What happened
On August 26, 2009, a Sukhoi Su-31M, registration I-JECT, was conducting an aerobatic training flight near the Gaggiano aerobatic zone in the vicinity of Cascina Stampa-Cusago, Italy. The flight, which departed from Bresso airport, was intended to prepare the pilot for upcoming aerobatic competitions.
During the execution of a maneuver known as a "frullino," the aircraft entered an uncontrollable flat spin. As the aircraft's altitude decreased rapidly, the pilot determined there was insufficient vertical margin to recover the aircraft to a normal flight attitude. Consequently, the pilot activated the onboard automatic ejection system. The pilot successfully egressed the cockpit and landed safely via parachute, while the aircraft impacted a cornfield, resulting in the total destruction of the airframe and a localized fire.
The investigation
The ANSV investigation examined the flight dynamics, the aircraft's technical condition, and the suitability of the aerobatic zone. The investigation confirmed that the pilot was properly licensed, physically fit, and experienced in aerobatic flight. Technical examination of the Sukhoi Su-31M showed no mechanical failures or malfunctions of the engine or flight systems prior to the loss of control.
Investigators also reviewed the characteristics of the Gaggiano aerobatic zone. It was noted that the vertical limits of this specific zone were significantly lower than the minimum altitude requirements suggested in the aircraft's flight manual for recovering from such maneuvers. Additionally, the investigation noted that the aircraft was missing its engine logbook, which hindered precise tracking of engine hours.
Findings
- The primary cause of the accident was the loss of control during an aerobatic maneuver, which induced a flat spin.
- The vertical airspace available within the Gaggiano zone was insufficient to allow for a safe recovery from the spin.
- The presence of the SKS-94 PC-38 ejection seat was the decisive factor in the pilot's survival.
- The aerobatic zone's boundaries partially overlap with populated areas, potentially allowing flight at altitudes lower than standard regulations for such density.