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med-taha

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Well the TGP has a laser rangefinder, so you'll get a range to target that you need to be able to tell if you're in range for a shot. The Mavs don't.

The Harrier MC gets it's IRMAV "in range" HUD cue using it's INS, Altitude and IR Seeker gimbal angle to estimate the slant range and check if the target is within the launch envelope.

 

I'm a little surprised the Hornet doesn't do something similar but it is what it is.

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The Harrier MC gets it's IRMAV "in range" HUD cue using it's INS, Altitude and IR Seeker gimbal angle to estimate the slant range and check if the target is within the launch envelope.

 

Sorry for OT, but isn't that equation missing terrain elevation? Does the Harrier have an elevation database like the A-10C? Or does it have another way to know or guess elevation at the direction the seeker is looking at? I guess I'm missing a piece of information here to make sense of how it works.

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Sorry for OT, but isn't that equation missing terrain elevation? Does the Harrier have an elevation database like the A-10C?

Yes it has a elevation database. However it *might* be used for other weapons/sensors/modes i.e. CCRP

 

Or does it have another way to know or guess elevation at the direction the seeker is looking at? I guess I'm missing a piece of information here to make sense of how it works.

 

AFAIK, the Harrier MC makes the assumption that the target vertical reference is correct i.e. the terrain is fairly level and it *may* still be down to the pilot to decide the exact optimum time/distance to launch.

 

OTOH, the 'assumed vertical reference' *may* be that the aircraft height above MSL is correct and 'locking' the IRMAV uses the terrain/elevation database to estimate the targets position and elevation.

 

 

Ranging information includes the IN RNG indication above the TGT indication and distance to target (slant range) in nautical miles.

 

Ranging information is based on IRMV gimbal angles and best available aircraft altitude when in IRMV track mode. The IN RNG cue indicates that the mission computer has determined that the target being tracked is within the missile launch envelope (it assumes vertical reference is correct).

 

Like the Hornet, the Harrier pilot can use other means to measure range i.e. DMT-TV, Designated Waypoint or TPOD/Laser if so equipped.


Edited by Ramsay
Add disclaimers i.e. *might*, *may*, etc. as I'm not 100% certain how the AV-8 estimates IRMAV slant range.

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The f18 has to have some elevation knowledge or the ccip would not work right?

AFAIK, the Lot 20 modelled in DCS includes digital terrain elevation data (DTED) as part of TAMMAC (the moving map) and it's used by the terrain avoidance warning system (TAWS) among other things.

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A good test is when flying toward a mountain with the radar off. Betty will give you a shout as you approach terrain indicating the F-18 has imbedded elevation data.

Another test is to fly toward a mountain with both radar and INS off/unaligned. If she still bitches at you then it’s either a bug or a DCS ‘cheat’. I’m away for a couple days so can’t try it myself but I’m curious about the results.

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The radar altimeter wouldn't issue a terrain warning when approaching a mountain anyway, or would it? It would only sound the altitude alarm.

 

As I understand it, quinncidence did indeed refer to the radar, not the radar altimeter, for this particular test. Nice thinking, BTW. :thumbup:

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The radar altimeter wouldn't issue a terrain warning when approaching a mountain anyway, or would it? It would only sound the altitude alarm.

 

As I understand it, quinncidence did indeed refer to the radar, not the radar altimeter, for this particular test. Nice thinking, BTW. :thumbup:

 

Yep, correct. After I posted I had a feeling people would think I meant radar altimeter. It can be left off too fwiw.

The “PULL UP, PULL UP” warnings should be tied to INS and terrain elevation data iirc.

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You still get the "PULL UP" bitching betty if you're inverted... and if you're inverted, your radar altimeter is pointing at the sky... so I think it's either that's a bug, or it's INS based, or ED is just cheating (not really rendering the system, just the effect).

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Yep, correct. After I posted I had a feeling people would think I meant radar altimeter. It can be left off too fwiw.

 

 

A, I see what you mean. Is this something that is actually implemented in the Hornet? I mean, with the radar in surface mode it is processing surface clutter returns, but in air to air? In that case it is rejecting clutter returns around Doppler zero. So to get a warning it would also have to process these (with associated required processing power). I'm not saying it can't be done, but do you know if it is an actual feature?

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