Hi there everyone,I'm having some trouble with the PMDG 747-400The problem seems to be that whenever I fly out from any airport, with the FMC correctly programmed and the VNAV and LNAV active, at some time during the flight, I will hear this horrible grinding noise and the VNAV switch deactivates and the FLCHG activates.Also during this occurrance, sometimes I can no longer activate the VNAV unless I reset the flight.I know it is an unusual problem and I can't quite put my finger on what is causing it.Please help!Also I can't delete route discontinuties sometimes, it appears to delete when I choose delete, or move the previous waypoint up, but once I click EXEC, it is still there. I know I have some unusual problems!Also how do you tune ILS frequencies? Can't figure it out. Yesterday on VATSIM I had to switch to VFR at the last second!

The grinding noise you are hearing is probably the stick shaker, which means that your 747 is near stalling. What's your airspeed and altitude when it happens? Something weird going on here. Are your throttles responding to the Autothrottle commands? I ran into a weird A/T disconnect problem and finally had to uncheck the two boxes in the PMDG Options menu under the AFDS selection. Try that.I'm not sure about your waypoint problem. The changes should show up before you have to press EXEC in case more changes are needed before you're finished.You should thoroughly read the FMC manual to get a full understanding of all the operations, but I'll give you a clue on ILS tuning. Go to the NAV/RAD page on the FMC and enter the frequency and runway heading by entering it in the scratch pad as such: xxx.xx/xxx and up-select it by pressing the left select (L4) key by the ILS entry. For example, type as such in the scratch pad, 110.90/130 and press L4. You'll now be in manual tuning mode.Kim

Maybe you are trying to fly it above its Max Cruise altitude for that weight. Check the Cruise page of the VNAV in the FMC to find out what that is.