What happened
On September 12, 2004, a private Sukhoi Su-29, registration RA-3266K, was engaged in a ferry flight between Montauban and Narbonne. Following a departure from Montauban, the aircraft flew toward a local residence for a social gathering. During this period, the aircraft was observed performing high-speed, low-altitude maneuvers at approximately 100 feet. Witnesses observed the aircraft climbing at a steep 60-degree angle and performing extreme aerobatic turns with bank angles exceeding 90 degrees.
During these maneuvers, the engine power decreased, and the aircraft descended toward a cornfield. While attempting to avoid an overhead power line, the pilot increased the descent rate. The aircraft struck the ground with a left-wing bank, slid laterally, bounced, and eventually came to rest on its back, where it caught fire. The impact resulted in two fatalities, involving the pilot and one passenger, and the total destruction of the aircraft.
The investigation
The investigation focused on the fuel system configuration and the pilot's flight management. The aircraft was equipped with one 70-liter main tank and two 100-liter auxiliary tanks. Investigators found that all three tanks contained fuel at the time of the accident, with the fuel selector set to the main tank. However, the fuel system design requires the main tank to maintain sufficient volume to accommodate a 10% fuel return flow from the auxiliary tanks.
Analysis of the flight sequence suggested that the pilot likely selected the auxiliary tanks for the flight. The investigation established that the pilot had a habit of carrying only the minimum required fuel for ferry flights. Because the main tank had been depleted during a previous flight, the pilot may have relied solely on the auxiliary tanks without ensuring sufficient volume in the main tank to handle the return flow.
Findings
- The primary cause of the accident was inadequate fuel management during flight.
- The fuel system likely unprimed (lost pressure) during high-G or high-inclination maneuvers because the main tank could not accommodate the return flow from the auxiliary tanks.
- The flight manual explicitly prohibits aerobatic maneuvers while using auxiliary tanks, as fuel delivery cannot be guaranteed in all aircraft attitudes.
- The pilot was performing maneuvers at an extremely low altitude, leaving insufficient time to identify a suitable emergency landing site or to re-prime the fuel system after the loss of power.
- An attempt to avoid power lines at a very low altitude disrupted the pilot's ability to manage the emergency landing effectively.