Incident Overview
A student pilot and flight instructor were flying a Cessna 172N, registration N6101F, southeastbound at an altitude of 2,000 feet toward the WSBR 740 AM radio tower. As they approached the tower, another airplane appeared suddenly very close in the right corner of their windshield, having come from behind the blind spot created by the right wing. The student pilot stated that the other pilot appeared to see them at about the same time, and both initiated right turns to avoid each other. As the student turned right, the other airplane moved across the windshield from right to left, just above the glare shield. The student then felt an impact as the left wing of N6101F collided with a portion of the other airplane. N6101F tumbled and entered a spin to the left. During the spin, the student saw another airplane about 250 to 300 feet below, appearing inverted. The flight instructor confirmed the student's account and immediately took control, executing an emergency landing on a dirt road.
The other aircraft, a Cessna 172M registered N9840V, impacted the ground at a near vertical angle and was destroyed.
Aircraft Damage
Initial examination of N9840V revealed that the outboard portion of the right horizontal stabilizer/elevator segment, as well as the vertical stabilizer/rudder assembly, had detached from the empennage. The detached vertical stabilizer/rudder had a scrape and crease stretching from the leading edge aft through the entire assembly.
The left wing of N6101F sustained a scrape mark beginning 49 inches from the root, outboard. A gouge and hole commenced about 6 inches outboard of the scrape mark at station 136, continuing along the undersurface of the wing aft at an angle of approximately 53 degrees relative to the leading edge, to the main spar, terminating at station 172.
Examination Findings
A missing left elevator counterweight, an 11- by 7.25-inch section that had been absent from the aft portion of N9840V's elevator, had penetrated the wing of N6101F, creating the gouge and wedging itself at station 172. As the counterweight traveled through the wing, the spar and ribs at stations 154 and 172 fractured.
Paint transfer consistent with the impact was found on the left side of N9840V's stabilizer/rudder in the area of the scrape and gouge, as well as on the outboard leading edge of the left wing of N6101F.