VRP/PUP minimum altitude?

[Nealius]

Is there a minimum altitude for the VRP and PUP symbology? Inputting 200ft or 100ft puts the HUD cues at around 350~400ft; they won't seem to go any lower. The F-16 manual doesn't mention any altitude limits.

[LieutenantFalcon]

TGT-VRP/PUP altitude is set relative to the steerpoint altitude ASL. If you want the VRP or the PUP (for some reason) to be below the steerpoint, use the (0-) MSEL key to set a minus before the altitude.
Afaik, this should also apply to the Offset Aimpoints (accessible through the DEST page, and good references for your pulldown and egress).

Example: TGT altitude is 400ft ASL, you want to set the PUP for 1500ft ASL. 1500-400 = 1100ft, which is what you enter.
                TGT altitude is 1200ft ASL (say a radio tower on a hill), VRP is a town at 400ft ASL. 400-1200 = -800ft

FWIW, planning all this is makes much more sense for VIP and not VRP. VIP is used for pop-up attacks where you use a landmark as your Visual Ingress Point as your navigation fix (pre-GPS) and set a fixed TGT based off of that landmark. Linked below is a great tool for that, although it doesn't support the newer maps sadly.

VRP is moreso for referencing something that comes up along the way in the mission and using the target (which you can see visually) as a reference point. Can't say I've found much of a use for it but hey.

I hope that helps

[Nealius]

Ah, it's relative. I've been brainwashed by years of BMS where the elevation is referenced from sea level. OA1 and OA2 are not relative to the waypoint elevation, correct?

30 minutes ago, LieutenantFalcon said:

VRP is moreso for referencing something that comes up along the way in the mission and using the target (which you can see visually) as a reference point.

That's opposite what the manual says: VIP for something that comes up, VRP for pre-planned attacks like popups.

Edited August 1, 2024 by Nealius

[LieutenantFalcon]

3 minutes ago, Nealius said:

That's opposite what the manual says: VIP for something that comes up, VRP for pre-planned attacks like popups.

ig interpretation is up to the pilot, but that's how I see the use case. VIP for popup attacks where your IP is a known landmark you can do a fix on, and your TGT is actually your target you get symbology on. I'd imagine this is more for SAM sites or targets that might have otherwise moved slightly. VRP for where you're referencing off of your target to get a visual point on something. 

I know you can use VRP for popups too if you know the TGT location like an airbase, but to me it seems kinda weird as you're often talking about an IP 6-8 miles out (which you now have to convert to ft) and you're now fixing the INS bases off of a target you might not be able to approach (so use OFLY fix on). To me it makes more sense to use VIP for pre-planned popup attacks in a situation where you have to do an INS fix, which is what these features were designed for around this time in the F-16's life.

[Nealius]

I've read through the manual a few times but am really lost on the functional difference between VIP and VRP.

In VRP, I have the target on a STPT, and the VRP is simply a HUD visual cue to start my attack run to the PUP. Nav/steering and CCRP symbology is to the STPT (Target).

If I'm understanding VIP correctly, I would have the IP on a STPT, but no STPT for the target itself. Nav/steering is to the IP STPT, Target (TD box) is on whatever the programmed offset from VIP (IP STPT) is. But is CCRP symbology to the TD box rather than to the IP STPT? The manual seems to indicate so, but the picture on page 210 shows the ASL to the VIP and not to the TD box. 

Follow up to that, if using the TPOD, would the TPOD be slaved to the IP STPT (VIP) or to the TD box referenced from it?

Edited August 1, 2024 by Nealius

[LieutenantFalcon]

7 hours ago, Nealius said:

If I'm understanding VIP correctly, I would have the IP on a STPT, but no STPT for the target itself. Nav/steering is to the IP STPT, Target (TD box) is on whatever the programmed offset from VIP (IP STPT) is. But is CCRP symbology to the TD box rather than to the IP STPT?

This is correct yes. I think there might be an issue with the manual image you're referring to, but the ASL is always going to refer to the TD box thus the STPT. The range indication interestingly does refer to whatever sightpoint you have it set to in VIPCRP, so it's worth following the 'intended' workflow in VIP as described in the manual.

One thing to be aware of is what your sightpoint is set to. In VIP, your sightpoint is initially set to the IP so you can fly there (bottom-right of the FCR page indicates this). From there with HUD SOI, you'd overfly the point you'd have your IP on and TMS Up Short to confirm that location to cancel out any INS drift. Once you do that, your sightpoint gets set to the TGT point. At any time you can change your sightpoint in VIPCRP-submode (and VRPCRP too I assume) by pressing TMS Right Short with FCR or HUD as SOI. 

This post contains the most recent behavior for the F-16. The manual doesn't quite reflect on it sadly but put the 2 together and it should hopefully complete the picture.

I haven't tested it, but I think that the TGP can be slaved to both the IP as well as the TGT that way, just a simple TMS Right with HUD as SOI. I wouldn't be surprised if this didn't work like this anyways, both in DCS as well as the real jet. I feel like VIP and VRP very much are exceptions to how you'd think SPI would normally work.

7 hours ago, Nealius said:

In VRP, I have the target on a STPT, and the VRP is simply a HUD visual cue to start my attack run to the PUP. Nav/steering and CCRP symbology is to the STPT (Target).

 

FWIW, I wouldn't get hung up on forcing yourself to use VIP if you can get VRP to work fine, especially if you don't plan to do pre-GPS missions. Even if you do, setting a simple steerpoint a bit further out and using that to fixtake should be fine too. TMS Up Short over IP in VIPCRP doesn't actually fix the INS it just applies a delta which you can later CZ, but in effect it does the same thing.