What happened
On March 23, 2022, a Cessna F 172N took off from Bonn-Hangelar airport for a scheduled maintenance test flight. The flight was intended to verify recent repairs, which included the replacement of several control components. Shortly after takeoff from runway 11, the pilot experienced a lack of response from the elevator. In an attempt to correct the flight path, the pilot adjusted the trim to a "nose-up" (tail-heavy) position. However, due to a mechanical error, this action caused the aircraft to pitch down abruptly.
The aircraft failed to gain sufficient altitude, striking trees in the departure area before hitting a field. The momentum carried the aircraft across an embankment, where it collided with a garden house, resulting in the aircraft flipping onto its back. The pilot and a passenger both sustained two broken ribs.
The investigation
The BFU investigation focused on the control system and the recent maintenance performed on the aircraft. Investigators examined the wreckage and found that the elevator trim tab was functioning in reverse; moving the trim wheel toward a nose-up setting actually caused the tab to move in a direction that forced the nose down.
While the maintenance team had followed the service manual and performed a dual-person check (one in the cockpit and one at the tail), the BFU determined that a communication failure occurred during this verification process. Furthermore, the pilot's pre-flight inspection, while following the standard checklist, did not include a specific check of the trim tab's direction, as that specific movement was not explicitly required by the checklist used that day.
Findings
- The primary cause of the accident was the incorrect installation of the elevator trim system, which caused the trim tab to move in the opposite direction of the cockpit controls.
- The pilot's decision to attempt to correct the flight path using the trim, rather than initiating an immediate aborted takeoff, contributed to the loss of control.
- A communication breakdown during the post-maintenance inspection prevented the reversed trim movement from being detected.
- The pilot's reliance on a standard checklist that lacked a specific trim direction check limited the ability to identify the error during the pre-flight walkaround.