What happened
On 17 November 2005, a Grumman AA-1B, registration G-BDLS, departed Cranfield for a local flight. The pilot, who had recently obtained a Private Pilot’s Licence, was accompanied by one passenger. After refueling the aircraft to its maximum capacity, the flight proceeded on a north-westerly track at 5,000 feet.
At approximately 1237 hrs, the pilot reported to air traffic control that the aircraft was overhead Northampton. Shortly thereafter, the pilot issued a distress call, stating the aircraft had entered a spin and was losing altitude rapidly. Witnesses observed the aircraft in a flat spin, rotating several times before impacting a field near Bugbrooke. The impact resulted in two fatalities.
The investigation
The AAIB investigation examined the aircraft's wreckage, engine, and flight data. Analysis of the engine and flight controls revealed no mechanical defects or control restrictions prior to the accident. The engine was found to be in a condition typical of its age, and the stall warning system was fully functional.
Investigators used GPS data to track the flight path, noting a significant drop in groundspeed just before the spin. Calculations based on the fuel load, the weights of the occupants, and the known empty weight of the aircraft revealed that the aircraft was significantly over its maximum take-off weight. Furthermore, the centre of gravity was found to be beyond the permitted aft limit.
Findings
- The aircraft was overweight and the centre of gravity was positioned beyond the aft limit.
- The aircraft's longitudinal stability was reduced due to the aft centre of gravity.
- The pilot's recent flying experience was limited, having completed only a few hours of flight time on this specific type.
- A combination of the aircraft's weight, the out-of-limits centre of gravity, and the pilot's inexperience led to the unintentional entry into a spin from which recovery was likely impossible.