Workarounds for 747-8 autopilot bugs

[N7470 26]

Here are some workarounds I have found to help with the various autopilot bugs on the 747.

Flight Plans: Create your flight plan in the main menu, not on the FMC in the aircraft.  For long flights don't forget to select "High IFR" routing.   This generates more realistic and reasonable flight plans and activates them in the FMC automatically.   The FMC generates weird flight plans with some FMC-generated waypoints (symbol USR).

AP tries to flip the plane upside down when turning: Set "BANK LIMIT" to anything other than "AUTO".  This dial is located on the AP glaresheild controls right below the heading display.  Apparently AUTO = infinite bank limit.

LNAV can't handle sharp turns:  If your departure or arrival procedure has any significant angle turns you will need to hand fly these segments.   Once past the sharp turns, use "Heading SEL" to vector yourself to a straight part of the flight plan.   Once you are within about 2nm and 10 degrees of the magenta line you can safely enable LNAV and it will track correctly until it gets to a sharp turn.

"Altitude HOLD" mode does not hold altitude:   The AP logic does not understand how slowly the stabilizer trim adjusts so it oscillates up and down in an unstable manner until there isn't enough stab trim.  A workaround is to set your target altitude 1000 feed above (if climbing) and use "V/S" mode to get there.   When you get close to your actual assigned altitude change "V/S" to zero feet per minute.   It will hold this altitude perfectly.  By setting your target 1000 feet further you prevent it from automatically switching to "Altitude HOLD" mode.

AP defaults to "Altitude HOLD" mode after takeoff:  Make sure you switch to "V/S" before you enable AP.

Selecting "V/S" mode does always fully enable it: When this happens you won't see the magenta vertical speed bug on the PFD.  A workaround is to briefly select "VNAV" first and then select "V/S" and dial in the desired vertical speed.   Check your autothrottle setting as it may have changed when you were briefly in "VNAV" mode.

VNAV mode is pitcing up/down wildly: Similar to LNAV the key is to get the plane close to where it needs to be.  Make sure that your airspeed is close to the target and vertical speed is something reasonable like 1000-2000 fpm before switching to "VNAV" mode.  "VNAV" will automatically switch to "Altitude HOLD" when it reaches the selected altitude so you will neeed to use the "Altitude HOLD" workaround nead the end of the climb/descent.

FMC Tips: Don't forget to set the "Init POS" in the FMC by clicking on the button next to the current GPS position to copy it to the clipboard and then use that to set the current posision.   Select desired takeoff flaps setting in the FMC.  The cruise altitude and speeds should have been auto-populated from the main menu flight plan.   You can adjust the climb settings in the FMC without breaking anything.