Harrier Experten...

[Harlikwin]

So,

 

How does the harrier get the slant range for the rocket/guns CCIP calculations? No radar, no LRF, and no ARBS "lock/track" and even if it did its not all that accurate in a dive where the angle is not changing much. Is it just Baro-alt/dive-angle (assuming perfectly level ground again)? And if so, it seem a wee bit too accurate. I noticed the other day in the hornet that the gun piper "turned off when pointed above the horizon, presumably because there was no radar return, and it got me thinking about the Harrier.

[Harry.R]

So,

 

How does the harrier get the slant range for the rocket/guns CCIP calculations? No radar, no LRF, and no ARBS "lock/track" and even if it did its not all that accurate in a dive where the angle is not changing much. Is it just Baro-alt/dive-angle (assuming perfectly level ground again)? And if so, it seem a wee bit too accurate. I noticed the other day in the hornet that the gun piper "turned off when pointed above the horizon, presumably because there was no radar return, and it got me thinking about the Harrier.

 

 

It's got an angle rate bombing system and a laser spot tracker, but I'm not sure exactly what you're asking.

[some1]

In the real aircraft the preferable method is through ARBS lock and angle rate measurement. Pilot has to designate target beforehand of course.

If not available, then it's altitude measurement using radar, baro, gps or wpt coordinates, depending on the selected options, but most assume even terrain unless the pilot adjusts target elevation.

Edited February 4, 2019 by some1

[Harlikwin]

It's got an angle rate bombing system and a laser spot tracker, but I'm not sure exactly what you're asking.

 

I've got a pretty good idea of how the ARBS works in theory. The issue with getting a slant range from the ARBS is that if you for example have the target locked up with the DMT and the actual angle is changing it can calculate the slant range, and provide a targeting solution. This is great during a level bombing run with a locked target. IF your aircraft is diving directly at the target, your angle rate change is 0 so the ARBS doesn't really work, or works "badly".

 

The other "method" I alluded to is basically you have a height and angle above ground and you can solve for the slant range with basic trig since its a right triangle and you have 1 side (alt) and 2 angles (90 and whatever your dive angle is).

 

The problem with the second method (baro alt/radar alt), is that it is inherently inaccurate, and can VERY wrong (lets say shooting/bombing a target on a hill if you are using your radar alt). Or lets say you take off from sea level and go bomb something in the Caucus where ground level is 8000ft ASL, You are at 10,000 ASL. Your "gunsight" should be giving you a solution as if you were attacking something from 10,000' AGL, while you are only 2000' AGL therefore you miss.

 

What I'm seeing with my simulated experiences in the harrier is that the gunsight/CCIP is always very accurate regardless of where you are flying, where the reticle goes, so doe the boolits/bombs, and I almost never lock up targets with the DMT when using guns/CCIP. Anyone else have a different experience?

Edited February 4, 2019 by Harlikwin

[some1]

I've got a pretty good idea of how the ARBS works in theory. The issue with getting a slant range from the ARBS is that if you for example have the target locked up with the DMT and the actual angle is changing it can calculate the slant range, and provide a targeting solution. This is great during a level bombing run with a locked target. IF your aircraft is diving directly at the target, your angle rate change is 0 so the ARBS doesn't really work, or works "badly".

 

Usually you would lock ARBS target before you start the dive. In this situation, as long as ARBS lock is maintained, the computer would have a decent calculation of target position from before the dive.

 

The problem with the second method (baro alt/radar alt), is that it is inherently inaccurate, and can VERY wrong (lets say shooting/bombing a target on a hill if you are using your radar alt). Or lets say you take off from sea level and go bomb something in the Caucus where ground level is 8000ft ASL, You are at 10,000 ASL. Your "gunsight" should be giving you a solution as if you were attacking something from 10,000' AGL, while you are only 2000' AGL therefore you miss.

 

In real life it could be solved, or at least mitigated in several ways. If this is a pre-planned target, then the target altitude will be set in the waypoint coordinates and the Mission Computer will use that. For a target of opportunity, a TOO waypoint can be created (the moment you create TOO waypoint, radar altimeter is fired and stores ground elevation in the waypoint). If not available, then the pilot can set target elevation manually. The pilot can also select if he wants to use baro, radar or GPS alt, so I'm pretty sure he won't be strafing targets in the mountains like they're at the sea level.

 

I don't think the Harrier has a detailed elevation database for the whole area of operation like A-10C has.

 

As I said, that's how it's done in real life. How it works in Razbam's Harrier? Probably magic and unicorns.

[CallsignFrosty]

I've got a pretty good idea of how the ARBS works in theory. The issue with getting a slant range from the ARBS is that if you for example have the target locked up with the DMT and the actual angle is changing it can calculate the slant range, and provide a targeting solution. This is great during a level bombing run with a locked target. IF your aircraft is diving directly at the target, your angle rate change is 0 so the ARBS doesn't really work, or works "badly".

