What happened
On May 25, 2024, at approximately 18:19 UTC, a Robinson R44 Raven I, registration OK-STR, was conducting a recreational flight over the High Tatras mountains. The flight originated from Ružomberok (LZRU) with one pilot and two passengers on board. While flying near the Chata pod Rysmi area, the pilot experienced a decrease in main rotor RPM.
Following an unsuccessful attempt to restore full engine power, the pilot initiated an emergency landing on a surface covered with frozen snow. The landing site proved unstable, causing the helicopter to tilt to one side. This movement resulted in the main rotor blades striking the ground, which subsequently caused the aircraft to capsize onto its right side. The pilot sustained minor head injuries, while the two passengers remained uninjured. The aircraft sustained significant damage during the rollover.
The investigation
The investigation focused on the performance capabilities of the R44 in high-altitude environments and the pilot's operational preparation. Investigators analyzed the aircraft's weight (approximately 878 kg) and environmental conditions, noting an ambient temperature of 4°C.
Technical analysis utilized the R44 Pilot's Operating Handbook to determine the aircraft's performance envelope. The investigation examined the 'service ceiling' and 'hovering ceiling' relative to the terrain altitude (approximately 2250 m.a.s.l.). It was noted that while the theoretical maximum altitude for this weight configuration was approximately 8000 ft, factors such as wind, vertical air currents, and the potential use of carburetor heat (which can reduce ceiling by up to 730 m) significantly impact actual performance.
Findings
- The pilot likely failed to perform adequate preparation required for flight in high-mountain terrain.
- The aircraft exceeded its performance parameters established by its flight envelope, specifically regarding the ability to maintain power in the high-altitude environment.
- The landing surface was unstable due to the presence of frozen snow, contributing to the rotor strike and rollover.