Hughes Falcon to GAR-X

[SOC]

Some of the Falcons that missed in Vietnam were near-misses estimated in the 10-15 foot range, and yes, everything else (AIM-9, AIM-7) did rely on proximity fuzing. A proximity fuze might've fixed the issue to some extent, but they still had a very small warhead. Although, I find the "puny warhead" concerns to be a bit misleading as well. OK, you're talking about a 2.75 pound warhead (as in HBX-1 explosive content, total warhead weight was 8.4 pounds) for the AIM-4D. That's bigger than the warhead for MANPADS, and they've shot down fast jets. Don't know how close a near-miss would need to be to get a kill with a proximity-fuzed Falcon, but it couldn't have hurt (hence the later tinkering with the XAIM-4H).

I'll contemplate your designations in brackets idea, that might not be a bad thing.

 

[pathology_doc]

Don't know how close a near-miss would need to be to get a kill with a proximity-fuzed Falcon

Close enough to puncture the canopy or the cockpit sides and put fragments into the pilot would do nicely - even if he survives and ejects, that's a kill. Of course then we're getting into all sorts of variables like what sort of delay you should put on the proximity fuze in order to explode it in the best spot, and what's good for a MiG-17 or -21 might not suit killing a Tu-95.

(While I'm here, I've always wondered about SARH for the AIM-26A - surely having to keep your nose pointed at the enemy and moving towards him at several hundred mph when you've just shot a nuclear warhead at him is... not the best thing? At least with AIR-2 you can squirt the trigger, turn and run!)

 

[SOC]

You can fire the AIM-26 from a range of up to just over 11 miles head-on, using HOJ mode. That, coupled with the "small" 1.5 kT warhead, and the fact that you don't need to have that significant of a closure rate, would probably be enough to keep you safe. SARH was intended to increase accuracy in a head-on attack (IR was proving not so effective at this just yet), with the added bonus of the smallish nuke warhead accounting for the inaccuracy of the era's SARH guidance modes.

 

[pathology_doc]

Just caught this bit:

-The Rb.28 was a license-built AIM-4C, but Sweden modified its weapons with the AIM-4G seeker during the late 1960's, making them de-facto AIM-4Ds. Further improvements were also made, but details are not known. Believed to include proximity fuzing.

Thus making them de-facto AIM-4H's!

(I don't recall whether you found information on the timing of deletion of the three-missile door; but looking at the CF-101 parked at the air museum in Gander, Newfoundland, what I took to be the AIM-4 side of the weapons pallet is in the "out" position and there are only two missile troughs. I've got all-around pictures of this A/C somewhere, and I can probably get you a serial number if this helps.)

 

[pathology_doc]

...aaaand since we've not long had a thread put up asking about a Phantomless world and what that would mean, and the discussion extended to what it would mean for the US, I felt it was appropriate to refresh this thread and get SOC's and others' opinions on what that might mean for Falcon development.


The assumption I start with is that the Convair deltas are called upon to perform the USAF's air superiority mission in Vietnam, and that Falcon perforce becomes the default frontline dogfight AAM for the Air Force.

 

[SOC]

I think you would've seen something like the AIM-4H appear earlier once they realized that the in-service Falcons didn't quite cut the mustard against small, maneuvering targets like the MiG-21. Some of the AIM-4D's problems related to external carriage, so they'd have been mitigated, but a proximity fuzed warhead would've been a big help. I could see making the AIM-4Ds proximity fuzed, and producing AIM-4F/G derivatives with proximity fuzes for the F-106.

 

[pathology_doc]

Against the advantages of not suffering inclement treatment on the racks, however, one must surely consider the FOV blanking of the airframe in a missile held inboard and swung out close to the aircraft's belly shortly before launch. Not as important in a low-G or collision-course intercept of a heavy bomber, but arguably significant in a swirling dogfight? Or is the effect not as significant as I thought?

 

[SOC]

Against the advantages of not suffering inclement treatment on the racks, however, one must surely consider the FOV blanking of the airframe in a missile held inboard and swung out close to the aircraft's belly shortly before launch. Not as important in a low-G or collision-course intercept of a heavy bomber, but arguably significant in a swirling dogfight? Or is the effect not as significant as I thought?

Only really matters for the IR Falcons. The others would be SARH guided, and would be hunting for reflected radar energy from the target. Of course, the IR Falcons take initial target direction from the FCS as well, so the FOV issue might not be as big a deal as you'd think either. I lnow some Six drivers were able to use the AIM-4F in ACMI pretty effectively, so there should be some reason for optimism I guess.

