What happened
On 28 March 1999, a Whittaker MW-6S (Modified), registration G-MZIN, was operating a private flight from a private airfield in Newnham, Hertfordshire. Following several taxi runs, the pilot attempted a short flight in the local area before a planned departure to Chatteris.
During the flight, the aircraft performed a normal takeoff and initial climb, but as it transitioned onto a wide downwind leg, it was observed flying at a lower altitude and slower speed than usual. While attempting a landing, the aircraft passed over a hangar amidst local turbulence. Witnesses observed the engine power increase as the pilot initiated a go-around; however, the aircraft began a progressively increasing right-hand bank. The nose then dropped, and the aircraft entered an incipient spin, striking the ground in a steep, nose-down attitude with the right wing low. The pilot sustained fatal injuries.
The investigation
Investigators examined the wreckage and the aircraft's instrumentation. The engine was found to be functional and capable of reaching near-maximum power, and the fuel system was intact. However, a critical issue was identified with the airspeed indicator (ASI). The instrument had been installed with brass dust caps still covering the pitot and static ports, with only a small hole present in the pitot cap. Testing revealed that while the ASI was accurate at higher speeds, it became extremely sluggish when responding to speed reductions below 45 kt.
Furthermore, the investigation scrutinized the pilot's safety harness. While the four-point harness remained attached to the airframe, the shoulder straps were joined together behind the pilot's neck. This configuration did not meet recommended geometric standards, as it failed to provide immediate rearward restraint to the upper torso.
Findings
- The sluggish response of the airspeed indicator likely prevented the pilot from recognizing an incipient stall as the aircraft's speed decreased during the turn.
- The aircraft was subjected to low-level turbulence and wind conditions that contributed to the loss of control.
- The improper installation of the pilot's shoulder straps meant there was no immediate restraint of the upper body during the impact, allowing the head to move forward and strike the airframe.