Introduction
On August 13, 2014, about 1215 mountain daylight time, a Piper PA-28-236 airplane, registration N2190H, was substantially damaged during an emergency landing near Lemhi County Airport (KSMN), Salmon, Idaho. The aircraft was operated by a private pilot as a personal cross-country flight under visual flight rules. Visual meteorological conditions prevailed at the time of the incident. The pilot was not injured, and the sole passenger received minor injuries.
Flight History
The flight originated from Gooding Municipal Airport (KGNG), Gooding, Idaho, approximately 1054, with a planned destination of Kalispell City Airport (S27), Kalispell, Montana. No flight plan was filed. During preflight run-up, the pilot noted a lack of engine vacuum indication. The aircraft was taken to a maintenance facility at Gooding, where the vacuum pump was replaced. The pilot reported that a leak check was not performed after the replacement. The mechanic instructed the pilot to give a "thumbs up" signal if vacuum was observed upon engine start. After starting the engine and confirming vacuum, the pilot signaled and departed.
About 150 miles north of Gooding, the pilot heard an unusual engine noise and observed a loss of engine oil pressure. He turned toward the nearest airport, Lemhi County, and broadcast a mayday call on 121.5 MHz. Believing he had sufficient altitude and airspeed to reach the airport, the pilot continued. However, approaching the airport, it became clear he would be short, and he elected to land in a hayfield adjacent to the airport. After touchdown, the aircraft encountered a road perpendicular to its direction of travel, causing the landing gear to collapse. The aircraft then slid through the airport's perimeter fence.
Engine Examination
The aircraft sustained substantial damage to its wings and fuselage. No pre-accident mechanical anomalies were reported other than the vacuum pump replacement and subsequent loss of engine oil pressure and power. An examination of the engine revealed several holes in the top of the crankcase near the centerline joint, with deformation consistent with force from inside the case. The engine was covered in oil residue, and oil was pooled in low areas. The oil filter was cut open and found to contain metal fragments.
The recently installed dry vacuum pump, which does not rely on pressurized crankcase oil for lubrication, was located on the upper aft right side of the engine. The area around the pump was covered in oil residue. The pump was mounted with four studs and nuts, with a fiber gasket in place. Upon removal, the pump's internal cavity was partially filled with oil, and all internal parts had oil residue. The fiber gasket showed oil staining on both sides, particularly around the accessory pad's oil passage hole, with staining extending along the internal cavity edge to the exterior perimeter on three sides. The gasket appeared intact with no tearing or surface damage.
The engine accessory mounting pad had remnants of gasket material adhered to it, making the surface rough and uneven. The oil passage hole used for a wet pump installation was not plugged. The engine was designed for a wet vacuum pump, which uses pressurized crankcase oil for lubrication. In contrast, the installed dry pump does not require such oil, so the oil passage hole serves no purpose if properly sealed.
Additional Information
The engine manufacturer published Textron Service Instruction No. 1369 dated October 6, 1978, which recommends sealing off the oil passage by installing a threaded plug to prevent oil loss in the event a vacuum pump becomes loose. This instruction was not followed in the accident aircraft's installation.