What happened
On 3 July 2011, a Monnett Moni, registration G-INOW, was performing a private local flight from Sandown Airport, Isle of Wight. After taking off from Runway 05, the engine failed to develop full power. The pilot attempted to maintain a height of approximately 6 to 10 feet to accelerate to climb speed, but the aircraft began to lose airspeed.
Realising that the aircraft would not clear trees bordering a nearby golf course, the pilot executed a left turn to avoid obstacles. During this manoeuvre, the engine power dropped further and eventually ceased entirely. The aircraft subsequently stalled from a height of roughly 6 feet, impacting marshy ground at an angle of approximately 20 degrees. The impact caused the canopy to break, resulting in minor facial injuries to the pilot, though no other injuries were reported. The aircraft sustained damage to the nose, main landing gear, canopy, and the left wing spar and inner wing.
The investigation
The investigation focused on the sudden loss of engine power during the takeoff roll. While the pilot's subsequent inspection of the engine revealed no mechanical failures, an examination of the fuel system identified debris within the fuel filter element.
Analysis of the fuel tank revealed a small amount of brown and black residue at the bottom of the aluminium tank. The AAIB examined residue from the fuel tank outlet wire mesh filter. Laboratory analysis using a scanning electron microscope identified the debris as a mixture of organic and fluorocarbon material, black rubber particles (including chlorinated rubber), unidentified fibrous matter, paint, sealant, and small metallic particles. The investigation also noted that the pilot had mixed two-stroke oil with motor fuel using plastic jerry cans prior to refuelling.
Findings
- The engine power loss was likely caused by fuel starvation at takeoff power.
- This starvation may have been caused by the accumulation of various debris within the fuel system, specifically at the fuel tank outlet screen and the filter.
- The debris found included organic matter, rubber particles from seals or tubing, and metallic fragments from the fuel tanks and fittings.