Updated: Nov 28, 2021
Birdstrikes on an aircraft are a regular occurrence, figures vary but for example, the FAA estimates 10.000 birdstrikes occur each year. On this day in 2004, a KLM - Royal Dutch Airlines Boeing 737-406 took off from Schiphol Amsterdam Airport destined for Barcelona and suffered a birdstrike
PH-BTC, Boeing 737-406 taking off (date unknown)
At 15:46 take-off was initiated on Runway 18L, 1 second after the "Rotate" call a bird hit the nose landing gear. At that time the aircraft had reached a speed of 152 knots (175 mph - 281 kph) and a pitch up attitude of ~2 degrees. The birdstrike was noticed by the crew as it could be heard in the flight deck. ATC was informed and the landing gear was selected up, ATC reported back after some time that some remains of a small bird were found on the runway. The aircraft continued its climb to cruise level with all indications normal. Via ACARS the crew informed several company departments of the birdstrike, stating that the operation was not affected. The flight continued to Barcelona without any further issues.
After a normal descend towards Barcelona the landing gear was selected down on the approach with the gear indicating down and locked, "three greens". At 17:40 the main landing gear touched down in the touchdown zone of Runway 25R of Barcelona Airport, the speed was 140 knots (160 mph -260 kph). The nose was lowered, the auto brake had activated and the reverse thrust was selected.
As soon as the nosegear touched down the aircraft pulled slightly to the left, which was arrested by the PF (Pilot Flying). With speed bleeding off, more and more rudder input was required to stop the aircraft from deviating to the left. The (reverse) thrust was checked and found symmetrical but at one point with full right rudder, the aircraft started drifting to the left. (under ISA Vmcg = 159 knots for a Boeing 737-400)* The aircraft continued to deviate to the left, even with the crew applying differential breaking. At 17:41 the aircraft left the paved area of the runway at a ground speed of approximately 82 knots (airspeed ~90 knots). when the aircraft entered the unpaved area adjacent to the runway the nose landing gear collapsed rearward and the lefthand main landing gear separated. Just before a 15 meter (49 feet) wide, 1,5 meter deep drainage canal, the aircraft came to a stop.
The final position of the aircraft close to the edge of the canal
The captain ordered the first officer to start the evacuation procedure and left the cockpit to assess the situation in the cabin. Shortly after the aircraft came to a stop the captain selected the EVAC(uation) signal to on and gave the evacuate command via the Passenger Address system. The aircraft was promptly evacuated, 5 passengers sustained light injuries during the evacuation. An investigation was launched by the Civil Aviation Accident and Incident Investigation Commission (CIAIAC), Spain.
The cause of the accident was described in the investigation report as follows (copied from the official investigation report:
It is considered that the accident probably happened because during the takeoff a bird strike broke one of the cables of the nose wheel steering system of the aircraft and jammed the other, which made that the nose wheels were rotated to the left during landing, causing a veering to the left that could not be arrested by full rudder deflection as the aircraft decelerated. The subsequent application of brakes and other actions by the crew could not avoid that the aircraft went outside the runway surface. Contributing to the breaking of the cable was the fact that it was severely worn locally. The wear could be traced back to the incorrect application of grease to the cable system during maintenance.
View of the front part of the NLG after aircraft recovery. The NSWB cable was found broken. The NSWA cable did not break, although it was also worn in the zone of the trunnion seal and its pulley had bird remains
The aircraft was considered Damaged Beyond Repair and subsequently broken up at Barcelona.
The full (107 pages) investigation report can be found by clicking here
* Vmcg = V minimum Control Ground (the minimum speed where the aircraft can be controlled aerodynamically on the ground, ie. the flight controls are effective)