NTSB Identification: DEN87LA084.
The docket is stored on NTSB microfiche number 33840.
Accident occurred Sunday, April 05, 1987 in CONRAD, MT
Probable Cause Approval Date: 05/19/1989
Aircraft: AIR TRACTOR AT-301, registration: N23069
Injuries: 1 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.

AN AG PLT WAS RETURNING FROM AN AERIAL APPLICATION. SIX MILES FROM THE DESTINATION ARPT THE ENGINE QUIT. THE PLT ATTEMPTED TO LAND ON A ROAD BUT THE ACFT STRUCK THE EDGE OF A PIT, SPUN ACROSS THE ROAD AND CAME TO REST FACING 180 DEGREES FROM THE ORIGINAL HEADING. ENGINE EXAMINATION DISCLOSED SUPERCHARGER IMPELLER DAMAGE TYPICAL OF FOREIGN OBJECT INGESTION. FIVE OF THE NINE CYLINDERS HAD LOW COMPRESSION AND SHOWED METAL PARTICLES ON PISTON AND VALVE SURFACES. THE LEFT MAGNETO HAD BRASS, COPPER, AND ALUMINUM PARTICLES THROUGHOUT THE INTERIOR AND FAILED TO PRODUCE SPARK WHEN ROTATED. THE RIGHT MAGNETO DID PRODUCE SPARK WHEN ROTATED BUT THREE OF THE NINE PLUGS SERVED BY THIS MAGNETO WERE METAL FOULED IN THE ELECTRODES.

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

ENG ASSEMBLY,BLOWER/IMPELLER/INTEGRAL SUPERCHARGER..FOREIGN OBJECT DAMAGE

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

MAINTENANCE..IMPROPER..OTHER MAINTENANCE PERSONNEL


Contributing Factors

TERRAIN CONDITION..DIRT BANK/RISING EMBANKMENT


Contributing Factors

PROPER TOUCHDOWN POINT..MISJUDGED..PILOT IN COMMAND


Contributing Factors

IGNITION SYSTEM,MAGNETO..FAILURE,TOTAL


Contributing Factors

IGNITION SYSTEM,SPARK PLUG..SHORTED

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