Event Summary
The pilot encountered smoke in the cockpit during flight, with oil spewing onto the windshield and engine oil pressure dropping. The pilot performed an emergency landing on an abandoned dirt strip approximately 1,400 feet long. However, the airplane overran the runway into a ravine and overturned.
Maintenance Background
Maintenance completed the day before the accident included an oil change and replacement of the crankshaft nose seal. A run-up after maintenance revealed no oil leaks.
Engine Examination
Post-accident examination found no visible engine damage resulting from the forced landing. Visual inspection showed no evidence of catastrophic mechanical malfunction or fire. A significant amount of engine oil had emanated from the nose cowling where the engine and propeller flange protruded, with an oil film proceeding aft onto the windscreen and horizontal and vertical stabilizers.
The spark plugs, cylinder walls, valves, and pistons exhibited no mechanical damage. Oil lines within the engine compartment were secure on their fittings, and the propeller governor was secure and not leaking. The oil filter and oil filter converter plate were properly installed and secure, with no visible contaminants in the oil filter or suction screen. The propeller was removed, but there was no evidence of oil leakage at the propeller seal.
The crankshaft oil seal was found out of its bore and resting on the crankshaft. One oil ring was cracked, but no compression rings were broken. There was evidence of overheating from running lean.
The breather hose had been mounted over the motor mount rather than under it. In this location, the hose was pinched when the cowling was installed. This plugged the breather hose and pressurized the case, forcing oil out through the front seal.
Cause
The accident was caused by the breather hose being mounted over the motor mount rather than under it, resulting in pinching when the cowling was installed. The pinched hose plugged the breather system, leading to case pressurization that forced oil out through the front seal.