AIM-54 guidance

[D4n]

During it's up to 120 seconds flight time (right?) I wonder if the Phoenix missile will keep flying a straight path towards general direction of target, or will it continuously calculate the intercept point (like current DCS missiles do) and will pilots be able to easily slow down the missile when they keep turning? Or is there some "smart" navigation in the AIM-54's guidance computer?

[Nooch]

I don't know if it's realistically modelled in this video but from what we can see there the phoenix will climb very high and then dive on its target

 

[D4n]

Woooow... so many radar modes... :P Is every single one of them even useful? What conditions?

[Beamscanner]

Little material can be found on the guidance process of the AIM-54..

 

But here is what we know.

 

Missile is launched in autopilot for a period of time

 

at some point a time multiplexed SARH mid-course guidance takes over, with the AWG-9 painting the targets at specified intervals (information on a AIM-54 datalink has yet to be found, and likely does not exist)

 

the missile or missiles passively receive these reflections off their specified target and correct themselves as required

 

The missile seeker will go active when it believes the target is within detection range of its seeker. (presumably a greater distance then the AIM-120 seeker, due to it's larger antenna)

 

What we don't know..

 

How does the missile get target range information during mid-course? (needed for lead intercept solutions and seeker activation)

 

How does the missile distinguish the reflection from its intended target during mid-course if multiple targets rest inside the beam of the AWG-9 at that moment. Given the range of these engagements, the AWG-9s beam must be relatively large. Better yet, can it distinguish its intended target given these circumstances, or does it just home in on the biggest reflection?

Edited April 17, 2016 by Beamscanner

[D4n]

Well wouldn't it make sense to home in on strongest reflection? Probably Leatherneck will get information, as this missile isn't in service anymore in the US Navy... (Officially at least)

[Grundar]

Apparently aircraft like the E2 could guide launched AIM-54's as well which significantly improves the lethality of the F-14. If after launch an E2 can provide course correction updates to the AIM-54 it allows the F-14 to engage other targets. Given in TWS mode the AWG-9 can track 24+ targets simultaneously and theoretically could launch and guide 6 AIM-54

 

I think it is often overlooked (on paper) that the F-14's capability was enhanced by the presence of E-2's (something that really made the USN have an exceptional capability over other Naval forces who don't employee AWAC type aircraft from the carrier)

 

From: http://www.designation-systems.net/dusrm/m-54.html

 

The AN/AWG-9 FCS uses a TWS (Track While Scan) pulse-doppler radar, and can track up to 24 targets simultaneously at ranges of up to 240 km (130 nm). Therefore, an F-14 can effectively attack 6 targets simultaneously. When an AIM-54A is launched, its Rocketdyne MK 47 or Aerojet MK 60 solid-fueled rocket motor (in an MXU-637/B propulsion section) propels it to a speed of Mach 4+. For mid-course guidance, the missile's AN/DSQ-26 guidance section employs an autopilot, which gets regular target position updates by semi-active radar tracking. The FCS radar periodically illuminates every target to which a missile has been dispatched. For maximum range, the missile flies an optimized high-altitude trajectory for reduced drag, and the AIM-54A can engage head-on targets at a distance of up to 135 km (72.5 nm). For the final 18200 m (20000 yds) of the interception, the Phoenix switches to active radar homing for high terminal accuracy. Minimum engagement range is about 3.7 km (2 nm), in which case active homing is used from the beginning. The 60 kg (132 lb) MK 82 blast-fragmentation warhead is detonated by a fuzing system consisting of a MK 334 radar proximity, an IR proximity, and an impact fuze.

 

The AIM-54 though remains classified afaik, so it obviously has systems that are still in use and valuable/secret.

Edited April 18, 2016 by Grundar

[BlackLion213]

There is also an interesting report in the VF-2 command long of the Bounty Hunters guiding an AIM-54 with the TCS only.

 

[ame]http://www.history.navy.mil/content/dam/nhhc/research/archives/command-operation-reports/aviation-squadron-command-operation-reports/vfa/vfa-2/pdf/1987.pdf[/ame]

 

Go to page 11, heading "j" - "Conducted first firing ever of an AIM-54A with TCS lock only"

 

Another interesting technique for ambushing your foe! :thumbup:

 

Like Grundar said, it seems there were some interesting ways of steering the AIM-54, even without RADAR.

