What happened
On 28 December 2009, a Mooney 201 M20J, registration N321KL, was preparing for a private flight from Stapleford Aerodrome. During the pre-flight inspection, the pilot identified a small amount of water in the left fuel tank but, after further sampling, determined the fuel was clear. The engine was started using fuel from the right tank before switching to the left tank for taxiing.
Following a normal takeoff from Runway 2ually 22L, the landing gear was retracted. However, at an altitude of approximately 50 ft, the engine experienced a surge and subsequently lost all power. The stall warning activated, prompting the pilot to pitch the aircraft nose down. Due to the low altitude, there was insufficient time to extend the landing gear. The pilot performed a forced landing on the adjacent grass runway, 22R. The aircraft slid for approximately 100 metres before coming to a stop. The uninjured pilot exited the aircraft, which sustained damage to the propeller, underside-mounted aerials, and abrasions to the lower fuselage.
The investigation
Investigators examined the aircraft's maintenance history and fuel system. It was noted that the aircraft had been parked outdoors for approximately three weeks in weather conditions involving rain and snow. A subsequent maintenance check revealed that the left fuel tank filler cap was not properly fitted.
Upon draining the fuel tanks, investigators found that the left tank contained roughly 50 litres of fuel along with approximately 500 ml of water. This water had spread throughout the fuel system, reaching as far as the fuel injectors. While the right tank contained a very small amount of water, the left tank was the primary source of contamination. The investigation also noted that the area around the left fuel tank filler port had recently been repainted during an annual inspection.