What happened
On September 30, 2016, at 12:32 UTC, a student pilot was conducting solo training flights at Poznań-Łastica Airport (EPPO). After completing several successful touch-and-go maneuvers and a period of rest, the pilot attempted a full landing on runway 28.
Upon touchdown, the Cirrus SR20GTS, registration SP-ATO, bounced twice on the runway surface. Following the second bounce, the pilot applied a correction that resulted in a heavy impact on the nose gear. This impact triggered a significant nose gear shimmy, causing the aircraft to lose directional control. The aircraft veered left off the runway onto the grass, approximately 30 meters from the edge of the paved surface. During the excursion, the left wing struck a lighted runway sign, causing substantial structural damage to the wing's leading edge. The pilot exited the aircraft immediately due to concerns regarding a visible oil leak, though no injuries were sustained.
The investigation
The PKBWL investigation examined the flight history, the pilot's training progress, and the mechanical state of the aircraft. The investigation confirmed that the student pilot was performing his fifth solo flight and had been cleared for solo operations by his instructor. The aircraft'1s maintenance documentation, weight and balance, and airworthiness were all found to be in order.
Investigators also analyzed the mechanical cause of the oil leak. They determined that the impact with the uneven terrain at the runway edge caused the nose gear strut to compress violently. This shock caused the lower engine cowling to strike the engine's oil drain valve, forcing it open and resulting in the leak. The investigation also noted that the aircraft's nose gear geometry, characterized by a significant forward tilt, makes it susceptible to shimmy oscillations under heavy loads.
Findings
- The primary cause of the accident was pilot error during landing, specifically an improper touchdown that resulted in multiple bounces.
- An incorrect attempt to correct the error led to a heavy nose gear impact, which initiated the nose gear shimmy.
- A crosswind component during the landing phase acted as a contributing factor.
- The specific design of the aircraft's nose gear geometry facilitated the onset of the shimmy oscillations.