History of the Flight
Around 15:30 local time on 10 August 2019, a Robin DR400-140B registered F-GJZT took off from Puy Loudes aerodrome (Haute-Loire) for an introductory flight. The pilot and three passengers were on board. Approximately seven minutes into the flight, at an altitude of 4,500 feet, the pilot observed a decrease in engine power and noted that the fuel pressure warning light was illuminated. He activated the electric fuel pump, but the engine continued to lose power and eventually stopped delivering power. The pilot selected a field for a forced landing. During the landing, the aircraft touched down hard, causing the nose gear and left main gear to collapse. The aircraft slid several metres and came to a stop. The aircraft was severely damaged.
Additional Information
Meteorological Conditions
The estimated weather at the accident site included calm wind, visibility greater than 10 km, a broken sky with cloud base at 4,700 ft, temperature 24 °C, and QNH 1021 hPa.
Pilot Information
The pilot held a private pilot licence for aeroplanes (PPL(A)) and had logged approximately 2,000 flight hours.
Aircraft Information
The aircraft was equipped with a main (fuselage) tank of 110 litres and a range extension tank of 50 litres. Fuel quantity could only be checked via the fuel quantity indicator needles, as there was no visual inspection method. Average fuel consumption per the flight manual was about 30 litres per hour at 65% power between 0 and 4,000 ft. The low fuel warning light, located in the cockpit, was part of the main tank's fuel gauge system. The fuel gauge transmitter used a float arm and a variable resistor; in the last quarter of the arm's stroke, one contact plate (A) slid along a guide to complete the circuit for the low fuel light, while another plate (Q) transmitted the fuel quantity indication.
The accident flight was the first flight after a 1,000-hour maintenance inspection. The maintenance manual listed a calibration check of the transmitter every 500 hours, but the methodology for verifying calibration was not defined. Some workshops performed a drain-and-fill procedure.
Examinations
The accident site was in a recently harvested wheat field at an altitude of 2,800 ft. Ground marks indicated a north-easterly landing direction. The distance from the initial impact point to the final resting position was about 20 metres. Examination of the aircraft showed that the engine was not delivering power on landing and that both fuel tanks were empty. The main tank fuel quantity indicator needle was just below "1", and the range extension tank needle pointed to "0". A light test confirmed the low fuel warning light functioned when tested.
A review of the journey logbook indicated that the main tank had been filled on 4 August 2019 at Mende Brenoux aerodrome, followed by a 47-minute flight to Puy Loudes. The aircraft then underwent the 1,000-hour maintenance.
Examination of the fuel gauge transmitter revealed a malfunction: the float arm was stuck during the last quarter of its travel. The contact plate (A) abutted against the tip of the guide instead of sliding along it, causing the second contact plate (Q) to also remain stuck. The indicated fuel quantity was fixed at approximately one-quarter tank, regardless of the actual amount. Oxidation on the contact plates and the guide tip likely prevented the low fuel warning light from illuminating.
Statements
The president of the aero club stated that the fuel pump at Puy Loudes was unavailable, so fuel had been drained from F-GJZT to transfer to another aircraft. He filled three 20-litre cans via the drainage system, estimating 10 to 15 litres spilled. The 60 litres added to the second aircraft were logged, but the removal of 70 to 75 litres from F-GJZT was not recorded in its logbook.
The pilot reported that during the pre-flight inspection, he saw the main tank gauge at "1" and the range extension tank at "0". Believing the flight would last 30 minutes and the indicated fuel corresponded to about one hour, he proceeded. He did not notice the inconsistency between the gauge reading and the logbook entries, which would have suggested the main tank needle should have indicated "3" based on previous flight time since refuelling.
The maintenance mechanic stated that for the calibration check, he only verified the gauge reading against the logbook before the fuel drainage; the needle was near "3", consistent with the last flight.
Conclusions
The investigation concluded that the accident occurred during a forced landing following a loss of engine power in-flight due to fuel starvation. Contributing factors included the pilot's failure to cross-check the journey logbook with the fuel gauge, the omission of recording the fuel drain in the logbook by the club president, a malfunction of the fuel quantity transmitter that indicated more fuel than present and disabled the low fuel warning light, and an insufficient calibration check method by the mechanic.