Instrument Pilot Encountered Severe Icing Before Accident

Casualties unknown • Flagstaff, AZ, US

A pilot flying under an instrument clearance encountered significant icing and pitot-static system failure while unable to maintain the required minimum enroute altitude.

What happened

During a preflight weather briefing, the pilot was advised that icing conditions were forecast below 16,000 feet along the intended route of flight, which involved flying between two frontal systems. The pilot was also informed that several inbound aircraft had previously encountered icing at 9,000 feet. Based on this information, the pilot filed for and received an instrument clearance to fly at a minimum enroute altitude (MEA) of 11,000 feet.

Approximately 34 minutes after takeoff, the pilot reported that the aircraft was picking up ice and that the pitot/static system had iced over. Because the pilot was unable to climb to the assigned MEA, an approach clearance for a nearby airport was issued. While cruising at altitudes between 9,200 and 9,700 feet—below the required 11,000-foot MEA—the pilot reported continued heavy icing and an opaque windshield. At the time of the report, the aircraft was 17.9 miles from the airport.

In July 1995, the aircraft was located 14.5 miles and 353 degrees from the airport. This location did not correspond to any federal airway or route structure associated with the instrument approach procedure being used. The pilot had received an instrument rating only three weeks prior to the accident.

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Frequently asked questions

What happened in the 1994-11-18 Piper PA-32-300 accident near Flagstaff, AZ?

A pilot flying under an instrument clearance encountered significant icing and pitot-static system failure while unable to maintain the required minimum enroute altitude.

What aircraft was involved and where did it happen?

The accident on 1994-11-18 involved a Piper PA-32-300, registration N4108R, operated by Stephen M. Mumford, at Flagstaff, AZ.

What was the probable cause of the accident?

the pilot's intentional flight into known adverse weather conditions, his misjudged evaluation of the weather, and his inexperience in actual instrument flying.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001206X02614. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.

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