 

[pathology_doc]

*nods* Thanks for clearing that up. I know the FCS and missile were well-integrated, but I wasn't sure just how much scope the IR Falcon had for lock-on-after-launch.


Can you tell me to what extent the F-4D and the AIM-4D were (or were not!) similarly integrated? On the one hand, you at least have a wide FOV for the missiles, and they can uniformly acquire on the rail; on the other, that may not be such a good thing if "eyes wide open" acquiring on the rail is necessary to compensate for the lack of FCS integration...

 

[SOC]

The F-4C/D/E and AIM-4D were barely integrated at all, apart from the addition of a special LAU-42/A pylon for two AIM-4Ds carrying the nitrogen coolant for the seeker heads. Pilots had to activate the coolant to acquire a target as part of the prepare-to-fire process, and the limited coolant supply, good for about two minutes, often meant that F-4Ds over Vietnam got to tote around unfired AIM-4Ds if they didn't get good enough launch parameters before the coolant ran out. They also had to wait four seconds for the seeker to cool before launch.

That was all automated in the jets using a dedicated FCS. The IR Falcon's weren't LOAL either, they just received extra info from the FCS to tell them where to look when the doors opened. The only LOAL Falcon was the AIM-47A, although I don't think they ever got far enough in testing to evaluate the entire flight envelope of the missile. IIRC all of the kill shots were at ranges of less than 40 miles, less than half the design range.

 

[pathology_doc]

The F-4C/D/E and AIM-4D were barely integrated at all ... That was all automated in the jets using a dedicated FCS. The IR Falcon's weren't LOAL either, they just received extra info from the FCS to tell them where to look when the doors opened.

My italics. Silly me, getting those confused! *headdesk*


I guess we can draw parallels with (for example) the Firestreak installation on the Javelin, Sea Vixen and Lightning as compared to any potential lashup installations on the Avon Sabre, Hunter or Swift (I read somewhere it was considered for the Aussie Sabre until it was realised the support systems would have required removal of the Adens). I know Firestreak doesn't have more than 20deg angle of look away from boresight, but being able to point the seeker those extra 20 degrees vs. having to point it right at the target before launch might make the difference.

 

[Voodoo-Guy]

Belated thanks for the awesome report Sean.

 

[pathology_doc]

I have to admit, I always wondered about the whole "run out of nitrogen" thing. The original Sidewinder seeker was, IIRC, uncooled. Now the AIM-4D's cooled seeker seems to have been better whenever the missile worked (10% kill ratio even without a prox fuze), but given that uncooled seekers WERE used on other missiles and DID work, why is the -4D suddenly no more than a 140lb paperweight when the LN2 runs out?


Having done a fair bit of reading of 50's-era missile design manuals (thank you, AbeBooks and Amazon!), I think I have part of the answer; but for obvious reasons they're short on specifics for what was then front-line state of the art, and I'm interested in others' explanations. I suspect it's because the nature of the signal changes, dropping too low in the now-uncooled seeker's electronics package to be properly amplified; or even if there IS a useful signal in amplitude terms (a lit afterburner less than a mile away, for example) the seeker sends signals that the control-loop transfer functions weren't written to handle and the missile goes berserk and fails.

 

[Hobbes]

An IR seeker is cooled to reduce the thermal noise produced by the seeker itself. If you switch off the cooling, the picture drowns in thermal noise.


From Scramble.nl:

With an infra-red guided missile such as the Sidewinder, the discriminating ability of the seeker head — i.e. the ability to discriminate between different heat sources and their respective backgrounds — depends on the seeker head's own temperature, relative to the temperature of the ambient air. Therefore, the seeker head of an active missile is cooled up to minus 160 degrees Celsius in order to establish optimal sensitivity. The effective range of a cooled missile is 10-16 km, depending on the weather conditions — clouds tend to "mask" infra-red radiation — and the degree of humidity. The initial AIM-9B was uncooled. As a result, target acquisition and lock-on was extremely difficult, as experienced in combat by he US services. From the AIM-9D model on, the infra red detector was cooled. The US Navy and US Marine Corps used 6 litre nitrogen bottles in the LAU-7 launch rail, providing for 2.5 hours of seeker cool down, reflecting the primary fleet defence requirement. The US Air Force opted for Peltier thermoelectric cooling, allowing unlimited cooling time while the missile was on the launch rail (and – of course – power was applied). Later models use an internal Argon cooling system, eliminating the need for use of nitrogen bottles or internal bottles. The seeker head is cooled with specially treated air (officially the expensive Argon should be used instead). The air is filtered and de-hydrated, then compressed to 345 bar (5,000 psi) and stored in a small stainless-steel bottle, which is placed near the missile foreplanes. The de-hydration process is necessary in order to prevent the head from being frozen. A small amount of compressed air is continuously being expanded, causing a small stream of air, cooling the seeker head. Within two minutes the seeker head temperature is at the required level. The initial cooling is taking up most of the air; maintaining the temperature at the required level is taking up relatively less air. Nevertheless, the time the seeker head temperature can be maintained at the required level is limited. During long missions, the amount of compressed air available must be used wisely. Therefore, in most cases the missiles will only be activated when they actually will be used.

