During a check flight the pilot applied full power prior to conducting a timed climb. However, the engine rpm suddenly increased and it became apparent that the drive to the propeller had become disconnected. The aircraft was damaged in the subsequent forced landing, although the occupants were uninjured. It was found that the drive belt that connected the engine driveshaft to the propeller shaft, located immediately above the engine driveshaft, had migrated out of the groove in the lower pulley. This may have been the result of a degree of misalignment between the engine driveshaft and propeller shaft.
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A pilot had to ditch his plane into a field after the engine suddenly "ran away" when out on a test flight.
The two-seater Quad City Challenger II light aircraft was flying from North Coates Airfield in May when it crash landed into a ditch in Grainthorpe.
As reported at the time, the two people on board walked away unhurt but there was damage to the aircraft which landed in farmland off Wragholme Road at around 3.30pm.
Firefighters from Louth and North Somercotes as well as paramedics rushed to the scene and police were also called.
A report into the accident from the Air Accidents Investigation Branch (AAIB) found that the drive belt that connected the engine to the propeller had moved, causing the incident.
The pilot, aged 69, had almost 300 hours of flying experience prior to the flight, the report said.
The plane was on a test run after it had been inspected for revalidation of its Permit to Fly just days before the crash.
During the flight the pilot applied full power prior to a timed climb but the engine rpm "suddenly increased" and "it became apparent that the drive to the propeller had become disconnected," the report said.
It was found that the drive belt that connected the engine driveshaft to the propeller shaft, above the engine driveshaft, had moved, according to the report.
The pilot had taken the aircraft to over 1,000 feet over an open area when he began the timed climb, but at around 1,200 feet the engine rpm suddenly "ran away".
He immediately throttled back and lowered the nose so that the aircraft settled into a glide at approximately 55 mph.
He checked with his passenger what he had heard and, as a check, opened the throttle again. The engine rpm increased rapidly, suggesting the drive to the propeller had been lost.
The report said the pilot chose an arable field for a landing, bisected by a drainage ditch which he intended to land 10 metres to the eastern side of.
It later became apparent that the ground on the far side of the ditch was a few metres higher than on the approach side.
The report said: "This prompted the pilot to pull back sharply on the stick, causing the aircraft to stall and land heavily on top of the embankment on the eastern side of the ditch.
"Neither of the occupants of the aircraft was injured, although considerable damage had occurred to the landing gear and fuselage underside."
An examination of the aircraft revealed that there was "excessive wear" on the internal surface of the pulley on the engine driveshaft, with a corresponding build-up of aluminium alloy material.
It was concluded that there had been a slip between the two components.
The pilot later commented that he had been aware of occasional "blips" in the engine rpm, but attributed these to carburetor icing.
He considered this may have been a symptom of the drive successively slipping and locking, the report found.
The Light Aircraft Association (LAA) noted that this type of propeller drive system has largely been replace by more modern and reliable gearboxes.
Source: http://www.grimsbytelegraph.co.uk Fire crews from Louth and North Somercotes were called out this afternoon to a light aircraft which made an emergency landing in a field near Grainthorpe.
Lincolnshire Police were also present on scene at around 5.30pm on Friday (May 2), but no further action was required.
The nature of the emergency landing, at this stage is unknown.
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Story and photo: http://www.louthleader.co.uk
