Flight History
On July 20, 1997, at approximately 15:55 local time, a Kamov KA-26 helicopter, registration LY-HAI, operated by UAB Klaipėdos avialinijos, departed from Palanga aerodrome for a demonstration flight as part of an aviation festival. The weather was reported as simple meteorological conditions with wind from 60° at 16 knots gusting to 22 knots, visibility over 5 km, and temperature +24°C.
After completing a portion of the demonstration, the helicopter climbed towards runway 01 at an altitude of about 40-50 meters. While flying at a course of approximately 10° and a speed of 50-60 km/h, the pilot felt two consecutive impacts in the rotor plane: the first weak, the second much stronger. Following the second impact, vibrations began. The pilot decided to land immediately and initiated a left turn. During the turn, the main rotor blades collided. The pilot turned into the wind and landed on grass adjacent to the runway. The engines operated normally at about 92% rpm throughout the event. From the onset of vibrations to landing, less than 40 seconds elapsed.
Damage and Injuries
No injuries to persons occurred. The helicopter sustained damage to its main rotor blades. No damage was caused to third parties.
Investigation
The investigation commission examined the accident site and recovered blade fragments scattered within a 40-45 meter radius. Video footage showed an unidentified object approximately 5-7 cm in diameter moving towards the rotor disc, followed by a sharp descent in a left spiral. Analysis of the video concluded that the pilot's maneuvers could not have caused the accident.
Probable Cause
The commission was unable to determine an objective and indisputable cause for the rotor blade contact. The most likely cause was identified as the failure of a rotor blade due to material aging and fatigue, leading to imbalance and subsequent blade collision. A less likely possibility was collision with the unidentified object visible in the video.
Recommendations
The investigation recommended that operators ensure rotor blades and hubs are not used beyond their service life, conduct additional inspections of blades and hubs before demonstration flights, and submit demonstration programs involving evolutions not covered in the flight manual for aerodynamic and technical analysis and approval.