What happened
On December 7, 2017, a Robinson R44 Astro, registration OK-EIN, was performing a training flight near Brno/Tuřany Airport (LKTB). The pilot, accompanied by a passenger, had been practicing takeoff and landing techniques at a nearby airfield in Strachotín. Upon returning to LKTB, the pilot intended to land at the "South Base" operational area.
During the approach, the pilot chose to perform a landing maneuver with a tailwind to avoid flying over a hangar. This decision placed the aircraft in a flight regime outside of the ground effect, at a speed and altitude that deviated from the manufacturer' and flight manual recommendations. As the pilot transitioned from forward flight to a hover, a gust of wind likely caused the aircraft to settle. The pilot responded with an uncoordinated and improper control input, involving an excessive increase in collective pitch and a heavy application of right pedal.
This sequence of actions triggered a rapid right-hand rotation. During the developing spin, one of the main rotor blades struck the tail boom, causing the tail boom to sever and the tail section to separate from the fuselage. The uncontrolled Robinson R44 Astro subsequently struck the ground, resulting in the total destruction of the aircraft. The pilot sustained serious injuries and was transported to a hospital.
The investigation
The ÚZPLN investigation examined the flight data, including SSR position records, and interviewed the pilot and the passenger. The investigation focused on the pilot's decision-making regarding the approach, the aircraft's flight parameters during the critical phase, and the mechanical state of the helicopter. Technical inspections of the wreckage confirmed that the structural damage, including the severed tail boom and broken rotor blades, occurred during the flight and upon impact. The investigation also verified that the engine and all primary flight controls were fully functional prior to the accident and that the aircraft was within its maximum takeoff weight.
Findings
- The pilot chose to perform a landing maneuver with a tailwind, failing to utilize the option to land in an open area and then transition via ground effect.
- The pilot underestimated the difficulty of maneuvering the helicopter during a tailwind approach without the benefit of ground effect.
- The approach was conducted outside the recommended speed and altitude envelopes specified in the flight manual.
- The pilot's uncoordinated response to the aircraft's vertical movement—specifically the simultaneous use of excessive collective pitch and right pedal—directly caused the development of a right-hand rotation.
- The pilot failed to react in time to stop the increasing rotation, leading to the rotor blade striking the tail boom.