Mooney crashes after pilot gets carbon monoxide poisoning

The accident occurred during the commercial pilot’s third flight of the day in the Mooney M20C.

The pilot, who used the airplane’s heater throughout the day, reported having a headache and experiencing “butterflies” in his stomach during the end of the first flight. The headache subsided after the flight, and he felt fine during the second flight, but the headache returned after he landed.

Before the third flight, he expedited his time on the ground because he was concerned about getting the engine started in the cold weather. He started the engine and sat in the airplane while he filed his flight plan and got organized for the flight.

While taxiing to the runway, he still had the headache, and he experienced another episode of “butterflies.” He stated that the symptoms were more intense at that time than they had been in the morning, but that they subsided by the time he reached the runway, and he felt “good,” but became “hyper focused.”

He performed an engine run-up and repeated the takeoff checklist three or four times until the controller asked if he was ready to take off, which “snapped” him out of repeating the takeoff checklist. He was in the airplane with the engine running for about 12 minutes before takeoff.

He remembered being cleared to a heading of 240° and setting the autopilot heading bug before taking off. He stated that, while climbing out, he experienced another case of the “butterflies.” He added that he began a turn and activated the autopilot during the turn. The last thing he remembered was being cleared to 6,000′ on a heading of 240°.

After he attempted to check in twice with departure control (he was still on the tower control frequency), air traffic controllers repeatedly attempted to contact the pilot without success.

Radar data showed that the airplane climbed higher than 12,000′ and was off course. The airplane continued to fly until it ran out of fuel and crashed in an open field near Ellendale, Minnesota. The pilot was not conscious until after the airplane hit the field.

He stated he was very confused and had loud ringing in his ears at this point.

He freed his legs from the wreckage and got out of the airplane. He stated he was very weak and had difficulty with his balance and ability to walk as he made his way to a nearby house.

A post-accident examination revealed that the both fuel tanks were empty. The cabin heat was found on, and the cabin vent control was found off. The exhaust muffler had several cracks, one of which contained soot/exhaust deposits on the fractured surfaces, indicating it existed before impact. The crack would have allowed exhaust gases to enter the cockpit/cabin.

The airplane was not equipped with a carbon monoxide (CO) detector.

A review of maintenance records showed that a new exhaust system was installed on the airplane on Jan. 25, 2007, at a tachometer time of 2,343 hours. The last annual inspection was conducted on Feb. 2, 2016, at a tachometer time of 2,998 hours. The tachometer time at the time of the accident was 3,081 hours.

The pilot’s CO level, when tested over 4-1/2 hours after the accident, was 13.8%. Given the half-life of CO in the blood stream over four to five hours while breathing ambient air, the pilot’s CO level at the time of the accident was at least 28% and likely significantly higher because oxygen was administered in varying amounts during the first few hours of his post-accident medical care.

The pilot’s high CO level led to his incapacitation due to CO poisoning and the airplane’s continued flight until it ran out of fuel and hit terrain.

Probable cause: The pilot’s incapacitation from carbon monoxide poisoning in flight due to cracks in the exhaust muffler, which resulted in the airplane’s continued flight until it ran out of fuel and its subsequent collision with terrain.

NTSB Identification: CEN17LA101

This February 2017 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.