Incident
On September 27, 2016, about 1745 eastern daylight time, a Ryan Navion B, registration N5327K, was substantially damaged during a forced landing following a total loss of engine power while in cruise flight near Hurt, Virginia. The private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight conducted under 14 CFR Part 91. The flight had departed Culpeper Regional Airport (CJR), Culpeper, Virginia, about 1700, destined for Long Island Airport (NC26), Long Island, North Carolina.
According to the pilot, about 45 minutes into the flight at an altitude of 3,000 feet mean sea level, the engine suddenly began to vibrate. He informed Roanoke Approach air traffic control (ATC) of his intent to land at the nearest airport, New London Airport (W90), Forest, Virginia. A few seconds later, a loud bang was heard, the vibration worsened, smoke and oil emanated from the engine compartment, and the engine lost power as the propeller continued to windmill. The pilot then advised ATC that he would not be able to reach the airport and performed an emergency landing to a mowed hay field. During the landing rollout, the airplane struck and rolled through a post-and-wire fence, resulting in substantial damage to the right wing.
Investigation
Examination by a Federal Aviation Administration inspector revealed that the right wing leading edge sustained substantial damage, and fence wire was wrapped around the propeller flange. The top left side of the engine crankcase was damaged, with holes near cylinders 6, 4, and 2. A connecting rod protruded through the hole near cylinder No. 4, and no oil was present in the crankcase. A teardown examination of the engine at the manufacturer's facility, under supervision of a National Transportation Safety Board investigator, showed that the internal engine components exhibited heat distress consistent with a lack of lubrication.
Further examination revealed that the oil temperature probe was safety wired but could be moved by hand. When an air pressure hose was attached to the oil cooler and 30 psi applied, bubbles were noted around the crush washer seal of the oil temperature probe. Oil residue was found on the oil cooler and surrounding engine area. The oil temperature probe was removed, and the crush washer was found installed backwards. The temperature probe was an airframe item, not installed by the engine manufacturer. The engine was delivered with a plug in the oil temperature probe port; the installer could remove the plug and replace it with a probe.
Maintenance
A review of the 1951 Navion B Service Manual revealed no specific torque values for tightening the oil temperature probe. The maintenance manual for the accident engine provided a torque range for the oil temperature port plug (with crush washer) as 190 to 210 in/lbs, but the version in effect at the time of the accident did not specify the orientation of crush washers. Maintenance records indicated the airplane's most recent annual inspection occurred on September 16, 2016, at which time the airplane had accrued 4,488 total flight hours, and the engine had 832 hours since overhaul.