is there somewhere in the manuals that explain what the various messages the FMS sends mean? The one that's got me confused THIS time is "check alt constraint". It pops up during preflight after I hit the perf init key.

In this Swiss thread it's explained as an ALT constraint being busted during flight:

http://www.flightforum.ch/board/index.php?/topic/40425-feelthere-erj145-check-alt-constraint/?p=345350

 

Doesn't make much sense, though, during preflighting.   :huh:

 

It might also mean that the ALT CSTRs don't line up properly for an achievable vertical profile. But's that's just wild guessing on my part ...

Ensure you have entered a cruise altitude into the FMC, before pressing confirming the initialization. If you haven't entered this, the FMC will treat your cruise altitude as '0', and thus any constraints will be invalid.

tested again, making double sure that i have the alt in the FMS.  In fact it seems that I'm not able to "confirm perf init" AT ALL without an altitude in the system.  I still got the message.

 

Do you think that it might be because the departure I programmed has me taking off then flying "as assigned" before my first actual waypoint.  That caused a discontinuity before I reached cruise altitude.  Could that by why the FMS is confused? Because it can't construct a vertical path between those two points?

 

 

Do you think that it might be because the departure I programmed has me taking off then flying "as assigned" before my first actual waypoint.  That caused a discontinuity before I reached cruise altitude.  Could that by why the FMS is confused? Because it can't construct a vertical path between those two points?

 

I wouldn't be surprised if that's exactly what's causing the problem.

The ALT CONSTRAINT messages you get are advisory reminders that there are altitude constrictions in your flightplan, usually during departure as well as the arrival portion of the flight. You can clear them by pressing the CLR button. They are just reminders. You can spot the altitude constraints in the flightplan as a capital letter A immediately after the waypoints altitude, ie 2500A.

 

The "as assigned" message are for departures that don't have a fixed flighpath, normaly you'd get vectors/clearence from a controller for this portion. So what you do is either 1) fly as the ATC/controller directs you, either manualy or add your clearence WP's into the FMC or 2) in case you don't have ATC, fly according to published departure maps or simply just make your way toward the first waypoint at your own discression.

 

To remove the DISCONTINUITY, either press DIR (direct to) and then the waypoint you want to fly to, or just delete the DISCONTINUTY by pressing DEL (delete) and then the LSK next to where it say's DISCONTINUITY. That should make the first waypoint active. You can now engage the AP and it should fly your flighplan.

thanks you for the explanation Scarp!  I knew how to clear the discos, but i wasn't sure what the ALT Constraint message was trying to tell me.  Thanks!