Accident Overview
On November 15, 2019, at approximately 1430 eastern standard time, an experimental, amateur-built Rans S7 Courier (registration N831RS) was substantially damaged during a forced landing to a field in West Liberty, Kentucky. The private pilot, the sole occupant, was not injured. The personal cross-country flight was conducted under Title 14 Code of Federal Regulations Part 91 in visual meteorological conditions. No flight plan had been filed. The flight originated from Jackson County Airport (I18) in Ravenswood, West Virginia, around 1220 and was destined for Smyrna Airport (MQY) in Smyrna, Tennessee.
Pilot Account
According to the pilot, while en route, the engine lost total power "like someone turned off" the magnetos. He primed and restarted the engine, but it only produced power for 3 to 4 seconds before losing total power again. He repeated the process with the same result. On the third restart attempt, the propeller would not rotate. The pilot then executed a forced landing to a nearby field. During the landing roll, the airplane struck a fence post, resulting in substantial damage to the left wing and engine mounts.
Engine Examination
A Federal Aviation Administration inspector examined the engine and found that the propeller could be rotated through 360° by hand. The oil reservoir was empty. Fuel samples from both wings were free of debris.
An examination by an NTSB investigator and a manufacturer representative revealed that the engine remained attached to the fuselage. The propeller could be rotated through 360°, and compression was confirmed on both cylinders. Fuel in both carburetors was free of debris. Spark plugs exhibited normal wear and were not oil-soaked. The oil system showed no leaks, and the oil injection tank was empty. No oil pooling was observed in the carburetor oil ports. When the exhaust y-pipe was removed from the cylinders, the aft piston exhibited vertical scoring and was not lubricated. The front piston had no scoring and was slightly lubricated. The fuselage had no oil streaking. Oil was added to the oil injection tank, and no leaks were noted.
Oil System and Manuals
The flight manual stated that the engine's oil consumption was approximately 0.2 quarts per hour at 5800 rpm (1 quart in 5 hours), equivalent to about 6.4 ounces per hour. It also stated that the oil tanks held about one gallon and should supply enough oil for 20 hours of continuous operation. However, examination revealed only one oil tank on the airplane, capable of containing about 2 quarts. No other oil tank that injected into the pistons was observed. Logbooks contained no maintenance entries regarding the oil tank.
The engine operator's manual specified an oil injection rate of 8.2 cubic inches per hour per outlet, which with two outlets converts to about 9 ounces of oil per hour.
Preflight Checklist
The preflight checklist included instructions to check the engine oil, hoses, wires, and cables prior to engine start.
Damage
The left wing and engine mounts sustained substantial damage due to impact with a fence post during the forced landing.