Don't understand "Fix Points".

[Siinji]

I need help understanding the procedure to sync the INU with fix points.

 

As I've read in the manual and seen on youtube videos, the INU is always, more or less, drifting and getting out of sync. That's why we need these Fix Points, to "update" or "reset" the position. But what's the meaning in having these fixpoints in the INU itself??? If the INU is out of sync, then the fix points, which are programmed into the INU, are ALSO;) out of sync, right?

 

Can someone explain?

[Bobcat]

Good question; I wish I had the answer. The ekran was nagging me last night to do something about updating my position. I checked the manual but couldn't find the answer (it was midnight).

 

BC

[EvilBivol-1]

The idea is that the Fix Point is a known coordinate. The coordinates are pre-programmed into the INS through the PVI-800 (this is done automatically at mission start as part of the data loading process when you have a Fix Point set on the editor map). When you fly over that point (or designate it with the Shkval), you're "telling" the INU that you are currently over that known coordinate, so it can set itself accordingly.

[Siinji]

But as the INU drifts, the information about the current helicopter coordinates drifts. If you then move the helicopter to a fixpoint, you are NOT at that fixpoint, because of drift-error.

 

I mean: How can you sync the INU to the INU itself?!?:huh:

[miguez]

You don't. You are synching the INU to a known coordinate. How do you now where that coordinate is? Visually. You should use points such as crossroads, river crossings, etc., to be able to identify them with ease. then, fly over them, and hit the update.

[Bobcat]

ny chance of an "idiots" guide? please....

 

BC

[Siinji]

Okay. I was a bit confused on the syncing, because of the producers note movie. In that movie he just syncs "on the fly", not very precise then.

 

Yes, a small guide would be cool!

 

So we can sync overflying and with shkval right? Any other methods?

[EvilBivol-1]

In the Producer's Note, Matt used the GPS (ABRIS). Using the GPS is just as accurate as a landmark, because the GPS provides accurate position information, independent of your INS.

[Frederf]

Gyroscopic navigation systems drift over time so Fix Points are ways to correct where the INS thinks it is to where it actually is. I think the PVI-800 gets updates from GPS in normal mode anyway.

 

Updating off landmarks is a relic from the pre-GPS days where you'd have to update the INU position by saying every once in a while "Hey plane, you be here." Pilots still train for it in case GPS system breaks or is jammed.

[miguez]

Frederf brings up a good point, the manual does indicate the PVI gets updates from the GPS, so why would there be a need for the INU update via a fix? Is it just a provision for if GPS is not available for whatever reason?

[EvilBivol-1]

The INS does not get updated from the GPS. They function independently.

[Frederf]

Ah, the INU update switch only changes from skhval position to overfly. I thought it was between GPS/manual. My brain is still in F-16 mode from Open Falcon.

 

As it stands a drifted PVI is plenty accurate for route navigation. I figure if I'm trying to attack a fixed preplanned target, updating on a hotel building the ridge before engaging would make sure the preplanned target would land directly in the gates.

 

P.S. How does one know the status of the INU during alignment? In the F-16 there's a counter that shows how far into alignment it is to let you know when it's OK to move around.