What happened
On February 26, 2018, a Cirrus SF50 Vision Jet, registration N3AD, was performing a non-commercial delivery flight from Canada to Europe when it experienced a runway excursion at Nuuk Airport (BGGH), Greenland. The aircraft was landing on runway 05 under visual meteorological conditions with good visibility and light winds.
During the landing roll, the pilot applied the brakes but quickly encountered a total loss of pressure in the left brake pedal. This caused the aircraft to veer toward the right side of the runway. In an attempt to maintain directional control, the pilot released pressure on both pedals and even had the passenger attempt to apply the brakes, but the left-side failure persisted. Realizing the aircraft could not stop within the remaining runway length, the pilot opted to use only the right toe-brake. This maneuver caused the aircraft to run off the side of the runway and come to rest in a parallel snowbank. There were no injuries to the two occupants, though the aircraft sustained minor damage to the nose wheel door, left main wheel door, and wing profile fairings.
The investigation
The AIB Denmark technical investigation focused on the aircraft's braking system and the mechanical failure. Investigators examined a sealed brake tube fitting located beneath the flight crew seats. Upon breaking the torque seal, they discovered that the fitting could be tightened to the manufacturer's specifications, indicating it had not been properly secured during assembly.
Findings
- The primary cause of the partial brake failure was the insufficient torqueing of a brake tube fitting, which allowed hydraulic brake fluid to leak over time.
- While the aircraft manufacturer had quality control measures in place, the investigation concluded that these measures failed to detect the improperly secured fitting during the brake assembly process.
- The pilot's decision to steer the aircraft into the snowbank was considered an appropriate action that reduced the overall severity of the incident.
Safety action
Following the investigation, the aircraft manufacturer issued two safety communications to address the issue: Service Advisory SA-18-01 in March 2018 and Service Bulletin SB5X-32-03 in June 2018.