13 Aug 20157:01 reconstruction614 views

Pilot Stops Responding — N427LE Flies for Four More Hours

Flight Follower Editorial Team

A high-altitude experimental Lancair continued on autopilot after the pilot’s last radio call, was intercepted by military aircraft, and eventually descended into the Pacific.

Accident Facts

Item: Detail
Incident date: August 13, 2015
Registration: N427LE
Aircraft: Bartels Lancair Evolution (experimental)
Location: Pacific Ocean, about 490 nm northwest of San Francisco
Operation: Part 91 personal flight
Category: Fatal crash — pilot incapacitation
NTSB probable cause: The pilot’s incapacitation for reasons that could not be determined because the airplane was not recovered from the ocean
NTSB report: WPR15LA242
Reconstruction: ATC audio reconstruction

Timeline — all times Pacific Daylight Time (PDT)

1. 18:15 PDT —

N427LE departed Phoenix Deer Valley Airport for Hesperia.

2. 18:25:24 PDT —

The pilot contacted Albuquerque Center at 18,100 ft and reported climbing.

3. 18:29:54 PDT —

The pilot made his last radio transmission while climbing through about 22,800 ft; he correctly read back a frequency change.

4. About 18:32 PDT —

The aircraft reached 25,000 ft and continued along its programmed route.

5. About 18:50 PDT —

The aircraft turned south-southwest, then continued west after an S-turn and route changes.

6. About 19:00 PDT —

Two F-15s and a KC-135 intercepted the aircraft near Fresno.

7. After the interception —

The fighters attempted to attract the pilot’s attention with maneuvering and flares; there was no response.

8. Later —

The aircraft continued west at about 25,000 ft and overflew its destination.

9. About 22:35 PDT —

After approximately 4 hours 22 minutes of flight, the aircraft descended into the Pacific, consistent with fuel exhaustion.

A Flight That Looked Normal on the Radio

The pilot’s first ATC transmission showed a high-altitude climb and normal communication. His final radio transmission four minutes later was coherent enough to correctly read back the next frequency.

Then There Was Silence

The controller attempted to establish contact again several minutes later. There was no response. Radar, however, showed that the aircraft continued along its programmed route and reached 25,000 ft.

The Autopilot Kept Flying

The aircraft’s continued flight was consistent with autopilot operation. It crossed waypoints and eventually overflew the planned destination without any evidence that a pilot had intervened to change the flight path.

The Military Intercept

Two F-15 fighters and a KC-135 tanker intercepted the aircraft near Fresno around 19:00. The fighters attempted to attract the pilot’s attention through maneuvering and flares. One fighter pilot maneuvered to about 200 ft and, using night-vision equipment, reported seeing what appeared to be a tightly forward shoulder harness in the cockpit. There was no response. The aircraft nevertheless continued west at approximately 25,000 ft.

Why Hypoxia Was Considered

The aircraft was operating at high altitude, so investigators examined the pressurization and oxygen systems. The aircraft had previously had a cabin-pressure discrepancy that had reportedly been corrected. A new carbon-monoxide detector had also been installed earlier that year. Because the aircraft sank and was not recovered, investigators could not physically examine the systems after the accident.

The Long Final Flight

The aircraft remained airborne for about 4 hours 22 minutes. Its eventual descent into the Pacific was consistent with fuel exhaustion after the pilot had become incapacitated. The NTSB could not establish the specific medical or physiological reason for the incapacitation.

What Could and Could Not Be Proven

After impact the aircraft remained afloat for at least 42 minutes before sinking. The NTSB noted that this was evidence against a catastrophic decompression event that would have caused the pressure vessel to fill rapidly with water. Because the wreckage was never recovered, investigators could not conclusively determine the condition of the pressurization or oxygen systems. The formal probable cause therefore remained incapacitation for an undetermined reason.

Conclusion

N427LE is unusual because the aircraft continued to perform much of the flight normally after the pilot apparently stopped functioning. ATC lost the pilot but not the aircraft, and the military interception confirmed that the airplane was still flying without effective pilot response. The NTSB could establish incapacitation, but not why it occurred.

Primary Source / Investigation Record

Investigation reference: WPR15LA242

Sources & Reconstruction Note

https://data.ntsb.gov/Docket?NTSBNumber=WPR15LA242

Audio from the original air traffic control recording, sourced from public recordings and released investigation records. The reconstruction, animation and written account are our own.

Primary Investigation Reference

NTSB accident number: WPR15LA242