Incident Overview
According to the pilot's report, a dual vacuum pump failure occurred while the aircraft was operating under instrument flight rules (IFR) at flight level 220 (FL220). Although a standby electric artificial horizon was installed, control was lost during the pilot's attempt to descend to the reported cloud base of 13,000 feet. The airframe was subjected to loads beyond its design limits, causing the right wing to separate.
Laboratory Findings
Post-accident laboratory examination of the vacuum-driven gyroscopes revealed no evidence of high rotation at the time of impact. Both vacuum pumps displayed signatures consistent with failure prior to impact. The check valve manifold was too damaged to determine its operational status before the event.
Sequence of Events
The pilot initiated a descent from FL220 to 13,000 feet in IFR conditions. During this maneuver, aircraft control was lost. The resulting overstress caused structural failure of the right wing. The dual vacuum pump failure likely deprived the pilot of primary attitude reference, though a standby electric horizon was available. However, the specific reasons for the loss of control are not further elaborated in the source.