N98550Piper J3C-65

On August 13, 2017, about 1700 eastern daylight time, a Piper J3C-65, N98550, operated by Berkshire Aviation Enterprises Inc., was substantially damaged during a forced landing into trees, following a total loss of engine power in cruise flight near Salisbury, Connecticut. The flight instructor and student pilot sustained minor injuries. The local instructional flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and a visual flight rules flight plan was filed for the flight that departed Walter J Koladza Airport (GBR), Great Barrington, Massachusetts, about 1640.

The flight instructor reported that he was providing an introductory flight to the student pilot in that particular make and model airplane. About 20 miles south of GBR at 2,800 feet mean sea level, the airplane experienced a total loss of engine power. The flight instructor took control of the airplane from the student pilot and positioned the carburetor heat to on. He also verified that the fuel selector was in the on position and the magneto switch was set to both, but the engine did not regain power. There were no suitable landing areas nearby and the flight instructor elected to perform a slow landing into treetops. The airplane subsequently collided with trees and came to rest nose-down entangled in the trees.

The airplane was equipped with a Continental Motors C90-8F, 90-horspower engine. The airplane's most recent annual inspection was performed on July 13, 2017. At that time, the airframe had accumulated 2,093 hours of operation. Review of the engine logbook revealed that maintenance records prior to 1994 were lost and a new engine logbook was created in June 1994, indicating that the engine was overhauled at a total estimated time of 1,300 hours. In October 2013, at 689 hours since major overhaul, the engine was disassembled and inspected after being involved in a previous accident (NTSB ID # ERA11LA379). During that work, the crankshaft was replaced per "Continental Overhaul Manual dated 1-1994." The engine had accrued about 317 hours from the time of the most recent crankshaft replacement, to the most recent annual inspection.

Examination of the wreckage by a Federal Aviation Administration inspector revealed substantial damage to the wings and fuselage. When the inspector rotated the crankshaft by hand, he was unable to confirm thumb compression to two cylinders or continuity to the rear accessory section.

A teardown examination of the engine was subsequently completed at the manufacturer's facility, under the supervision of an NTSB investigator. The examination revealed that the crankshaft gear screws were fractured, and the crankshaft gear was separated from the crankshaft. Fretting was observed near two of the four crankshaft screw holes and corresponded to two elongated screw holes on the crankshaft gear. The crankshaft gear contained an oil stain witness mark in an area that coincided with a dowel pin hole on the crankshaft; however, the crankshaft and crankshaft gear did not contain a dowel pin as specified in the most current version of the manufacturer illustrated parts catalog (IPC) and overhaul manual (OM). Additionally, the crankshaft gear did not contain a dowel pin hole, which was consistent with a crankshaft gear for a C65 engine and not a C90 engine. The manufacturer's most recent IPC and OM were published in August 2011, which was more than 2 years prior to the most recent crankshaft replacement in 2013. Both publications contained numerous instructions and references to use a crankshaft gear with a dowel pin hole and align the gear to the crankshaft with a dowel pin, which would pilot the crankshaft gear on the crankshaft.

On July 5, 2011, about 1700 eastern daylight time, a Piper J3C-65, N98550, registered to a private individual, experienced a partial loss of engine power and collided with trees shortly after takeoff from the Walter J. Koladza Airport (GBR), Great Barrington, Massachusetts. The personal flight was operated under the provisions of Title 14 Code of Federal Regulations Part 91 with no flight plan filed. Visual meteorological conditions prevailed. The airline transport pilot was not injured and passenger received minor injuries. The flight was originating at the time of the accident.

According to the pilot, the accident flight was the first flight in the airplane in 6 months and he performed an extensive engine run up, visually checked the fuel level and quality, noted 7 gallons of fuel prior to takeoff, and did not note any anomalies with the airplane. Then, he performed a "normal" takeoff and about 150 feet above ground level, the engine rpm decreased from takeoff power, around 2200 rpm, to 1700 rpm. The pilot decreased the pitch angle of the airplane and began searching for a place to land. He unsuccessfully attempted to regain full engine power by checking the magnetos and the carburetor heat. In addition, the pilot noted the gauges that indicated the oil pressure and temperature were within "normal" ranges. He elected to land the airplane between two houses. During the landing roll, the airplane subsequently struck underbrush and trees, and then came to rest in trees and foliage.

Examination of the wreckage 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 the tube was bent aft. The left wing leading edge was impact damaged and dented in several locations. The upper engine cowl and engine baffling was impact damaged. The carburetor was examined and fuel was noted inside the carburetor and there was no debris in the fuel screen. The tachometer located in the cockpit indicated time of 689.6 hours.

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, and at that time it had accumulated 1,776 total hours of flight time and a tachometer time of 689 hours. In addition, the mechanic who performed the annual inspection completed a compression check on the engine cylinders. The compression test results indicated that the cylinders had compression that ranged from 74 to 78. The most recent overhaul of the engine was noted as June 5, 1994, at a tachometer time of 221.5 total hours.

A postaccident engine examination revealed that the No. 2 and No. 3 cylinders did not display any anomalies when a compression test was performed. During the compression test, cylinder No. 1 was leaking out of the exhaust valve through the exhaust system and resulted in a compression ratio of 50/80. The No. 1 rocker cover was removed and the rocker arm was "tapped" with a mallet. A compression test was performed again to the No. 1 cylinder and the compression came up to a ratio of 60/80. The No. 4 cylinder compression test resulted in a compression ratio of 42/80. Disassembly of the No. 4 cylinder revealed that the exhaust valve was leaking out through the exhaust system. In addition, it revealed a scored intake valve and valve guide. The intake valve would not operate and had to be removed from the valve guide with a mallet and drift.

According to the engine overhaul manual, in a section labeled "engine troubles and service repair," it indicated that if the engine produced low power, it could be a result of scored valve stems.

In addition, the engine overhaul manual stated "obviously even then proper steps must be taken on engines used infrequently to lessen the possibility of corrosion. This is especially true if the aircraft is based near the sea coast or in areas of high humidity and flown less than once a week. In all geographical areas the best method of preventing corrosion of the cylinders and other internal parts of the engine is to fly the aircraft at least once a week long enough to reach normal operating temperatures which will vaporize moisture and other by-products of combustion. Aircraft engine storage recommendations are broken down into the following categories: Flyable Storage (7 to 30 days) Temporary Storage (up to 90 days) Indefinite Storage."

Indefinite storage of the engine included a procedure of replacing the engine oil with oil that has anticorrosive properties, installing cylinder dehydrator plugs, sealing all openings in the engine. The process of returning the engine to service after storage included removing the engine seals, removing the cylinder dehydrator plugs, draining the corrosion preventive mixture and reservicing the engine with the recommended lubricating oil. The entire process can be found in the engine manual excerpt in the docket for this case.