Bartels LANCAIR N427LE

The commercial pilot was working on the development and modification of hardware and software systems for the experimental airplane, which was being adapted for unmanned flight; however, the purpose of the flight was for personal reasons. The flight was delayed a day so the pilot could work on the airplane and perform unknown maintenance to restore functionality to the batteries, which had been drained. After takeoff, the pilot contacted air traffic control, stating that he was at 18,100 ft and climbing to 21,000 ft. The controller responded that he was cleared to climb and maintain 25,000 ft, which was the altitude listed in the pilot's flight plan. About 4 minutes later, the pilot made his last radio transmission, which was a response to the controller's frequency change instructions. The pilot read back the new frequency correctly; he also made a slight stutter at the beginning of the transmission and double clicked the microphone. The controller checked to see if the pilot was on the frequency about 5 minutes later but did not receive a response. There were insufficient voice communications to determine if the pilot was experiencing hypoxia. Radar data indicated that the airplane made a continuous climb until reaching 25,000 ft and tracked a jet route, passing over a series of waypoints, consistent with the autopilot controlling the airplane. After the controller did not receive a response from the pilot, two military jets intercepted the airplane. Despite trying to get the pilot's attention, they were unable to get a response from or see the pilot inside the cockpit. The airplane overflew the destination airport and eventually descended into the ocean after 4 hours 22 minutes in flight, which was likely when the engine lost power due to fuel exhaustion. The airplane's flight track and the pilot's lack of responsiveness are consistent with pilot incapacitation. After impacting the water, the airplane floated for at least 42 minutes before it sank, which indicates that no catastrophic decompression event occurred because the airplane's pressure vessel was intact enough to not rapidly fill with water. The airplane eventually sank and was not recovered, which precluded any physical examination of the wreckage. Therefore, the configuration and status of the airplane's pressurization and oxygen systems could not be determined. The pilot had received training in the airplane and would have known how the pressurization system operated. He had been in a hypobaric chamber and was likely familiar with the symptoms of hypoxia. He reportedly did not use any medications and was in good health. Because the pilot's body was not recovered, an autopsy and toxicology testing could not be conducted. One of the military pilots who intercepted the airplane stated that, although he could not see anyone in the airplane, he saw what he believed to be a seatbelt shoulder harness fully forward and extremely tight. It is likely that the accident pilot was not visible because he was fully slumped over into the right seat or on the floor.

Quoted verbatim from the NTSB record.