Accident Overview
The airplane was destroyed during an in-flight breakup and subsequent impact with terrain. According to communications, the pilot advised the controller that the airplane was losing its gyros and that he needed to descend. The pilot later reported that the gyros appeared to be working. The controller advised the pilot that the airplane was on a southwest heading and that the pilot could fly whatever altitude he was able to maintain.
Pilot Communications
The controller asked if the airplane was in the clouds, and the pilot replied affirmatively. The pilot's last transmission stated that the airplane was going into a spin. Radar contact was lost around that time.
Witness Observations
A Sheriff's report included statements from two witnesses. They reported hearing thunder or jets, followed by a high winding noise from the plane's engine directly above their position, then a loud bang. They observed the airplane at an estimated 1,500 to 2,000 feet above ground level, spinning straight down without its wings. They also noted something hanging from the tail section.
Meteorological Conditions
A Meteorological Factual Report compiled for the flight indicated that the plotted radar track showed the airplane in layered clouds, with visual flight rules weather conditions below the clouds. Recorded groundspeed varied between 130 and 160 knots. Winds aloft were headwind and quartering winds.
Aircraft Information
The airplane's information manual limitations section stated maneuvering speeds: 4,000 pounds – 130 knots indicated airspeed (KIAS), 3,350 pounds – 119 KIAS, 2,700 pounds – 106 KIAS, with a remark: "Do not make full or abrupt control movements above this speed."
Post-Accident Examination
Examination of recovered wreckage revealed a flapper valve in the vacuum manifold that exhibited deterioration and a crack. General observation of the manifold indicated it had been disassembled and reassembled with non-manufacturer specified rivets. No further airframe or engine preimpact anomalies were detected. Examination of instrument gyro rotors revealed rotational scoring.
Post-accident toxicology evaluation of specimens from the pilot was consistent with the intermittent use of fluoxetine (a prescription antidepressant often known by the trade name Prozac). The pilot did not indicate any mental conditions or the use of any psychiatric medications on applications for airman medical certificate.