What happened
The flight was operating under visual flight rules at an altitude of 9,500 feet with air traffic control providing flight following services. The pilot, who did not hold an instrument rating, communicated to controllers that he was unable to maintain visual meteorological conditions and subsequently climbed to 11,000 feet. He again informed air traffic control that he could not maintain VFR and intended to descend.
Air traffic control observed the aircraft enter a left turn starting from a south-southeasterly heading, continuing through north and west before it disappeared from the radar scope. A pilot witness on the ground heard the engine power fluctuate as the aircraft was inside the clouds. This witness then saw the aircraft emerge from the cloud base in a spin with a portion of the right wing missing. The aircraft crashed into a swamp, resulting in the deaths of 3 fatal occupants.
At the time of the accident, weather conditions at ground level were visual with a cloud base estimated at 2,000 feet and visibility of at least five miles.
The investigation
Investigation revealed that on the day prior to the accident, a mechanic had advised the pilot that the engine-driven vacuum pump was inoperative. Both the attitude indicator and the heading indicator rely on vacuum power for operation. The loss of these instruments likely contributed to the pilot's inability to maintain control when he encountered instrument meteorological conditions.
Findings
The primary factors leading to the accident were the pilot's decision to continue flight into clouds while unable to maintain VFR without an instrument rating, and the failure of the vacuum system which rendered critical flight instruments inoperative. The combination of these factors resulted in spatial disorientation and loss of control.