| Crash location | 35.870278°N, 98.197777°W |
| Nearest city | Omega, OK
35.870319°N, 98.197842°W 0.0 miles away |
| Tail number | N7279Z |
|---|---|
| Accident date | 10 May 2015 |
| Aircraft type | Piper PA-25-235 |
| Additional details: | None |
On May 11, 2015, about 2015 central daylight time, the engine on a Piper PA-25-235, N7279Z, overheated and lost partial power. The pilot was unable to maintain altitude and was forced to make an emergency landing on a dirt road near Omega, Oklahoma. During the landing roll, the left wing struck a fence, crushing the leading edge and spinning the airplane around. The pilot was not injured. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from Watonga Regional Airport (KJWG), about 1930.
The pilot told a first responder and a Federal Aviation Administration (FAA) inspector that the oil temperature was extremely high and the engine was having a problem making power. The recovery crew said there was fuel in the fuel tanks. The accident site was on County Road E 830, about 0.2 miles east of County Road N2680 in Omega, Oklahoma, or about 11.2 miles east and 2 miles south of Watonga, Oklahoma.
On June 17, 2015, the engine was examined at Air Salvage of Dallas, Lancaster, Texas, under the auspices of the National Transportation Safety Board. The investigator reported finding metal particles in the engine oil, oil pump, and oil sump.
On July 31, the investigator partially disassembled the engine and said the number 2 compression piston ring on the number 4 piston had a broken ring. The number 5 cylinder had chrome peeling off the cylinder wall. He noted the piston rings were also chrome plated. There was evidence of a light oil leak on the top back section of the engine. The oil was black and smelt "burnt."
According to the maintenance logbook, the engine, a Lycoming O-540-G1A5, serial number L-23273-40, was manufactured on July 9, 1981. The following are pertinent entries:
• August 1, 1981: The engine was installed in N8731L
• February 13, 1992: The engine was removed from N8731L. Engine total time was 858.9 hours.
• September 20 1993: The engine was installed in N7279Z. Tachometer time was 4,233.0 hours, and engine total time was 859.9 hours.
• August 1, 2006: The engine was overhauled using six ECI nickel carbide cylinders. Tachometer time was 5,042.0 hours, and engine total time was 1,613.81 hours
• April 28, 2011: Six new ECI nickel carbide cylinders were installed. Tachometer time was 5,252.5 hours, and engine total time was 1,824.31 hours.
• July 5, 2013: Cylinders 1 and 2 were removed, honed, re-ringed, and reinstalled. Tachometer time was 5,320.71 hours, and engine total time was 1,892.52 hours.
Other entries between these dates were routine annual and 100-hour inspections. At the time of the accident, the tachometer read 5,448.16 hours, and the engine had accrued 2,019.97 hours since new.
Cylinder and piston number 5 and associated rings were removed and shipped to the National Transportation Safety Board's Materials Laboratory for metallurgical examination. According to its report, dated February 22, 2016, the cylinder was manufactured by Engine Components, Inc., or ECi. The coating on the upper surface of the cylinder barrel had peeled away. The thickness of the coating measured approximately 0.0058 inch. Energy dispersive spectroscopy (EDS) analysis of the cylinder (base metal) produced a spectrum that contained a major elemental peak of iron and minor elemental peaks of nickel, chromium, silicon, and carbon, consistent with a steel alloy. The spectrum of the coating contained a major elemental peak of nickel and minor elemental peak of silicon, carbon, and oxygen, consistent with a nickel silicon carbide A wedge test, using the tip of a screw driver, revealed the inner coating could be peeled away from the top half portion of the barrel, ranging from "easy" to "moderate," but the inner coating could not be removed from the bottom half portion of the barrel.
Improper base metal preparation or contamination of the No. 5 cylinder wall before it was coated, which resulted in the coating peeling off of the cylinder wall and contaminating the engine oil and the subsequent partial loss of engine power.