"GC HOLD" on GC INS alignment

[JetJake76]

Hello,

Sometimes, when I do a cold start, and set INS alignment to GC mode, I randomly get the "GC HOLD" message on HUD, and alignment does not resume anymore. The aircraft does not move at all, wheel chocks are placed. Any ideas, what stops the alignment?

[ike444]

There are lots of confusing things going around about what causes the alignment to fail, and I don't claim to understand it myself, but I do know that any micro-adjustment of the 3 control axis will cause the alignment to go to HOLD.
No the brake-hold does not have to be on, the wheel chocks are optional as well, but one or the other has to be on since the jet will roll at idle.

I have the same issue but in my case it's mostly caused by: input jitter, throttle position not completely to idle, or server/multicrew desync.

You can retry even a failed SH alignment by flipping the INS off and then back to align until it goes to NO TAXI. I use this method to try fixing SH HOLDs and it works quite well. It will take a couple switch flips until it stops asking for PP REQD and goes to NO TAXI. Re-entering the coordinates when the correct coordinates are already entered in an attempt to clear PP REQD often causes the INS to fail its' alignment by either going straight to HOLD, or the especially frustrating count down of alignment error only for it to revert back to GC NO TAXI on finish.

Edited June 29, 2023 by ike444

[DSplayer]

Another particularity that I've found when aligning is that if you started your alignment too early after starting your engines (starting before they reach idle RPM), your alignment will kick to the HOLD mode when your engine(s) reach idle RPM. Advice is to wait at least 10 seconds for your engines to reach idle RPM before starting your alignment (this might or might not be accurate to IRL since on the Tomcat you want to avoid having any issues by having the INS ruined by voltage fluctuations iirc).

Another issue that others and I have observed that can cause a HOLD condition is rearming while aligning. 

[Caldera]

Hey All,

I am having problems with alignment as well. 

Typically, stuff like:  GC HOLD, GC NAV DEGR, GC PP REQ, GC NO TAXI (And typically with no rhyme or reason to them, at least that I can figure out.)

I wait to start the alignment until both engines are running at idle and the parking brake switch is set to on.  The alignment will go through the whole process of GC NO TAXI --> countdown --> then return to  GC NO TAXI where it locks up and will not progress to GC OK.  I have to keep switching the INS alignment switch to off, waiting a bit of time and then restarting the alignment over and over again until it finally seems to work.

To check that my procedure was correct, today I ran the training lesson again.  I followed the entire lesson faithfully and guess what happened during the alignment part?

GC NO TAXI --> countdown --> GC NO TAXI --> lock up

Baffling to me.  Any others experiencing anything like this behavior?

Caldera

[felixx75]

Already fixed for the next patch...

[AvgWhiteGuy]

Re: Fixed: INS Alignment too sensitive to movement.

A bit vague but hopefully resolves the ridiculous sensitivity of a 15 ton warplane, with 2 operators on board that can't even scratch their nutz or sneeze during alignment.