Accident Overview
On June 1, 2016, at approximately 0854 eastern daylight time, an Aeronca 7AC, registration N83547, was substantially damaged during a training flight near Toughkenamon, Pennsylvania. The airplane was operated under Title 14 Code of Federal Regulations Part 91 as an instructional flight. The student pilot and flight instructor sustained minor injuries.
Flight Sequence
The student and instructor were conducting takeoffs and landings on grass adjacent to a runway at New Garden Airport (N57). During the downwind leg of the traffic pattern, the instructor directed the student to demonstrate a simulated engine failure followed by a go-around. The student performed a power-off landing, making a steep turn to base and an even steeper turn to final approach. As the airplane was still above the grass and about one-quarter of the way down the parallel runway, the student initiated the go-around. The instructor told him to move the airplane over the center of the runway. At that point, the engine “sputtered” and then lost all power.
According to the instructor, after the power loss when the airplane was about 200 ft above ground, he assessed landing options and decided against continuing forward due to many obstacles. He took the controls and turned the airplane left 90°, positioning it over a hangar for a touchdown and rollout on the grass uphill to dissipate speed. As the turn progressed, he realized the airplane would likely not clear the top of the hangar. He pulled the airplane into a 45° nose-up position so the engine would penetrate the metal door before the fuselage. The airplane then penetrated the hangar wall and came to rest inside the hangar.
Postaccident Examination
Examination of the airplane revealed extensive damage: the fabric covering had multiple tears and punctures; both left and right main landing gear were collapsed and displaced; both wing spars were broken and wings folded aft; the horizontal stabilizers, elevators, vertical stabilizer, and rudder showed crushing and compression damage. Flight control continuity was established. The propeller spinner was crushed; one blade was bent back under the engine, and the other was straight, with no evidence of S-bending, leading edge gouging, or chordwise scratching.
The engine was examined: the air filter was clean, spark plugs normal, carburetor venturi clear, and clean bright fuel consistent with 100LL aviation gasoline was present. Oil was found. The engine was test run with no anomalies noted. No preaccident mechanical malfunctions or failures were found that would have precluded normal operation.
The engine control panel was missing a grommet that normally supported the fuel shutoff rod and provided resistance to movement. The aperture where the grommet would be installed was elongated. The fuel shutoff rod was loose and could be moved easily; the universal joint connecting the rod was worn and also moved easily.
Seat and Restraint System
The airplane seats were primarily tubing with seat bottom and back cushions. The original restraint system was lap belts only, but at some point, shoulder harnesses were installed on both front and rear seats, creating a 4-point system. Maintenance records did not show when or by whom the shoulder harnesses were installed. During impact, the front seat shoulder harness functioned as designed, but the rear seat shoulder harness pulled loose from its mounting. The instructor sustained minor injuries when he struck the front seatback and control stick. The front shoulder harness was secured to the rear spar carry-through with bolts through a metal reinforcing channel. The rear shoulder harness was not bolted or positively secured; it was clamped over two 5/8-inch diameter tubes with upper and lower triangular attachment brackets. Examination of the rear brackets showed permanent bending deformation and yellow paint transfer marks consistent with the bracket assembly being pulled or sliding over the structural tubes. The manufacturer of the shoulder harness assembly could not be determined as it had no part or serial numbers.
Additional Details
The student reported that during the go-around, when he attempted to put the carburetor heat control back in, it was possible he closed the fuel shutoff valve instead. The instructor reported checking the magnetos, carburetor heat, and fuel shutoff valve after power loss, and all appeared in proper positions.
The airplane was constructed of welded tubing and fabric-covered fuselage. The fuel tank was behind the firewall, gravity-feeding fuel to a gascolator and then the carburetor. A float-type fuel gauge was on top of the fuel tank. The fuel shutoff valve, ignition switch, and carburetor heat control were on the engine control panel. The airplane was not equipped with an optional fuel shutoff valve handle guard.
The most recent annual inspection was completed on March 8, 2016, at which time the airplane had accrued about 6,410 total hours of operation.