investigating INS ATT?

[SharpeXB]

My Left DDI says “INS ATT” I got yellow caution and my FPM is flashing. What’s up?

[Tholozor]

Cold start or hot start?

[SharpeXB]

Cold. On the carrier. I completed the INS alignment. 

[Tholozor]

Did you put the INS knob to NAV or IFA?

[SharpeXB]

11 minutes ago, Tholozor said:

Did you put the INS knob to NAV or IFA?

IFA. Isn’t that the normal position if you have GPS, which I assume we do? Can that vary in MP?

[Tholozor]

It depends. If the mission year is set prior to when GPS itself was in service, or the aircraft is part of a coalition that doesn't have access to GPS (with the Unrestricted SATNAV option unchecked), IFA does the in-flight alignment procedure instead of engaging Aided INS (AINS).

 

After alignment, if GPS is available, you should get the 'P/INS' advisory with the INS knob in the NAV position. If not, leave it in NAV.

Edited January 3, 2021 by Tholozor

[fitness88]

p.109

1. Verify the Parking Brake is set.
Releasing  the  parking  brake  before  alignment  is  complete  may  result  in  an  invalid  alignment.  The alignment will need to be reinitialized.

[Swift.]

INS ATT is also indicative of the Attitude switch being in standby (the thing under the UFC, far right). A flashing VV is indicative of the VV being ADC driven iirc, which makes me think its not the Attitude switch being in the wrong position. I think it would be super helpful to have pics of the HSI, the HUD, and the LDDI.

[SharpeXB]

6 hours ago, fitness88 said:

p.109

1. Verify the Parking Brake is set.
Releasing  the  parking  brake  before  alignment  is  complete  may  result  in  an  invalid  alignment.  The alignment will need to be reinitialized.

Right. That wasn’t the case here. 

[SharpeXB]

8 hours ago, Tholozor said:

It depends. If the mission year is set prior to when GPS itself was in service, or the aircraft is part of a coalition that doesn't have access to GPS (with the Unrestricted SATNAV option unchecked), IFA does the in-flight alignment procedure instead of engaging Aided INS (AINS).

 

After alignment, if GPS is available, you should get the 'P/INS' advisory with the INS knob in the NAV position. If not, leave it in NAV.

 

That makes sense. There are SP missions set in the 1980s. This was MP on Growling Sidewinder. I don’t know what that was set for. 

2 hours ago, Swiftwin9s said:

INS ATT is also indicative of the Attitude switch being in standby (the thing under the UFC, far right). A flashing VV is indicative of the VV being ADC driven iirc, which makes me think its not the Attitude switch being in the wrong position. I think it would be super helpful to have pics of the HSI, the HUD, and the LDDI.

AFAIK that switch defaults to Auto. I’ll check that out next time. 

[Swift.]

10 minutes ago, SharpeXB said:

AFAIK that switch defaults to Auto. I’ll check that out next time. 

It does, but sometimes people change it or maybe the autostart changes it idk.

[SharpeXB]

2 minutes ago, Swiftwin9s said:

It does, but sometimes people change it or maybe the autostart changes it idk.

I did manual start. 

[Swift.]

16 minutes ago, SharpeXB said:

I did manual start. 

Ah then I doubt its that. Like I said then, more info would probably be needed. Pictures of the cockpit maybe even a short track if you have one.

[SharpeXB]

Here's the track, when I move to taxi the INS ATT comes up on the left DDI and the yellow caution is lit

https://www.dropbox.com/sh/wsao4hy0vort1kh/AAAdoMK5hKxv4ypd07kzhSBza?dl=0

[Tholozor]

Looking at your track, the INS ATT advisory came on the instant you moved the INS knob to NAV. The P/INS advisory also briefly appeared and was resolved when the knob was moved to IFA. POS mode correctly indicated AINS. ATT switch was in AUTO. Opening the mission in the editor shows Random Failures were disabled.

 

Not sure what the issue is. Are you able to reproduce the problem?

Edited January 4, 2021 by Tholozor

[Zomba]

I've encountered this from time to time. Moving the mode knob back to it's alignment mode and redoing the alignment clears it. I'm not sure what the cause is.

[SharpeXB]

Of course you have to rotate the knob through Nav to get to IFA. I see the P/INS appear as the knob is turned. I always start up this way and never have trouble, indeed I don’t know that there’s another way. I’ve only had this happen once and not been able to reproduce it. 

[Tholozor]

Do you normally begin alignment after starting the right engine? Making sure to rule out a generator tie problem regarding the mission computers.

[SharpeXB]

18 minutes ago, Tholozor said:

Do you normally begin alignment after starting the right engine? Making sure to rule out a generator tie problem regarding the mission computers.

Now that there’s an INS alignment time, yes. Just to start the alignment ASAP. The manual has you starting the alignment after the left engine but I haven’t noticed that this matters. I have the same cockpit flow every time. 

Edited January 4, 2021 by SharpeXB

[Foka]

45 minutes ago, Tholozor said:

Do you normally begin alignment after starting the right engine? Making sure to rule out a generator tie problem regarding the mission computers.

I do it all the time and there's no problems.

 

I don't know why the error pop ups, but I'll give you other hint - when right engine is cranking turn on AMPCD (bottom monitor) (you can turn others too, but for the hint it doesn't matter), when right engins will start and generator starts working the AMPCD will turn on, then switch INS knob to start alignment (CVN or GND) and then press STD HDG on HSI (bottom line of buttons, second from the left). The alignment will take 90 secs.

[SharpeXB]

I had this happen again and I think it could be caused by changing the scale on the HSI map prior to completing the alignment

 

Track file:

https://www.dropbox.com/sh/hg83d2qyrao9624/AADs9kvft1CYmGO7je7bXaV1a?dl=0

Edited January 20, 2021 by SharpeXB

[dorianR666]

you might be onto something

 

it happened to me twice today that i did stored heading alignment on ground, waited for OK, switched to IFA - and instantly lost the alignment. mission date is 2021 and am playing as blueforce (usa).

i did the procedure correctly, i play with hornet every couple of days with cold starts, so surely no problem there.

 

i tried replicating it, but cant.

Edited January 24, 2021 by dorianR666

[dorianR666]

could someone run this?

look at how i get OK on HSI, switch to IFA, and INS ATT appears on left DDI.

 

ins_bug_b.trk

[dorianR666]

 

On 1/20/2021 at 1:34 AM, SharpeXB said:

I had this happen again and I think it could be caused by changing the scale on the HSI map prior to completing the alignment

it indeed seems to be caused by changing HSI scale.

 

 

@BIGNEWY

another track attached. there is definitely a bug in INS.

 

pic attached is what appears for roughly 2 seconds after switching to IFA, then it disappears. INS ATT stays though.

 

ins_bug_c.trk

Edited January 24, 2021 by dorianR666

[dorianR666]

hm, i just managed to trigger it without changing HSI scale and while using ground power.

i suspect its related to generators switching on with particular timing.