normal alignment procedure - assistance required

[AngryViper.101]

Good evening

Need some advice.

While playing on one of the Buddy Spike servers (Syria, 80's) I encountered a problem.

Situation 

After crash landing at an airport. I shut down the engine, waited, asked for repairs. After some time the ground crew were happy to repair the Jet. 

Then I proceeded with a cold start. However, I did not move the jet an inch. In fact I had the parking brakes on. I then performing a 'normal' alignment procedure.

1. turning the knob to the normal alignment position

2. waited for the bearing to correctly adjust, that happens rather quickly

3. click on the enter button to confirm the North, East and elevation

4. Wait .... 

5. Then on the HUD the align starts flashing (after counting down to .../10) as per usual

6. Then turn the alignment knob to the Nav position

Problem

All looks good on the Hud, bearing etc.

But, when I reach my target the TGP correctly 'shows' the target picture, but on the Hud the block with the dot points at an incorrect location? This causes me to not be able to use any GPS guided bombs?

What could I be doing incorrectly in the procedure above?

P.S I actually turned around, landed safely ... and did the Normal alignment procedure again... waiting for the flashing on the HUD after it counted down from .../99 to .../10 .. long wait. and again, same story?

Any advice / guidance would be much appreciated.

Cheers

[Aquorys]

Sounds like a bug to me. Have you tried selecting another steerpoint, and then the intended steerpoint again, and cursor-zero on the TGP? Power cycled the TGP?

[Tom Kazansky]

@warford

Are you sure that the coordinates/altitudes you confirmed right at the starts of your alignments were identical with those of the F10 map (if available)?

Edited July 7, 2022 by Tom Kazansky

[AngryViper.101]

Hi

Yes, I actually tried it two different ways.

1. Firstly, I manually input the coordinates based on a 'tag' on the map, then cursor zeroed etc. (tried TGP and FCR ground radar)

2. Secondly, I actually used the TGP to create a Markpoint, which I then set as the active steerpoint, and also tried the cursor zero on both TGP and FCR ground radar with no luck

I will try again tomorrow, same load out with a newly spawned jet to see if the GPS guided bomb works after creating similar steerpoints ;-(

Surely there must be a way to have the jet repaired and then setup alignment correctly? and go off and mark targets correctly for dropping of bombs?

[Tom Kazansky]

Thanks for the clarification. Good luck. I'm curious about your results tomorrow. Would you mind sharing those with us here?

[AngryViper.101]

Hi Tom, yes I will definitely keep this post updated.

I watched another video just now, apparently, during normal alignment one must actually input the North and East coordinates manually, which I did not do, I simply accepted them as correct and hit enter on both? Is this a fact, that one must manually lookup one's position on the F10 map and input the N and E coordinates again when performing a normal alignment?

- I will also try and test this scenario after forcing a crash landing, repair the aircraft, and do what I explained in the paragraph above.

[Tom Kazansky]

Thanks. If the coordinates and altitude that are shown on the DED of your viper are correct then it is enough to confirm them by pressing ENTER (for each of the 3 lines) within the first 2 minutes after starting the alignment process.

Edited July 7, 2022 by Tom Kazansky

[Aquorys]

I just tested various alignment procedures, and in the more unusual ones, it does all kinds of funny things that it's not supposed to do and doesn't do others that it should do, so I guess you encountered some situation that is not fully implemented yet.

One other thing you could try is an in-flight alignment, but I doubt that it will fix the problem, because it looks more like a data divergence problem in DCS between the TGP and the aircraft and less like a problem with actually aligning the INS.

[Frederf]

Can you make a track (Caucuses if it can be recreated there) of this behavior?

[AngryViper.101]

Good morning,

Alright, tested with a new jet, on the same server, and the GPS guided JDAM hit spot on to my input coordinates (verified via TGP).

Now, I will also test, after  crash landing and waiting for a full normal alignment, perhaps the coordinates were incorrect.

[AngryViper.101]

During a normal alignment procedure, which coordinate system must we use to input our coords?

I used the F10 map and left ALT + Y and this was the closest coordinate format I could find, however, the F16 alignment DED page does not allow for the last decimal digit?

 

Edited July 8, 2022 by warford

[Tom Kazansky]

That's not the right one:

17.1' is not too close to 17'11'' because

1' = 60'' and so 17.1' = 17'06'' (or 17'6'')

You need the format with the decimals despite the Viper has only 1 digit after the period.

edit: looks like NXX°XX.XXX WXXX°XX.XXX

(you have to round those last 3 digits .XXX to .X)

(edit2: I'm testing this but it seems that only 1 digit is very inaccurate. I get deviations to more than 100 meters. do I miss something? Is there a way to get more precise coordinates to the alignment page?)

Edited July 8, 2022 by Tom Kazansky

[AngryViper.101]

Thank you for the reply.