 

[SOC]

The problem is that the AIM-4D simply adopted the seeker of the AIM-4G...which was part of a weapon system optimized for shooting down bombers. Sure, the seeker was actually very good for the era, but it was still restricted by the way the coolant supply was handled.

 

[pathology_doc]

Thanks, all.

 

[tiikki]

A Finnish Draken pilot confirmed proximity fuse in Falcon missiles sourced from Sweden.


edit: He probably meant only SARH version.

 

[pathology_doc]

A Finnish Draken pilot confirmed proximity fuse in Falcon missiles sourced from Sweden.

Thanks for this. Which model? (I seem to recall reading that the conventional model of the SARH AIM-26 DID have one, but that at least the US-built AIM-4 series was always lacking. Perhaps SOC could clarify or correct as required. If the missiles you're talking about are the IR version, that's quite significant.)

 

[tiikki]

A Finnish Draken pilot confirmed proximity fuse in Falcon missiles sourced from Sweden.

Thanks for this. Which model? (I seem to recall reading that the conventional model of the SARH AIM-26 DID have one, but that at least the US-built AIM-4 series was always lacking. Perhaps SOC could clarify or correct as required. If the missiles you're talking about are the IR version, that's quite significant.)

Second pilot said that IR Falcon didn't have proximity fuse (around 1985), while SARH version had...
Conflicting sources are lovely.

 

[SOC]

A Finnish Draken pilot confirmed proximity fuse in Falcon missiles sourced from Sweden.

Thanks for this. Which model? (I seem to recall reading that the conventional model of the SARH AIM-26 DID have one, but that at least the US-built AIM-4 series was always lacking. Perhaps SOC could clarify or correct as required. If the missiles you're talking about are the IR version, that's quite significant.)

Second pilot said that IR Falcon didn't have proximity fuse (around 1985), while SARH version had...
Conflicting sources are lovely.

Maybe they got some of the un-upgraded IR weapons initially? Sweden did license build the thing and also imported some initially, so maybe they transferred extant imported models first.

 

[tiikki]

A Finnish Draken pilot confirmed proximity fuse in Falcon missiles sourced from Sweden.

Thanks for this. Which model? (I seem to recall reading that the conventional model of the SARH AIM-26 DID have one, but that at least the US-built AIM-4 series was always lacking. Perhaps SOC could clarify or correct as required. If the missiles you're talking about are the IR version, that's quite significant.)

Second pilot said that IR Falcon didn't have proximity fuse (around 1985), while SARH version had...
Conflicting sources are lovely.

Maybe they got some of the un-upgraded IR weapons initially? Sweden did license build the thing and also imported some initially, so maybe they transferred extant imported models first.

I spent good portion of yesterday on the library of local aviation museum. I found following information about Falcon missiles in Finnish use from Air Force manuals dated 1990.

There were 3 radar guided versions:
RB 7S
RB 27S
RB 27S (AF)

I'm assuming that these are related with Hawé modifications on Draken radar.
Old manual only mentioned RB 7S so, I'm thinking that it is the original radar guided Swedish RB27 missile.
Hawée modification I increased the ECCM capability and Hawée II gave basically look down / shoot down capability and made the missile effective in lower altitudes.
This missile was with influence fuse (according to the Swedish museum information), no mentioning on the influence fuze on handling manuals. (edited)

Infrared Falcons
Only mentioned version (there may have been other, as manuals are not complete, but only this version was mentioned in oldest manuals)
RB 8S

edit:
Handling manual for part common for both IR and SARH:

Handling manual for the ground crew states: "Cover the influence fuze" when handling the missile. The page was marked changed on 1990 (like most of the pages in the manual, the change date may not have anything to do with the influence fuse).


