What happened
On June 5, 2025, a W-3A Sokół helicopter, registration SP-SXW, operated by TOPR (Tatra Volunteer Search and Rescue), was conducting training flights near Hala Goryczkowa in the Polish Tatra Mountains. The crew, which included two pilots, a hoist operator, and two rescuers, was performing a simulated rescue mission. Due to the terrain, the crew decided to perform a hover at approximately 20 meters above the ground to deploy a rescuer via the onboard hoist.
After the rescuer successfully reached the ground and disconnected from the hoist, the crew heard a loud bang at approximately 12:00 LMT. This was immediately followed by a loss of power and several cockpit warnings, including fuel maximum and engine failure indicators for the left engine. The pilot executed a right-hand maneuver to transition from a hover to forward flight to regain maneuverable airspeed.
Because the terrain prevented an immediate precautionary landing, the pilot elected to continue the flight using only the remaining right engine. The crew maintained stable flight parameters, including a rotor speed of 103% and a forward speed of 80 knots, while descending toward Nowy Targ (EPNT) airport. The aircraft landed successfully using a forward flight technique at 12:12 LMT. There were no injuries to the crew or ground personnel.
The investigation
The investigation examined the mechanical state of the engine components and the operational procedures of the crew. The PKBWL reviewed the final report and documentation provided by the HUSAIR investigation commission. The investigation focused on the sudden loss of power and the specific mechanical failure within the engine's fuel regulation system.
Findings
- The primary cause of the left engine failure was the failure of the output shaft of the ALRP-5 pump-regulator, resulting from wear on the spline of the shaft and a worn, sheared spline on the driven gear.
- A contributing factor was identified in the pump cover assembly, where a disengaged spring was found. This disengagement created increased clearance between the shaft and the seal, which may have contributed to the development of torsional vibrations during operation.
- The crew's actions during the emergency were appropriate and did not contribute to the incident.