NTSB Factual Report

On September 27, 2016, about 1745 eastern daylight time, a Ryan Navion B, 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, which was conducted under the provisions of 14 Code of Federal Regulations Part 91. The flight 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 try to land at the nearest airport, which was New London Airport (W90), Forest, Virginia. A few seconds later he heard a loud bang, 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 make the airport, and he then 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.

Examination of the airplane 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, and there were holes in the crankcase near cylinder Nos. 6, 4 and 2. A connecting rod protruded through the hole near cylinder No. 4. No oil was present in the crankcase. A teardown examination of the engine was subsequently performed at the manufacturer's facility, under the supervision of a National Transportation Safety Board investigator. The examination revealed 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, however it could be moved by hand. An air pressure hose was attached to the oil cooler and when 30 psi was applied, bubbles were noted around the crush washer seal of the oil temperature probe. Oil residue was also noted all over the oil cooler and surrounding area of the engine. See Figure 1. The oil temperature probe was removed, and the crush washer was found installed backwards.

The temperature probe was considered an airframe item and was not installed by the engine manufacturer. The engine was delivered with a plug in the oil temperature probe port, and the installer could remove the plug and replace it with an oil temperature probe. 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 in/lbs to 210 in/lbs. The version of the manual in effect at the time of the accident did not specify the orientation of crush washers.

Maintenance records revealed that the airplane's most recent annual inspection occurred on September 16, 2016. At that time, the airplane had accrued a total of 4,488 flight hours, and the engine had accrued a total of 832 hours since overhaul.

NTSB Probable Cause

Incorrect installation of the oil temperature probe and an inadequate annual inspection that failed to detect leaking oil around the loose probe, which resulted in a catastrophic engine failure due to oil starvation.