What is the difference between Stored INS align and Normal INS align in the F-16C Viper?

[Eggitheegg]

What is the difference between Stored INS align and Normal INS align in the F-16C Viper? I'm asking because I noticed that it takes much longer to align normal INS than Stored and I wanted to know what the difference is. 

Spoiler

Comic sans ftw

Thanks to everyone who responds!

[Frederf]

Stored alignment is a prepared alignment. Someone comes before, starts airplane, does alignment, then shuts down airplane without moving it. Then you come along and used that saved info to align a lot faster.

 

A big part of alignment is called gyrocompassing which is figuring out which direction you are facing by letting the Earth turn and watching the gyros. Different headings have different motions while stuck to the spinning Earth ball. Stored heading isn't as good as a normal alignment in some ways because the longer align allows finer calibration of some velocities but it's nearly as good and since it's GPS-coupled normally it will never be noticeable.

[Eggitheegg]

Okay, thanks for this information! 

[Machalot]

10 hours ago, Eggitheegg said:

Okay, thanks for this information! 

You asked a good question, but I would just like to give some constructive feedback -- that font is hard to read, especially in red. 

[Machalot]

17 minutes ago, Desert Fox said:

OP:

Asks a good question

Uses comic sans

 

Like factor: 8/10 (could have used different colors for each character)

Hm, for me it's not Comic Sans, it's a very stylized cursive. Maybe a smart phone font issue? 

[Northstar98]

1 hour ago, Machalot said:

You asked a good question, but I would just like to give some constructive feedback -- that font is hard to read, especially in red. 

 

Come to the dark side - it's fine there (apart from the comic sans).

[Machalot]

4 minutes ago, Desert Fox said:

 

might be your phone simply banned that font.

 

 

Here's what I see:

[=Panther=]

7 hours ago, Machalot said:

 

Here's what I see:

I saw the same.

[Furiz]

I like different font, and different colors, it is so cool ;D

[SpaceMonkey037]

On 4/8/2021 at 9:16 AM, Frederf said:

Stored alignment is a prepared alignment. Someone comes before, starts airplane, does alignment, then shuts down airplane without moving it. Then you come along and used that saved info to align a lot faster.

 

A big part of alignment is called gyrocompassing which is figuring out which direction you are facing by letting the Earth turn and watching the gyros. Different headings have different motions while stuck to the spinning Earth ball. Stored heading isn't as good as a normal alignment in some ways because the longer align allows finer calibration of some velocities but it's nearly as good and since it's GPS-coupled normally it will never be noticeable.

It is worth while to add/clarify that you cannot move from the coordinates entered for the original alignment. You have to stand still from the very moment you go INS knob - NORM to when you do the scramble start and do INS knob - STOR HDG. For this reason you cannot do an EIA (enhanced interrupted alignment), and for that reason you can only ever achieve status 10 in stored heading. It is also important to mention that even though our INS is constantly getting corrected for drift by the GPS (GPS does not calibrate the INS mid-flight, it only removes drift), we will still notice a bad INS alignment because our INS never knows its groundspeed perfectly and so our radar will have reduces efficiency the worse the alignment quality is because the accelerometers aren't calibrated precisely. The radar will have reduces efficiency because with false ground speed it will have a harder time figuring out what is ground. The radar does not have any fancy functions to remove ground clutter and requires INS to do be able to get rid of ground clutter. For that reason if you have time you will always do an EIA where you will increase INS alignment quality and as a result will get better radar performance. The INS temporarily stores data (like drift) after each flight, and remembers it for follow up flights, don't know the exact number of flights, but I'd guess that it's no more than 100. This means that if you've done multiple good alignments you can do one really bad alignment and you won't really notice much different, but if you keep doing bad alignments over and over again you will notice a degrade in FCR efficiency. Because of this though you will in most cases never have any big INS issues when doing STOR HDG.

In summary, what Frederf said is mostly correct with the little exception that bad INS alignments will be noticeable even with GPS.

[Nealius]

Reviving the thread, but is there a procedure difference between Stored and Norm? I normally do Stored align until 8.0/10, but this time I decided to do a Norm align to 8.0/10 since (old knowledge here) 8.0/10 should be good even for a full Norm align. Unfortunately for me it wasn't, and NAV was flagged OFF with the STPT tadpole cue caged to my FPM. I don't know what I missed, as I thought the procedures were identical between Stored and Norm, other than the obvious INS selection change.

[Machalot]

1 hour ago, Nealius said:

Reviving the thread, but is there a procedure difference between Stored and Norm? I normally do Stored align until 8.0/10, but this time I decided to do a Norm align to 8.0/10 since (old knowledge here) 8.0/10 should be good even for a full Norm align. Unfortunately for me it wasn't, and NAV was flagged OFF with the STPT tadpole cue caged to my FPM. I don't know what I missed, as I thought the procedures were identical between Stored and Norm, other than the obvious INS selection change.

In Norm you have to confirm the initial lat/lon within the first two minutes by hitting the ICP Enter button when the DED cursor is on each value. In Stored this is not necessary. 

[Frederf]

Confirming L/L post 2min restarts the normal alignment.

 

Stored heading confirming L/L is not only not necessary it shouldn't be done. If you confirm L/L during stored heading alignment the system switches to best available true heading (BATH) alignment and aborts stored heading alignment. BATH alignments are not desirable.

 

There's more going wrong than just not confirming L/L though. I did a norm alignment without confirming L/L down to status 48 and took off with FPM functioning as expected. That's a pretty crud alignment and there were no ADI flags or FPM anomalies.