What happened
On September 30, 2015, a Bombardier DHC-8-402 was performing a scheduled flight leg from Luxembourg to Hamburg via Saarbrücken. During the takeoff roll on runway 09 at Saarbrücken Airport, the aircraft reached rotation speed. As the pilot initiated the rotation, the landing gear lever was moved to the 'UP' position. This caused the landing gear to retract while the aircraft's nose was pitched up at approximately 5 degrees.
Without the support of the main landing gear, the aircraft's tail struck the runway. This impact caused the aircraft to bounce and subsequently slide on its fuselage for approximately 875 meters, coming to a halt about 425 meters before the end of the runway. The impact was severe enough to cause the cockpit voice recorder and flight data recorder to cease operation. Due to smoke and odors in the cabin, the crew immediately evacuated the aircraft. There were no fatalities and no injuries among the 16 passengers or the four crew members, though the aircraft sustained heavy damage.
The investigation
The BFU examined the aircraft's flight recorders, the cockpit voice recorder (CVR) transcripts, and the aircraft's mechanical systems. The investigation focused on the sequence of the takeoff callouts and the design logic of the landing gear retraction mechanism. Investigators also reviewed the airline's operational manuals and conducted simulator tests to replicate the event. The investigation also looked into the functionality of the inertia switch, which had cut power to the recorders during the high-G impact.
Findings
The primary cause of the accident was the premature retraction of the landing gear during the takeoff rotation. This action was a 'slip'—an unintended error during a routine, highly practiced task—performed by the pilot non-flying (PNF). The investigation found that the aircraft's design logic allowed the gear to retract as soon as the nose gear left the ground, even while the main gear was still in contact with the runway.
Contributing factors included:
- A reduced level of attention by the PNF during the takeoff phase.
- A disruption in the standard sequence of takeoff callouts.
- The design of the landing gear control logic, which permitted retraction when only the nose gear was airborne.
- The specific design of the gear lever, which required the simultaneous depression of a 'Lock Release' button, making it possible to inadvertently move the lever to the 'UP' position.