Accident Overview
On 9 May 2020, a JA 600 aircraft (SkyLeader 600), registration LZ-ACS, operated by a pilot owner, was involved in an accident during landing at Lesnovo Airfield. The aircraft sustained severe damage, and the pilot was hospitalized with low back pain. The Air, Maritime and Railway Accident Investigation National Board of Bulgaria (AMRAINB) classified the occurrence as an accident and appointed an investigation commission.
Flight Sequence
At approximately 13:17 local time (10:17 UTC), the aircraft took off from runway 28 at Lesnovo Airfield, intending to fly a route to the Rila Lakes area. Prior to departure, the pilot performed a pre-flight inspection, inflated underinflated tires, and checked fuel levels, finding 25 liters in each tank. After initially starting the engine with a longer-than-usual rotation, the pilot decided to extend the route and added 20 liters of fuel to each tank. The engine was restarted without issue, and the pilot allowed it to warm up for 8 to 10 minutes before takeoff.
Once airborne, the pilot reported abnormal engine operation and decided to return to Lesnovo Airfield. The aircraft attempted to land on runway 10 at 13:21 local time. During a low-speed turn to correct the approach trajectory, the aircraft stalled and struck the runway first with the right semi-wing, followed by the fuselage.
Injuries and Damage
The aircraft sustained severe damage. The pilot was hospitalized with low back pain. No other injuries were reported.
Investigation Findings
The investigation commission identified several findings. The pilot's license had expired, and there had been a prolonged interruption in piloting activity, resulting in insufficient recent flight experience. The pilot made the decision to return and land after experiencing abnormal engine operation associated with power loss. The landing approach involved a violation of proper technique, including configuring the aircraft for landing at an inadmissible low altitude and low speed.
In addition, the normal engine operation was disrupted due to enrichment of the air-fuel mixture, attributed to incomplete and incorrect implementation of the aircraft maintenance plan by a person holding a Certificate of Maintenance. The investigation also noted reduced oversight by inspectors from the Airworthiness Department of the Civil Aviation Authority regarding the maintenance plan and technical documentation.
Probable Causes as Determined by Investigation
The investigation pointed to the following as main reasons: the pilot's wrong decision to conduct a flight with an expired license, prolonged interruption of piloting, and insufficient flight experience; the pilot's wrong decision to return and land after abnormal engine operation; and violation of landing technique. Accompanying reasons included disruption of engine operation due to incomplete maintenance and reduced oversight by aviation authorities.