 

The other "method" I alluded to is basically you have a height and angle above ground and you can solve for the slant range with basic trig since its a right triangle and you have 1 side (alt) and 2 angles (90 and whatever your dive angle is).

 

The problem with the second method (baro alt/radar alt), is that it is inherently inaccurate, and can VERY wrong (lets say shooting/bombing a target on a hill if you are using your radar alt). Or lets say you take off from sea level and go bomb something in the Caucus where ground level is 8000ft ASL, You are at 10,000 ASL. Your "gunsight" should be giving you a solution as if you were attacking something from 10,000' AGL, while you are only 2000' AGL therefore you miss.

 

What I'm seeing with my simulated experiences in the harrier is that the gunsight/CCIP is always very accurate regardless of where you are flying, where the reticle goes, so doe the boolits/bombs, and I almost never lock up targets with the DMT when using guns/CCIP. Anyone else have a different experience?

 

Yes unfortunately proper DMT/ARBS is not yet simulated it seems. I say 'yet' in the vein hope that one day it will be.

 

In your first example I would imagine that if the DMT track doesn't move enough or is 'flown at' since the beginning of the contrast lock, the target location icon will be on the HUD but slant range will be not be calculated. The ARBS ties the DMT track angle with the INS so target angle is fine but slant range - I don't think so.

 

Baro and GPS elevation bombing can be accurate as long as the target elevation is accurate.

[Mumby]

ARBS should work when pointing directly at the target in a dive, the only problem is that the correct weapon release point in time and space coincides precisely with the aircraft crashing into the target. In some ways this is the easiest solution to compute!

[CallsignFrosty]

ARBS should work when pointing directly at the target in a dive, the only problem is that the correct weapon release point in time and space coincides precisely with the aircraft crashing into the target. In some ways this is the easiest solution to compute!

 

Surely this is only true if the manoeuvre leading to the dive had enough angle rate change to compute a solution before entering the head on state. Also - he is talking about guns not bombs.

 

Edit -

Why do you think it is easier to calculate a release solution? All you would know is that the target is 'somewhere' on a line directly in front of you with no ranging information at all. It's the whole point in having an angle tracking camera in the first place.

Edited February 5, 2019 by CallsignFrosty

[Vatikus]

Various ways for solving the triangle:

 

p.s. that is how it is in rl... however in game it most of the systems are not simulated (yet), so it is simply cheating with perfect information

[Harlikwin]

Actually I don't to what extent the ARBS actually is simulated or not.

 

For example.

 

Basically when you don't have a DMT lock the target alt is zero on the weapon select mfd (there is a line with target alt) When you select a target or bit of ground with the DMT, it stays ZERO, UNTIL you refresh the display, I.e. select/unselect gun or bombs, then it displays the correct target ALT. So that "seems to work" not sure on if it should just auto update the field though so that may be a bug.

 

The question as to if it "matters" is another one. Currently I'm not good enough at dumb bombing to be able to say if the alt field 0 vs correct altitude is gonna give me bombs on target or a miss. In theory it should miss, but I miss alot due to the auto mode being bugged. I also miss alot with CCIP, perhaps someone can do some testing.

 

Also, the Gun reticle is different with a target locked vs unlocked, you can see that in the 2 gun runs I make. However with no target lock you still get a range tape counting down (maybe based on alt 0).

 

I've included a track of my test range north of Creech to illustrate. Keep checking the weapon mfd for changes in target altitude. Ignore the glorious fireball at the end where I'm not paying enough attention on the gun run.

 

One thing that is bugged/not implemented correctly I think is the various symbology.

It should be AUTO/CCIP IF you have a locked target with the DMT. Bauto and Rauto (and ccip) correspond to baro and radar bombing modes if the DMT doesn't have a target, or if you are using an INS point for it.

 

TOO (Target of opportunity) is also bugged, it should create a bomb point directly below the aircraft using a radar ping. Currently it creates one, but its at the current Baro-alt of the plane.

Dumb bombing n guns.trk

[Harlikwin]

I also noticed that the waypoint bombing seems to be working, it will provide target alt to bombing system. You can turn a waypoint into a target point by hitting DESG on the map mode. Still can't hit anything due to the ASL issue, but it does seem to work as a method.

 

Actually I think the way its working in the sim, is that if you select AG mode and there is any waypoint in the INS that alt is set as the default target alt BEFORE you hit the DESG button (not sure if thats actually how its supposed to work IRL) and again you have to cycle the bomb mode to update the target alt.

 

As an aside, can anyone explain how waypoint offset is supposed to work in the IRL plane (WOF).

[Harlikwin]

Various ways for solving the triangle:

 

p.s. that is how it is in rl... however in game it most of the systems are not simulated (yet), so it is simply cheating with perfect information

 

Well at least it looks like there are a few ways to get the correct alt into the weapon display MFD. But yeah not sure if the bombing system is actually using them. Once the ASL line is fixed I'll do some testing.

