What happened
On 1 August 1999, a Piper PA-22-150, registration G-ARAX, was conducting a private local flight originating from Old Sarum Airfield in Wiltshire. While the aircraft was descending from 3,000 feet during a tight turn, it encountered turbulence. As the pilot levelled the aircraft at approximately 2,500 feet, the windscreen suddenly shattered.
In response to the failure, the pilot attempted to reduce the airspeed by pulling back on the control yoke. The passenger also instinctively assisted with this maneuver. Following the incident, the pilot successfully returned to the airfield and landed the aircraft without further difficulty. The pilot initially suspected that the structural stress from the tight turn combined with the turbulence might have caused the failure.
The investigation
Investigators examined the aircraft and the circumstances surrounding the breakage. The maintenance organization responsible for the aircraft conducted an inspection which confirmed that there was no permanent deformation to the airframe. Furthermore, by reassembling the fragments of the windscreen, it was determined that the failure was not caused by an impact from an external object.
Records indicated that during the most recent annual inspection, a small crack had been repaired using a standard stop-drilling technique. However, the investigation established that the failure did not originate from this previous repair.