What happened
While operating in instrument meteorological conditions (IMC), the pilot notified approach control that the aircraft had experienced a loss of its vacuum system. In an effort to reach visual meteorological conditions (VMC), the pilot requested a lower altitude. However, the pilot subsequently reported being unable to locate visual conditions. The airplane eventually departed controlled flight and impacted the terrain.
The investigation
Investigators examined the aircraft's vacuum components following the accident. The primary vacuum pump was found to be inoperative, exhibiting fractures within the rotor and vanes. Additionally, the standby system was determined to be incapable of operation. This failure was caused by a restriction within the system, resulting from the migration of a gasket or sealing material which blocked a hole drilled for the installation and operation of the standby system.