 

-Nick

[Beamscanner]

Well wouldn't it make sense to home in on strongest reflection?

Naw, you may have larger RCS aircraft behind the intended target, who are well out of range of the missile..

 

Probably Leatherneck will get information, as this missile isn't in service anymore in the US Navy... (Officially at least)

 

Lets hope!!

 

 

The E-2 targeting would indicate the inclusion of a datalink.. However, I can't find anything on the 54 using one. All I've seen is mid course via SARH. Though they may just mean to say that the E-2 could provide range data to the aircraft when the AWG-9 was being jammed..?

 

 

Also, nice find blacklion. But I think the typical range for the TCS is 10nm and the seeker on the 54 is about the same if not better. So they probably did a TCS 'handoff' to the missiles seeker in this case.

Edited April 18, 2016 by Beamscanner

[D4n]

What's TCS? And I wonder at which range the radar can burn through ECM (from Su-27 for example)...

 

And HOJ mode for Phoenix will probably reduce range to 50-100 km I guess... (because in HOJ the missile will fly straight towards the target...)

[Hadwell]

so then, basically, if the missile is launched more than 18km away, it's practically unguided? running in a straight line except for a periodic update in while SARH mode?

 

meaning, while the missile is more than 18KM away from its target, the F-14 needs to maintain a radar lock?

Edited April 18, 2016 by Hadwell

[BlackLion213]

Also, nice find blacklion. But I think the typical range for the TCS is 10nm and the seeker on the 54 is about the same if not better. So they probably did a TCS 'handoff' to the missiles seeker in this case.

 

Thanks, I agree that it's not a "long-range" solution, but it gives a bit of insight into the system. I would guess that the TCS (which can be slaved to the radar) gave azimuth data for a short period before the AIM-54s active seeker began guiding. (Which is basically what you said :)).

 

To me, this makes we wonder what else could be done given the Tomcats datalinks, etc.

 

-Nick

[red_coreSix]

so then, basically, if the missile is launched more than 18km away, it's practically unguided? running in a straight line except for a periodic update in while SARH mode?

 

meaning, while the missile is more than 18KM away from its target, the F-14 needs to maintain a radar lock?

 

Not running in a straight line but proportional navigation. The system averages the received updates to fly a intercept course to the target.

And to be honest who knows if the Phoenix uses SARH for mid-course guidance it sounds very unpractical. Especially when engaging more than one target at once, you'd need an ESA radar to illuminate the targets with STT...

[Dudikoff]

And to be honest who knows if the Phoenix uses SARH for mid-course guidance it sounds very unpractical. Especially when engaging more than one target at once, you'd need an ESA radar to illuminate the targets with STT...

 

Why ESA? As it would not be a terminal SARH guidance, but just mid-course position updates, I don't see why e.g. TWS pulses (coded for each missile) would not suffice.

 

But, of course, as the exact technology behind it hasn't been declassified and there are just SARH hints in various books available, I'm just guessing here.

Edited April 18, 2016 by Dudikoff

[Sierra99]

so then, basically, if the missile is launched more than 18km away, it's practically unguided? running in a straight line except for a periodic update in while SARH mode?

 

meaning, while the missile is more than 18KM away from its target, the F-14 needs to maintain a radar lock?

 

I'm not sure "practically unguided" is a good description. It receives initial guidance / tracking solution from the AWG-9 and sets a course to intercept the target based on that information at launch. It also receives mid course correction information from either the AWG-9 or E-2C and fine tunes the intercept solution.

 

I'm not sure where in the process the F-14 can completely break lock.

[red_coreSix]

Why ESA? As it would not be a terminal SARH guidance, but just mid-course position updates, I don't see why e.g. TWS pulses (coded for each missile) would not suffice.

 

Well, that's what I'm saying. I also don't see why they wouldn't use TWS and datalink (maybe they haven't had that back then?) because going STT on a target would make you loose every other target that you have been tracking or shooting on. So the radar would've to go back to search and reacquire the targets, it just doesn't seem practical.

[Seaeagle]

Why ESA? As it would not be a terminal SARH guidance, but just mid-course position updates, I don't see why e.g. TWS pulses (coded for each missile) would not suffice.

 

Define mid-course SARH guidance.

