What happened
On 18 December 1999, a Piper PA-28-140, registration G-OSOW, was conducting a private trial lesson departing from Bournemouth International Airport. The flight was intended to be a 40-minute local area familiarisation involving a student and a passenger. After taking off from Runway 26, the aircraft climbed to approximately 350 feet before the pilot levelled off and initiated a left turn. During this manoeuvre, the aircraft began to yaw and increase its bank angle. The aircraft subsequently descended and struck the ground with its left wing and nose, resulting in 3 fatalities.
The investigation
The AAIB investigation examined the wreckage, the engine, and the flight controls. The engine and all related systems, including the propeller and fuel systems, were found to be structurally intact and free of mechanical defects. The investigation noted that the aircraft's elevator trim was set to a 65% nose-up position, which may have contributed to a pitching moment if forward pressure was not maintained.
Investigators also reviewed the pilot's recent experience and the cockpit environment. The instructor had recently obtained his rating and had limited recent experience on this specific aircraft model. Additionally, the Air Speed Indicator (ASI) featured a complex, multi-scale display that was difficult to read from the right-hand seat, and the cockpit transparencies were noted to be heavily misted during the taxi phase.
Findings
- The primary cause of the accident was a reduction in engine power likely caused by carburettor icing, as the carburettor heat control was found in the 'cold' position during conditions highly susceptible to icing.
- The pilot's attempt to maintain altitude during the turn, combined with the loss of power, led to a decay in airspeed and an eventual wing drop at the stall.
- The nose-up elevator trim setting likely aggravated the aircraft's tendency to pitch up.
- The instructor's limited recent experience on the PA-28-140 and the difficult visibility of the airspeed indicator from the pilot's position hindered effective airspeed management.
Safety action
- The CAA is advised to ensure that Air Speed Indicators on passenger-category aircraft do not use multiple scale indications and are positioned for easy viewing from all pilot positions.
- It is recommended that newly appointed instructors undergo a flight assessment with a Chief Flying Instructor to confirm their ability, particularly when operating aircraft types different from their primary training.