MIA99LA019

The engine lost power and while making a forced landing in a field the aircraft collided with a power pole and then crashed on top of a pile of railroad ties. Postcrash examination of the engine showed the no. 1 exhaust valve guide and valve stem were eroded, the valve guide had partially separated due to progressive cracking, and the valve head had separated from the stem. The reason for the valve stem and guide erosion was not determined. The engine had accumulated 2,225 flight hours since the last major overhaul, at which time the valves and valve guides were replaced with new parts. The recommended overhaul interval for the engine is 2,400 flight hours.

On October 28, 1998, about 0855 eastern standard time, a Cessna 152, N25037, registered to Gause Aviation Services, Inc., crashed while making a forced landing following engine failure, near Douglasville, Georgia, while on a Title 14 CFR Part 91 instructional flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was destroyed and the commercial-rated flight instructor received minor injuries. Theand student pilot were not injured. The flight originated from Palmetto, Georgia, the same day, about 0830.

The instructor stated that while making a 360-degree turn at 2,300-2,500 feet, the engine lost power and did not respond to throttle movement. He informed his student that they had an engine failure and took control of the aircraft . He turned toward a field for landing. Attempts to regain engine power were unsuccessful. As they approached the selected landing field, they were high and he executed a 360-degree turn to lose altitude. After the turn they were still high, and he lowered full flaps and slipped the aircraft to get down. He then executed a slow 180-degree turn and the aircraft collided with a power pole at the edge of the field. The aircraft then descended and crashed on a pile of railroad ties lying in the field.

Postcrash examination of the engine was performed by a FAA inspector. Examination showed the No. 1 cylinder exhaust valve had failed. No other precrash failures or malfunctions were reported. (See attached Inspector Statement)

Examination of the failed No. 1 cylinder and the No. 1 cylinder exhaust valve was performed by the NTSB Materials Laboratory, Washington, D.C. Examination showed the No. 1 exhaust valve was separated at the neck, and the head was found imbedded in the cylinder, adjacent to the seat for the exhaust valve. The No. 1 piston had damage from impact with the separated exhaust valve head. The intake valve and guide were intact. A portion of the exhaust valve guide had separated at the valve port end and was not located. Circumferential erosion was present on the exhaust valve stem corresponding to the area of the missing portion of the valve guide. The fracture surface of the exhaust valve guide had features suggestive of progressive cracking. The inside diameter of the exhaust valve guide was larger than specifications due to erosion damage. The reason for the erosion could not be determined. (See attached NTSB Material Laboratory Factual Report)

Aircraft and engine logbook records show the engine was last overhauled on March 10, 1992, and had accumulated about 2,225 flight hours since this overhaul. Lycoming Engines recommends the O-235-L2C engine be overhauled after 2,400 flight hours. Records show that during the 1992 overhaul, the exhaust valve guides and exhaust valves were replaced with new parts. (See attached logbook records)