History of the Flight
The pilot arrived at the aircraft at approximately 0900 hrs to prepare for a parachute drop flight. The aircraft had been outside overnight and a heavy frost was present. After removing the windscreen cover and conducting a pre-flight check, the pilot observed no ice or frost on the upper wing surfaces. He completed his pre-flight planning in the operations building and returned to start the engine at 1000 hrs. While the engine warmed, eight parachutists boarded, including three instructors connected to three students, two videographers, and the jump supervisor.
After the engine warmed, the pilot performed a power check and before-takeoff checks, selecting flaps to takeoff. All indications appeared normal. He taxied onto Runway 06L and selected takeoff power (29 inches MAP, 2,500 rpm). The acceleration seemed normal, but although VR was 60 kt, the pilot delayed rotation until 65 kt. Around rotation, he selected flaps to full.
As the aircraft crossed the hedge at the upwind end of the runway, the pilot began a left turn, a standard noise-abatement maneuver to avoid buildings on the extended centerline. During the turn, he realized the aircraft was descending. He checked the engine instruments, which indicated normal MAP, fuel pressure, and rpm. He called "brace, brace, brace" and the aircraft hit the ground immediately after in a left-wing-low attitude. After crossing a ditch, the landing gear detached and the aircraft skidded to a halt in the next field. The pilot exited through the left door but could not stand due to a leg injury. The rear sliding door was jammed, so the parachutists exited through the same door. One parachutist suffered whiplash; the others were unhurt. The pilot was airlifted to hospital.
Witness Evidence
Five parachutists, who had flown in G-CDYA many times, noted that the takeoff seemed longer than usual. Shortly after the aircraft entered the turn, it began to lose altitude, and one parachutist recalled it "shaking a bit" as it descended. A ground witness thought the aircraft stopped climbing after starting its turn, not exceeding about 100 ft agl, and began losing altitude halfway through the turn.
Accident Site Details
The aircraft contacted the ground on a track of about 340°M, immediately in front of a 1.5 m high hedge between two fields. Beyond the hedge were a ditch and an agricultural concrete track. Ground marks indicated heavy contact from the outboard left wing and left landing gear. The nose and right landing gears also left marks as the aircraft passed through the hedge; all landing gears were torn off when striking the ditch. The nose wheel was found embedded on the far side of the ditch. The aircraft slid on its belly, slewing left and coming to rest on a heading of 240°M, approximately 25 m beyond the hedge. Ground marks indicated a bank angle greater than 25° left and approximately level pitch.
On-Site Examination
The AAIB examination began about four hours after the accident. The air temperature remained below freezing; frost about 1 mm thick, similar to medium-grade sandpaper, was present on the wing upper surface, difficult to see against the white paint. No frost was on the windscreen, so it was concluded that the wing frost had likely been present all day. The flap lever was found in the takeoff setting (middle detent), corresponding to the right flap position; the left flap was damaged by impact. The inboard trailing edge of the left wing was deflected downward, impinging on the sliding door and preventing its opening. The nose leg stub and propeller blades left scuff marks on the concrete track; propeller blade tips were curled over, indicating considerable engine power at impact.
Detailed Examination of the Wreckage
Fuel samples from each tank appeared consistent with Avgas, with no water or debris. The fuel selector was found in the on position. Approximately 20 litres of fuel were drained from the left tank, with little in the right tank, attributed to the aircraft's resting attitude and a leak near the collector tank. Refueling records suggested about 70 litres of fuel should have been on board (total capacity 350 litres); the recovered amount exceeded that needed to sustain the engine.
The sliding door was difficult to slide even with the wing removed, due to distortion in the lower fuselage frames. A protective panel behind the co-pilot's seat had been deflected forward by a parachutist leaning against it during the accident, but this did not impede egress.
Engine Examination
The engine had little visible damage except scuffing on the oil cooler. The nose landing gear fitting had penetrated the oil filter, causing a small oil spill. The engine was removed and test-run at an overhaul agent; after starting difficulties attributed to the test cell setup, it ran normally and achieved about 250 bhp at 2,700 rpm (specified max 300 bhp for a new engine). The overhaul agent noted the output was somewhat short of specification.
Probable Cause
The AAIB stated the probable cause as: "Shortly after takeoff the aircraft stalled at a height that was too low to allow a recovery. There was probably frost on the wing, which caused the aircraft to stall at a speed that was higher than expected."