WPR20LA136

Shortly after takeoff on runway 30, as the airplane reached about 300 to 400 ft above ground level, the engine lost partial power. The pilot prepared for a downwind landing to runway 12 and when he realized the airplane had excess energy, he deployed the flaps and performed a forward slip maneuver. The airplane touched down about halfway down the runway and continued off the end and through a fence. The airplane then passed over the two westbound lanes of a road and nosed over in the median. Examination of the engine revealed low compression on two of the six cylinders (around 25 to 75 percent compression loss on cylinder numbers 3 and 5). The valve rocker arms were tapped with a rubber mallet and compression recovered to approximately 25 percent loss in the number 3 cylinder and 15 percent loss in the number 5 cylinder. An internal borescope examination of the engine cylinders revealed the piston tops and cylinder sidewalls appeared normal and no evidence of foreign object ingestion was observed. No other pre-impact mechanical anomalies were identified during the examination. Although the reason for the low compression could not be determined, it was noted that the engine was disassembled 1.9 hours before the accident flight.

On May 2, 2020, about 0930 Pacific daylight time, a Cessna 172N, N734NW, was substantially damaged when it was involved in an accident near Sierra Sky Park Airport (E79), Fresno, California. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated the airplane had recently undergone maintenance; this was to be the third flight after the maintenance, and he planned to stay in the local area. He conducted a preflight inspection and observed 28 gallons of fuel in the fuel tanks; he also confirmed there was no contamination in the fuel by visually checking the fuel strainer. The pilot estimated the wind was about 9 to 10 knots straight down runway 30 (headwind). He initiated a takeoff and when the airplane reached about 300 to 400 ft above ground level, the engine power began to fluctuate. The engine then remained at “low” power and the pilot pitched the airplane to maintain 70 to 80 knots of airspeed. He prepared for a downwind landing on runway 12 and when he realized the airplane had excess energy, he deployed the flaps and performed a forward slip maneuver. The airplane touched down about halfway down the runway and continued off the end and through a fence. The airplane then passed over the two westbound lanes of a road and nosed over in the median. A postaccident examination was performed on the airplane and engine. The crankshaft was rotated by hand using the propeller. Rotational continuity was established throughout the engine and valve train. Equal movement was observed on all of the intake and exhaust valve rocker arms. Thumb compression and suction was obtained on four of the six cylinders. Cylinder numbers 3 and 5 had very minimal thumb compression. A differential pressure gauge was connected to the numbers 3 and 5 cylinders, which exhibited around 25 to 75 percent compression loss. The valve rocker arms were tapped with a rubber mallet, and compression recovered to approximately 25 percent loss in the number 3 cylinder and 15 percent loss in the number 5 cylinder. An internal borescope examination of the engine cylinders revealed the piston tops and cylinder sidewalls appeared normal. No evidence of foreign object ingestion was observed. Examination of the fuel strainer revealed the drain pull handle used for draining the strainer was inoperable. An examination of the fuel strainer found the drain valve cable to be dirty without evidence of frequent actuation (the cable showed no signs of sliding in and out of the cable housing). The fuel strainer drain valve cable was disconnected and the drain valve was opened manually without restriction. The fuel strainer housing (bowl) was removed, and the internal screen was free of debris. The fuel remaining in the strainer bowl was clear and bright. Examination of the maintenance records for the airplane revealed the engine was disassembled and the carburetor and fuel strainer were overhauled 1.9 hoursbefore the accident flight.