Accident Details
Three Piper J3 Cubs departed from an airport located in a valley surrounded by higher terrain. The density altitude at the time was approximately 3,000 feet. Each airplane turned toward rising terrain consisting of lower finger ridges and canyons, and a higher main ridge.
The first airplane, carrying only a pilot, climbed faster than the terrain and turned downwind without incident. The second and third airplanes each carried a pilot and a passenger. The pilot of the third airplane, which was operated about 100 pounds (9%) over its gross weight, reported that he watched the second airplane descend into trees. After overflying the second airplane, he encountered descending air that drove him into the trees.
The pilot of the third airplane reported no problems with the airplane or engine. Prior to the flights, the pilots had been briefed on alternate departure routes that would not require an immediate climb over rising terrain, but those routes were not used.
Environmental and Operational Factors
FAA publications advise of the need to reduce weight when operating under higher density altitudes and to approach ridgelines at a 45-degree angle to provide an escape path in case of turbulence or descending air. No further details on weather conditions or visibility were provided.