Jodel D140A Mousquetaire F-BIZF forced water landing at Lac du Moutchic

Accident Overview and Flight Details On 14 August 2013, at approximately 16:00 local time, a Jodel D140A Mousquetaire, registration F-BIZF, operated by a company, was conducting a banner-towing flight in the Lacanau area. The aircraft departed from Andernos-les-Bains aerodrome for a low-altitude banner-towing operation. While approaching the south shore of Étang de Moutchic at an altitude of about 300 feet, the aircraft encountered strong turbulence. At the same time, the engine experienced misfires and then stopped. The pilot made a forced water landing along the shore. The hard contact with the water surface caused the landing gear to break and resulted in minor injuries to the pilot. The aircraft was heavily damaged. ## Wreck Examination and Pilot Account The fuel selector was found in the rear tank position. The rear tank was full of fuel, while the front tank contained a very small amount of fuel. Its gauge on the instrument panel indicated a quantity slightly above zero. The auxiliary pump was in the “ON” position. The pilot stated that he had taken off from Andernos-les-Bains using the front tank, intending to consume some of the fuel in it and then switch to the rear tank upon reaching the work area. After about half an hour of flight, the front tank gauge indicated a low remaining quantity, described as two needle widths above zero. The pilot decided to change tanks. He reported that at that moment the aircraft was subjected to strong turbulence, which led him to interrupt the tank-change procedure. He banked the aircraft sharply to the left to leave the area and used the opportunity to check the banner attachment. During this maneuver, the engine misfired and stopped. The pilot said he selected the rear tank, but this did not allow the engine to restart immediately. He decided to make a water landing after releasing the banner. The pilot added that he did not usually use the front tank during banner towing and attributed the error to the pace of flights and end-of-season fatigue. He believed that the left turn, made in some urgency, was not perfectly symmetrical. The small amount of fuel was then projected to the side of the tank, causing air to enter the fuel circuit and the pump to lose prime. ## Pilot Experience and Aircraft Information The pilot held a professional pilot license for airplanes since 1976 and had a total of approximately 7,000 flight hours, including 60 hours on type in the preceding three months. The F-BIZF was equipped with a rear tank of 125 liters and a front tank of 90 liters. A manual three-position fuel selector (Front-Closed-Rear) allowed the engine to be supplied from either tank. On Jodel D140 aircraft equipped with such indicators, the “End of tank” and “Low pressure” lamps on the instrument panel illuminate when the remaining quantity is 10 liters for the front tank and 12 liters for the rear tank, respectively, allowing about fifteen minutes of flight at 75% of the engine’s rated power and a tank change. Banner towing is performed at a speed of 100 km/h with the flaps retracted. In this configuration, due to the induced drag from the banner, the aircraft has a significant nose-up attitude. With such an attitude and a fairly low quantity of fuel in the front tank, the risk of losing prime is high. This aircraft, serial number 020, manufactured in 1958, was not equipped with a visual alarm indicating low fuel level in the tanks. The flight manual, partly reproduced in the Particular Activity Manual (MAP), recommended taking off with the front tank empty during banner towing. The bottom of the front tank has a strainer in the center, to which one of the fuel circuit pipes is connected. ## Meteorological Conditions The estimated meteorological conditions at the site were as follows: wind from 020° at 10 knots, gusting to 20 knots, on the eastern part of the lake; wind from 340° at 14 knots, gusting to 20 knots, on the western part of the lake. For both parts of the lake: CAVOK, temperature 26°C, dew point temperature 10°C, QNH 1,022 hPa. Turbulence was moderate at the convergence between the northwesterly flow and the north/northeasterly coastal breeze. ## Findings and Conclusion The loss of power, resulting from the loss of prime in the fuel circuit, followed by engine stoppage at low altitude, led the pilot to make a forced water landing on a lake. The accident is explained by the combination of the following factors: inadequate fuel management leading to the near-emptying of a tank whose use was not recommended by procedures; a sustained reflex maneuver to clear a turbulence zone; and the low altitude, which reduced the possibilities for action in the event of a temporary or permanent loss of engine power. Fatigue accumulated during the season may have been a contributory factor.