What happened
On 14 August 2003, a Fred Series 2, registration G-BMMF, was conducting an air test near Ross-on-Wye, Herefordshire, to support the renewal of its Permit to Fly. The aircraft was operating at its maximum take-off weight from an airstrip situated at the end of a valley during favorable weather conditions.
Shortly after departing, while climbing through approximately 350 feet, the engine began to misfire and the RPM decreased. The pilot attempted to use carburettor heat, but the engine performance did not improve, prompting the pilot to prepare for a forced landing in a nearby field. During the circling maneuver, the engine power unexpectedly returned to normal, allowing the pilot to climb and attempt a return to the airstrip.
However, as the aircraft turned back toward the airfield, the engine malfunction recurred with increased severity. At an altitude of roughly 650 feet, the pilot faced limited landing options due to the rising terrain. The pilot executed a forced landing in a field obstructed by trees, telephone wires, and hay bales. Due to the high weight of the aircraft and the limited landing distance, the impact was heavy, causing minor damage to the landing gear, though the pilot escaped without injury.
The investigation
Investigators examined the engine and fuel system following the accident. While the pilot did not believe carburettor icing was the primary cause, the investigators noted that such icing could not be entirely excluded given the environmental conditions. Post-accident inspections of the engine and fuel components failed to identify a specific mechanical or systemic reason for the intermittent power loss.