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Cockpit Smoke Caused by Overheated Switch During Descent (N854AW)

Mosinee, WI, US

On February 26, 1994, a British Aerospace ATP (registration N854AW) operated by United Feeder Service was involved in an aviation accident near Mosinee, WI. No fatalities were reported. Investigators recorded the probable cause as: the inadequate design of the PBSI electrical switch(es), and the operator's failure to expeditiously implement corrective Service Bulletins. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

Flight crew encountered smoke in the cockpit during descent, traced to a red-hot push button selector indicator switch. The copilot discharged a fire extinguisher, stopping the smoke. Maintenance found the switch scorched and melted, with heat damage to adjacent wiring.

Incident Overview

While descending from cruise altitude, the flight crew observed smoke in the cockpit and declared an emergency. The copilot identified the source as a red-hot push button selector indicator (PBSI) switch for the flight idle baulk test. The copilot discharged a portable fire extinguisher onto the switch, after which the smoke ceased.

Maintenance Findings

Following the incident, maintenance personnel removed the PBSI switch. Examination revealed the switch was scorched and melted. Additionally, adjacent wiring exhibited heat damage.

Manufacturer Service Bulletins

The manufacturer had previously released two service bulletins addressing PBSI switch malfunctions linked to water ingress into the cockpit near the switches. At the time of the incident, the operator had not implemented these voluntary service bulletins.

Related events

Same operator

Frequently asked questions

What happened in the 26 Feb 1994 British Aerospace ATP accident near Mosinee, WI?

Flight crew encountered smoke in the cockpit during descent, traced to a red-hot push button selector indicator switch. The copilot discharged a fire extinguisher, stopping the smoke. Maintenance found the switch scorched and melted, with heat damage to adjacent wiring.

Were there any fatalities in the 26 Feb 1994 British Aerospace ATP accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 26 Feb 1994 involved a British Aerospace ATP, registration N854AW, operated by United Feeder Service, at Mosinee, WI.

What was the probable cause of the accident?

the inadequate design of the PBSI electrical switch(es), and the operator's failure to expeditiously implement corrective Service Bulletins.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001206X00725. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.