Okay, so my second test done.

I forced a crash landing, fire and tip of right wing missing... (luckily did not die).

Then powered down all the darn switches, waited for a repair, then booted up, cold start.

Then did the normal alignment using the images above for the coordinates.

1.  The good news, armed with JDAMS, and managed to release on my target location (previously / yesterday I could not release INS was messed upcompletely)

2. BUT as you pointed out I missed my target by  a few 100 meters +- not sure, had to get out of there darn Stingers!

In summary, my issues yesterday, could have been due to the fact, that after an aircraft repair I did not turn off ALL switches and do a full cold boot. Also, at the time I was refueling, and this time I even enable ground jett ... So the aircraft was untouched in my successful run this morning.

 

This leaves us with the one question, when performing a full alignment, how do we input the correct coordinates, given that the input allows for one decimal place?

 

Cheers!

[itn]

10 minutes ago, warford said:

This leaves us with the one question, when performing a full alignment, how do we input the correct coordinates, given that the input allows for one decimal place?

Simply round the Degree Decimal Minutes (DDM) coordinates from three to one decimal when entering them for INS alignment.

If you're in a freshly pitted cold start jet, the coordinates should match so you will just confirm the coordinates and elevation each with ENTR (and dobber down to switch line).

Edited July 8, 2022 by itn
Clarified the need to verify each line with ENTR

[Tom Kazansky]

@warfordthanks for the info.

I have just found another interesting one:

in this grim reapers video about alignment @2:10 min. it is claimed that the altitude in the F10 map is the ground level (no news) but the INS box is 6ft above that level and one has to add those 6ft to the altitude value of the F10 map. Ok, I woud say that 6ft is a verry small deviation compared to the 0.1' (max) error of the coordinates. So I agree: The question is: how to get the coordinates in the Viper alignment more precise?)

4 minutes ago, itn said:

Simply round the Degree Decimal Minutes (DDM) coordinates from three to one decimal when entering them for INS alignment.

If you're in a freshly pitted cold start jet, the coordinates should match so you will just confirm the coordinates and elevation with ENTR.

that's what I said before, but it leaves you with an error of up to 150m for each N/S and W/O direction.

Edited July 8, 2022 by Tom Kazansky

[Tom Kazansky]

I was just searching for more info on alignment accuracy, and all I found was a video where the alignment of an Airbus A320 is explained, and they also use only one digit.

(it starts at 1:40 min but you already see it in the YT-video-screenshot)

that INS accuracy seems to be standard.

 

[itn]

I think you should be able to do a squat fix (ground overfly) before departure. You would use a known location with a steerpoint on it. Steerpoint is represented to three-digit accuracy, so it would be more accurate. Based on my quick test on the ground, i'm not sure if the ground overfly update works as it should.

And in current DCS context, if GPS in available, It Just Works and you need not bother with any of this. Without GPS you need to provide in-flight FIXes due to inaccuracies and INS drift.

[Tom Kazansky]

19 minutes ago, itn said:

I think you should be able to do a squat fix (ground overfly) before departure. You would use a known location with a steerpoint on it. Steerpoint is represented to three-digit accuracy, so it would be more accurate. Based on my quick test on the ground, i'm not sure if the ground overfly update works as it should.

And in current DCS context, if GPS in available, It Just Works and you need not bother with any of this. Without GPS you need to provide in-flight FIXes due to inaccuracies and INS drift.

thanks

[AngryViper.101]

Thank you everyone, I think we have a lot of information here and happy to close off this topic.

Happy flying!

[AngryViper.101]

Hang on, why is the rounding for the EAST coordinate not rounding up? Check this:

I did not touch anything, spawned in a new jet, started the default stored alignment.

And on the map it reads E035'17.772, and the alignment DED shows E035'17.7, 

Should it not be E035'17.8? looks more like they just chop off the last two digits?

[Tom Kazansky]

Well, after knowing that INS has an accuracy of about +/- 75m in both dimensions, I don't think hitting a target right on the spot (in DCS) has anything to do with the INS, as long as it isn't completely off. And yes, it should round correctly, what it does not atm, but I'll go with @itn and won't care too much about it, as long as GPS does its magic. The thread was/is still interesting for me though. Thanks for that.

 

[Aquorys]

1 hour ago, Tom Kazansky said:

Well, after knowing that INS has an accuracy of about +/- 75m in both dimensions

It is not that inaccurate, what you enter is just a rough start position. The gyros in combination with the GPS will figure out what the exact attitude, position and heading is, and the INS is continuously updated with INSM data, including GPS data, during flight (unless the alignment is completely screwed for whatever reason, and in that case, you would perform an in-flight alignment). A properly aligned INS is very accurate during flight, even without GPS updates, especially in the first hour of the flight, where the CEP (circular error probable) can be reduced to 60% of what it normally would be with an extended alignment procedure on the ground.