inu 1 and 2 at startup Alignment without GPS - HowTo?

[QuiGon]

How to align the INS on missions where GPS is not available?

[secretcode]

Also, does anyone know if alignment on a ship modeled? and if so how to do it.

[QuiGon]

I just saw the tag that got added to the thread, but what does "INU 1 and 2 at startup" supposed to mean?
If I just let them align normally they never go green if no GPS is available.

[frostycab]

37 minutes ago, QuiGon said:

I just saw the tag that got added to the thread, but what does "INU 1 and 2 at startup" supposed to mean?
If I just let them align normally they never go green if no GPS is available.

I thought that's what the doppler was for, but admit that it's something I turn on and forget about. 

Out of curiosity, why are you not getting GPS signal? It's not something I've encountered yet.

On 3/19/2022 at 9:06 PM, secretcode said:

Also, does anyone know if alignment on a ship modeled? and if so how to do it.

If you look at the bottom of the TSD-UTIL page at B1, there is a label reading NAV LAND. If you click this it changes to NAV SEA, adding alignment options at R4 and R5. However I don't believe this is functional yet.

[QuiGon]

24 minutes ago, frostycab said:

I thought that's what the doppler was for

That's odd. How can a doppler radar aid in aligning the INU on startup? All a doppler radar usually does is measure speed and direction across the ground, which can be used to correct for INS drift. I don't see how this would be useful for a stationary INS alignment though?

24 minutes ago, frostycab said:

Out of curiosity, why are you not getting GPS signal? It's not something I've encountered yet.

GPS is not available if you're playing on red side or if the mission date is before 1994.

Edited March 21, 2022 by QuiGon

[frostycab]

8 minutes ago, QuiGon said:

That's odd. How can a doppler radar aid in aligning the INU on startup? All a doppler radar usually does is measure speed and direction across the ground, which can be used to correct for INS drift. I don't see how this would be useful for a stationary INS alignment though?

Yes, I suppose that makes sense now that I think about it.

9 minutes ago, QuiGon said:

GPS is not available if you're playing on red side or if the mission date is before 1994.

Ah, ok. In that case I would surmise that at some point in the future we may get the option to manually enter our starting location into the navigation system to account for that rather than having it auto-populate as it does now. (Of course, this may be something that is done by the ground crew when readying the aircraft, but I have no idea.) My very limited knowledge of INUs from older civil aviation aircraft also makes me wonder why GPS would be required for alignment as it certainly wasn't an option back in the days of the 707 and other such aircraft which relied purely on inertial and radio navigation.

[QuiGon]

3 minutes ago, frostycab said:

My very limited knowledge of INUs from older civil aviation aircraft also makes me wonder why GPS would be required for alignment

GPS is not required for an alignment IRL, but it makes it easier or more "hands-free" if you have GPS, as it aids the process.

The question remains, how this works in DCS?

Edited March 21, 2022 by QuiGon

[Raven (Elysian Angel)]

Perhaps the current implementation is simply a placeholder, just as it was for the Hornet? Has anyone tried not aligning at all and see if that makes a difference?

[QuiGon]

4 minutes ago, Raven (Elysian Angel) said:

Perhaps the current implementation is simply a placeholder, just as it was for the Hornet?

I guess so, but this is quite frustrating if you want to play on a server with a mission date of 1990 like the BlueFlag Syria server...
 

[frostycab]

Just a thought, and I've not tested to see if affects things after you've started to move around, but it seems that the INUs have a confidence of 55m when you power up the aircraft. 55m seems like a fair degree of accuracy for an older navigation method. It's also worth noting that we don't have an indication of INU alignment in the cockpit, only position confidence, so there's no way of telling if we're "good to go" right away or if there are any detrimental effects from not allowing confidence to improve.

For me personally I'd be happy to go with 55m. The GPS satellites are boxed at just under 2 minutes from power being applied to the system, with INU confidence turning green roughly 2 minutes later, with accuracy increasing to 17m. I tried leaving the whole thing alone for a further 10 minutes and confidence only improved to 14m. 

For the time being I don't see 55m being a problem. That's less than the width of 2 FARP landing pads, and the Apache isn't really meant for precision instrument flying. I think for now I will just regard this as another WIP item. It'll be interesting to see how it develops. 

EDIT: One issue I did suddenly think of was adding TSD points, as coordinate entry uses the aircraft's present position to populate the KEU field, but I guess for now we'll just have to enter the full MGRS grid manually.

Edited March 21, 2022 by frostycab

[Sarix]

I'm not sure if I'm about to necropost (if I did then sorry) but:

On 3/20/2022 at 3:58 AM, QuiGon said:

How to align the INS on missions where GPS is not available?

Provide power to the aircraft (I only tested with engines running but the APU alone should be suffice?), go to TSD-UTIL. Reset both INUs.

Go back to the TSD, there should be a white "PSN" on the bottom left and a "HDG" above it. Selecting "PSN" changes it to "POSITION" and selecting it again boxes it. Enter the MGRS coordinates (with 4 easting/northing digits each, so 8 digits following the letters) and hit enter.

"POSITION" would become "UPT" (update). Hit the button to update ownship position. Wait for ~6? minutes and alignment would complete, but the position confidence doesn't seem to turn green at all.

The manual for the Apache states that we should enter the position before "HDG" is removed (if it is removed we need to reset both INUs and enter the position again within a minute), but "HDG" is removed a bit too fast imo, I am not sure if this has any impact on alignment quality though..

Edited August 24, 2022 by Sarix
IMU - INU. I can't type :(

[QuiGon]

1 hour ago, Sarix said:

I'm not sure if I'm about to necropost (if I did then sorry) but:

Provide power to the aircraft (I only tested with engines running but the APU alone should be suffice?), go to TSD-UTIL. Reset both IMUs.

Go back to the TSD, there should be a white "PSN" on the bottom left and a "HDG" above it. Selecting "PSN" changes it to "POSITION" and selecting it again boxes it. Enter the MGRS coordinates (with 4 easting/northing digits each, so 8 digits following the letters) and hit enter.

"POSITION" would become "UPT" (update). Hit the button to update ownship position. Wait for ~6? minutes and alignment would complete, but the position confidence doesn't seem to turn green at all.

The manual for the Apache states that we should enter the position before "HDG" is removed (if it is removed we need to reset both INUs and enter the position again within a minute), but "HDG" is removed a bit too fast imo, I am not sure if this has any impact on alignment quality though..

Great info, thanks a lot! I will have to test this, but I guess it isn't implemented properly yet.

[Raptor9]

Yes, the INU simulation is still very much still WIP.