 

It should be testable with regard to the 0 alt setting and a target at much higher altitude. I need to find a map where to do that, caucus maybe, it also needs to be a flat area. This should be possible in CCIP mode at least, not sure if I can have the wrong altitude for CCRP ever as it relies on a target designated point.

 

I'm also pretty sure none of the inherent errors for Baro or radar are modeled, but it would be easy to do.

[Ramsay]

As an aside, can anyone explain how waypoint offset is supposed to work in the IRL plane (WOF).

 

RL examples would be entering the target as an offset of the IP waypoint, if the target was at a different altitude to the waypoint or a TACAN offset for it's IAF (initial approach fix) / holding point.

[Harlikwin]

RL examples would be entering the target as an offset of the IP waypoint, if the target was at a different altitude to the waypoint or a TACAN offset for it's IAF (initial approach fix) / holding point.

 

Hi Ramsay,

 

I'm just curious why you would designate target like that though, would it not be simpler to just have a waypoint pre-entered as the target waypoint. I can see the TACAN/IAF thing though. Also, waypoint overfly mode doesn't make sense to me either, why would you want to overfly the waypoint. And would the new target point be automatically generated? Sorry if I'm being a bit thick here.

[Dangerman]

Offsets are basically a way of updating or ensuring your nav system is accurate for weapon delivery. Can be used in radar bombing if the target doesn’t/won’t stand out on radar, but the offset will. For other non precision bombing methods, it ensures correct target position for the computed weapon release and correct overlay of target diamond on target.

 

Essentially you are aiming at the offset but the target position is tied to it.

 

Simply plan the offset, mark the offset with visual manipulation of mark in hud if required (or radar for other types) .....and the fixed bearing/ range offset to target that you dialled in will move by the same amount as the correction you make.

 

Continue the attack and know that your target diamond is in the correct place because you moved / checked the mark on your offset (or the ip waypoint).... therefore weapon release is calculated with correct parameters.

 

That’s how I’ve done it in a previous life.

[Harlikwin]

Hi Dangerman,

 

Thanks for the explanation. I'm still not clear if in pre-planning wouldn't you just be able to use the known target coordinates? I can see doing it on the fly or with an old school JTAC I suppose, I.e. lock up some known well visible feature (Burj Kalifa, or that big flag pole over yonder), and then you know your target is 800m on bearing 342 or whatever.

[Dangerman]

The issue is a many part problem.

 

The first is the aircraft nav kit. For real it is a mix of various inputs depending on the aircraft type. Old school tornado and Cold War jets used a computer position that is gettting info from perhaps a single INS with inputs from Doppler and some algorithms to predict transport wander and other errors induced. Couple that with a radar or visual fix then you have an updated nav computer position that is different from the INS position ... but is the best position available. If the navkit was way off, you would ignore the map and use your skill as an ace fighter/recce pilot to get to the target and get bombs off using whatever visual method you prefer.

 

When IRS was available, it made the basic position info a bit more accurate but there would still be inputs from other sources

 

GPS becomes available and that becomes a very compelling and accurate input into the aircraft position as seen by the navkit computer... These days GPS is so accurate that the navkit position is primarily driven by it.

 

Add some GPS jamming and the jet goes back to getting its position derived by the IRS(or equivalent) and other inputs.. perhaps fixed by the pilot like in the old days

 

The second issue is this.... Let’s say the target position is known and you fight your way through to the target without getting wasted by Sam 10/11/12.... you look at the target diamond in the HUD and hope the target is underneath it. Would be useful to check that the navkit is accurate before you get to the target..... that’s where an offset comes in... or you can use the previous waypoint to see how accurate the navkit is. If it isn’t showing the offset in the correct place you have to move the navkit position by reference to the offset (or perhaps the previous waypoint). That now has put the target diamond over the LAT LON you have for the target.. (let’s hope target intelligence was good for the coords)

 

Finally, the third is the scenario HARLIKWIN just described above. An offset is also visible or radar point that you will not mistake. Picture a hut in the desert that is not so visible as target with a large mast approx 7-10 miles short of it on your LOA that you can’t mistake for anything else. That could be your offset pairing. Incidentally it also describes a visual IP-TGT run.

 

1. Offsets can be used to drag navkit back to reality

2. Ofsets can verify navkit accuracy

2. Offsets can be used to help find a target that isn’t very visible by eyeball or on radar using an offset that is easily found.

 

I expect many DCS pilots still choose random points on the ground as their waypoints on ground attack missions ...rather than waypoints you can navigate via map and stopwatch... and use as offsets and IP’s. For real, you would navigate by recognisable points. If the navkit goes down leading the ground attack 4 ship, nobody has sympathy for you if you feel you need to handover the lead because you forgot how to navigate as you were taught at Tactical Weapons Unit

 

Don’t become a “kit baby” ... but, if you choose to rely solely on it, make sure it is updated and correct... is the moral of the story.