Loss of FMC's in flight 757/767
Has any of you 757/767 pilots lost all of your FMC's just as you reach cruise altitude or shortly thereafter ? I have had three instances one in a 767 and two in the 757. All of a sudden the FMC's go blank, (on the 757 they go to the ACARS/FMC prompt and display Timeout). The windows above the EADI go blank (Except the autothrottle) The Autopilot stays engaged but all the information on the EADI ( except the pitch ladder)and Map Displays go away displaying only the lubber line . By the time you utter an expletive or two, things start to come back one at a time. I don't remeber the order, but the windows above the EADI show LNAV and VNAV PTH but they have lines thru them. It's back to normal after 6-7 seconds. I guess for me it's a case of "What the hell is it doing now ?? I dunno but I've seen it before." My apologies if this has been covered at length before. By the way our training department didn't have an answer.