History of the Flight
On 17 November 2005, a recently qualified private pilot departed Cranfield Airport with a passenger for a local navigation exercise. The aircraft was refuelled with 47 litres of Avgas at 1140 hrs, filling both wing tanks. After starting the engine, the pilot contacted ATC at 1200 hrs for taxi instructions and departed Runway 21 at 1218 hrs. Three minutes later, he transferred to London Information, reporting at 1222 hrs that he was two miles north of Woburn en route to Northampton. At 1237 hrs, he reported overhead Northampton at 5,000 feet, estimating his position over Corby at 1250 hrs. At 1239 hrs, the pilot made a distress call stating, "mayday mayday mayday golf lima sierra has gone into a spin losing height rapidly." No further transmissions were received.
Witnesses observed the aircraft in a flat spin near Bugbrooke, about 17 nm northwest of Cranfield. The aircraft spun through five to eight rotations before hitting the ground in a field. Witnesses reported hearing the engine stop and seeing a white trail from one wing tip. Members of the public arrived quickly; the pilot had died, and the passenger sustained serious injuries. The passenger spoke a few words but could not explain what happened. Emergency services transported the passenger to hospital by air ambulance, where he died that evening.
Aircraft Information
The Grumman AA-1B (registration G-BDLS) is a two-seat, low-wing aircraft with a fixed tricycle undercarriage, sliding canopy, and side-by-side seating. It is powered by a Lycoming O-235-C2C piston engine. The aircraft had a maximum take-off weight (MTOW) of 1,560 lbs and a center of gravity (CG) range of +78.25 to +80.0 inches aft of the datum. The aircraft was equipped with a stall warning system and a placard stating that spins are prohibited. The manual described the AA-1B as "the most responsive and high performing light aircraft on the scene today" and noted stall characteristics with elevator buffeting occurring 3 mph above the stall. The manual also stated that an audio stall warning horn sounds 5 to 10 mph above the actual stall. The manual described recovery techniques for an inadvertent spin, though spins are prohibited.
Weight and Balance
Post-accident analysis estimated the aircraft's weight and balance at the time of the accident. The aircraft was found to be overweight, and the CG was beyond the aft limit. The last weighing occurred on 23 June 2004. The aircraft had been regularly maintained, with the last Annual Star on 15 June 2005. No defects were noted before the accident.
Spin Characteristics
The aircraft was not certified for spinning. The AA-1 series had a history of spinning difficulties, leading to prohibition by the CAA and FAA. The position of the CG significantly affects spin recovery; a CG aft of the limit can make recovery difficult or impossible. The pilot had 80 hours total flying experience, with 6 hours on type, and had flown only 4 hours in the last 90 days.
Weather
The Cranfield ATIS at 1200 hrs reported wind 300° at 8 kt, visibility 15 km, few clouds at 2,000 ft, temperature +5°C, dew point 0°C, QNH 1017 mb. A Met Office aftercast for the accident area at 1200 hrs indicated wind at 5,000 ft of 330° at 24 kt with no turbulence, visibility 20-40 km, and shallow cumulus between 2,000-2,500 ft.