What happened
On 9 August 1998, a modified Piper L18C, registration G-BLMR, was conducting banner towing practice at Sandown Aerodrome, Isle of Wight. Following the successful release of a banner, the pilot attempted to execute a landing. During the approach, the pilot applied full power; however, the engine failed to respond, leading to a heavy descent onto the aircraft's right main landing gear. While the aircraft was taxiing across the perimeter track after the landing roll, the landing gear collapsed. This caused the propeller to strike the ground, which subsequently stopped the engine. There were no injuries to the pilot, though the aircraft sustained damage to the fuselage longeron and landing gear, and the engine required a shock-load inspection.
The investigation
The investigation examined the engine's performance and the environmental conditions at the time of the accident. A specialist company performed a shock-load inspection on the Lycoming O-320-C3B engine. While several minor issues were identified and rectified, none were deemed likely to have caused the power loss. Subsequent rig testing of the engine was successful, and no changes had been made to the carburettor prior to the test.
Investigators also analyzed meteorological data and the pilot's actions. The pilot reported that the engine power loss occurred while carburettor heat was being selected during flight at approximately 1,000 feet. The investigation focused on whether rapid throttle movement in icing conditions contributed to the engine's failure to respond.
Findings
- Meteorological data indicated that at 1,300 feet, conditions were on the boundary of being favorable for serious icing at cruise power, and remained favorable for icing at glide power.
- The pilot's rapid movement of the throttle may have caused a temporary over-rich operating condition.
- Engines of this type are sensitive to rapid throttle transitions; moving from closed to full throttle too quickly can cause a significant divergence in the mixture ratio, especially if residual ice is present in the carburettor throat.