Alignement INS

Hello,

Is it possible to re-align the INS in flight?

I tried put in flight the switch on "Stand-by, the result is the lost all navigation and EFIS indications.

Hello,

 

Is it possible to re-align the INS in flight?

 

I tried put in flight the switch on "Stand-by, the result is the lost all navigation and EFIS indications.

You simply cannot realign an INS in a moving aircraft by its very own nature, no matter on what aircraft.

…and yet they had to do it on a regular basis on the Apollo capsule. :rolleyes:

…and yet they had to do it on a regular basis on the Apollo capsule. :rolleyes:

They corrected their INS with the help of a sextant. That is a complete different story. What the OP was trying, was to start the alignment process in the air, which would generate a huge mess, but nothing useful for navigation.

And the counter-point is that realigning your INS while moving, or even in the air, is not even remotely impossible and is indeed a feature of pretty much all INS-equipped aircraft in DCS. Some of them can even start their alignment process while in motion because they wouldn't be of much use to anyone if they couldn't.

What you mean is updating or correcting INS while in flight. Shutting it down and aligning again is simply not possible, as you have lost all reference.

The carrier alignment is a different case, as the aircraft is continously fed with the ships very own INS and is basically slaved to it.

...and thus, we have one of many ways in which an INS can be realigned while moving, same as how the process is done in a number of different airplanes. All you need is a good reference for position and movement, neither of which are particularly difficult to get a hold of.

We have half a century worth of INS systems that can be realigned (and even just pain aligned) while in motion. Is it far easier and more precise if you're standing still? Sure. Is it completely impossible if you're not? Far from it.

DCS explicitly models in-flight INS alignment in the AV-8B N/A.

It can take a long time and is suspended while the aircraft is pitching or rolling too much so it's preferable to align while stationary on the ground but it's an option when necessary

DCS explicitly models in-flight INS alignment in the AV-8B N/A.

 

It can take a long time and is suspended while the aircraft is pitching or rolling too much so it's preferable to align while stationary on the ground but it's an option when necessary

Absolutely right, and the INS position MUST BE update in flight by others systems, like DME, VOR, GPS. Otherwise the rotation of the earth causes it a drift by 15 ° per hour if we go further east or west (i don't remember). This is even easier today as the systems are integrated.

Oh, right, the actual original question… :D

What you're looking for is probably more along the lines of the position update function on the UFCP, but I haven't seen any documentation on how it works yet, and if you're in INS+GPS mode it really shouldn't be necessary to being with. It might not even be fully implemented yet.

I did some checks with the INS. It's impossible to align in flight. The only way is to be on the ground, but when you try to align a second time, you can't go further than "fast Align". So a complet alignment is impossible when you miss the first one.

Oh, right, the actual original question… :D

 

 

What you're looking for is probably more along the lines of the position update function on the UFCP, but I haven't seen any documentation on how it works yet, and if you're in INS+GPS mode it really shouldn't be necessary to being with. It might not even be fully implemented yet.

Also PU only has the OFLY method available, which is much less accurate than using the DESIGNATE method with WMD7 or DBS2 radar

There is no in-flight cold alignment capability.

AFAIK no INS can COLD START in the air. Even those systems with in-flight alignment still perform "rough platform alignment" on the ground, and already know where true north is through either stored heading from last shutdown or pilot input, but even then the system is subject to reduced accuracy and much higher than normal drift rates.

Such modes are usually used for emergency scrambles where they must fly RIGHT NOW and even a quick alignment is too long.

There is no in-flight cold alignment capability.

 

AFAIK no INS can COLD START in the air. Even those systems with in-flight alignment still perform "rough platform alignment" on the ground, and already know where true north is through either stored heading from last shutdown or pilot input, but even then the system is subject to reduced accuracy and much higher than normal drift rates.

 

Such modes are usually used for emergency scrambles where they must fly RIGHT NOW and even a quick alignment is too long.

Finally someone.

I did some checks with the INS. It's impossible to align in flight. The only way is to be on the ground, but when you try to align a second time, you can't go further than "fast Align". So a complet alignment is impossible when you miss the first one.

That's because the align knob is for pre-flight ground alignment. It is not there for any realignment, and there should never be any real need to align a second time — especially not if you're in the air. In-flight realignment is done through position updates, which is a completely different system.

So the question here is, what is it you're trying to achieve by “aligning a second time”?

Also PU only has the OFLY method available, which is much less accurate than using the DESIGNATE method with WMD7 or DBS2 radar

I suspected as much. It would be nice if other methods were available, but then again, that doesn't particularly matter unless and until all kinds of damage states and degraded functionality (internally or externally) are implemented.

Finally someone.

You understand, of course, that this was never in question… and that there is in principle nothing that inherently makes it impossible to start your alignment in air. It's just that building a system for doing that is utterly pointless — airplanes start on the ground, and you'd be building a very complex system to yield poor precision to handle a situation that never occurs. It's not done because it can't be done but because it's a pointless waste of time and effort.

What if the engine quits and you loose electric power and with it your alignment, but you're able to restart the engine? How do the various INS handle this?

What if the engine quits and you loose electric power and with it your alignment, but you're able to restart the engine? How do the various INS handle this?

In airliners, they stay inop. Thats why you have multiple.

In airliners, they stay inop. Thats why you have multiple.

But what about fighter jets where we don't have multiple?

Edit: What's the advantage in this case anyway if all INS aboard are affected by a temporary power outtage?

You fall back on GPS and/or good old radio beacon navigation, and try not to rely too much on the spinning balls that show up on the instrument panel (for a bonus funtime, break the INS platform in the Tomcat — mainly because it's probably the easiest one to do it in — and see what your instruments are telling you :D).

My guess would be, that they stay inop in most fighters too. I mean you do not really need them for flying anyway.

In case of airliners, you have them on multiple busses and at least the older units would fall back to battery if power was lost. IIRC there is even an audible alarm on the ground if the INS would be powered by battery, so that they dont drain them.

I see, thanks.

I did some checks with the INS. It's impossible to align in flight. The only way is to be on the ground, but when you try to align a second time, you can't go further than "fast Align". So a complet alignment is impossible when you miss the first one.

The point was when you lost your INS position (Align Switch to standby in flight for exemple). After landing, I tried to realign my INS posistion. But as I said, it's can't go further than "Fast ALIGN". No more complet alignment is possible.

Anyway, thanks for your replies.

Nah, that's just operator error — keep your fingers away from the align knob unless you really mean it, and land asap if you can't. ;)

Nah, that's just operator error — keep your fingers away from the align knob unless you really mean it, and land asap if you can't. ;)

I think you're right

In the Jeff, power loss in flight means loss of INS, but you still have SAHRS, and GPS.

On commercial airliners, they have ATT mode, so if an INU becomes unusable for navigation in flight, it can still be used for attitude data.