Purpose of overhead Update INS?

[Crunchy]

I'm just reading the Nav section of the manual and I'm a bit stuck with something. I'd just like to know what is the purpose of the overhead INS Update? When would you use this and is it actually modeled in this sim if you can use it? It's on page 224 of the manual.

[Luzifer]

It's to maintain high accuracy of the INS by clearing accumulated errors. You tell the INS that you're over that point with the known coordinates and the INS can reset its computed position to that.

 

The A-10C has GPS units to continually correct INS drift like all modern INS equipped planes, so you don't need this.

 

I don't know if the function is implemented, at least INS drift isn't. It is perfectly accurate at all times even without GPS.

[kontiuka]

I played with this recently and tried to "trick" the INS into thinking I was somewhere else but it didn't work.

[baltic_dragon]

I think it works but you would have to disable EGI ans enable HARS to be able to use it. HARs was a primary navigation system in A10A, but in C it is a backup one, being much lesss acurrate. No need to use it, really, as long as you have EGI.

[PFunk1606688187]

INS drift was a serious issue for A models and without an INS update during a long flight it was possible that drift could make all coordinates good for little more than an "in the ballpark" estimation of position. I read one story of a long long CSAR flight done during Desert Storm where the A-10 pilot had suffered so much drift due to not being able to update that coordinates he had on the downed pilot's location were basically useless and he had to use a combination of visual references to the terrain and homing to the strength of the radio signal (by flying til it didn't degrade, not by using some fancy homing mode) in order to find then re-find the pilot after tanking.

 

GPS is amazing isn't it? Though lets be aware that in real life GPS jamming is a real problem for a proper hot war and as such I believe that elements of things like Red Flag involve simulated GPS jamming (I think). In that situation INS drift is likely to re-enter the equation, though not for us since GPS is not actually simulated in DCS, its imitated and so there's no way to even pretend its jammed except by turning EGI off. Even so I don't believe HARS is fully modeled either.

[TIMBER SOUR]

DCS contains ephemeris data for the GPS constellation, so even things like predictive RAIM are possible to calculate. Unfortunately, DCS A-10C doesn't seem to use the data, nor does it model INS drift which makes the whole point moot anyway.

 

Red Flag is a perfect opportunity to practice Contested & Degraded Operations (CDO), which include degraded/denied GPS environment. Too bad we won't be able to use it in the upcoming NTTR theater.