The concern sheet
Text extracted from the PDF.
Airworthiness Concern Sheet
Bryan J. Easterwood Aerospace Engineer Federal Aviation Administration Wichita ACO ACE-119W (Electrical) 1801 Airport Road Wichita, Kansas 67209 316-946-4132 Bryan.Easterwood@faa.gov Make, Model, Series, Serial No.: Raytheon Aircraft Company (RAC) Beech Baron Series Airplanes Models 58, 58A, 58P, 58PA, 58TC, and 58TCA Reason for Airworthiness Concern: Potential internal failure of switch style circuit breakers that could cause the switch to get hot enough to produce smoke in the cockpit.
Date: October 1, 2004 FAA Description of Airworthiness Concern: There have been several Service Difficulty Reports (four of the most recent SDR’s are attached) and a safety recommendation (03.125) regarding the failure of switch style circuit breakers that could fail in such a way to cause smoke and the inability to select off. Eight failed switches were removed from various model aircraft above and evaluated by Raytheon along with the FAA and three of these switches were observed to get very hot to the touch and one eventually produced smoke, and could not be selected off. The circuit breakers in question operate several aircraft functions, including but not limited to, Anti-Ice (PITOT, WSHLD, PROP), Landing Lights, Strobe Lights, Taxi Lights, and Rotating Beacon. These switch style circuit breakers are Raytheon Part Numbers: 35-380132-xx, where xx defines the current rating and were originally manufactured by Wood Inc (P/N: 548-210-xxx), then manufactured by Potter & Brumfield (P/N: W31-X1001-xx), and most recently by Tyco (P/N: W31-X1001-xxx). There has also been a write up in the Aviation Maintenance Alert Advisory Circular 43-16A released April 2002 concerning these switches (attached).
Raytheon is planning on publishing a Recommended Service Bulletin with a corrective action to replace these types of switches with an improved switch, that addresses known issues with this component.
The attached Risk Assessment (calculator and chart) was completed utilizing Appendix VI of the FAA Small Airplane Directorate Airworthiness Directives Manual Supplement (Airworthiness Concern Process Guide) and derives a Safety Risk Factor of 11 with a safety effect of hazardous selected. This falls into the area on the chart of a potential routine AD.
Request for Information: The FAA is considering possible Airworthiness Directive (AD) action for the outlined concern. This is an advanced notice, so please make your comments known to us within 30 days.
Attachments: *SDR(s) *A/IDS *SL(s) *SAIB *FAASR/*NTSBSR *AD *AMOC *RA
Notification: FAA *AOPA *EAA Type Club *TC Holder Other: RAA & NBAA
Response Requested _10-21-2004: Emergency (10 days) Alert (30 days) Information (90 days) (Space Bar Adds “X” to Check Boxes) *Service Difficulty Reports (SDRs); Accident/Incident Data System (A/IDS); Service Letter (SL); Special Airworthiness Information Bulletin (SAIB);
Federal Aviation Administration (FAA)/National Transportation Safety Board (NTSB) Safety Recommendation (FAASR/NTSBSR); Airworthiness Directive (AD); Alternate Method of Compliance (AMOC); Risk Assessment (RA); Aircraft Owners & Pilots Association (AOPA);
Experimental Aircraft Association (EAA); Type Certificate (TC) This Airworthiness Concern Sheet (ACS) is intended as a means for FAA Aviation Safety Engineers to coordinate airworthiness concerns with aircraft owner/operators through associations and type clubs. At this time, the FAA has not made a determination on what type of corrective action (if any) should be taken. The resolution of this airworthiness concern could involve an AD action or an SAIB, or the FAA could determine that no action is needed at this time. The FAA’s final determination will depend in part on the information received in response to this ACS.
The FAA endorses dissemination of this technical information to all manufacturers and requests association and type clubs comments.