What happened
On November 9, 2010, a Robinson R22 Beta helicopter, registration I-ETEC, was performing an aerial survey of a natural gas pipeline. The flight departed from the Chavez Marini helipad in Masera, heading toward Vigevano. The crew consisted of two pilots, one of whom was acting as an observer.
Approximately 44 minutes into the flight, while cruising at an altitude of roughly 1,000 feet, the engine ceased operation. The pilot successfully executed an autorotative maneuver, performing a forced landing in a rice field near Sozzago, approximately two nautical miles south of the Cameri NDB. There were no injuries to the crew, no damage to the aircraft, and no damage to third parties on the ground.
The investigation
The ANSV investigation focused on the discrepancy between the fuel levels reported by the pilot and the actual state of the fuel system following the landing. At the time of takeoff, the pilot reported that the fuel gauges indicated one-half of the main tank and one-quarter of the auxiliary tank, and noted that the "LOW FUEL" warning light had not activated. However, post-landing inspections revealed that both tanks were completely empty. While the fuel level indicators were malfunctioning—showing more fuel than was actually present—the "LOW FUEL" warning light was found to be functioning correctly.
Investigators analyzed the aircraft's technical logs, which showed an unusual increase in fuel consumption during the two flights following the last refueling. While the standard consumption rate was approximately 0.58 liters per minute, it rose to 0.79 liters per minute during the flights leading up to the event. This discrepancy suggested that the aircraft was not refueled to its full capacity.
Findings
- The primary cause of the engine failure was fuel exhaustion.
- The investigation identified a failure to properly verify fuel quantities via visual inspection prior to departure, as recommended by manufacturer safety notices.
- It is suspected that during the last refueling, the process may have been interrupted after the main tank appeared full, leaving the interconnected tanks underfilled.
- The pilot did not perform the necessary continuous cross-checks between fuel gauges and engine running time to detect the decreasing fuel levels.