IP nav fix required for CCPL PI bombing. Should be optional

[gnomechild]

For CCPL PI and CCPI PI bombing, the M-2000C RC6 manual states 

Quote

The PI navigation fix in not necessary but will greatly improve the accuracy of the attack by reducing the accumulated INS drift. Once the once the navigation fix has been performed, or the PI has been overflown, the SNA is locked in the selected sub-mode, the only way to exit it is to de-select the bombs or select another weapon

However, in game, the roll order wings are not displayed on the VTH after overflying the initial point. A nav fix is required to get the symbology to display. Unsure if this is an error in the manual or the module. But there it is. 

 

Steps to reproduce: 

1. Create waypoint with associated BAD

2. Select waypoint, select bombs, select PI on PCA

3. Overfly IP, observe VTH symbology and IDN direction do not update

 

Track file attached. 

 

Thanks!

M2K PI overfly bug.trk

[Galinette]

It’s a manual error. You need to designate the IP in order to activate steer wings 

[Frederf]

Is it possible to use an overflight update instead of an oblique?

[gnomechild]

3 hours ago, Kercheiz said:

It’s a manual error. You need to designate the IP in order to activate steer wings 

Yeah I think you're right. Looking at the real Mirage 2000 manual it list the steps and the IP fix doesn't appear to be optional. 

 

Actually, the manual I have is for an RDM equipped Mirage. So I don't know if that's different on an RDI model.

Edited December 11, 2021 by gnomechild
New information

[Galinette]

38 minutes ago, Frederf said:

Is it possible to use an overflight update instead of an oblique?

No, unfortunately

[Shiroka]

I guess it’s optional to accept the update after you’ve performed it? On the PCN?

[Frederf]

Yes. The update takes effect during the attack but unless saved is temporary. If you VAL the update it applies permanently.

[gnomechild]

Yes that part is optional, but the manual specifically states the guidance symbology appears "Once the once the navigation fix has been performed, OR the PI has been overflown" (emphasis mine). 

Would be a cool feature to have to allow a nav fix prior to the IP in a safer area or easier area.

But from reading the manual and my (hypothetical) understanding of the CCPL computing it seems unlikely to be the case that this is truly an optional step and requires the designation to be on the But with the target BAD to allow release symbology.

Either way would be nice to get confirmation from the team what the intended behavior is. 

[Galinette]

6 hours ago, gnomechild said:

Would be a cool feature to have to allow a nav fix prior to the IP in a safer area or easier area.

Then IP should just be in a safer or easier area!

In the M2000C, for CCRP bombing, you have to designate a point.
 - Either by directly designating the target point
 - Or by designating another point not too far from the target knowing the exact coordinate offset between IP and target.

Even if it looks like a nav fix and work in a similar way, it's not really a nav fix as you don't update your INS. You just designate an offset point.

So in both cases (direct CCRP or IP CCRP) a designation is required, and the current implementation is correct. The manual may need some rephrasing

 

 

Edited December 13, 2021 by Kercheiz

[gnomechild]

5 hours ago, Kercheiz said:

Then IP should just be in a safer or easier area!

In the M2000C, for CCRP bombing, you have to designate a point.
 - Either by directly designating the target point
 - Or by designating another point not too far from the target knowing the exact coordinate offset between IP and target.

Even if it looks like a nav fix and work in a similar way, it's not really a nav fix as you don't update your INS. You just designate an offset point.

So in both cases (direct CCRP or IP CCRP) a designation is required, and the current implementation is correct. The manual may need some rephrasing

 

 

 

Yeah that's how I understood it as well. Basically the process is identical for both forms of CCPL bombing since the IP with the BAD has the target defined as a delta from that position, so theoretically the precision is (almost) the same whether you're designating the IP or the target itself. 

The nav update is more of a bonus side effect of telling the plane, "My target is  exactly here relative to my current position"

[Frederf]

PI bombing is almost certainly intended to toss bombing where directly designating the target is impractical. If you had the ability to visually designate on the target then simply do a normal CCRP (non-PI) attack.

[gnomechild]

14 hours ago, Frederf said:

PI bombing is almost certainly intended to toss bombing where directly designating the target is impractical. If you had the ability to visually designate on the target then simply do a normal CCRP (non-PI) attack.

Yeah certainly. What I meant by them being the same is that they both begin by designating a target location relative to the position of the aircraft with radar ranging. It doesn't really make a difference if you're designating the target or the IP, since in the case of a BAD the target is defined as a delta from the exact location you've specified. If that step were optional, and the aircraft displayed guidance symbology after overflying the point, it would be automatically designating a target point from your current position which would have the SNA function in two completely different ways for these bombing modes. Whereas if that designation is required the process is more or less the same from the systems point of view, you're just doing the normal CCPL procedure with an offset. Seems much more likely that the IP mode is a kind of "mod" or add-on to the existing CCPL mode which would mean that the nav fix is required exactly the same way that designating the target itself is required in normal CCPL mode. 

[Frederf]

If no update is performed then the system would work the same as with an update but without the refinement of position. The target would have defined position at BAD however it would be subject to a BUT position which may have drifted some.

I agree that PI is a small logical modification or addon. Not much has to change to make PI out of normal CCRP.

If I was designing the system I would have the system change from the PI designation phase to the attack on 3/9 passage of any update point (oblique or overfly) or a couple miles passing if no update was made. Target would be BAD regardless of update or not.

The last thing you want screaming at 600 knots at 500 over enemy territory is not getting rid of your bombs. Maybe you see the reference point too late for oblique but you could overfly or you don't get a chance to update at all. Probably you would do a normal INS update one point earlier than the attack so drift is minimal anyway. It's preferable to have imperfect aim than to not release at all. You aren't likely to get another chance.

[some1]

The PI mode currently works the same way as Computer IP Offset Bombing in the F-14. In both cases you have to visually designate "reference" point in a close proximity to target, because INS is not considered accurate enough to guide you for an automated bombs release otherwise. Makes sense.

That being said, if the current implementation is correct, then the last mission of the Caucasus campaign is broken. There is no reference point to designate at the last waypoint, so you can't initiate the bombing run without some guesswork. 

[Galinette]

You can’t do direct designation?

[some1]

Where, in the campaign?

[Galinette]

Yes

[some1]

The mission is specifically set up for offset bombing, so that you're lofting bombs from behind the mountain, without visual ID of the target.