History of the Flight
On 2 March 2021, the pilot, who owned the aircraft, and an instructor took off from Toussus-le-Noble airport for a flight to Pontoise. After about 20 minutes, the pilot contacted the Pontoise controller, stating they would approach, perform an airport circuit, and then a full stop landing for refuelling. At the end of the approach, the pilot conducted a touch-and-go and joined the left-hand downwind leg for runway 05. At the end of the downwind leg, the right engine power markedly decreased. The instructor took control and applied full power on both engines. Confirming the right engine failure, he shut it down and feathered the propeller. He then observed that the left engine power output was insufficient to maintain level flight. He raised the landing gear and kept flaps retracted. He informed the controller they would land in a field. Shortly before landing, he shut down the left engine and retracted the landing gear. The instructor landed in a field; the aircraft slid about 60 metres before stopping. The two occupants were unharmed and evacuated.
Additional Information
Site and Wreckage
The aircraft came to rest in a ploughed field, slightly left of the runway 05 axis, approximately 1.7 NM from the threshold. It lay on its belly with flaps retracted; lower fuselage was damaged. Both left engine propeller blades were bent backwards, consistent with a rotating propeller and little or no power on ground contact. The wingtip tanks and left auxiliary tank were empty; the two main tanks and right auxiliary tank contained fuel. Both fuel selectors were found in the OFF position; the pilot and instructor stated they had used the main tanks and set selectors OFF after landing. Examinations did not identify the cause of the reported engine failures, though anomalies indicating a lack of rigour in maintenance were observed, without a link to the occurrence being established.
Engine Examinations
The aircraft was equipped with two Lycoming IO-320 C1A engines. On a test bench, the right engine started with difficulty, vibrated, had jerky speed increase, reached maximum rpm 500 lower than expected, and stalled at about 1,300 rpm during deceleration. Cylinder No. 3 injector nozzle was completely clogged with a deposit; damage to the nozzle suggested cleaning with an unsuitable tool. The left engine delivered maximum expected power but showed delayed response and stepped speed increases on rapid throttle inputs, indicating a fuel metering fault. Examination of fuel servo injectors (FSIs) revealed a bent strainer in the right FSI allowing unfiltered fuel, and excessive fuel flow rates in both FSIs. Non-conformities in adjustments were noted.
Aircraft and Maintenance
The aircraft was built in 1966 with about 4,290 flight hours; left and right engines had 410 and 1,900 hours since overhaul, respectively. The last right engine overhaul was before 1991; left engine overhaul in 2000 after a propeller strike. In January 2021, a workshop performed an annual inspection per the manufacturer's manual. FSI strainers were removed and cleaned; the bent strainer went undetected. The injector nozzles were not inspected. On 18 February 2021, an authorized inspector signed the return to service after verifying airworthiness directives and tasks; a satisfactory run-up was recorded. The pilot flew a cross-country flight on 21 February without anomalies; the accident flight was the next.
Personnel
The 58-year-old pilot held a PPL(A) since 2010 and an MEP rating from January 2020, with about 990 flight hours, 50 in twin-engine piston. The 35-year-old instructor held an ATPL(A) since 2015 and instructor rating since 2009, with about 6,500 hours.
Meteorology
The 16:30 METAR at Pontoise airport reported wind from 060° at 3 kt and CAVOK.