 

Early SARH missiles used beam riding(rearward facing antennas tracking the beam emitted by aircraft radar) to guide the missile towards target until the seeker's forward looking antenna could pick up aircraft radar's target returns and home directly on them(SARH).

 

The AIM-54 is a long range missile and the small antenna of the SARH seeker obviously cannot home directly on target reflected energy from 100+ miles distance, so the only explanation I can see for the "SARH midcourse guidance" reference would be some combination of inertia/"periodic beam riding".

 

BTW the references to this that I have seen talks about "Semi-active radar guidance" - not Semi-active radar homing(SARH).

 

That is of course if the AIM-54 doesn't actually have INS/datalink. The SARH reference might not refer to midcourse guidance.....some seekers use combination of SARH and ARH for "pre-terminal" and terminal homing respectively. Upon activation, an ARH seeker first runs a search pattern to locate the target and the idea should be to shorten the search period by using SARH mode to "pre-align" seeker antenna with target.

[Seaeagle]

Well, that's what I'm saying. I also don't see why they wouldn't use TWS and datalink (maybe they haven't had that back then?) because going STT on a target would make you loose every other target that you have been tracking or shooting on. So the radar would've to go back to search and reacquire the targets, it just doesn't seem practical.

 

Thats the thing - its not STT.

 

The suggestion is that the radar is operating in TWS and somehow provides periodic mid-course updates to multiple in-flight missiles without datalink.

[Dudikoff]

Define mid-course SARH guidance. Early SARH missiles used beam riding(rearward facing antennas tracking the beam emitted by aircraft radar) to guide the missile towards target until the seeker's forward looking antenna could pick up aircraft radar's target returns and home directly on them(SARH).

 

Yeah, and with the advent of monopulse SARH seekers, this was no longer necessary. As the Soviet Union used those in mid-70's (R-23R), I don't see why the Phoenix couldn't have used a similar principle for mid-course guidance.

 

The AIM-54 is a long range missile and the small antenna of the SARH seeker obviously cannot home directly on target reflected energy from 100+ miles distance, so the only explanation I can see for the "SARH midcourse guidance" reference would be some combination of inertia/"periodic beam riding".

 

BTW the references to this that I have seen talks about "Semi-active radar guidance" - not Semi-active radar homing(SARH).

 

Yes, it cannot, but for those long ranges it uses a lofted trajectory anyway and it might start receiving reflected pulses once it gets on its downward part and close enough to the target.

Edited April 18, 2016 by Dudikoff

[Dudikoff]

Well, that's what I'm saying. I also don't see why they wouldn't use TWS and datalink (maybe they haven't had that back then?) because going STT on a target would make you loose every other target that you have been tracking or shooting on. So the radar would've to go back to search and reacquire the targets, it just doesn't seem practical.

 

Err, you said SARH mid-course updates are not practical and I said they might be as it doesn't have to be the continuous target illumination, but just TWS pulses since it's not used for terminal homing. I don't see how we're saying the same :)

 

EDIT: I see it was already discussed before and there are some detailed posts so why tread the same ground:

 

http://forums.eagle.ru/showthread.php?t=159837&page=5

Edited April 18, 2016 by Dudikoff

[Seaeagle]

Yes, it cannot, but for those long ranges it uses a lofted trajectory anyway and it might start receiving reflected pulses once it gets on its downward part and close enough to the target.

 

Don't understand your point Dudikoff - I don't see how being in a look-down situation should help with seeker acquisition range(rather the opposite I would think).

[red_coreSix]

Err, you said SARH mid-course updates are not practical and I said they might be as it doesn't have to be the continuous target illumination, but just TWS pulses since it's not used for terminal homing.

 

EDIT: I see it was already discussed before and there are some detailed posts so why tread the same ground:

 

http://forums.eagle.ru/showthread.php?t=159837&page=5

 

 

I said going STT isn't practical not SARH but having read the thread you linked I can see what you meant. Yes, maybe that's how the AIM-54 guidance works but the question is to what extend we will get that simulated as such a guidance isn't yet in the Sim.

 

And I also wonder if targeted planes will get a launch warning, because that would virtually eliminate BVR with the Tomcat...

[turkeydriver]

The biggest asset the AWG-9 had besides its raw power and detection range, was its sensitive receiver, so the AWG-9 tracked you at range without tripping your RWR. Of course espionage and the fall of Iran did the job of negating that asset. STT gives you the longest range launch with the AIM-54, TWS mode gave you the ability for multiple shots and didnt trip your RWR, at least back then.....

