Lufthansa Flight 2904 was an

Airbus A320-200 Airbus SE (; ; ; ) is a European multinational aerospace corporation. Airbus designs, manufactures and sells civil and military aerospace products worldwide and manufactures aircraft throughout the world. The company has three divisions: '' ...

flying from

Frankfurt Frankfurt, officially Frankfurt am Main (; Hessian: , " Frank ford on the Main"), is the most populous city in the German state of Hesse. Its 791,000 inhabitants as of 2022 make it the fifth-most populous city in Germany. Located on it ...

, Germany to

Warsaw Warsaw ( pl, Warszawa, ), officially the Capital City of Warsaw,, abbreviation: ''m.st. Warszawa'' is the capital and largest city of Poland. The metropolis stands on the River Vistula in east-central Poland, and its population is officia ...

, Poland that overran the runway at Okęcie International Airport on 14 September 1993.

Incident description

Lufthansa Flight 2904 was cleared to land at Okęcie International Airport Runway 11 and was informed of the existence of

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizont ...

on the approach. To compensate for the

crosswind A crosswind is any wind that has a perpendicular component to the line or direction of travel. This affects the aerodynamics of many forms of transport. Moving non-parallel to the wind's direction creates a crosswind component on the object and th ...

, the pilots attempted to touch down with the aircraft banked slightly to the right and with a speed about 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 touchdown, the assumed

turned out to be a

tailwind A tailwind is a wind that blows in the direction of travel of an object, while a headwind blows against the direction of travel. A tailwind increases the object's speed and reduces the time required to reach its destination, while a headwind has ...

of approximately . With the resulting increased speed, the airplane hit the ground at approximately and far beyond the normal touchdown point; its right gear touched down from the runway threshold. The left gear touched down nine seconds later, from the threshold. Only when the left gear touched the

runway According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface (often asphalt, concre ...

did the ground spoilers and engine thrust reversers start to deploy, these systems depending on oleo strut ( shock absorber) compression. The wheel brakes, triggered by wheel rotation being equal to or greater than , began to operate about four seconds later. The remaining length of the runway (left from the moment when braking systems had begun to work) was too short to enable the aircraft to stop. 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 and rolled 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. Two of 70 occupants died, including the training captain (seated in the right seat) who died on impact and one passenger who was unable to escape because he lost consciousness from the smoke in the cabin.

Causes of the accident

The main cause of the accident was the incorrect decisions and actions of the flight crew. Some of these decisions were made based on wind shear information that was received by the crew. The wind shear 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. Contributing to the cause was the lack of current wind information at the tower. For that reason, no up-to-date wind information could be transmitted to the crew. Further additional causes involved certain design features of the aircraft. Computer logic prevented the activation of both ground spoilers and thrust reversers until a minimum compression load of at least 6.3 tons was sensed on each main landing gear strut, thus preventing the crew from achieving any braking action by the two systems before this condition was met. Lufthansa Airbus A320 D-AIPN at Heathrow 1991

Lufthansa Airbus A320 D-AIPN at Heathrow 1991

Aircraft systems

To ensure that the thrust-reverse system and the

spoiler Spoiler is a security vulnerability on modern computer central processing units that use speculative execution. It exploits side-effects of speculative execution to improve the efficiency of Rowhammer and other related memory and cache attacks. Ac ...

s are only activated in a landing situation, the software has to be sure the aeroplane is on the ground even if the systems are selected mid-air. The spoilers are only activated if there is at least 6.3

ton Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses. Mainly it describes units of weight. Confusion can arise because ''ton'' can mean * the long ton, which is 2,240 pounds ...

s on each main landing gear strut or if the wheels of the plane are turning faster than . The thrust reversers are only activated if the first condition is true. There is no way for the pilots to override the software decision and activate either system manually. In the case of the Warsaw accident, neither of the first two conditions was fulfilled, so the most effective braking system was not activated. Because the plane landed inclined (to counteract the anticipated crosswind), the required pressure of 12 combined tons on both landing gears necessary to trigger the sensor was not reached. The plane's wheels did not reach the minimum rotation speed 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. Because of the braking distances in the heavy rain, the aircraft could not stop before the end of the runway. The computer did not actually recognize that the aircraft had landed until it was already 125 meters beyond the halfway point of Runway 11. Flight 29041129

Passengers and crew

As a result of the impact, a fire broke out and penetrated into the cabin, killing one of the passengers. The co-pilot also died as a result of the collision. A total of 51 people were seriously injured (including two crew members), and five were slightly injured.

References

External links