Accident Details
On July 5, 2011, at approximately 1700 eastern daylight time, a Piper J3C-65 (registration N98550) experienced a partial loss of engine power and collided with trees shortly after takeoff from Walter J. Koladza Airport (GBR) in Great Barrington, Massachusetts. The personal flight was conducted under 14 CFR Part 91 with no flight plan filed. Visual meteorological conditions prevailed. The airline transport pilot was not injured; the passenger sustained minor injuries. The flight was originating at the time.
Pilot Actions
The pilot reported that the accident flight was the first operation of the airplane in six months. He performed an extensive engine run-up, visually checked the fuel level and quality, noted 7 gallons of fuel before takeoff, and observed no anomalies. During a normal takeoff, at about 150 feet above ground level, the engine rpm decreased from approximately 2200 rpm to 1700 rpm. The pilot reduced the pitch angle and searched for a landing area. He unsuccessfully attempted to regain full engine power by checking the magnetos and carburetor heat. Oil pressure and temperature gauges indicated normal ranges. The pilot elected to land the airplane between two houses. During the landing roll, the airplane struck underbrush and trees, coming to rest in trees and foliage.
Aircraft Damage
Examination by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest about 3,000 feet from the departure end of runway 29. The fuselage skin was punctured by a tree branch. A fuselage tube was broken at the lower fuselage tubing cluster and bent aft. The left wing leading edge was impact damaged and dented in several locations. The upper engine cowl and engine baffling were impact damaged. The carburetor was examined and fuel was noted inside, with no debris in the fuel screen. The tachometer indicated 689.6 hours.
Aircraft and Engine Information
According to FAA records, the airplane was manufactured in 1946 and most recently registered to an individual in 2010. It was equipped with a Continental Motors C90-8F, 90-horsepower engine. The most recent annual inspection was performed on December 10, 2010, at which time it had accumulated 1,776 total flight hours and a tachometer time of 689 hours. A compression check during that inspection showed cylinder compression ranging from 74 to 78. The engine's most recent overhaul was on June 5, 1994, at a tachometer time of 221.5 hours.
Postaccident Engine Examination
A postaccident engine examination revealed that cylinders No. 2 and No. 3 displayed no anomalies during compression testing. Cylinder No. 1 leaked from the exhaust valve through the exhaust system, resulting in a compression ratio of 50/80. After tapping the rocker arm with a mallet, compression improved to 60/80. Cylinder No. 4 had a compression ratio of 42/80. Disassembly of cylinder No. 4 revealed a leaking exhaust valve and a scored intake valve stuck in its guide. The intake valve would not operate and had to be removed with a mallet and drift.
Engine Manual Excerpt
The engine overhaul manual, in a section labeled "engine troubles and service repair," stated that low power could result from scored valve stems. The manual also noted that proper steps must be taken for infrequently used engines to lessen corrosion, especially if based near the sea coast or in areas of high humidity and flown less than once a week. It recommended flying the aircraft at least once a week long enough to reach normal operating temperatures to vaporize moisture. Storage recommendations included flyable storage (7 to 30 days), temporary storage (up to 90 days), and indefinite storage. Indefinite storage involved replacing engine oil with anticorrosive oil, installing cylinder dehydrator plugs, and sealing all openings. Returning to service required removing seals and plugs, draining the corrosion preventive mixture, and reservicing with recommended lubricating oil.