Groton — The flight instructor aboard the twin-engine Piper PA-34-200 that crashed into a Groton home last month said the engine sputtered and he detected that the right engine was producing less power than the left engine, according to a preliminary report issued by the National Transportation Safety Board.

The report states that the small aircraft, with the instructor and a pilot under instruction aboard, initially departed Groton about 5 p.m. Aug. 17 for Bangor International Airport in Maine, where they filled the tanks with fuel.

The plane departed from Bangor about 8:02 p.m. for Augusta State Airport, where the pilot being trained performed one “touch-and-go landing” — landing on a runway and taking off again without coming to a complete stop — and then flew to Portland International Jetport for three touch-and-go landings, according to the report. The aircraft then departed for Groton.

After performing two touch-and-go landings at Runway 23 of Groton-New London Airport, the plane left and continued to fly in the traffic pattern for that runway.

As the plane began to descend while making a turn on the flight path, the instructor said “he heard an engine sputter” and made sure the controls were in the proper position. He then heard “the engine sputter again" and “felt the (plane) jerk,” so he took control of the plane, according to the report.

Because of the plane's altitude and closeness to the airport, he decided to leave the landing gear extended, the report said. He confirmed the malfunction was in the right engine, which he realized was still producing some power “but with less output” than the left engine. He looked for a landing spot and “maneuvered for landing on a street," the report said. As he was adjusting the controls to land, "he felt a collision.”

The plane landed on the roof of the house at 243 Ring Drive about 10:36 p.m., significantly damaging the home. The homeowner, Kenneth Johnson, was sleeping when the plane crashed and was able to leave the house without injuries.

The report said he was uninjured but his throat was irritated by odors from the plane's fuel.

The instructor and student pilot were taken to the hospital with minor injuries. The NTSB did not release their names in the report.

The visibility was 10 miles that night, according to the report.

The crash did not cause a fire or explosion, but the plane was substantially damaged, the report said. The state Department of Energy and Environmental Protection reported last month that 16 gallons of fuel potentially leaked from the plane, with most of it believed to be contained in the home. 

Federal Aviation Administration records show the small aircraft was built in 1974 and is registered to Upgrade Incorporated of 155 Tower Ave. in Groton.

Upgrade Incorporated President Ryan Gauthier was not immediately available to comment on Tuesday but said last month that the company was cooperating with the investigation.

Connecticut Airport Authority said the CAA has no further comment, as it is an ongoing investigation, “but will remain supportive of the NTSB investigative process.”

NTSB spokesman Eric Weiss said the preliminary report contains factual information about the crash, while the probable cause for the crash will be issued at the end of the investigation.

k.drelich@theday.com