AIM-7MH Issues

[MBot]

On 12/18/2020 at 5:03 AM, NeedzWD40 said:

In essence, it seems like the 7F and 7MH are aiming at some point behind the targeted aircraft and are either maneuvering too late or not enough. I tested against IL-76s set to no reaction, no chaff or flare, and ECM off. First shots at 25nmi, second at 19nmi, and third at 10nmi head on. All three shots with the F and MH fall behind the target, as if they're lagging behind somehow.

 

I had a look at this as well.

 

Target is a non-maneuvering Il-76 set to no reaction and no chaff, flying at 20'000 ft. Target aspect is 155° to give the missile some work with a little crossing angle. Shot AIM-7MH in PD-STT. Missile hits when shot at 25 NM and misses when shot at 27 NM or beyond.

 

Here is one of the 27 NM launches that misses:

 

Setup at launch.

 

Note missile speed 523 KTAS and 0.9 G.

 

Note missile speed 521 KTAS and 1.0 G.

 

What I noted with the 25 NM shot that hit is that the missile remained at 0.9 G to impact. It seems that when the missile speed drops to about 520 KTAS, the missile stops guiding and goes ballistic at 1 G, passing behind the target. Whether that is realistic or if the missile should be able to continue guiding at this speed I cannot judge.

 

I don't know the exact specs the AIM-7MH should have, but considering the setup (medium altitude, subsonic launch, subsonic target, crossing angle) a 25 NM range against a non-maneuvering target sounds plausible.

 

I have also shot the AIM-7F and AIM-7M against the same target, but since they do not loft they run out of speed way earlier and have no hope to connect beyond 15 NM. Again I don't know if that is realistic, but considering the setup (medium altitude, subsonic launch, subsonic target, crossing angle) it at least seems plausible.

 

I haven't checked against maneuvering targets and just wanted to check the theoretic performance against non-maneuvering which the quoted post suggest are wrong, which I cannot confirm.

[NeedzWD40]

Have you tried tail-on launches? That was where I suspected there was something odd going on with where the guidance position, as launches between 2.5-5nmi would result in the missile shooting up behind the target.

[Skysurfer]

2 hours ago, NeedzWD40 said:

Have you tried tail-on launches? That was where I suspected there was something odd going on with where the guidance position, as launches between 2.5-5nmi would result in the missile shooting up behind the target.

 

Yep, it seems to go into some weird lag-pursuit/stern convergence type of deal as if the missile was trying to get a gun solution on the target.

Edited December 20, 2020 by Skysurfer

[MBot]

14 hours ago, NeedzWD40 said:

Have you tried tail-on launches? That was where I suspected there was something odd going on with where the guidance position, as launches between 2.5-5nmi would result in the missile shooting up behind the target.

 

I can't reproduce this. AIM-7MH shots from <5 NM from the rear hemisphere with P-STT (PD-STT doesn't work under these circumstance) against a non-maneuvering Il-76 with no chaff are guaranteed hits for me. Can you set up a sample mission with the parameters where this happens for others to check?

 

Tail-on launch from 5 NM with AIM-7MH. Missile lofts (shouldn't loft be prohibited with a pulse lock?). Missile connects to a kill.

 

90° aspect shot with AIM-7MH from about 3 NM.

[NeedzWD40]

So here's the mission (requires Nevada map):

 

F-14A AIM-7 Failure.miz

 

The mission has the IL-76's start head on at 35,000ft while the F-14A slot is 25,000ft. Head on shots always seem to miss with the MH, while tail on shots seem to be picky about range and altitude launched at. They act like they're extremely G limited and can't seem to pull enough lead even though the target is well within energy parameters. They seem to drop an extreme amount downward before finally deciding to get up to speed and accelerate into the target, which comes too late to score a hit.

 

 

 

Right up until they pass the target, they're trying to pull into it, with just not enough G available to pull right into it (too high velocity? too low air density?) I've trialed tail on shots from 10nmi down to 2nmi and they all result in the above scenario. PAL, Jester, and boresight mode all achieve the same results.

 

[MBot]

Thank you, with your mission I could reproduce the problem and find the bug.

 

The missile misses if there are two aircraft in the target group. If you reduce the target group to only one aircraft, the missile tracks and hits.

Edited December 22, 2020 by MBot

[MBot]

On 12/22/2020 at 11:51 AM, MBot said:

Thank you, with your mission I could reproduce the problem and find the bug.

 

The missile misses if there are two aircraft in the target group. If you reduce the target group to only one aircraft, the missile tracks and hits.

 

Today's hotfix solves this.

[near_blind]

Initial prognosis is looking very good! The missile is hitting a lot more and while I'm still seeing misses, they look to be explainable either by the target notching or battery life time. Thanks for the work HB and ED! 

 

 

[Wizard_03]

For me the average PK seems has gone up. They seem to much closer to the hornets and Eagles now. Good work HB.