Aviation Investigation Report A98H0003
4.1.8 Circuit Breaker Reset Philosophy
- 22.214.171.124 - General
- 126.96.36.199 - Airbus
- 188.8.131.52 - The Boeing Company
- 184.108.40.206 - Transport Canada
- 220.127.116.11 - United States Federal Aviation Administration
- 18.104.22.168 - Swissair
As the SR 111 investigation progressed, it became evident that CB reset philosophies for the pilot, cabin crew, and maintenance communities were inconsistent across the aviation industry. A lack of a single approach created widely different interpretations regarding the best course of action in this regard.
Airbus issued CB reset policies that do not allow CB reset in flight except in emergency conditions, and then only when authorized by the pilot-in-command.
Boeing issued essentially the same policy as Airbus, except that it stipulated that no resets for fuel pump circuits were to be carried out under any circumstances.
In an effort to raise awareness on several issues surrounding the use of CBs, TC published an article in the 1/2001 issue of its Aviation Safety Letter.
On 21 August 2000, the FAA issued a Joint Flight Standards Information Bulletin for Airworthiness, Air Transportation, and General Aviation (Flight Standards Information Bulletin for Air Transportation 00-07A) to summarize the FAA's position on the issue of resetting tripped CBs. The overriding message is one of caution. In-flight resets are not allowed unless such action is consistent with the approved Flight Crew Operating Manual and is deemed necessary for safe flight and landing. A logbook entry is necessary to provide effective troubleshooting and corrective action by maintenance crews on the ground. Additionally, CB resets on the ground are only permitted after maintenance staff have determined the cause of the trip.
Swissair issued an AOM Bulletin (93/99) advising its MD-11 flight crews about a revision to CB reset procedures. The decision was made to allow a single reset during aircraft preparation prior to the aircraft moving under its own power. However, aircrews are not authorized to reset a tripped CB during taxi or in flight. The procedure to reboot a computer by cycling a CB, when stipulated by the manufacturer, will continue.
SR Technics, Swissair's maintenance provider, also reviewed its CB reset policy. Subsequently, the maintenance provider released Continuation Training Letter 041, which states that SR Technics expects that its technicians will use all available troubleshooting techniques to determine the cause of the electrical overload before any attempt is made to reset the CB. Additionally, SR Technics requires that all CB trips and resets are to be recorded as part of the maintenance log.
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