What happened
On August 27, 2016, a Gyroflug SC 01B-160, registration HB-UCV, was performing a private VFR flight at Bern-Belp Airport (LSZB). Following a scenic flight through the Bernese and Vaud Alps, the pilot initiated the landing sequence on runway 14. Immediately upon touchdown, the pilot applied both brakes but discovered that the left brake was non-functional.
Because ground steering in this aircraft type relies on differential braking of the main landing gear, the pilot was only able to steer toward the right. While the pilot initially managed to maintain the centerline using the independent left rudder, the effectiveness of the rudder diminished as the aircraft slowed and aerodynamic pressure decreased. To avoid striking runway lighting, the pilot steered the aircraft onto the adjacent grass strip by intentionally applying the functional right brake.
There were no fatalities and no injuries to the pilot or the passenger, and the aircraft sustained no damage.
The investigation
SUST examined the braking system of the HB-FCV to determine why the left brake failed. The investigation focused on the hydraulic disc brakes located on each main landing gear leg. Investigators inspected the transition piece that connects the rigid and flexible sections of the hydraulic brake lines.
Upon examination, the investigation identified cracks in the conical fitting at the flare—the point where the line transitions to the cone. These cracks allowed hydraulic fluid to escape, resulting in the loss of braking pressure on the left side.