What happened
On December 14, 2008, a Beech C90A King Air, registration N43KM, crashed into terrain near Rocksprings, Texas. The aircraft had departed Hondo Municipal Airport (HDO) for Phoenix Goodyear Airport (GYR) under instrument flight rules.
After climbing to 17,000 feet, the aircraft began a meandering flight path that drifted increasingly off course. Although the pilot acknowledged several instructions from air traffic control, the flight path remained erratic. While passing through 18,000 feet, the pilot made his final intelligible radio transmission. Upon reaching 24,000 feet, the pilot failed to respond to further controller inquiries. At 14:56, radar showed the aircraft descending to 21,000 feet before entering a rapid descent. Witnesses reported seeing the airplane falling in a slow spin with white smoke, and one witness noted seeing an engine appear to depart the aircraft shortly before impact. The pilot, the sole occupant, sustained 1 fatal injury.
The investigation
Investigators examined the wreckage and found the fuselage was upright but the rear fuselage had separated forward of the FS 364 bulkhead. Both engines had separated from their respective firewalls in a downward direction. The cockpit examination revealed that the throttle levers were forward, the landing gear lever was in the UP position, and the flaps were retracted.
Crucially, investigators found that both the left and right bleed air switches were in the closed position, and the airplane pressurization switch on the console was set to the DUMP position. The pilot's oxygen mask was found in the cockpit, but the connecting plug was broken off, and the pilot was not wearing the mask at the time of the crash. Testing of the cabin altitude warning switch showed it activated at approximately 10,800 feet, which was outside the required tolerance of 10,000 feet +/- 500 feet.
Findings
- The pilot failed to properly configure the aircraft's pressurization controls.
- The configuration of the bleed air switches and the pressure dump switch led to the pilot's impairment and subsequent incapacitation due to hypoxia.