What happened
On March 4, 2021, a student pilot was conducting a solo navigation flight from Mollis to Bern-Belp in a Breezer B600, registration HB-WZB. After receiving instructions from the air traffic controller to approach runway 32, the pilot transitioned from the previously expected runway 14.
During the final approach, the pilot noted the aircraft was flying above the desired glidepath, observing four white lights on the PAPI. While the approach was stabilized at approximately 60 knots, the airspeed dropped to about 50 knots in the final stages. As the aircraft neared the runway, the pilot retarded the throttle to idle and initiated the flare. The aircraft initially touched down on the main gear with a positive pitch angle at approximately 45 knots.
Following the initial touchdown, the aircraft bounced back into the air. The pilot attempted to correct the pitch by applying elevator inputs, which led to a series of subsequent bounces. The aircraft struck the runway a total of five times, with each impact increasing in intensity. On the fifth impact, the nose gear collapsed, causing damage to the nose gear fairing, the nose wheel, the engine cowling, and the fuselage floor. The pilot, who was uninjured, successfully exited the aircraft.
The investigation
SUST examined the pilot's flight history, radio communications, webcam footage of the landing, and physical tracks left on the runway. The investigation reviewed the aircraft's Pilot Operating Handbook (POH), which specifies a landing speed of 54 knots for flap setting 2 and mandates that the nose gear should be lowered only at low speeds after a gentle touchdown on the main gear.
Findings
- The final approach was conducted at a slightly high speed but was otherwise stabilized.
- The flare was initiated too late, causing the aircraft to touch down at a speed significantly above the minimum flying speed.
- The pilot's attempts to counteract the resulting bounces with elevator inputs created a pilot-induced oscillation (PIO), specifically a phenomenon known as "porpoising."
- The sequence of bounces became uncontrollable due to the corrective inputs, ultimately leading to the structural failure of the nose gear.