What happened
On March 27, 2022, an American Aviation AA-1B (modified) departed from the Konstanz airfield (EDTZ) for a flight to Aschaffenburg. The aircraft, which was carrying a pilot and one passenger, attempted a takeoff from the grass runway 30. During the initial climb, the aircraft struggled to gain altitude and exhibited an unstable flight condition. Witnesses observed the aircraft lifting off with difficulty and failing to maintain a stable attitude. The aircraft eventually drifted toward a wooded area, where it struck trees and impacted the ground in an uncontrolled, nose-high attitude. The collision resulted in two serious injuries and the total destruction of the aircraft.
The investigation
The BFU investigation focused on the aircraft's performance, the pilot's experience, and the takeoff conditions. Investigators analyzed flight data recovered from a tablet running SkyDemon, which revealed that the aircraft was operating in a high-drag, low-speed regime, specifically the "backside of the power curve." The investigation also examined the aircraft's weight and balance, discovering that the pilot had been using incorrect maximum takeoff weight (MTOM) data in his navigation software. While the aircraft was technically airworthy, the investigation found that the actual takeoff mass was approximately 741 kg, significantly exceeding the correct MTOM of 680 kg established by the aircraft's Supplemental Type Certificate (STC).
Findings
Several contributing factors led to the accident:
- Overweight takeoff: The aircraft was approximately 60 kg over its maximum allowable takeoff weight.
- Inaccurate performance data: The pilot relied on incorrect MTOM values, likely due to an error in a previous weighing report that was inadvertently adopted into his flight planning software.
- Lack of specialized training: While the pilot had significant general experience, he lacked specific training in handling the aircraft's characteristics during edge-of-envelope flight conditions, such as stalls or unusual attitudes.
- Failure to execute an aborted takeoff: The pilot failed to recognize the unstable climb and did not utilize the visible runway markings to initiate a timely abort once the aircraft failed to accelerate.
- Improper takeoff technique: The pilot likely did not apply the recommended soft-field takeoff techniques required for a grass surface.
- Environmental factors: A slight tailwind and the presence of trees encroaching on the obstacle clearance zone contributed to the loss of control.