What happened
On March 24, 2019, at approximately 11:01 EDT, a Pilatus PC-12/45, registration N944BT, was climbing through 20,000 feet near Fort Lauderdale, Florida, when the pilot heard a loud bang and the pilot-side windshield shattered. The aircraft was on an instrument flight plan from Fort Lauderdale Executive Airport (FXE) to Moore-Murrell Airport (MOR) in Morristown, Tennessee.
Following the failure, the pilot notified air traffic control of the emergency, initiated a descent, and returned to FXE. The aircraft landed uneventfully, and the pilot, two passengers, and crew were not injured. The flight was being conducted under 14 CFR Part 91. At the time of the event, weather conditions were visual meteorological conditions (VMC) with 10 statute mile visibility.
The investigation
An FAA inspector examined the aircraft and found the pilot-side windshield shattered but still attached to the airframe. The inspection showed the bottom left and upper corners of the windshield had been pushed outward, and the seal was torn. Additionally, the lower left heating element was found to be burnt.
Upon further examination by the manufacturer, it was discovered that approximately 80% of the fiberglass straps were missing. These straps had been removed by maintenance personnel, and there was no record of this action in the airframe logbooks. The absence of these straps caused the outboard ply to detach from the edge attachment. Moisture entered the bottom aft edge, leading to delamination and subsequent electrical arcing.