Sudden loss of engine power forced pilot into emergency landing

The crash site of the Yak C11 in Gransden. Picture: AAIB

The crash site of the Yak C11 in Gransden. Picture: AAIB - Credit: Archant

A sudden loss of engine power forced the pilot of a classic aircraft into an emergency landing at Little Gransden Airfield, a report issued by the Air Accident Investigation Branch (AAIB) has revealed.

The pilot of a Yakolev YAK C11, which dates from 1945, was attempting to complete a set of aerobatic manoeuvres at about 4.30pm on June 21 when the engine started to misfire.

An AAIB report into the incident noted: “The pilot flew a tighter circuit, but late during the final approach the engine lost power. As the aircraft could no longer reach the runway, the pilot made a successful wheels-up landing and the aircraft touched down 150m short of the runway threshold.”

In a wheels-up landing, a pilot is forced to use the underside of the aircraft to complete the landing because the landing gear has not been fully extended.

Of the landing, the report noted: “As the aircraft travelled across the ground it slewed slightly as the propeller dug into the ground before coming to a halt. The passenger was uninjured, but the pilot, who was wearing a helmet, struck his head on the gun sight.”

The YAK C11 was designed and built in the Soviet Union after the end of the Second World War and served primarily as a fighter training craft.

Following the incident, the owner of the aircraft arranged for a pair of magnetos (a device that supplies current for the ignition system) to be removed from the engine to be inspected and tested.

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According to the AAIB report, the testing was halted after both magnetos suddenly stopped working at higher temperatures, before working again when they returned to lower temperatures.

The owner of the craft said it had been in his possession for more than 20 years and that there had been “no recent issues” with either the plane or its engine.

The AAIB report concluded: “The testing of the magnetos indicates that that the most likely reason for the loss of engine power was a breakdown in the coils as the temperature of the magnetos increased.

“The pilot, who was an experienced YAK pilot, advised the AAIB that he had previously experienced misfiring and a loss of engine power on another YAK-type aircraft that was identified as the magneto coils starting to heat up and break down.”