What happened
On 29 September 2013, a Beagle Auster D5 Series 180 Husky, registration G-ATMH, was performing a private glider towing mission near Bovington Camp, Dorset. After successfully taking off while towing a Schleicher AS-K 13 glider, the pilot attempted to climb away from the airfield. During the initial climb, the pilot noticed that the engine was not providing the expected level of power. Despite maintaining full power, the aircraft failed to gain altitude and began to lose airspeed.
As the aircraft's speed dropped to approximately 40 knots, the glider was released and landed safely in an open area. The pilot, unable to clear the surrounding treeline to return to the airfield, identified a concrete road cutting through a spruce forest as a potential landing site. During the forced landing attempt, the aircraft's right wing struck a tree, causing the plane to spin 180 degrees. The aircraft came to a stop with the right main landing gear collapsed and damage to the propeller, cowling, and right wing. There were no injuries to the pilot.
The investigation
The investigation focused on the sudden reduction in engine performance. The pilot reported that the engine continued to run throughout the event but failed to produce sufficient thrust to maintain level flight. No engine misfiring was noted by the pilot. A technical examination of the engine was conducted, but no mechanical defects were identified that would explain the power loss. Investigators noted that the atmospheric conditions at the time were suitable for the formation of carburettor ice.