What happened
On August 9, 2018, a student pilot conducting his first solo flight departed from runway 14 at Bern-Belp Airport (LSZB) in an Aero AT-3 R100, registration HB-SRB. The flight was part of a training syllabus for a Private Pilot License. After completing the first circuit, the pilot initiated an approach that was too high, resulting in a hard touchdown and a subsequent bounce on the runway.
In response to the bounce, the pilot executed a go-around. During the application of power, the aircraft veered sharply to the left. The aircraft entered a high bank angle at a low altitude, struck the ground near taxiway A, and came to rest beneath the wing of a parked commercial aircraft. The pilot escaped without injury, but the Aero AT-3 R100 was destroyed. The incident caused minor damage to the parked aircraft and a small fuel spill on the ground.
The investigation
SUST investigators examined the aircraft's maintenance history and flight characteristics. The investigation confirmed that the aircraft was in a valid condition for VFR operations, with the weight and center of gravity within permissible limits. No technical malfunctions or external factors, such as wind or turbulence, were identified as contributing to the accident.
To investigate potential design risks, SUST conducted test flights of the aircraft type. While the model demonstrated stable handling for training purposes, the tests revealed a specific tendency for the aircraft to roll to the left during a go-around if power is increased rapidly, particularly when approaching the stall speed. This behavior is consistent with the physics of a single-engine aircraft with a right-turning propeller.
Findings
- The pilot initiated the landing approach at an excessive height, leading to a high sink rate and a hard landing.
- The subsequent bounce created a challenging aerodynamic state for the go-around maneuver.
- The primary cause of the loss of control was unsuitable control inputs by the pilot during and after the increase in engine power.
- The aircraft's natural tendency to yaw/roll left during rapid power application was not adequately compensated for by the pilot.