Accident Description
On 13 April 2017 at 16:10 LMT, a Tecnam P2008-JC operated by LOT Flight Academy was conducting training flights for a PPL(A) license with an instructor and student on board. During landing on runway 21 at EPPT, in the final stage of the landing roll, strong lateral vibrations of the nose landing gear developed. A cracking sound was heard, and the nose of the aircraft dropped, contacting the engine cowling with the ground. The rotating propeller struck the runway surface, resulting in destruction of its blades. The aircraft came to a stop after approximately 5 meters. The two occupants were not injured and exited the aircraft unassisted.
Aircraft Information
The aircraft was a Tecnam P2008-JC. The total flight time at the time of the event was 828 hours and 17 minutes. The aircraft was subject to maintenance bulletin SB 215-CS-Ed.1 Rev.0, which required a visual inspection of the nose landing gear every 25 flight hours. The last such inspection was performed on 4 April 2017 at 802.40 flight hours.
Investigation and Findings
After the event, the airport manager, police, and the Polish State Commission on Aircraft Accident Investigation (PKBWL) were notified. The crew was tested for alcohol (result 0.00‰). Traces on the asphalt runway indicated a normal two-point touchdown. Following nose gear contact, sinusoidal marks appeared, indicating a sudden onset of severe lateral vibrations leading to the fracture. On 14 April 2017, in coordination with PKBWL, the nose landing gear was removed by Bartolini Air for examination. Damage included destruction of the nose landing gear and propeller, damage to the engine cowling, and a local penetration of the fuselage skin at the contact point with the fractured gear.
Detailed examination of the fractured nose gear strut at the Institute of Aviation in Warsaw revealed a ductile fracture due to overstress. The fracture occurred at a structural node where diagonal braces connect to the transverse mounting axis, near the shock absorber bracket. Analysis indicated that the design concentrates loads at this node and that the load introduction and distribution were inadequate. The fracture initiated from a microcrack at a corrosion site in a weld connecting one of the braces to the strut. Corrosion initiation was also found in another weld location.
Probable Cause
The accident investigation identified the following causes: 1. Applied design solutions of the nose landing gear. 2. Occurrence of undamped lateral vibrations (shimmy) of the nose landing gear during landing.
A contributing circumstance was the intensive operation of the aircraft in training flights.
Preventive Measures
The operator implemented the following measures:
- Instructing training instructors that any unexplained vibration on the landing gear should result in immediate cessation of flights and inspection per the bulletin.
- Submitting remarks to the aircraft manufacturer regarding the quality of nose gear strut manufacturing.
- Informing Bartolini Air technical services to sensitize personnel to the quality of inspections of the nose gear area, with emphasis on photographic documentation and detailed description for creating a fault history.
The aircraft manufacturer introduced a new nose landing gear design with different structural solutions and is systematically replacing older nose gears with the new design.