PIPER PA-30 — Pond Creek, OK

What happened

The non-instrument-rated pilot and 2 passengers departed on a visual flight rules cross-country flight. Air Traffic Control (ATC) radar and Automatic Dependent Surveillance-Broadcast (ADS-B) data indicated that after takeoff the airplane tracked north and climbed to a cruise altitude of 8,500 ft and then later climbed to 16,500 ft. About an hour and 25 minutes later, the airplane began a descent and turned momentarily to the east. The airplane then turned west and back to the north while it descended. The ground speed decreased from over 200 kts to under 100 kts. Mode C position reporting data was lost followed by the loss of all track data. The airplane was not in contact, nor was it required to be in contact, with ATC.

A witness in the area reported that he heard what sounded like a motocross bike engine revving to full throttle. He then looked up and saw what he initially thought was a weather balloon coming straight down. He realized it was an airplane and videoed the airplane in its descent. The airplane was in a right-hand nose-down spin. The video showed the airplane descend until, moments before impacting terrain, it became obscured by tall grass. In the video, the airplane’s aft fuselage and empennage were separated and neither the propellers nor the outboard wings and fuel tip tanks were seen.

Instrument meteorological conditions (IMC) existed in the area, where Mode C position reporting and all track data was unavailable.

A postaccident examination of the airplane revealed no mechanical failures or malfunctions that would have precluded normal operation. The airplane had a serviced oxygen system; however, no oxygen masks or cannulas were found in the wreckage, and the pilot’s mechanic and flight instructor stated that they were not kept on board the airplane. Federal Aviation Regulations require all occupants on board to use supplemental oxygen above 15,000 ft mean sea level. The pilot’s operation of the airplane above this altitude for almost 90 minutes would have likely led to a performance impairment resulting from hypoxia. The airplane’s track deviations away from its intended destination could have been the result of one or more of the following: 1) an attempt to maneuver the airplane to avoid IMC; 2) the pilot’s impaired performance as a result of hypoxia; and/or 3) the onset of spatial disorientation. However, there was insufficient evidence from which to determine the degree to which hypoxia and spatial disorientation played a role in the sequence of events leading to the airplane’s departure from controlled flight.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.