Major Sovereign problem

[earhart]

http://www.aaib.gov.uk/cms_resources...0%20G-CJCC.pdf

 

[spxdriver]

Operating with the L ELEC button in EMER and the left generator off, with the right side bus/generator operating normally, can initiate an unintended transfer of fuel from the right fuel tank to the left tank.***** This can occur automatically during certain malfunctions or by pilot selection in response to AFM procedures.***** The potential for this to occur is indicated in flight by amber DC EMER BUS L and DC GEN OFF L CAS messages accompanied by cyan FUEL CROSS FEED and FUEL BOOST PUMP ON R CAS messages.***** If these are observed in flight, the resulting fuel imbalance may be minimized by turning the FUEL CROSSFEED selector to the OFF position and then pulling the R FUEL BOOST circuit breaker in the copilot’s circuit breaker panel in the cockpit.*****
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A Citation Sovereign recently experienced an amber DC EMER BUS L CAS message during flight indicating that the left electrical bus isolation relay had automatically opened.***** When not accompanied by an excessive battery current, the AFM procedure for this message requires switching the left generator off.***** When this is done, all systems on the left main electrical bus will lose power, including the left fuel quantity indication and left fuel boost pump.***** During the 20-30 minute flight back to the departure airport, the crew noticed an increasing need for right aileron input to maintain level flight.***** After landing, when power was restored on the airplane, the fuel gauges indicated that the left fuel tank was full and the right tank had 3300 pounds remaining.*****
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When power is removed from the left main electrical bus, the left Fuel Control Printed Circuit Board loses power.***** Further investigation revealed that this specific combination of events can cause an unintended fuel crossfeed command to the right Fuel Control Printed Circuit Board which then outputs commands to open the fuel crossfeed valve and turn on the right fuel boost pump.***** However, without power to the left Fuel Control Printed Circuit Board, the left motive flow valve will not close as it normally would during a right tank to left engine cross feed.***** Fuel will now be supplied to both engines from the right tank but, with the left motive flow valve open, motive flow fuel from the left engine will be returned to the left tank causing an increase in fuel quantity.***** An amber FUEL MOTIVE VLV FAIL L CAS message will also be observed since the left motive flow valve would normally be closed during right to left crossfeed.*****
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Testing has shown that, in this condition, turning fuel crossfeed off and then turning the right fuel boost pump off by pulling the R FUEL BOOST circuit breaker on the copilot’s circuit breaker panel in the cockpit will allow fuel to be supplied to each engine from its respective fuel tank thereby minimizing any resulting fuel imbalance.**********
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A similar scenario with the right electrical isolation relay opening and the right generator turned off will not cause fuel to transfer unless fuel crossfeed is already selected when the right main electrical bus loses power.***** However, since the position of the fuel crossfeed valve will be uncertain in this case (amber FUEL CROSS FEED TRANSIT message will be posted), the L FUEL BOOST circuit breaker in the pilot’s circuit breaker panel in the cockpit should be pulled to minimize any possible fuel imbalance.*****
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A Temporary Change to the AFM will follow closely and a permanent resolution is in work.
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Questions, please contact:
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Team Sovereign
316-517-1695 (Direct)
1-877-683-7344 (WATS)
[email protected]