[NO BUG] ACM Boresight AIM-54

[diditopgun]

Hi !

 

I fire 4 Phoenix at a Su-27 in a straight head on level flight at same altitude, all in ACM Boresight mode.

 

Distance at launch:

Missile1: 16.98nm

Missile2: 14.02nm

Missile3: 9.72nm

Missile4: 6.70nm

 

Only Missile4 acquire and kill the target. First three fly straight and never acquire the target even being on its fly path.

 

It looks like if the target isn't at missile seeker's range at launch time, the missile go with an inactive seeker.

Edited April 14, 2019 by IronMike

[Pougatchev]

+1

[diditopgun]

Up!

[diditopgun]

Any words on how AIM-54 is supposed to work in boresight mode ? No "maddog" capacity like AIM-120 ?

[IronMike]

in ACM/ brst mode the aim54 is limited to an active range of 10nm and really only acquires along its datum line. so it makes sense that it will not acquire the target outside of 10nm.

 

A better solution is to use PAL mode outside of 10nm and up to 20nm, which will make the phoenix go active in PSTT mode immediately on the target and not only along its own boresighted seeker.

 

 

EDIT: missiles 3 could be just outside the range, is it tacview that give you these precise ranges? this could be a bit off as well. so might be just outside 10, too.

[diditopgun]

Thanks for your answer IronMike.

 

Yes it's Tacview so maybe the target was at 10.01nm at trigger depress time. ^^

 

So if I well understand, if the missile seeker don't see the target before launch, it will go with an inactive seeker after launch. Pretty weird and useless on my point of view, but if it works this way I will deal with it.

[IronMike]

From the manual:

 

"The last mode is ACM active in which the missile is commanded active before launch making this the only mode where the missile is truly fire and forget. The AIM-54 missile receives the active message before launch from the WCS in addition to a command prepositioning the seeker-head to have it look at the current WCS track if available.

 

 

ACM active is commanded when BRSIT (boresight) is selected on the pilot ACM panel, when having the ACM active without a WCS track and when using a non pulse doppler radar mode or TCS track. When using boresight or ACM without a track the missile will launch along the ADL locking onto the first target seen while launching at a non pulse doppler radar track the seeker head will be prepositioned onto that track." (hence PAL is recommandable)

 

The problem is that you have to really aim well, as if I understand this correctly, the seeker's boresight view is around 10° (or was it even 5), I'd have to look it up. So if you do not aim precisely at the target, and it does not see a target immediately within these 10ish nm (depending on size, can be less, can be more, 6nm rear aspect), it will just fly straight. I need to ask Gyrovague, if it should acquire a target that flies through its active seeker after launch. I don't want to give false information. He will be able to answer this much better than me. I'll ask him and get back to you. (or maybe he will read this in the meantime and can chime straight in and correct my blunder..)

 

But in general, ofc, if using PAL or any type of PSTT lock (like ACM modes), the WCS will preposition the seeker onto this track, which of course helps with the guidance. PAL really is your pal. :-)

 

Personally I treat ACM cover up as a last second emergency mode, and else keep it closed 100% of the time.

[diditopgun]

The problem is that you have to really aim well, as if I understand this correctly, the seeker's boresight view is around 10° (or was it even 5), I'd have to look it up.

 

It's very narrow indeed, I thought it was wider.

 

I need to ask Gyrovague, if it should acquire a target that flies through its active seeker after launch. I don't want to give false information. He will be able to answer this much better than me. I'll ask him and get back to you. (or maybe he will read this in the meantime and can chime straight in and correct my blunder..)

 

That's precisely my question. :thumbup:

 

But in general, ofc, if using PAL or any type of PSTT lock (like ACM modes), the WCS will preposition the seeker onto this track, which of course helps with the guidance. PAL really is your pal. :-)

 

Yes PAL is my pal under 20nm :yes:

 

Personally I treat ACM cover up as a last second emergency mode, and else keep it closed 100% of the time.

 

Me too !