GERMANTOWN, KY, USA
N8299U
Cessna 172
The flight was en route at 5500' MSL, when the pilot noted a loss of oil pressure followed by a loss of engine power. A forced landing was made in an open field, where the airplane collided with a ditch. Inspection of the airplane revealed the lower fuselage was covered with oil. Examination of the engine revealed evidence of oil starvation in the main bearings, connecting rod bearings, and journals of the crankshaft. All of the cylinders were steel-barreled, except the #4 cylinder, which was chrome plated. The #4 cylinder was heavily scored in the chrome barrel, and the #4 piston was scored completely around its skirt. The #4 piston exhibited burning on the lower crown, which eroded a hole to the piston interior below the third piston ring groove. The piston rings were stuck due to aluminum from the piston skirts extruding over them. Heat had expanded the piston skirts into contact with the cylinder walls, scoring them and transferring aluminum from the piston skirt. According to a report from the manufacturer, chrome cylinders must use plain steel rings per TCM service literature; however, the #4 cylinder was installed using rings for a steel barreled cylinder, which have chrome plating on the top compression ring. The manufacturer's report also noted that chrome ring on chrome cylinder bore will not work and could create scoring, metal transfer, and eventually severe blowby conditions. The engine had accumulated 1075 hours of flight time since the last overhaul.
On October 13, 1996, at 1512 eastern daylight time, a Cessna 172, N8299U, experienced a loss of engine power during cruise flight, and impacted terrain in the vicinity of Germantown, Kentucky, during the resultant forced landing. The certificated flight instructor, the sole occupant, received minor injuries. The airplane was substantially damaged. Visual meteorological conditions prevailed for the flight, and a visual flight rules (VFR) flight plan was filed. The departure point was Cincinnati, Ohio and the destination was Prestonburg, Kentucky. The flight was operated under 14 CFR Part 91. The flight was en route at 5500 feet MSL when the pilot noticed a loss of oil pressure followed by the engine losing power. A forced landing was done on an open field where the aircraft collided with a ditch during the landing roll. The pilot reported that before the engine lost power, there was a 75 rpm reduction in power. Thinking it was due to carburetor ice, she applied carburetor heat, and the power was restored. Immediately after turning the carburetor heat off, the pilot "noticed the rpm dropping and the oil pressure going down to (zero) oil pressure." She radioed air traffic control, declared an emergency, and did the subsequent forced landing. Examination of the airplane by an FAA Inspector revealed the lower fuselage was covered with oil. The engine was transported to Teledyne Continental Motors (TCM) for internal examination under the supervision of an FAA Inspector. According to the TCM Analytical Inspection Report, all cylinders were steel-barreled, except the number 4 cylinder, which was chrome-plated. The top piston ring was also determined to be chrome-plated. The examination revealed evidence of oil starvation of the main bearings of the crankcase and the main journals of the crankshaft. The connecting rod bearings also had evidence of oil starvation. The examination, according to the TCM report, revealed the number 4 cylinder was heavily scored in the chrome barrel. The number 4 piston was scored completely around its skirt. The number pist4on exhibited burning on the lower crown eroding a hole to the piston interior below the third piston ring groove. The piston rings were stuck due to aluminum from the piston skirts extruding over them. Heat had expanded the piston skirts into contact with the cylinder walls, scoring them and transferring aluminum from the piston skirt. The TCM report indicated "Chrome cylinders must use plain steel rings per TCM service literature. This cylinder was installed using rings for a steel barreled cylinder, which have a chrome plating on the top compression ring. Chrome ring on chrome cylinder bore will not work and creates scoring, metal transfer, and eventually severe blowby conditions. According to the NTSB Pilot/Operator Aircraft Accident Report, the engine had 1075 hours since the last overhaul.
improper maintenance with the installation of an improper oil ring on the number four piston, which led to failure of both the ring and pistion, oil starvation, and subsequent loss of engine power.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
