What happened
On 10 August 2019, a Robin DR400-140B, registration F-GJZT, was conducting an introductory flight from Puy Loudes aerodrome in France. The aircraft was carrying a pilot and three passengers when, approximately seven minutes into the flight at an altitude of 4,500 feet, the pilot experienced a sudden decrease in engine power. The pilot observed that the fuel pressure warning light had activated and attempted to engage the electric pump, but the engine failed to recover power.
Recognizing the loss of power, the pilot selected a nearby field for an emergency landing. During the forced landing, the aircraft struck the ground with significant force, causing the nose gear and the left main gear to collapse. The aircraft slid approximately 20 meters through a harvested wheat field before coming to a halt. There were no fatalities, though the aircraft sustained severe damage.
The investigation
The investigation focused on the aircraft's fuel systems and recent maintenance history. The aircraft had recently undergone a 1,000-hour maintenance inspection. Investigators examined the fuel quantity transmitter and found that the float arm was mechanically stuck during the final quarter of its travel. This malfunction caused the fuel gauge to provide an inaccurate reading, showing more fuel than was actually present in the tank. Additionally, oxidation on the contact plates prevented the low fuel warning light from activating.
Investigators also reviewed the aircraft's journey logbook and interviewed the aero club president. It was discovered that during the aircraft's recent maintenance grounding, fuel had been drained from F-GJZT to refuel another aircraft. While the fuel added to the second aircraft was recorded, the amount removed from F-GJZT was not documented in its logbook. The mechanic performing the 1,000-hour inspection had verified the gauge against the logbook entries rather than performing a physical quantity check, which failed to reveal the mechanical seizure of the transmitter.
Findings
- The engine loss of power was caused by fuel starvation.
- A mechanical failure in the fuel quantity transmitter caused the cockpit gauge to indicate a higher fuel level than actually existed.
- Oxidation on the transmitter components prevented the low fuel warning light from functioning.
- The pilot did not cross-reference the fuel gauge readings with the aircraft's journey logbook entries.
- Incomplete documentation by the aero club regarding fuel transfers led to an inaccurate understanding of the available fuel.
- The maintenance calibration procedure used during the 1,000-hour inspection was insufficient to detect the stuck transmitter arm.