Question on Harm HAS ALIC and RWR display
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In 4.32 it would bee-line it for the target AGM-45 Shrike style. In 4.33 it’s different. I didn’t test if it was exactly the profile of a HAD or POS shot but qualitatively similar.
The display markings are in 20° increments horizontal, 22.5° vertical. The caveat is that while the straight lines suggest it’s supposed to be a B-scope format but the symbols are being positioned in a different way. The scale is only directly readable when a contact is on the central vertical line. As the contact changes in azimuth it follows a semi-circular path where the 1 o’clock position is 30° right, 2 o’clock is 60°, 3 o’clock is 90°. The horizontal scale works but you have to use your imagination to compare the curved path length vs the straight line scale. The extreme ends being 60° would curve around to the 2/10-o’clock positions. This is only really usable in the central ±20 degrees or so near where the straight horizontal line and the arc the contacts occupy come tangent.
The vertical scale will show the contact at the top when it is on the horizon (low altitude ownship + long range. Approaching directly the contact marches down the vertical scale to 45° down at the second tick and overflight at the 90° point is the “fourth tick mark” which is the end of the line. The 1st and 3rd ticks are 22.5° and 67.5° respectively. Contacts at a mixture of azimuth and elevation are nearly impossible to quantitatively judge. A contact 60° left in azimuth and 45° down in elevation will be drawn at the 2 o’clock position but at half the radius from the bottom-center of the display as one on the horizon.
The HARM can only maintain lock within ±90° azimuth and +?°/-90° in elevation. The contacts will remain visible on the pre-designate HAS display but will not be lockable and will drop lock outside these limits. Contacts beyond 90 degrees in az/el are clamped to the bottom of the display at their clock position in the rear hemisphere. For example a contact moving through 91 to 179 degrees azimuth will appear to slide along the bottom of the display from the bottom corner to the bottom center.
HAS has 4 search displays, wide, center, left, right. Wide and center appear to have identical display characteristics. The only noticed difference was that center detected contacts at a shorter range (40nm for SA-2/3/4). Wide detected these SAMs at much longer ranges.
Despite the shift in the vertical tick-marked line in left/right displays, contacts in the center of the display are still straight ahead. Contacts which are even slightly left azimuth in “RT” or right azimuth in “LT” are not shown.
HAS is stabilized in both pitch and roll. ALIC video (post-designate) is stabilized in pitch but not roll (which seems wrong). Post-handoff video puts the contact in the middle of the crosshairs when the elevation is 45 degrees downward and lower as overflight continues.
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Compared to reality: The pre-handoff video contact positions are most certainly supposed to be arranged in an X, Y grid where X is azimuth and Y is elevation so any point on the display is meaningful not this arc. The tick marks would span the entire FOR of the HARM which is unknown to me and much smaller in elevation (possibly 10). Looking straight down is silly and you’d be much more interested in minor depressions below the horizon. A cutaway view of the missile radar dish makes a wide range believable but so would a narrow capability especially for early models. HTS is often praised for its 180 degree coverage which wouldn’t get so much press if it wasn’t a significant improvement over the missile itself. Anyway if the HARM genuinely has ±90 then the tick marks would be at 30/60/90 for wide.
There’s no pre-handoff cursor. You press the OSB next to the threat type you want to handoff. If there are multiple (up to 4) after handoff you press uncage to step through them. No SOI, no slewing, no TMS-up’ing unless there was a software change.There is a HAS cursor. Pressing the threat is an alternate way.The threat tables are customizable (DTC), one might have Search, SA-3, and SA-10 on a table if you want. They interact naturally with the HARM DED page when the UFC link OSB (5) is pressed.
Post-handoff the video is from the missile’s point of view in roll and pitch (instead of azimuth and elevation as in pre-). Center of display, boresight of missile. If the contact is to the right, roll right until the contact is 12 o’clock and pull up to center the contact.
Scans can take a long time the bigger the FOR and number of contacts searched for (up to 5), like a minute and a half. 5-contact wide rarely takes more than 15s currently. “RS” restarts the scan, clearing the last contacts.
Center is a narrower scan centralized so the azimuth tick marks represent smaller angles and it finishes scans faster. Right and left scans would display a straight ahead contact on their respective 0 azimuth lines, not the center of the display.
Since there is no range information in HAS, the missile would either fly direct or g-bias minimally similar to Maverick.
Presence and operation of the HTS may or may not have an effect in HAS.
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The scales don’t seem to be of practical use. At 20,000 feet there’s not much movement at all. You only really see a lot of movement when SAM’s are in the air.
If centre range is 40 miles I would imagine the way to use it would be to use wide for situational awareness and drop down to centre to verify within a good range?
And what does DTSB stand for? Answer: detected threat status box
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In testing using the HARM training mission the SA-2 was present at WIDE above 60 miles, the SA-3 at 52 miles. In other words as soon as the mission started.
Both threats appeared at CENTRE at 36/37 miles.
That range is perfectly fine for the SA-2, but for reasons I’m unaware of a HARM fired at the SA-3 misses at those ranges. And I’ve fired a few missiles post designate, RDY, etc. I would have to do more testing but 30 miles or below would be my guess at that point, having missed at 36 miles and hit at 24 in my last test, with range taken from PPT 56. I’m guessing range is accurate as both SA-2 and SA-3 popped up at the same time at CENTRE and at the same PPT range.
Are there different effective ranges for different threat types?
I’m going to partially answer my own question: the SA-2 Fan Song has a 40 mile range, the SA-3 Low Blow 25 miles.
But still, what is the HARM sensor detecting at 36 miles with the SA-3?