What happened
On September 8, 2005, a Schleicher ASK-21 glider, registration PH-1334, was performing a local instructional flight at Terlet airfield. The flight, which included an instructor and a student, proceeded normally until the landing phase. As the aircraft touched down on the paved path, the instructor attempted to use the main wheel brake. While the aircraft initially slowed down, the instructor reported that the main wheel brake subsequently failed to function.
In an attempt to decelerate, the crew fully opened the airbrakes. However, the aircraft failed to slow as expected. While attempting to steer away from two parked gliders, the aircraft struck a parked passenger car with its left wing. The momentum of the glider continued until the nose struck a hangar door and the right wing impacted a hangar wall. During the excursion, the glider also struck two bystanders on the ground; one person managed to dodge the wing, while the other sustained minor injuries from the impact.
The investigation
Investigators examined the mechanical state of the braking system following the incident. A technician confirmed that there was no detectable brake pressure on the control lever immediately after the accident. While the hydraulic reservoir was sufficiently filled with the correct fluid and no leaks were visible, subsequent inspections by the aircraft owner found the braking system to be fully operational with normal pressure. Due to these conflicting findings, the OVV could not determine a definitive cause for the temporary loss of braking pressure.
Findings
- The investigation could not establish a definitive cause for the temporary failure of the braking system.
- The instructor had completed 13 prior flights that day in the PH-1334 without any noted issues with the brakes.
- The landing rollout was planned in a manner that left insufficient margin for error, as the instructor intended to stop near the hangar to minimize the distance needed to move the aircraft inside.
- The instructor's path was obstructed by parked gliders, a passenger car, and bystanders, leaving no safe path for evasion once the brake failure occurred.
Safety action
- A landing rollout should always be planned to be free of obstacles to ensure the pilot is prepared for unforeseen mechanical failures or emergencies.