What happened
On December 2, 2001, a Dornier 328-100 was performing a positioning flight from Braunschweig to Bremen with a crew of three and no passengers. The aircraft landed on runway 27 at Bremen using an ILS approach, encountering a light tailwind. Immediately after touchdown, the pilot in command engaged the reverse thrust.
As the aircraft decelerated to a ground speed of approximately 60 knots, it began to drift slightly to the right. The pilot attempted to correct this using the rudder, which caused the aircraft's longitudinal axis to swing left by up to 15 degrees. A subsequent corrective maneuver resulted in an abrupt and violent swing to the right, rotating the aircraft's heading by 135 degrees. During this excursion, the left main landing gear collapsed, and the left wing and propeller made contact with the runway surface. The aircraft eventually came to a stop on the right side of the runway. There were no injuries to the crew, but the aircraft sustained heavy damage.
The investigation
The BFU examined the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the sequence of events. The FDR revealed that during the reverse thrust phase, the airspeed indications became highly unreliable due to the interaction between the reverse thrust airflow and the tailwind. Specifically, the airspeed dropped to approximately 38 knots while the ground speed remained at 60 knots.
The investigation also analyzed the aircraft's handling characteristics. Testing by the manufacturer confirmed that during reverse thrust operations with a tailwind, the rudder's effectiveness is compromised, and the aerodynamic forces can lead to increased and frequent oscillations. The pilot reported that the rudder required unusually high physical force to maintain a correction, and the sudden high restorative forces from the pedals contributed to the pilot overcontrolling the aircraft.
Findings
- The airspeed indications in the cockpit became unreliable during the landing roll because the reverse thrust and tailwind vectors significantly altered the pitot pressure.
- The crew did not follow established procedures, which required reducing thrust to idle once the aircraft reached 60 knots.
- The Dornier 328 became directionally unstable during the reverse thrust phase under tailwind conditions.
- The pilot overcontrolled the aircraft due to the unexpected aerodynamic forces and the high physical effort required to operate the pedals.
- Discrepancies between the Airplane Flight Manual (AFM) and the airline's Operating Manual (AOM) regarding reverse thrust usage and airspeed errors contributed to the crew's decision-making.