What happened
On April 23, 2014, at approximately 12:30 UTC, a Robinson R44 Raven I, registration OK-VAC, was conducting training maneuvers near Velké Všelisy, Czech Republic. The flight, involving a student pilot and an instructor, was intended as a practice session for autorotation procedures in preparation for a private pilot helicopter (PPL(H)) practical exam.
During the third attempt at an autorotative landing, the crew was practicing power recovery. After performing a flare to reduce forward speed and vertical descent, the pilot attempted to level the aircraft and increase engine power. However, the aircraft made contact with the ground while still in a nose-high attitude. The impact caused the helicopter to surge on its skids, resulting in a sudden upward movement of the tail boom and a downward movement of the cabin. In an instinctive reaction to this movement, the pilot applied aft cyclic, which tilted the rotor disk plane and caused the main rotor blades to strike the tail boom.
The investigation
The ÚZPLN investigation examined the aircraft, the flight crew's qualifications, and the environmental conditions. Technical inspections of the Robinson R44 Raven I confirmed that the engine, transmission, and all control mechanisms were fully functional and that no mechanical failures had occurred prior to the impact. The damage to the tail boom, tail rotor, and main rotor blades was determined to have been caused solely by the contact between the blades and the tail boom structure.
The investigation also reviewed the flight instructor's actions and the student's performance. While the student pilot was performing the maneuvers according to the syllabus, the investigation noted that the training session was conducted away from the aerodrome in an area with significant cloud cover and wind gusts, which may have complicated the landing phase.