What happened
On November 18, 2022, a Robinson R22 Beta, registration YR-DEN, was conducting a training flight near Săcălaz, Timiș County, Romania. The flight was part of a continued training program for a student pilot, accompanied by an instructor pilot.
The flight involved various maneuvers, including climbing and descending turns, speed limit exercises, and simulated landing paths. At approximately 08:35 LT, while flying at a height of 500 feet, the instructor attempted to demonstrate hovering techniques to the student. During these low-speed maneuvers, the helicopter entered a vortex ring state.
The crew attempted recovery maneuvers, but they were unsuccessful. The helicopter descended rapidly and impacted the soft, wet ground. Upon contact, the left-hand skid sank into the soil, causing the aircraft to bank sharply to the left. This motion caused the main rotor blades to strike the ground, which severed the tail boom and resulted in major damage to the airframe.
The investigation
The AIAS investigation examined the flight parameters, maintenance records, and the aerodynamic conditions present during the accident. Although the helicopter was not equipped with a flight data recorder, investigators analyzed the pilots' statements and meteorological data.
The investigation focused on the transition from normal flight to the unstable aerodynamic state. Investigators considered whether an uncontrolled descent began unnoticed or if an attempt to stop the helicopter at a fixed point without maintaining sufficient forward airspeed triggered the phenomenon. The analysis also looked at the timing of the recovery attempts relative to the aircraft's altitude and the 'dead man curve' (height-speed diagram).
Findings
- The instructor and student pilots held valid licenses and medical certificates.
- The Robinson R22 Beta was fully compliant with its airworthiness and maintenance schedules.
- The main rotor entered a vortex ring state during hovering maneuvers.
- The recovery maneuvers were initiated too late to prevent the aircraft from reaching an unrecoverable descent rate at its existing altitude.
- The primary cause of the impact damage was the sinking of the left skid into soft ground, which induced a leftward tilt and subsequent rotor blade strike.