Accident Sequence
On 27 May 1999 at 1730 UTC, a Piper PA-28-151 (modified), registration G-BCIE, was operating a private flight from Perth Aerodrome, Scotland. The pilot, aged 18 with 126 total flying hours (16 on type), performed a landing on Runway 10, which has a landing distance available of 466 metres. The touchdown occurred approximately three-quarters of the way along the asphalt surface. The pilot elected to carry out a go-around, retracted the flaps, and applied power. Some lag was noted before the engine appeared to achieve normal take-off power.
The aircraft climbed to between 50 and 100 feet above ground level, at which point the engine power reduced to idle. The pilot recycled the throttle, lowered the nose to maintain airspeed, and performed a quick check for an obvious cause. He applied carburettor heat and recycled the throttle again. With little height remaining, he focused on landing safely. The area ahead was obstructed by a road, houses, and trees, so he turned left to avoid them but encountered more trees, necessitating a turn of approximately 90 degrees. A mayday call was transmitted during the turn. Airspeed decayed to 60 knots, and elevator authority was lost. The aircraft struck the ground in a nose-down and left-wing-down attitude. The impact removed the left wing, and the aircraft came to rest inverted. The hatch opened during the impact, and the occupants evacuated without external assistance. The passenger sustained minor injuries; the pilot was not injured. Lap and diagonal harnesses were in use.
Investigation Findings
Engineering staff from the operating company examined the aircraft. Substantial amounts of fuel were found in both fuel tanks and in the carburettor bowl. The engine turned correctly with appropriate compression on all cylinders. All elements of the gear train at the rear of the engine turned correctly with the crankshaft. The magnetos and ignition harnesses were tested off the engine and produced appropriate sparks down to very low rotational speeds. No rational explanation for the power loss could be determined.
Meteorological Analysis
Analysis of after-cast meteorological data for the accident time and location indicated that, throughout the height band from the surface to 2,000 feet above ground level, ambient temperature and dew-point were such that carburettor icing was a strong possibility. Conditions were most conducive to such icing at 2,000 feet, becoming less so as the surface was approached. Throughout that height band, conditions remained within the envelope known to produce serious icing at cruise power on some types of float carburettor. Therefore, at reduced power during the descent, conditions would have favoured carburettor ice formation.
While the aircraft gained significant height after power was applied, the possibility exists that ice, having formed at a benign location within the intake system, was shed after climb power was applied. It may then have been ingested by the engine or re-deposited in an area where it had a more critical effect on induction system airflow. The slight hesitation noted by the pilot when he first applied power may have been evidence of the presence of significant intake ice.