Gray Leasing

Piper PA-31 Cheyenne

The pilot had filed an instrument flight rules (IFR) flight plan for 25,000 feet mean sea level (MSL), and he amended it to 27,000 feet MSL en route. About 36 minutes after the altitude change to 27,000 feet, the pilot advised air traffic control (ATC) that he had lost cabin pressurization and needed an immediate descent. About 20 seconds later he was cleared to 25,000 feet, then 15 seconds later to 15,000 feet. Shortly after the pilot acknowledged the lower altitudes, the radio communications deteriorated to microphone clicks with no carrier. The aircraft started a shallow descent with slight heading changes, then was observed to make a rapid descent into desert terrain. About 10 months prior to the accident the aircraft had been inspected in accordance with the Piper Cheyenne Progressive Inspection 100-hour Cycle, event No. 1. According to the servicing agency, the aircraft inspection was completed and the aircraft was returned to service with a 12,500 feet MSL altitude restriction due to unresolved oxygen system issues. The last oxygen bottle hydrostatic check noted on the bottle was October 1989. The oxygen system was in need of required maintenance and the masks were in a rotted condition. The pilot failed to report his severe coronary artery disease condition, medications, and other conditions to his FAA medical examiner for the required flight physical.