ANC04FA084 · Cessna 170B

The private pilot was transporting friends to an unimproved airstrip on a riverbank to go fishing. A pilot, who had landed his airplane at the airstrip earlier, reported that the accident airplane made two slow passes over the landing area in opposite directions, about 2 feet above the ground. The witness said on the second pass he noticed that the right engine cowl was unsecured. He said the airplane had a tailwind, and that during the initial climb after the pass, the airplane started a turn to the right. He said "the upper wing stalled," the airplane inverted, and "went vertical into the ground." The airplane impacted the terrain approximately 60 degrees nose down. The four occupants of the airplane were fatally injured. The wings and fuselage of the airplane sustained extensive structural damage. Pilots in the area said they heard the pilot making routine position calls in the airstrip's pattern on the common traffic advisory frequency (CTAF). A video, made by the right front seat passenger, confirmed that the right engine cowl came open during the flight to the airstrip, and that the pilot did not appear overly concerned. The airplane's owner said there were no known mechanical anomalies with the airplane prior to the accident flight. An approximate weight and balance calculation indicated that the airplane was at or near maximum gross weight, and the center of gravity was at or near the aft limit at the time of the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset