On September 30, 2010, at 0825 universal coordinated time (UTC), a Cessna 680, G-CJCC, operated by Bookajet, experienced a left main bus electrical system fault, approximately 20 minutes after taking off from Luton Airport (EGGW), en route to the Milas-Bodrum Airport (LTFE), Milas, Turkey. The flight crew completed the required checklists and returned to EGGW. Upon landing at EGGW, it was determined that the left main fuel tank was full with 5,500 pounds of fuel and the right fuel tank contained 3,300 pounds of fuel. AAIB issued Special Bulletin S1/2010 on October 8, 2010. The bulletin states in part, "This incident and subsequent ground testing showed that removal of power from the left main bus will cause the fuel cross-feed valve to open and the right boost pump to operate without any crew selection, and the motive-flow shutoff valves will remain open. This allows motive-flow fuel to be returned to both tanks, resulting in uncommanded fuel transfer from the right to the left tank. During the 20 minutes that elapsed between selecting the left generator OFF and landing at Luton, sufficient fuel was transfered from the right to the left tank, via the left engine motive-flow system, to create a fuel imbalance of 2,200 lbs. The crew were not aware that this was occurring, as only the right fuel quantity indication was available." This incident is under the jurisdiction and control of the Air Accident Investigation Branch (AAIB). This report is for informational purposes only and contains only information released by or obtained from the government of the United Kingdom. Further information pertaining to this incident may be obtained from: Air Accident Investigation Branch Department for Transport Farnborough Copse Road Aldershot, Hampshire GU11 2HH, United Kingdom Tel: +44(0) 1252 510300 Email: investigations@aaib.gov.uk