Accident Sequence
On August 17, 2020, at about 2236 eastern daylight time, a Piper PA-34-200, registration N41382, was substantially damaged when it impacted a house near Groton-New London Airport (GON), Groton, Connecticut. The flight instructor and the pilot receiving instruction sustained minor injuries; an occupant of the house was not injured. The airplane was being operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
According to the flight instructor, the flight departed GON at about 1700 and flew directly to Bangor International Airport (BGR), Bangor, Maine, where they landed uneventfully and the fuel tanks were filled. The flight departed BGR around 2000 and proceeded to Augusta State Airport (AUG), Augusta, Maine, where the pilot receiving instruction performed one touch-and-go landing. The flight then continued to Portland International Jetport (PWM), Portland, Maine, where the pilot performed three touch-and-go landings. After the last touch-and-go at PWM, the flight proceeded to GON, where the pilot performed two touch-and-go landings to runway 23.
The flight then departed and remained in the traffic pattern for runway 23. While abeam the approach end of runway 23 with the landing gear extended and 10° of flaps extended, the pilot receiving instruction began a descent while turning onto the base leg. The flight instructor reported hearing an engine sputter, verifying the controls were in the proper position. He heard the engine sputter again, felt the airplane jerk, and took control. He maintained airspeed, verified the engine controls were full forward, retracted the flaps, but left the landing gear extended due to the altitude and proximity to the airport. He identified the malfunction as the right engine, which seemed to be developing some power but less than the left. He briefly pitched the nose down, then up, and when he noticed a high descent rate, he moved the right propeller control to the feather position and placed the right mixture control to idle cutoff. He looked for a landing area and maneuvered for a street. During the flare, he felt a collision. The airplane came to rest suspended by the roof structure of a house.
Examination of Aircraft Systems
Examination of the cockpit while the airplane was suspended on the roof was not performed by a Federal Aviation Administration (FAA) inspector due to safety concerns. A photograph taken before removal revealed that the left throttle control was full forward and the right throttle control was at the aft stop. The left propeller control was about 65% forward travel, the right propeller control was about 75% forward travel. The left mixture control was about 60% forward travel, while the right mixture control was at idle cutoff. The left cowl flap was closed; the right cowl flap was open. The left engine alternate air control was on; the right engine alternate air control was off.
The airplane was recovered for further examination. After removal, the FAA inspector reported that fuel was present at both fuel strainers and oil was present in each engine. Examination revealed that all engine controls remained attached to their respective attach points at each servo fuel injector and propeller governor. Flight control continuity for the ailerons, elevator, and rudder was confirmed, except where control cables were cut for recovery. The flap handle was in the down/stowed position, consistent with flaps retracted. Both auxiliary fuel pump switches were in the on position and both tested satisfactorily. Both fuel tanks in both wings were breached and did not contain any fuel; neither fuel strainer contained residual fuel.
The left fuel selector was in the ON position; the right fuel selector was in the CROSSFEED position. No obstructions in the fuel supply lines were noted. Both CROSSFEED drains were checked, and about 6 ounces of fuel drained from the bottom of the airframe. The fuel had an odor and viscosity consistent with 100LL aviation gasoline, but the liquid was cloudy and lacked the typical blue tint. No water was detected in the fuel sample. Operational testing of each fuel selector revealed no evidence of preimpact failure or malfunction.
Engine and Propeller Examinations
Examination of the left and right engines and their systems revealed no evidence of preimpact failure or malfunction. Both propeller governors and propellers were examined at the manufacturer's facility with virtual oversight from the National Transportation Safety Board. Examination of the left propeller revealed impact damage that precluded functional testing; disassembly showed no evidence of preimpact failure or malfunction. The damage to the propeller blades was consistent with the engine not developing high power at impact.
Visual examination of the right propeller revealed blades appearing to be on the start locks. The amount of engine oil drained from the right cylinder was greater than expected if the propeller were in the feathered position, consistent with the blades being in low pitch and the governor not having dumped oil to the engine. After removal of the start lock/feather stop sleeve assembly and when air pressure was removed, both blades moved to the feather position. Cycling of the propeller blades from feather to low pitch was performed several times using shop air with no discrepancies noted. No evidence of preimpact failure or malfunction was noted to the propeller, and the blades exhibited minimal damage consistent with the engine not developing power at impact. The right propeller was not disassembled.
Operational testing of the left propeller governor revealed several minor out-of-tolerance conditions: control lever travel, high rpm setting (40 rpm too low), and relief pressure (1 psi too high). All other checks, including feather check, were within limits. Operational testing of the right propeller governor revealed all checks within limits, except the high rpm setting was 21 rpm too low. Neither propeller governor was disassembled.