NTSB Factual Report

HISTORY OF FLIGHT

On May 16, 1998, at 1350 eastern daylight time, an Engineering and Research ERCO-415C (Ercoupe), N3230H, was destroyed during a forced landing to a field near New Lisbon, New York. The certificated private pilot and passenger were fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight being conducted under 14 CFR Part 91, that departed Cooperstown-Westville Airport, Cooperstown, New York, about 1315.

According to the passenger's husband, they were attending an Experimental Aircraft Association (EAA) pancake breakfast at the airport when the passenger was approached by the pilot. The pilot offered a ride to the passenger, and after some deliberation with her husband she accepted. She also agreed to pay 5.00 dollars to help with the operating costs associated with the airplane.

Prior to the accident flight, another pilot flew the airplane. In the NTSB form 6120.1/2 he stated, there were no mechanical problems, and he personally refueled the airplane prior to the accident flight.

According to the passenger's husband, the pilot that flew the airplane prior to the accident questioned the accident pilot when he saw him carrying a quart of oil to the airplane. The pilot said "it can't need oil I checked it this morning and it was fine." They discussed the situation with the mechanic that preformed the last annual inspection and decided the low oil level was caused by the engine being warm. The accident pilot then ran the engine up for a couple of minutes, shut it down, and the three men decided everything was fine. The pilot and passenger then departed Cooperstown.

No information was available regarding the flight after its departure from Cooperstown until a witness to the accident heard the engine "sputter and then quit."

After hearing the engine quit, the witness saw the airplane maneuver towards an open field, and impact the side of a hill in a level attitude. Approximately 2 seconds after the impact, it exploded, sending fire and smoke over 100 feet into the air.

The wreckage was located approximately 42 degrees, 36.44 minutes north latitude, and 75 degrees, 7.23 minutes west longitude.

PERSONNEL INFORMATION

The pilot held a private pilot certificate with ratings for airplane single and multi engine land. The pilot's log book was not recovered. On his last application for a third class medical certificate, dated October 18, 1996, the pilot reported 2,300 hours total flight time.

AIRCRAFT INFORMATION

A review of the airframe log book revealed an annual inspection was preformed on November 13, 1997. At the time of the annual inspection, the log book showed a tachometer reading of 360.6 hours and a total time of 719.6 hours.

A review of the engine log book revealed that the engine was last overhauled on June 10, 1996. The tachometer reading at the time of the overhaul was 192.0 hours

WRECKAGE AND IMPACT INFORMATION

The wreckage was examined on May 17 and 18, 1998, and all major components of the airplane were accounted for at the accident site.

The aircraft came to rest on a magnetic heading of 042 degrees facing down a featureless grassy slope that measured 8 degrees.

Approximately 80 feet to the south of where the airplane came to rest were initial ground marks of grass laid over on its side, similar in appearance to that caused by a light vehicle driving across a field. These marks were spaced constant with the airplanes landing gear and continued in the direction of the wreckage for about 12 feet. At the end of these marks was a 10 degree rise in terrain. With the change in terrain, the ground marks went from subtle indentations, to scrap marks that dug approximately 3-4 inches into the earth's surface.

In addition, where the slope of the hill increased, a deep gouge mark that measured approximately 3 feet in diameter and 2 feet deep with burned grass on its rim was observed. This mark was consistent in size and position with the engine and cowling section of the airplane. From this mark, airplane parts, gouge marks in the earth, and burned grass continued to where the airplane came to rest.

Examination of the leading edges on both wings revealed the most sever damage was inboard, becoming gradually less outboard. Both wingtips showed no signs of compression, impact, or fire damage.

Fire damage on both the left and right wings was symmetrical, with the majority of fire damage located where the wings join the fuselage. On both the left and right wings, 60 percent of the fabric was destroyed. Another 20 percent was grayish in color, and looked like plastic that had been exposed to heat. The remaining 20 percent of the wings surface area showed no signs of damage.

The last 6 feet of the empennage was intact and showed no signs of fire or impact damage. Forward of that point, only the cabin flooring remained until the firewall. In the cabin area flight control continuity could not be established because of fire damage.

MEDICAL AND PATHOLOGICAL INFORMATION

An autopsy was preformed on the pilot, May 18, 1998, at the Fox Hospital Oneonta, New York, 13820.

An autopsy was preformed on the passenger, May 17, 1998, at the Marry Imogene Bassett Hospital, Cooperstown, New York 13326.

A toxicological test was performed on both the pilot and passenger by the Federal Aviation Administrations Toxicology and Accident Research Laboratory, Oklahoma City, Oklahoma.

TESTS AND RESEARCH

On May 17 and 18, 1998, the engine was examined at Clipper Aviation in Oneonta, New York. Examination of the number 2 cylinder revealed no compression, and after removing the cylinder and piston, a melted hole consistent with detonation was observed on the head of the piston. The hole on the piston was about 1 inch long and 1/4 inch wide. It started on the top of the piston and traveled down its side approximately 1 1/2 inches.

Valve train continuity was established on all cylinders and when the crankshaft was rotated the engine accessory gears turned. All the spark plugs were light gray in color except for the number 2 spark plug which was covered with numerous metallic specks. Each speck was about 100th of an inch in diameter.

When the oil filter was removed, a dark colored liquid consistent with oil started to spill onto the hangar floor. In all, approximately 3 quarts of oil leaked from the engine during the examination.

The propeller assembly was intact with both propeller blades attached. Neither propeller blades displayed chordwise scratching, "S" bending, or leading edge gouges during the visual examination.

ADDITIONAL DATA/INFORMATION

According to a New York State Police Officer, the state police helicopter crew that responded to the accident, reported the crash site looked "level" from the air. However, when measured along the debris field axis with an inclinometer, the slope was 15 degrees up.

The Department of the Army Aeromedical Training for Flight Personnel defines Visual Illusion as "...false impressions or misconception of actual conditions."

Advisory Curricular 33.47-1, Detonation Testing In Reciprocating Aircraft Engines defines detonation as "the spontaneous combustion of an unburned charge which occurs ahead of the flame front after normal ignition."

Advisory Curricular AC 65-12A, Airframe and Powerplant Mechanics Powerplant Handbook defines the results of detonation. "The explosive burning during detonation results in an extremely rapid pressure rise. This rapid pressure rise and the high instantaneous temperature, combined with the high turbulence generated, cause a "scrubbing" action on the cylinder and the piston. This can burn a hole completely through the piston."

On May 18, 1998 the wreckage was released to the New York State Police. No components or parts of the airplane were retained.

NTSB Probable Cause

Detonation within the No. 2 cylinder resulting in melting and breaching of the piston, and the pilot's selection of unsuitable terrain for landing. Contributing factors were the uphill terrain encountered during the landing and the visual perception (illusion) that the terrain was not sloped.