1) When I follow the startup procedures in the manual, it seems that when starting the fuel pumps, it is not necessary to press the L aft fuel pump switch. Shouldn't this light up for me to ask me to "press it"? There is fuel in both the L & R tanks?2) No matter how closely I follow the manual in reference to fuel planning, the FMC always gives me an error message saying "insufficient fuel". The planning seems to go perfectly during the flight - I have nearly exactly the amount it says I would uopn arrival at my destination, & I have NEVER run out of fuel. I can't understand why I get this FMC message repeatedly (even during setup & initializing!), even though I am never out of fuel & I am following the fuel planning by the book.3) Sometime when I am flying LNAV & I get to my next waypoint, I get a message that says "FMC exception caught in DllIdle" Then LNAV seems not to work until I recapture my intended path. Anyone know what this is about?4) For some reason tonight on my flight from Cleveland to Atlanta, VNAV would NEVER let me press its bitton - I kept getting an FMC message "Perf/VNAV unavailable". What does this mean & why could I never press VNAV. I always can on all my other flights. Everything was initialized as normal in the FMC - but tonight it just seemed to NOT WORK. Anyone know what this was about? Was it just a bug?Thanks all for your great support.Sincerely,Chris Catalano

Hey Chris,Sounds like you are enjoying the 757To answer your questions1) The reason the Left Aft Boost Pump light is out is because the APU is running. The APU on the 757 (and most modern A/C) is controller by the APU Control. When the APU is started, it automatically turns on the Left Aft Boost pump to supply fuel pressure to the APU. 2) The FMC that is in the PMDG model was what came with the original 757 and was based on 1970's technology. The original 200K FMC was never very good at calculating fuel burn since it was always based on current consumption rates. The upgraded Pegasus System installed in late model versions handles it much better (maybe because it has 28meg of memory :-eek ) . Use the fuel charts and ignore the FMC. 3) I have never seen this so can't comment. :-)4) Message is caused by loss of the FMC T/O temp that you enter during Preflight. Known anomally but so far can't seem to nail down why the T/O Temp number disapears occasionaly when you climb in modes other than VNAV for extended periods of time. I just end up using FL CH instead.hope this helpsRegardsPaul:-cool