What happened
In 2019, three distinct ground collisions occurred during taxi operations at Limburg Regional Airport (EBST). The incidents involved three different small aircraft: a Piper Warrior PA-28-161, a Piper PA-46-350P, and a Diamond DA40 TDI Star.
In the first incident on 29 January 2019, a Piper Warrior PA-28-161 landed and attempted to exit the runway. Due to a recently installed fence obstructing the original taxiway, the pilot attempted to backtrack on the runway. While following the taxiway, the aircraft's left wing struck the edge of a newly installed gate, resulting in substantial damage.
On 30 April 2019, a Piper PA-46-350P experienced a similar collision when its left wingtip struck the same fence while taxiing to the parking area.
Following these two events, the aerodrome operator implemented improvements, including red and white markings on the fence ends and a revised taxiway line. However, on 5 October 2019, a Diamond DA40 TDI Star, operated by a student pilot, struck the gate with its right wingtip while taxiing toward the runway.
The investigation
The AAIU(Be) conducted a limited-scope investigation into these three events. The investigation examined the physical configuration of the airport, the visibility of the obstacles, and the pilot's adherence to taxiway markings. The investigators reviewed the installation of the fence, which was placed 90 meters from the runway centerline following the removal of a grass runway. The investigation also assessed the adequacy of the aerodrome operator's subsequent mitigation efforts and the communication of new airfield configurations to visiting pilots.
Findings
Several contributing factors were identified across the three occurrences:
- Inadequate infrastructure design: The gate and fence were installed in a manner that required complex maneuvering. The gate was not perpendicular to the taxiway, necessitating a curved taxi line that increased the risk of collision.
- Poor visibility: The fence was painted dark green, making it difficult to distinguish from the surrounding grass background.
- Non-compliance with separation standards: The installation did not meet recommended separation distances between taxiway centerlines and objects.
- Pilot monitoring: In the first two cases, pilots failed to follow the taxiway line or notice the obstruction. In the third case, the student pilot's lack of experience and potential stress during a solo flight contributed to the error.
- Lack of communication: The new airfield configuration had not been updated in the AIP, and pilots were not notified of the changes during prior permission requests.
Safety action
Following the first two accidents, the aerodrome operator improved markings and taxiway geometry. However, the AAIU(Be) notes that the third accident demonstrates that prevention is better than cure regarding infrastructure design. The investigation emphasizes that when infrastructural changes create new risks, they must be assessed and mitigated before construction, and any remaining risks must be clearly communicated via the AIP, visual signage, or oral notifications.