Casualties unknown

1991-08-01: Piper PA-12 (N4436M) — William Grahn — Alton, NH

Alton, NH, US

On August 1, 1991, a Piper PA-12 (registration N4436M) operated by William Grahn was involved in an aviation accident near Alton, NH. Investigators recorded the probable cause as: THE PILOT'S IMPROPER USE OF CARBURETOR HEAT, WHICH RESULTED IN A LOSS OF ENGINE POWER. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 1781061362Data APIEditorial standards

During a descent, a pilot experienced a drop in engine RPM when reapplying power. Despite using carburetor heat, the RPM loss continued, leading to a landing in trees. The pilot suspected carburetor ice. The FAA chart indicated conditions conducive to serious carburetor icing at cruise power.

Event Details

During the flight, the pilot reduced engine power and initiated a descent to 2,000 feet. When he attempted to apply power again, he noticed the engine RPM beginning to decrease. He selected carburetor heat, hoping to resolve the issue, but the RPM continued to drop. Faced with a loss of engine power, the pilot landed the airplane in trees.

Pilot's Assessment

The pilot attributed the power loss to carburetor ice. He remarked that after five years of flying in a desert environment, he had become unaccustomed to the conditions that lead to carburetor icing.

Meteorological Information

The FAA's published chart for conditions favoring carburetor ice formation indicated that the temperature and dew point at the time were within a range that could cause serious icing at cruise power settings.

Pilot Background

The pilot's flight experience in the PA-12, the aircraft involved, amounted to 1.5 hours total.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001212X17948. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.