Overview
Three Piper J3 aircraft departed from an airport situated in a valley, with higher terrain in the vicinity. The reported density altitude was approximately 3,000 feet. Each airplane turned toward rising terrain, which consisted of lower finger ridges and canyons, as well as a higher main ridge.
Sequence of Events
The first airplane, carrying only a pilot, climbed at a rate faster than the terrain and turned downwind without incident. The second and third airplanes, each carrying a pilot and a passenger, attempted to follow similar flight paths.
The second airplane was operating at gross weight. The pilot reported encountering descending air that forced the aircraft downward until it struck trees. The pilot further stated that there were no engine or airplane problems during the flight.
Aircraft and Equipment
The second airplane was equipped with a cruise propeller, which increases cruise speed but reduces the airplane's rate of climb. No other mechanical issues were noted.
Pilot Actions and Prior Briefing
Prior to departure, the pilots had been briefed on alternate departure routes that would not have required an immediate climb over rising terrain. However, those routes were not used during the actual departures.
FAA Guidance
FAA publications advise that when operating with higher density altitudes, pilots should reduce aircraft weight and approach ridgelines at a 45-degree angle to allow for an escape path in case of turbulence or descending air.