History of the Flight
On 15 September 2012, a Piper PA-22-150 Caribbean, registration G-ARHN, was operating a private flight south of Popham Airfield, Hampshire. Two pilots were on board: Pilot 1 occupied the left seat and had not flown within the previous 90 days, last flying the accident aircraft in August 2010. Pilot 2 occupied the right seat and was acting as a 'check' pilot under group policy. After refueling to full tanks, the pilots conducted approximately 35-45 minutes of upper air work before returning for circuits. Touch-and-go landings were not permitted on Runway 26, so full stop landings were followed by taxiing to the takeoff point. During the final approach, flown by Pilot 1, the right fuel tank had reduced to ¼ capacity, so Pilot 1 selected the left tank. Assessing the aircraft was too high, Pilot 1 initiated a go-around and applied full power. Almost immediately, the aircraft began an undemanded left turn. Pilot 2 reported full power but low airspeed, and just before impact the aircraft appeared to stall with the right wing dropping. A witness observed a gentle left turn at about 10° bank, slow speed, and failure to gain height; the engine sound did not change until impact. The aircraft struck treetops, fell to the ground, and both pilots sustained serious injuries. The aircraft suffered substantial damage.
Fuel System
The aircraft was fitted with two 15 imperial gallon fuel tanks, one in each wing root, gravity-fed to the engine via a fuel cock on the left cockpit wall. The Flight Manual prohibited takeoff with the right tank selected if less than ⅓ full but did not specify other fuel asymmetry limitations. At the time of the accident, the left tank was nearly full and the right tank was at ¼ capacity.
Pilot Currency and Group Policy
Pilot 1 held a National Private Pilot’s Licence (44 years old, 88 total hours, 8 on type) and a Private Pilot’s Licence (60 years old, 940 total hours, 341 on type). Pilot 1 had not flown in the 90 days preceding the accident. Group policy stated: "If a member undergoing check has exceeded the 90 day, 3 take off and landing limit, then the check pilot has to be P1." Pilot 1 believed Pilot 2 was pilot-in-command. The investigation found evidence that Pilot 2 acted as PIC until Pilot 1 completed three takeoffs and landings to satisfy 90-day currency, but later stated the group policy was an incorrect interpretation of the Air Navigation Order (ANO). The ANO defines PIC as the person in charge of piloting without direction from another pilot. Under Schedule 7, a Private Pilot Licence holder may not fly as PIC carrying passengers unless they have made three takeoffs and three landings as sole manipulator in the preceding 90 days. The CAA clarified that only a flying instructor can supervise a pilot regaining currency; a non-instructor check pilot would be a passenger. Pilot 2 was not a flying instructor.
Analysis
The engine appeared to produce full power during the go-around, but the aircraft flew unusually slowly as it entered the undemanded left turn. The fuel asymmetry (near-full left tank, ¼ right tank) could not be discounted as contributing to the uncommanded left turn at low speed. Contaminated fuel from the left tank was considered unlikely as the engine produced power until impact. The slow speed likely placed the aircraft in a high-drag configuration preventing climb.
Conclusions
The most likely cause of the accident is that the handling pilot allowed the speed to reduce during the go-around. This, possibly combined with the asymmetric fuel loading, made control of the angle of bank difficult causing the aircraft to turn to the left prior to stalling as it entered the treetops.