INS alignment

[sirrah]

I asked roughly the same question in the EGI thread with regards to the 8 vs 4 and when/why it changed. I never got an answer. Someone out there probably knows, but it isn’t me.

 

Just asked a friend of mine, years ago we both did base maintenance (mechanical) on the F-16 MLu (RNLAF) and he switched over to avionics a few years back.

 

He told me he does alignments on regular basis. Though he never timed it, his best guess would be ~4 minutes without GPS (GPS set to no track). So that'd be in line with what we see in Wags startup video. My friend promised me to time it soon as he gets the chance, as he was now curious himself :P

Edited October 2, 2019 by sirrah

[Rainmaker]

Just asked a friend of mine, years ago we both did base maintenance (mechanical) on the F-16 MLu (RNLAF) and he switched over to avionics a few years back.

 

He told me he does alignments on regular basis. Though he never timed it, his best guess would be ~4 minutes without GPS (GPS set to no track). So that'd be in line with what we see in Wags startup video. My friend promised me to time it soon as he gets the chance, as he was now curious himself :P

 

From my understanding, it went to 4 vs 8 sometime after 10 years or so ago. It used to be 8 minutes for an INS alignment, and it was improved to 4, at least with some aircraft (not sure about all). I’m taking a guess that it’s the GPS improvements that helped, but that is only a guess.

 

I guess we’ll see eventually what ED is choosing to model.

[Harlikwin]

From my understanding, it went to 4 vs 8 sometime after 10 years or so ago. It used to be 8 minutes for an INS alignment, and it was improved to 4, at least with some aircraft (not sure about all). I’m taking a guess that it’s the GPS improvements that helped, but that is only a guess.

 

I guess we’ll see eventually what ED is choosing to model.

 

Nah the lasers in the gyros got faster :megalol: :helpsmilie:

[Tomsk]

Nah the lasers in the gyros got faster :megalol: :helpsmilie:

 

Ha this made me chuckle, especially since (as I understand it) the entire reason laser ring gyros work is because the speed of light is the same in all reference frames (including rotating ones).

[Harlikwin]

Ha this made me chuckle, especially since (as I understand it) the entire reason laser ring gyros work is because the speed of light is the same in all reference frames (including rotating ones).

 

Yup, that was the joke.

 

I also have no idea why it went down from 8 to 4.

 

In the sim I know that the bit of code that says how long do we make these guys wait before we let them pull up the nav screen says 4 minutes.

[Stubbies2003]

In relation to the OP question.

 

I always thought that the F-16 alignment took more or less 8 minutes and that, when stopped earlier, it would greatly reduce accuracy (kinda similar to the Cat). Or is this only the case for the F-16A/B MLu versions?

 

Maybe someone with some F-16 avionics background can clarify this?

 

 

So a few things. Lets just assume we are talking the original RLG with the 8 minute timer. The RLG has the capability to perform interrupted alignments so long as you don't take more than 10 minutes to go back to align and you didn't exceed like 80 knots of speed. So you could do two minutes worth of alignment, go to NAV mode, taxi to EoR, go back to align and finish out at EoR.

 

There is also an enhanced interrupted alignment procedure to tighten the INS that much more than a normal.

[Stubbies2003]

I do not have an avionics background, but the alignment time would depend on the Inertial Navigation Unit (INU) used on the aircraft, the type of alignment being performed, whether you are inside of a Harden Aircraft Shelter (HAS) or not, etc.

 

 

Uh being in a HAS doesn't affect the INS.

 

 

And yes, if not fully align there will be degradation of accuracy over time.

 

 

If the pilot doesn't finish the alignment then correct.

[Stubbies2003]

If GPS can get a signal, Alignment method will change

 

 

Not for a basic gyrocompass alignment no. GPS data isn't required for the INU to sense the Earth's movement while setting up the platform.

[Stubbies2003]

Hmmm, you sure? You can tell the aircraft where it is by entering your current co-ordinates, so how would GPS help? The plane already knows where it is.

 

 

More than just "you can" enter current position that is required as part of the normal gyrocompass alignment. Only stored heading alignments don't require entering of current lat/long.

[mvsgas]

Uh being in a HAS doesn't affect the INS.

 

 

Not for a basic gyrocompass alignment no. GPS data isn't required for the INU to sense the Earth's movement while setting up the platform.

 

As I explain here:

https://forums.eagle.ru/showpost.php?p=4054292&postcount=20

Talking about the time to align, method would change. So, on the line or outside of the HAS, with Good GPS signal, You can just put the Knob in Norm alignment and move on with the launch if using and EGI. If inside the HAS, you would have to set GPS not track, then enter the coordinates manually before starting the alignment. Then immediately prior to taxi, deselect GPS no track to allow the MMC to reset the GPS.

 

Non of this would mater using RLG, GPS is not a factor there.

So

I was talking specifically about time to align. again, depending on the system, the INU, the method to align and whether GPS has a signal or not. If no GPS signal, depending on the system, additional steps are needed prior to alignment, thus changing time to align..

 

STOR HDG alignment will have different time also

 

In the end it doe not matter in DCS. Last time I saw no GPS/GNSS coverage was in the KA-50 years ago in DCS. I have not seen this in a while.

Edited October 3, 2019 by mvsgas

[Stubbies2003]

Talking about the time to align, method would change. So, on the line or outside of the HAS, with Good GPS signal, You can just put the Knob in Norm alignment and move on with the launch if using and EGI. If inside the HAS, you would have to set GPS not track, then enter the coordinates manually before starting the alignment. Then immediately prior to taxi, deselect GPS no track to allow the MMC to reset the GPS.

 

 

Okay I get what you are saying then. So yes the methodology would be different as apparently it expects to get the initial coordinates from the GPS to start the alignment and the HAS procedure is the work around/old school procedure. The INS is aligning exactly the same it is just the road traveled to get there is different.

 

 

Non of this would mater using RLG, GPS is not a factor there.

 

That was my frame of reference as that is exactly what we had to do.

 

 

STOR HDG alignment will have different time also

 

 

Not sure Stored Heading would change at all between old and new school as it only took 90 seconds and you didn't have to enter coordinates thus GPS or no GPS wouldn't be a factor. Perhaps EGI could do it a bit faster than 90 seconds.

 

 

In the end it doe not matter in DCS. Last time I saw no GPS/GNSS coverage was in the KA-50 years ago in DCS. I have not seen this in a while.

 

 

Very true. This is just real world talk.

[SmokeFan]

So, where do I find if the INS is aligned or not, while I wait the 4 min?

[Tomcat84]

am I correct that F-16A/B MLu alignment takes approx. 8 munutes, while the F-16C/D block50 aligns in 4 minutes (as the OP checked on his stopwatch)? Or is the correct alignment time not implemented yet maybe?

 

 

MLUs took that long when they didn't have the EGI yet. After they got the EGI in the M5 upgrade about ten years ago the alignment time reduced to the 4 minutes.

 

 

 

Alignment time is higher (about 5 minutes) if you get closer to the north pole. (higher Latitudes).

[QuiGon]

So, where do I find if the INS is aligned or not, while I wait the 4 min?

No alignment yet (as I predicted on the first page of this thread):

Currently, the INS is always aligned. Later on we'll add the full simulation of the INS and GPS systems with their indications.

 

Coordinate entry is WIP.

 

Thanks

[SasRZ]

After the last update it does work every now and then. It is not consistent. Sometimes aligns in 2 minutes and goes straight to NAV after blinking for few seconds whereas in other ocasions it just does nothing when it gets to 10 (for stored) or 6 for NORM.

 

Does anyone know why?