[Beamscanner]

And I also wonder if targeted planes will get a launch warning, because that would virtually eliminate BVR with the Tomcat...

 

First off, by "mid-course SARH" we don't necessarily mean using STT. As we all know, up to 6 AIM-54s could be launched on 6 different targets. So being a mechanically scanned radar, you couldn't use STT for a multi-target engagment..

 

What we really mean when we say "mid-course SARH" is 'bi-static radar reception'. The AIM-54 isn't homing in on the target like a AIM-7 or R-27. But it is using

the radar reflections off the target to update the targets relative azimuth and elevation from the missile during mid-course flight.

 

I had your same thought process awhile back too when I was still learning more about the AWG-9 engagement process. You would think that you'd need an ESA to time-share a CW illumination for accurate missile tracking on multiple targets(Like what some Russian ESAs may do). But the AIM-54 doesn't need a continuous illumination during mid course.. It doesn't need to be updated every microsecond. Instead, the AWG-9 runs it's normal TWS mode (no CW illumination) and the missiles presumably get reflections from the intended target every couple seconds.

 

No launch warning should ever be present for the AIM-54. The target should only see the missile once its go active at terminal.

 

Ingame launch indication requires 2 things. (only talking missile launch, not active missile seeker indications)

1. A hard lock from a threat radar

2. An active datalink from the same radar(or at least the same direction in space)

 

If your missing one or both of these things, you should not be able to know a missile has been launched on you specifically. This is a logic based conclusion. For instance, a RWR may see a ton of missile datalinks at a given time(any datalink within 100+ miles), but they may not be at your own aircraft. Likewise a radar may lock you up, but not fire a missile. neither by themselves mean that you've been launched on. As such, you need both to indicate that a missile was probably launched at your aircraft.

 

So no warning should ever be given if a missile is launched in TWS. Additionally, if the AIM-54 does not use a datalink, then it shouldn't give a launch warning even if launched in STT.(similar to AIM-7 launched in Flood mode)

 

See my previous posts for more details

http://forums.eagle.ru/showpost.php?p=2687175&postcount=37

http://forums.eagle.ru/showpost.php?p=2669661&postcount=43

Edited April 19, 2016 by Beamscanner

[microvax]

Afaik the AIM54 guidance worked as follows:

 

There are two main modes for the Missile to be guided until 18km to the target, INS, which makes it fire and forget or SARH. If 18km to the target, the missile switches to infrared [in case of the A variant] or active radar [C and later] seeker. If the Seeker detects jamming, it directly switches to HOJ, if the jammer is turned off again, it directly switches back to active radar. Since HOJ only happens in final approach, after the missile has climbed to 30km in case of the C and is falling to the target, it should not be that much of an range reduction. [speed is somewhat hard to get, but its said to be mach 5 when its at the highest point of its trajectory.]

 

For the mentioning of Datalink: There is one Statement which kind of implies that C and C+ had datalink course update etc.. Its been said, that if the missile detects it has gone for chaff and lost the target, the tomcat can designate a new target. I dunno how that is supposed to work but with datalink.

 

 

I do not have enough sources to be sure everything is correct and some parts are missing.

For example if you choose to fire in SARH, is the missile getting course corrections in the climb phase at all ? If not, how is made sure that the missile catches the target reflection on pitch down.

All stuff which is kinda unclear and kinda makes the datalink course updates in flight very credible.

 

 

Anyway, will be very interesting how high the hit rate against a even mildly maneuvering fighter will be. After all its a 500Kg missile flying at pretty damn high approach speeds which implies some unreal amount of intertia.

[captain_dalan]

Not exactly sure where i read this (considering missile coding), but if memory serves each 54 was "color coded" before plane launch, in such a way that it corresponded to only one AWG9 "module". The coding might actually have been "physical", as in inserting a piece of electronics in the guidance system. The most direct consequence is that each 54 on your palettes will have one and only one "slot" in your missile firing sequence. In a way it will guide to only one "beam" and changing targets (if at all possible) could only be done by "shifting the beam" and not by switching the missile to another beam. Again, this was a long time ago, and i can't trace the source, so i might be off. I can't even recall the exact mechanism of beam recognition (it could be beam frequency, or something else similar to FOF).