Accident Overview
On August 12, 1993, an airplane operated by two certified Alaska guides crashed into mountainous terrain. On-scene evidence indicated that the aircraft impacted at a steep angle while rotating to the left.
Aircraft Modifications and Weight
The airplane was equipped with an FAA-approved factory auxiliary 32-gallon belly fuel tank. However, no weight and balance revision was found in the airplane's records. At the time of the accident, the airplane's weight exceeded the maximum allowable by over 20%. Additionally, no flight test or performance data were available for the airplane with the auxiliary fuel tank installed.
The airplane was also fitted with tundra tires. No supplemental type certificate (STC) was recorded for this modification, and no certification flight test had been conducted to determine the center of gravity (CG) envelope with the tundra tires installed.
Investigation Findings
The investigation documented the absence of required documentation for the modifications. The lack of weight and balance data and flight performance information for the modified configuration was noted. The airplane was recovered on August 12, 1993.