NTSB NYC91LA092 — 1991-03-23 · WESTBROOK, Maine, United States

N4155P has since been reassigned. It is now registered to a different aircraft (AIR TRACTOR INC AT-502B, built 2008), which was not involved in this event.

Aircraft involved

N4155P Piper PA-23-160 None

Probable cause & findings

IMPROPER EMERGENCY PROCEDURES BY THE PILOT. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOT'S LACK OF EXPERIENCE AND FLIGHT TIME IN TYPE OF AIRPLANE, THE PILOTS DECISION TO TAKE AN AIRPLANE WITH A KNOWN MECHANICAL DEFECT, A LEAKY ACCELERATOR PUMP SEAL ON THE CARBURETOR, AND INSTRUMENT METEOROLOGICAL CONDITIONS.

Factual narrative

ON AN IFR FLIGHT IN IMC CONDITIONS THE RIGHT ENGINE STARTED TO SHUDDER AND PRODUCE BLACK SMOKE, AND THEN THE PROPELLER WENT INTO FEATHER WITHOUT ACTUATION OF THE PROPELLER CONTROL. THE PILOT WAS UNABLE TO MAINTAIN ALTITUDE AND THE PILOT MADE A FORCED LANDING IN AN OPEN FIELD. THE RIGHT ENGINE OIL WAS DILUTED BY GASOLINE, DUE TO A LEAK IN THE ACCELERATOR PUMP OF THE CARBURETOR WHICH CAUSED THE ENGINE TO RUN RICH. INTERVIEWS DISCLOSED THE PILOT HAD 'DENIAL' ON THE ENGINE PROBLEM, DID NOT SECURE THE ENGINE, AND DID NOT DECLARE AN EMERGENCY WITH ARC. BOTH ENGINES WERE HIGH TIME WITH HIGH TIME SINCE OVERHAUL. HARTZELL PROPELLERS PERSONNEL VERIFIED DILUTED OIL COULD CAUSE A PROPELLER TO GO INTO UNCOMMANDED FEATHER. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12

Verbatim from NTSB's published report. Source file NTSB_1991_NYC91LA092.txt. Findings + structured fields enriched from FAA avall.mdb. Full investigation docket on data.ntsb.gov ↗.

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