What happened
On 29 April 2006, a Mainair Blade, registration G-BZLM, was performing a private flight from a grass airstrip at St Boswells, Scottish Borders. Following a flight from Eastfortune, the pilot and a passenger prepared for a return leg. The takeoff was initiated using the longest available portion of the 250 m runway.
While the aircraft reached an altitude of approximately 30 to 40 feet, it ceased its climb. The pilot noted no audible engine roughness or drop in power, though the engine RPM was not specifically verified at that moment. In an attempt to regain altitude, the pilot made a large forward movement of the control bar. This maneuver caused the left wing to strike a light stanchion, after which the aircraft continued forward briefly before impacting the ground near a building. Both the pilot and the passenger sustained broken bones, though the use of protective helmets likely mitigated more severe injuries.
The investigation
The investigation examined the aircraft's engine performance and maintenance history. It was noted that the pilot had experienced a similar engine RPM decay during a flight on 15 April 2006, which had involved engine misfiring. Following that previous incident, the pilot had cleaned the fuel filter, which was found to contain debris, and checked the spark plugs.
Investigators also looked into the engine oil usage. It was revealed that while the previous owner had used a fully synthetic two-stroke oil, the current owner was using mineral oil. The investigation considered how the use of mineral oil might contribute to residue buildup within the fuel system.
Findings
- The loss of climb capability was linked to a contaminated fuel filter containing fluff and dirt.
- The use of mineral oil, as opposed to fully synthetic oil, was identified as a potential factor, as it can leave an oily film in the filter if not changed frequently.
- The pilot's large forward movement of the control bar during the climb was a contributing factor to the wing striking the stanchion.