NTSB Identification: SEA92LA072.
The docket is stored on NTSB microfiche number 46816.
Accident occurred Friday, April 10, 1992 in MISSOULA, MT
Probable Cause Approval Date: 06/30/1993
Aircraft: PIPER PA-23-160, registration: N3494P
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE PILOT AND PILOT RATED PASSENGER (RIGHT SEAT) DEPARTED IN THE PA-23 AND CLIMBED TO 11000 FEET ON A LOCAL ROUND ROBIN FLIGHT. THE AIRCRAFT WAS NOT EQUIPPED WITH WING OR PROPELLER DEICE/ANTI ICE SYSTEMS. MISSOULA REPORTED SEVERAL SCATTERED, BROKEN AND OVERCAST CLOUD LAYERS BELOW 11000 FEET DURING THE AFTERNOON AND THE SURFACE TEMP PEAKED AT 44 DEGREES F. AT 11000 FEET THE PILOTS ENCOUNTERED A VIBRATION AND LOSS OF LEFT ENGINE POWER AND INITIATED A RETURN TO MISSOULA FOR LANDING. UNABLE TO MAINTAIN ALTITUDE WITH PARTIAL POWER A FORCED LANDING WAS EXECUTED SHORT OF RUNWAY 25 AT THE MISSOULA AIRPORT. ALTHOUGH AN ATTEMPT WAS MADE TO LOWER THE LANDING GEAR PRIOR TO THE FORCED LANDING THE NOSE LANDING GEAR COLLAPSED DURING ROLLOUT WHEN IT STRUCK A GOPHER HOLE. AIRPORT ARFF PERSONNEL OBSERVED ICE DETACHING FROM THE AIRCRAFT WING(S) FOLLOWING THE ACCIDENT AND FAA PERSONNEL INSPECTING THE AIRCRAFT SUBSEQUENT TO THE ACCIDENT REPORTED THAT THE LEFT INDUCTION AIR FILTER WAS HEAVILY SOAKED WITH WATER.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

PARTIAL BLOCKAGE OF THE LEFT ENGINE INDUCTION AIR FILTER, INABILITY TO MAINTAIN THE PROPER RATE OF DESCENT, AND DELAYED EXTENSION OF THE LANDING GEAR. FACTORS CONTRIBUTING TO THE ACCIDENT WERE ICING CONDITIONS, WING ICE, AND ROUGH/UNEVEN TERRAIN.

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