What happened
On 27 August 2021, a Jodel D120A, registration G-AVLY, was departing Halwell Airfield in Devon for a flight to Tatenhill Airfield in Staffordshire. The aircraft, operated for private use, had recently undergone a 25-hour engine service, and both the propeller and magnetos had been replaced with reconditioned components two days prior to the event.
Following a standard pre-flight inspection and a normal engine run-up, the pilot commenced the takeoff on Runway 0 and began the climb. During the climb, the engine note changed abruptly, and the engine lost power. The pilot managed to execute a forced landing into a nearby field. The aircraft sustained substantial damage to the engine and airframe, but the pilot, who was wearing a full harness, escaped with minor injuries.
The investigation
The AAIB examined the aircraft and the fuel delivery system. During the recovery process, the pilot noted that when disconnecting the fuel hose from the carburettor, the inner section of the hose remained attached to the inlet union. This hose consists of an inner Nitrile rubber layer, a synthetic fibre mesh for rigidity, and an outer protective sheath.
Investigators observed that the internal diameter of the hose (6 mm) was smaller than the outer diameter of the carburettor's inlet union (7.75 mm). Upon inspection, the pilot noted that some fibre mesh material had bunched against the face of the carburettor's fuel inlet. It was suspected that this material may have migrated through an internal split in the hose, potentially obstructing the fuel flow. The investigation also noted that the hose appeared brittle due to age, with maintenance records indicating the carburettor system had not been serviced since April 2010.
Findings
- The engine power loss occurred during the climb phase of flight.
- A potential restriction in fuel flow caused by migrating fibre mesh from the fuel hose was identified as a possible cause.
- The fuel hose was found to be brittle, and its internal diameter was smaller than the inlet union it was attached to.
- The investigation could not rule out other causes for the power loss as other aircraft components were not examined.