Christen Industries Inc PITTS S-1T N77MN accident near Alkali Lake, Oregon

Probable cause

The loss of engine oil during cruise flight due to the failure of the front bearing oil seal.

NTSB analysis

The pilot reported that, during cruise flight, a large amount of oil suddenly covered the windscreen, causing her to initiate a precautionary off-airport landing as the oil pressure dropped to zero. Because of the uneven terrain in area in which she was flying, suitable landing sites were minimal. During the landing, the pilot attempted to pitch the tail-wheel airplane upward in order to drag the tail along the ground to slow the airspeed. The pilot stated that she had no response from the elevator or ailerons. The airplane impacted the uneven terrain in a nose-low attitude and cartwheeled, resulting in structural damage to all four wings and the fuselage. Examination of the recovered engine revealed that the front bearing oil seal was partially extruded from the crankcase nose seal bore. No additional mechanical anomalies were noted during the examination of the engine or airframe. The reason for the front bearing oil seal becoming extruded from the crankcase bore area was undetermined.

Text from the NTSB. Open the NTSB docket for WPR11LA290 for the full record.