What happened
On July 2, 2006, at approximately 21:00, a Synairgie Skyranger ultralight, identified as 33-QI, was conducting a flight from Sarlat to Cabanac. During the flight, the pilot observed that the fuel level in the right tank was decreasing more rapidly than the level in the left tank. Despite this observation, the flight continued.
While on final approach to runway 27 at the Caban and airfield, the engine lost power. The pilot was forced to perform an emergency landing in a clearing located approximately 500 meters east of the Cabanac ultralight platform. There were no fatalities among the two occupants, though the aircraft sustained damage to its landing gear.
The investigation
The investigation focused on the fuel system of the Synairgie Skyranger, which utilizes two 30-liter tanks connected via a T-junction. The system relies on a mechanical pump to deliver fuel to the carburetors through rubber hoses secured by clamps.
Investigators discovered that the right tank had been completely depleted, while approximately fifteen liters of fuel remained in the left tank. Examination of the fuel lines revealed that a hose clamp securing a rubber hose to the fuel pickup in the left tank was insufficiently tightened. The geometry of the fuel line elbow at this connection point facilitated a partial disconnection of the hose, which allowed air to enter the fuel system.
Findings
- The primary cause of the engine failure was an insufficiently tightened hose clamp, which led to a partial disconnection of the fuel line and subsequent air ingestion.
- The pilot had failed to recognize the severity of a recurring fuel imbalance. Earlier that morning, during a flight from Cabanac to Sarlat, the pilot had noted a similar discrepancy in fuel levels and had added 20 liters to the right tank to compensate.
- The pilot had not performed the internal or external inspections of the fuel hoses recommended by the maintenance manual, as they had not considered such checks necessary for local flights.