What happened
On 13 June 2009, a Grob G102 Astir CS77, registration G-CFSZ, was engaged in a private cross-country flight from Aston Down Airfield to Husbands Bosworth Airfield. The flight began with a winch launch at 1334 hrs. During the outbound leg, the pilot performed several thermalling manoeuvres at an average altitude of approximately 4,000 ft.
As the flight progressed, the aircraft encountered weak thermal conditions. At 1605 hrs, the glider began manoeuvring to find lift at 2,300 ft, but its altitude dropped to 1,900 ft. Following another attempt to thermal at 1613 hrs, the aircraft exited the manoeuvre at 1,200 ft. The pilot then flew south towards the village of Ratley.
At approximately 1619 hrs, the pilot appeared to select a field for landing that was positioned downwind. While attempting a sharp left turn to establish a final approach track, the aircraft descended to a height of less than 200 ft. During this turn, the nose dropped, and the aircraft entered a state consistent with a stall. The glider struck the sloping ground with a high rate of descent, resulting in one fatality.
The investigation
Investigators examined the wreckage and recovered data from a GPS-linked data logger. The examination of the G-CFSB structure revealed no evidence of any mechanical failure or pre-impact defect in the flying controls or airframe. The cockpit's wheel gear lever was found in the down position, indicating an intention to land.
Analysis of the terrain and meteorological conditions suggested that the aircraft may have encountered a localised downdraft caused by south-westerly winds crossing the ridge north of Ratley. The investigation also considered the pilot's visibility of alternative landing sites, noting that larger, more suitable fields were located at a lower elevation and would have been difficult to identify during the low-altitude turn.
Findings
- The primary cause of the accident was the loss of sufficient altitude due to weak thermal activity, which was likely worsened by encountering a descending air mass.
- The pilot attempted to land in a field that was positioned downwind, necessitating a sharp, low-altitude turn.
- The aircraft entered a stall during this manoeuvre at an altitude too low to recover.
- The selection of the landing site was complicated by the rapid decrease in height and the difficulty of spotting alternative fields while crossing the ridge.