What happened
On September 5, 2009, a privately owned Robinson R44, registration JA33TH, was conducting a solo familiarization flight at the Miho Temporary Operation Site in Shizuoka City. After previously completing a flight with passengers, the pilot attempted to air-taxi the helicopter to a designated parking spot on the runway.
During the maneuver, the aircraft was subjected to a crosswind with intermittent gusts. While hovering at a very low altitude, the pilot experienced a sudden pitch-up movement. In an attempt to stabilize the aircraft and land before losing control, the pilot rapidly lowered the collective. This resulted in a hard landing on the grassy area adjacent to the runway. The impact occurred on a rough, uneven surface featuring a significant rise in the terrain. The aircraft sustained substantial damage, including deformation to the left-hand lower fuselage frame and the lower portion of the vertical stabilizer. No injuries were reported.
The investigation
The JTSB investigation focused on the flight dynamics and the physical state of the aircraft and site. Investigators examined the aircraft's center of gravity, noting it was positioned toward the aft limit. Technical measurements were also conducted in collaboration with the manufacturer in the United States to determine the tail strike angle.
Analysis of the site revealed that the touchdown point was characterized by stepped terrain, with a height difference of approximately 50 cm. The investigation also reviewed meteorological data, which confirmed the presence of northeast winds with gusts reaching 11 knots. The investigation confirmed that the engine and control systems were fully operational prior to the impact and that the damage was caused by external forces during the landing.
Findings
- The pilot attempted to land the aircraft in a rushed manner without properly assessing the surrounding terrain and conditions.
- The aircraft's center of gravity was shifted toward the aft limit, which can cause the tail rotor to sit lower and increase the risk of over-control during rudder applications.
- The presence of fitful gusts and the weathercock effect made maintaining a stable hover difficult, leading to an unstable aircraft attitude.
- The rough surface and uneven terrain at the touchdown site contributed to the deformation of the vertical stabilizer as the tailskid struck the ground elevation.