Piper PA34 N14GQ accident near Minden, Nevada

Probable cause

The pilot's loss of airplane control due to spatial disorientation while maneuvering in instrument meteorological conditions. Contributing to the accident was the pilot's impairment from the use of a sedating antihistamine.

NTSB analysis

The instrument-rated airline transport pilot was maneuvering the airplane from about 14,500 ft mean sea level (msl) while descending to the destination airport. Throughout the flight, the pilot was communicating with his son via text messaging to ask about the weather conditions at the destination airport, near where his son was located. The pilot's son described a broken cloud layer and advised the pilot that, if the airplane stayed above the clouds, he could then "drop in over the valley." About 2 minutes before the accident, the pilot told an air traffic controller, "I'm going to orbit here to the south…south over the airport I can see it, maneuvering through a hole," GPS data showed that, as the airplane continued to turn to the right, its airspeed increased rapidly, and the right turn tightened.

After completing a full revolution, the airplane exceeded its maximum structural cruising speed and never-exceed speed. The airplane's flight load increased throughout the turn, exceeding the airplane's maximum flight load factor. Immediately afterward, the flight data became unreliable; this point was likely when an in-flight breakup occurred. The location of the separated components in the debris field and the damage to the components were consistent with a tail-first in-flight breakup.

The airplane flight path before the in-flight breakup were consistent with a graveyard spiral caused by spatial disorientation. The pilot's statement to the controller regarding his intent to maneuver through a hole in the cloud layer indicated operation near instrument meteorological conditions (IMC). The airplane's excessive bank, pitch, and load factor coincided with the height of the reported cloud tops (13,000 ft), further indicating that the pilot was likely flying in and out of the clouds as he was attempting to spiral down to the airport. Given the reports of ceilings at 9,500 feet, the in-flight breakup likely occurred in IMC or within seconds of the airplane exiting IMC, precluding the pilot from taking recovery action upon reentering visual meteorological conditions.

The investigation could not determine whether the pilot was using supplemental oxygen while operating the airplane above 14,000 ft msl, as required by federal regulations. However, the communications between the controller and the pilot revealed that the pilot had no appreciable change in speech rate, coherence, or response time, indicating that the pilot was not experiencing hypoxia while in contact with air traffic control.

Although the pilot's coronary artery disease placed him at an increased risk for a sudden cardiac event, no evidence indicated that such an event occurred. Toxicology testing identified diphenhydramine, a sedating antihistamine, in the pilot's cavity blood and liver specimens.

Because experienced instrument-rated pilots should be able to identify spatial disorientation, the pilot's use of diphenhydramine likely contributed to this accident by degrading his judgment and slowing his responses.

Text from the NTSB. Open the NTSB docket for WPR18FA091 for the full record.