What happened
On 4 July 2008, a Scottish Aviation Bulldog 120, registration G-CBBC, was conducting a private aerobatic flight approximately 3 nautical miles north of Basingstoke, Hampshire. The pilot had departed from Blackbushe Airport after performing pre-flight inspections, which included verifying the security of the hand-held fire extinguisher located in the rear luggage area. All other loose items and equipment had been removed from the cabin prior to departure.
The flight sequence began with a loop, a stall turn, and two slow rolls. However, during a third slow roll, the aircraft entered an inverted position under approximately -1.5 g. At this moment, the fire extinguisher became detached from its mounting and struck the Perspex canopy, causing the transparent material to break. Despite the damage to the canopy, the pilot was able to maintain control of the aircraft and return to Blackbushe Airport for a safe landing. There were no injuries resulting from the incident.
The investigation
The investigation focused on the security of the extinguisher within the control tunnel bracket. The extinguisher was held in place by a standard quick-release sprung latch, which was attached to a bracket mounted on the central control tunnel. Post-flight inspections revealed that the latch itself appeared to be in serviceable condition. However, the pilot noted that a large box of servicing supplies had been removed from the aircraft just before the flight, suggesting that the movement of these items might have inadvertently dislodged the latch.
Findings
- The fire extinguisher became unfastened during the application of negative g during an inverted slow roll.
- The latch on the extinguisher bracket may have been dislodged during the removal of other equipment from the aircraft prior to takeoff.
- The impact of the unsecured extinguisher was sufficient to break the aircraft's canopy.