What happened
On 12 December 2020, a DA 40 NG, registration G-CTSB, was involved in a serious accident at Cranfield Airport. The aircraft, operated by a commercial Approved Training Organisation (ATO), was performing an aerial work flight when it stalled and struck the ground shortly after takeoff from a height of approximately 100-200 feet. The flight lasted only about 12 seconds.
Prior to departure, the aircraft had been loaded with five 25-litre containers of de-icing fluid. One of these containers was positioned upright in the front right footwell. While the aircraft was within its maximum takeoff weight, it was operating near its aft centre of gravity limit. During the takeoff roll, the aircraft's wings were observed to rock, followed by a wing drop and a subsequent stall that led to the impact. The pilot sustained serious injuries.
The investigation
Investigators examined the wreckage and the cockpit layout to determine if the cargo had interfered with the aircraft's operation. Physical evidence showed that the container in the front right footwell had been punctured and moved during the impact, confirming its upright position during flight.
Testing conducted by the AAIB on an identical aircraft model demonstrated that a container placed in that specific footwell prevented the control stick from moving fully forward. This restriction meant the pilot could not apply the necessary nose-down pitch to recover from the high nose-up attitude caused by the aft centre of gravity.
The investigation also reviewed the operator's management practices, the technical log entries, and the classification of the cargo. It was noted that the de-icing fluid, Marcon DTD406b, was likely mislabelled by the manufacturer, as the provided safety information was inconsistent with the chemical properties of the fluid.