Incident Overview
The crew was informed that the aircraft's vacuum pump system was inoperative due to a sheared pump driveshaft. The copilot noted that the Flight Service Station (FSS) had forecast broken clouds at 25,000 feet and expressed that the pump was not necessary.
Flight Sequence
At 1735, the pilot contacted air traffic control center and requested radar advisories to Brownsville. Later, at 1812, the pilot requested and was granted permission to deviate around a weather cell. Approximately 12 minutes after the deviation, the aircraft's radar target disappeared.
Wreckage Examination
Examination of the wreckage revealed that the tail and right wing had separated from the aircraft in flight.
Weather Conditions
Weather radar indicated a VIP Level 1 echo within 5 miles east of the accident site and a VIP Level 3 echo within 10 miles southeast. Moderate to severe convective turbulence, along with updrafts and downdrafts, would have been present below 10,000 feet.
Toxicology Results
Analysis of the pilot's liver tissue produced an ethyl alcohol concentration of 96 milligrams percent, while mixed tissue fluid showed 112 milligrams percent.