What happened
On 19 October 2018, a Grob G109A, registration G-CINK, was conducting a training flight at Deenethorpe Airfield in Northamptonshire. During the landing phase, the student pilot failed to pull the airbrake lever far enough back to engage the mainwheel brakes effectively. As the aircraft slowed, the instructor issued three verbal prompts for "more brake." Misinterpreting these instructions, the student pilot engaged the aircraft's ratchet-style parking brake. This caused sudden, uncontrolled braking, leading the aircraft to tip forward. The impact resulted in a broken propeller, damage to the nose cowling, and damage to the canopy. There were no injuries to the two crew members on board.
The investigation
The investigation examined the specific braking mechanics of the Grob G109A. This model utilizes a dual-function lever where pulling the lever deploys airbrakes and further rearward movement applies the mainwheel brakes. The investigators established that the student pilot did not provide sufficient deflection to the lever to achieve necessary braking force. The instructor's testimony revealed that while they intended to intervene more forcefully earlier, they initially sought to preserve the student's confidence following a successful landing. The investigation also noted that the instructor's verbal commands were interpreted by the student as a prompt to use the parking brake rather than more lever pressure.
Findings
- The student pilot misidentified the instructor's verbal prompts for increased braking as a signal to engage the parking brake.
- The application of the parking brake caused hard, uncontrolled braking that the instructor could not immediately counteract.
- The instructor's use of non-explicit terminology contributed to the student's error.