I would say that this is the confirmation for the influence fuze on Swedish IP Falcons.... (edit error in my part on reading the manuals)

On the attachment item 1.5 place cover on seeker and influence fuze. In Finnish: Aseta ohjuksen etsinpään ja lähisytyttimen suojukset paikoilleen. (Google translate doesn't know lähisytytin, but finnish wikipedia knows it and http://fi.wikipedia.org/wiki/L%C3%A4hisytytin and it links to english proximity fuze)

 

[SOC]

Good stuff. I'm willing to bet that Rb 7 and Rb 8 are probably typos, I've never seen the missiles referred to anything other than Rb 27 or Rb 28.

One question would be the image at the bottom of the sheet. On the left you've got a cover on the IR missile's seeker head, while on the right you've got covers on the SARH missile's seeker head and proximity fuzes. Do they show any other covers on the Rb 27, or is it just that image? They might also be directing ground crews messing with the IR missile to cover or otherwise avoid touching the contact fuze in the wing leading edges. From what I can tell the fuze fittings were at least still present on Rb 28s, and they'd be far more fragile than the rest of the metal airframe.

 

[tiikki]

Good stuff. I'm willing to bet that Rb 7 and Rb 8 are probably typos, I've never seen the missiles referred to anything other than Rb 27 or Rb 28.

Finnish Air Force calls them RB7S and RB8S

One question would be the image at the bottom of the sheet. On the left you've got a cover on the IR missile's seeker head, while on the right you've got covers on the SARH missile's seeker head and proximity fuzes. Do they show any other covers on the Rb 27, or is it just that image? They might also be directing ground crews messing with the IR missile to cover or otherwise avoid touching the contact fuze in the wing leading edges. From what I can tell the fuze fittings were at least still present on Rb 28s, and they'd be far more fragile than the rest of the metal airframe.

Damned... After looking more of those pages the part of the guide mentioning covers was for both missiles. The Rb27 nor Rb28 specific parts are about disconnecting the motor. And as you mentioned, the pictures show two covers on Rb 27 and one on Rb28.

You are expert and I'm a novice no doubt about that
What would be your conclusion on this? Finnish Rb28/Rb8S did not have proximity fuze?

 

[tiikki]

Or actually, in Finnish use I've seen Rb 28S, Rb 8S, Rb 28 and Rb 27S, Rb 27, Rb 7S. Finland is Suomi in Finnish and the S comes from there. On SARH version the Finnish missile lacked some of the guiding channels (Finnish used only channel G, Swedish A-F)

 

[Orionblamblam]

Hrrrrmph. I could swear that I saw discussion of a recently published book about the Falcon. I think written by a forum member. But searches turn up nothing. Have my years of wild hedonism finally caught up with me? Or is there really such a book?

 

[Arjen]

Reply #37 of this thread has a link:

A revised version is online here (I haven't changed the downloadable file yet):

http://www.ausairpower.net/Falcon-Evolution.html#mozTocId859220

Major alterations include the addition of some data regarding the GAR-11's nuclear warhead, and the mention of another GAR-9 derivative I managed to miss. There's also an annex at the end with some info from a former F-102 pilot, which is where the GAR-11 info came from.

He's got some other good stuff that'll be worked in there eventually, along with some more data I've got. And regarding the Genie, I've decided to include it in the next revision as a separate annex or chapter, not sure which one yet. Probably a separate chapter between The Ultimate Falcon and Employing the Falcon, which will then allow me to incorporate Genie firing information into the employment chapter. That'll probably necessitate a title revision as well, but whatever.

Not sure if that's what you're looking for, though.

 

[SOC]

That's it (there's also a download link to the PDF "book" version there as well), and updating it is currently #3 on my list of crap to do.

 

[tiikki]

That's it (there's also a download link to the PDF "book" version there as well), and updating it is currently #3 on my list of crap to do.

If you like I can visit the local museum library and take some more photos of Finish guides and pictures of the missiles in the exhibit. Please inform which data would be most interesting.

 

[sferrin]

That's it (there's also a download link to the PDF "book" version there as well), and updating it is currently #3 on my list of crap to do.

Any chance there is some information on the original AIM-47's solid motor? (XM59 as I recall.) The one that was suppose to enable Mach 6 speeds but had to be replaced because of problems with cracking (I think).

 

[Grey Havoc]

Via HP&CA, this gem:

Original link.

 

[SOC]

I saw that! I mention it in there someplace. That story's been floating around for a while.

 

[overscan (PaulMM)]

Preliminary GAR-X shape and size details from Convair report XP-8-042 (Installation of GAR-X on F-102A)

SDASM Archive

 

[sferrin]

 

[sferrin]

The doors on the F-106 are definitely a lot slicker than those on the F-22/35.

 

[sferrin]

 

[publiusr]

I would have loved to have seen that...

 

[sferrin]