Could Not Determine A Reason For Pilot's Incapacitation

In a probable cause report stemming from a September, 2009 accident involving a Mooney M20M, the NTSB found that the accident was likely caused by the incapacitation of the pilot, but could not determine the cause of that incapacitation. The investigation turned up nothing overtly wrong with the pilot or the airplane, though the pilot of an F-16 sent to intercept the Mooney said the pilot appeared to be slumped against the pilot-side cockpit window.

NTSB Identification: CEN09FA610
 14 CFR Part 91: General Aviation
Accident occurred Wednesday, September 30, 2009 in Albany, IN
Probable Cause Approval Date: 10/03/2011
Aircraft: MOONEY M20M, registration: N400DE
Injuries: 1 Fatal.

The pilot became unresponsive to the air traffic controller after his last radio transmission, made as the airplane was climbing through 24,000 feet. The airplane leveled off at its assigned cruise altitude of 25,000 feet and continued northbound to a navigational fix, where it made a planned course reversal to the south and proceeded back toward the departure airport. A plot of the radar track data was consistent with the airplane being flown by its autopilot. A military F-16 fighter jet pilot, who had intercepted and escorted the flight, noted that the accident pilot was lying against the pilot-side cockpit window, unresponsive and possibly hypoxic. The airplane continued on a southerly course for over an hour, after which it entered a series of right turns that were followed by a gradual descent on a north-northeasterly course. After reaching 22,000 feet, the airplane descended rapidly to the ground, colliding with trees and terrain before a ground fire ensued.

The postaccident investigation revealed no preimpact mechanical malfunctions or failures that would have prevented the normal operation of the airplane. The extensive impact and fire damage to the airplane's oxygen system prevented a determination of whether the pilot was actively using supplemental oxygen during the accident flight. A review of the flights since the most recent oxygen cylinder service, completed about 6 months before the accident, indicated that under normal usage there should have been sufficient oxygen available for the accident flight. A review of available medical information did not reveal any findings that would have resulted in pilot incapacitation, including a cardiovascular event, carbon monoxide poisoning, or the use of unapproved medication, illegal drugs, or alcohol.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The incapacitation of the pilot during high-altitude cruise flight for undetermined reasons. (File photo Mooney M20M)

FMI: www.ntsb.gov