape because he lost consciousness as a result of the smoke in the cabin.
[edit] Causes of this accident
The cause of the accident was incorrect decisions and actions of the flight crew, the actions of the crew were also affected by design features of the aircraft. The design features affected the way the braking system worked. Some of the incorrect decisions were taken when information about windshear was received by the crew. The windshear was produced by the front passing over the airport; accompanied by intensive variation of wind parameters as well as by heavy rain on the runway itself.
[edit] Details about the design features of the aircraft
To ensure that the thrust-reverse system and the spoilers are only activated in a landing situation, all of the following conditions have to be true for the software to deploy these systems:
- there must be weight of over 12 tons on each main landing gear strut
- the wheels of the plane must be turning faster than 72 knots (133 km/h)
- the thrust levers must be in the idle (or reverse thrust) position
In the case of the Warsaw accident neither of the first two conditions was fulfilled, so the most effective braking system was not activated. Point one was not fulfilled, because the plane landed inclined (to counteract the possible windshear). Thus the pressure of 12 tons on both landing gears required to trigger the sensor was not reached. Point two was also not fulfilled because of a hydroplaning effect on the wet runway.
Only when the left landing gear touched the runway did the automatic aircraft systems allow the ground spoilers and engine thrust reversers to operate. Due to the braking distances in the heavy rain the aircraft could not stop before the end of the runway. The computer did not actually know the aircraft had landed until it was already 125 meters beyond the half way point of runway 11.
