Sequence of Events
According to a witness, the airstrip owner, an airplane approached from the west and landed on the airstrip. The pilot then taxied to the west end and took off to the east. The witness described the takeoff as "perfect." After losing sight of the airplane, the witness heard what sounded like two shots. He assumed that "two guys were shooting muzzle loaders" and that the airplane had "scared up some elk for them to shoot at." The witness expected the pilot to return and land, but the airplane never came back. Approximately 30 minutes later, a friend informed the witness that the airplane had gone down.
The witness's wife reported seeing the airplane begin a left banking turn, then observing "two puffs of smoke" coming from the airplane, and hearing "two bangs" before losing sight of it.
Airstrip and Pilot Observations
The airstrip owner, who knew the pilot, stated that this was the first time the pilot had landed at that airstrip. He noted that when the airplane took off, the engine sounded normal. The owner, who flies his own Maule in and out of the airstrip, commented that taking off to the east would put the airplane in a canyon, whereas taking off to the west through the larger part of the valley was preferable.
Examination Findings
An examination of the airplane revealed no anomalies. However, all of the engine spark plugs were noted to be light brown in color, which is indicative of the engine being operated at a lean fuel-air mixture setting.
Technical Information
According to a manufacturer's representative, with the turbocharger installed, the operator must run the engine at the rich mixture setting to achieve the same performance at higher elevations as the engine would at sea level. Any leaning at all would produce backfires and loss of performance.
The density altitude calculated for the area was 11,246 feet above mean sea level. Turbocharger information indicated that at an altitude of 13,000 feet and 76 percent horsepower, the airplane's climb rate was 500 feet per minute.