BOZEMAN, MT, USA
N7551C
Forney F-1
The pilot shut down the engine and made a forced landing on a dirt road after losing oil pressure in cruise flight. The airplane sustained substantial damage when it contacted sage brush, which forced it off the right side of the road and down an embankment. According to the pilot, the dip stick indicated the airplane had 2.3 quarts of oil remaining after the forced landing. The pilot noted that after the airplane was recovered, the dip stick indicated 1.5 quarts. He had departed on the flight with the dip stick indicating 2.4 quarts of oil in a system that he believed to have 4.25 quarts capacity. Type Certificate Data Sheet information stated that the oil capacity was 5 quarts on this installation. Two quarts was considered to be minimum operating oil supply.
On August 25, 1996, approximately 1520 mountain daylight time, a Forney F-1, N7551C, sustained substantial damage during a forced landing on a road near Bozeman, Montana. The pilot and his passenger were uninjured. No flight plan was filed for the flight, which was conducted in visual meteorological conditions and had originated in Townsend, Montana about 1500. There was no report of the ELT actuating. The pilot stated that he had departed Bozeman about 1310 with 2.6 quarts of oil showing on the dip stick. About 1.5 hours later, he landed at Townsend to check the oil level (the pilot stated that the airplane "throws a little oil"). Oil level at that time was 2.4 quarts. The pilot took off for a return flight to Bozeman. He stated that oil pressure remained normal during climb; about 15 minutes into the flight while cruising, the oil pressure dropped about 2 psi to 33 psi. The pilot stated that about 20 minutes after takeoff from Townsend, he experienced a complete oil pressure loss. He said he shut the engine down and picked out an abandoned railroad bed, which is used as a farm road, as a forced landing site. He said that touchdown was normal, and the airplane rolled several hundred feet , when sagebrush on the right side dragged on the airplane, forcing it off the road into a ditch on the right side, where substantial damage was caused as the airplane rolled down the embankment. The pilot said he checked oil level after landing, which he said was about 2.3 quarts; when the wreckage was recovered, the dip stick recorded 1.5 quarts. He believed normal oil capacity on the airplane to be 4.25 quarts. FAA Type Certificate Data Sheets \note that total oil capacity is 5 quarts maximum, and 2 quarts minimum operating supply on this installation. The pilot noted that on his previous flights in the airplane, he had considered the minimum oil level to be 3 quarts for flight; for some reason on this flight, he had thought he should burn the oil down to 2 quarts before adding a quart.
the pilot's failure to adequately service the engine with oil before flight, which resulted in a loss of oil pressure and a subsequent forced landing. The high vegetation and embankment at the forced landing site were related factors.
Source: NTSB Aviation Accident Database
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