Flight Details
The flight involved mountain flying techniques. During the flight, the student observed that the aircraft was not climbing normally. The CFI suggested reducing speed to 70 knots. The student initiated a turn toward a wide valley, but the CFI directed him to continue toward the mountains, which led the aircraft into a narrower valley with rising terrain.
Loss of Climb Capability
After the student reported that the aircraft was not climbing at all, the CFI took control. He was unable to re-establish a climb and determined that a turn-around was no longer a safe maneuver. He slowed the aircraft and mushed it into the trees.
Carburetor Heat and Flap Usage
The CFI reported that he applied carburetor heat when they were no longer able to climb, but after noticing a drop in RPM within 15 seconds, he switched carburetor heat back to cold. He then slowed the aircraft to 57-58 knots and extended 10 degrees of flaps.
Aircraft Performance Reference
The Cessna 172P Pilot's Operating Handbook (POH) indicates that the best angle of climb speed (Vx) varies from 60 to 65 knots from sea level to 10,000 feet. The POH suggests flaps up to obtain best angle performance.
Accident Outcome
The aircraft came to rest inverted, leaving the occupants inverted. They reportedly had difficulty releasing their seat belt buckles.