Incident Overview
A charter flight, on a return tour trip after landing at Grand Canyon National Park Airport, experienced an engine problem shortly after departure. The airplane had been on the ground for three hours without fueling or maintenance. After takeoff from runway 21, the pilot transmitted that he had a problem and declared an emergency, stating '...I'm single engine right now....' The airplane was observed at 100-200 feet above the terrain at that time.
Sequence of Events
The airplane continued flying for about six minutes, maneuvering through a crosswind, downwind, and right base leg for runway 21 before colliding with trees approximately 2.5 miles northeast of the airport.
Environmental Factors
The airport is situated in terrain that slopes upward from south to north and west to east. Winds were gusting to 29 knots, and the density altitude was 6,870 feet. These conditions were noted as factors in the accident.
Investigation Findings
Examination of the suspect left engine did not reveal any evidence of failures or malfunctions. The investigation identified deficiencies in the Federal Aviation Administration's oversight of the airline's maintenance program and in the airline's extension of the time-in-service interval of the engines. The airline's Airworthiness Assurance Inspection Program (AAIP) did not require a maximum rated power check of the engines as specified by the engine manufacturer's service instruction. Additionally, the time between overhauls (TBO) of the engines had been extended from 1,800 to 2,400 hours.
Probable Cause
The probable cause, as stated in the official findings, is a loss of power on one engine for an undetermined reason(s), and the pilot's improper decision to return to the departure airport for landing which necessitated maneuvering over increasingly higher terrain. Factors in the accident were: the high gusting wind, the high density altitude, the rising terrain, and the reduced single-engine performance capability of the airplane under these conditions.