Alternative AAM history: AIM-4H enters service.

AIM-4s working fine for USAF units. Probably some kind of ego issues more than with the machines. Be it maintenance crews not wanting to put on the correct equipment to use them, or pilots refusing to use them correctly. AIM-4s didn't need to ride in trucks to get to the planes, which may be why AIM-7 was so unreliable. So its really maintainers or pilots where the responsibility rested. Nobody was going to own up to manufactured incompetence when both benefit from the result.
 
The F-4D fighter units in South Vietnam and Thailand weren't properly trained in how to use the AIM-4D along with the F-4D not having the proper fire-control system, the ADC units on the other hand in the CONUS (And Alaska) had interceptors with FCSs designed for the AIM-4 AND were properly trained to use the Falcon.​
 
NMaude said:
the ADC units on the other hand in the CONUS (And Alaska) had interceptors with FCSs designed for the AIM-4 AND were properly trained to use the Falcon.
Click to expand...
The question that begs itself here is how much difference the ADC pilots' training would have made, without the FCS they were familiar with to back them up.
 
MadRat said:
AIM-4s working fine for USAF units. Probably some kind of ego issues more than with the machines. Be it maintenance crews not wanting to put on the correct equipment to use them, or pilots refusing to use them correctly. AIM-4s didn't need to ride in trucks to get to the planes, which may be why AIM-7 was so unreliable. So its really maintainers or pilots where the responsibility rested. Nobody was going to own up to manufactured incompetence when both benefit from the result.
Click to expand...
They worked fine for ADC units that had the FCS the missiles were designed for. And the overarching SAGE system that talked to those FCS.

While over Vietnam, there was no SAGE system. So I suspect that even the F-102 or F-106 squadrons would struggle with IR Falcons, but the radar Falcons would be fine.

AIM-4s had 2 issues:
  1. Lack of proximity fuze on all versions.
  2. Too little cooling for the IR seeker versions.
Prox fuze is fixable, just takes money. If you could talk the USAF into the cheap option, you steal the Sidewinder prox fuze. Downside is that Sidewinder is a Navy program and the USN is the enemy (of the USAF budget).

Cooling may require significant redesign for the planes, to fit a much larger liquid nitrogen bottle. 5-10x larger bottle! It would not be a problem providing the liquid nitrogen for the cooling, as each base has a way to make liquid oxygen already. And liquid nitrogen is a byproduct of the process to make liquid oxygen.
 

View topic - F-106 - Gun and AIM-4's combined? • F-16.net

Military aviation forum since 2003, with high quality discussion focusing on the F-16, F-35 and F-22 jet fighters and the C-130.
www.f-16.net

Gums posted 06 Nov 2008
"...The AIM-26 came off of a rail, so prolly a smooth launch.

3) The Falcon missiles did not have a sensor fuze. They had to actually hit the target.

The AIM-4 was ahead of the 'winder at that time, as it had a "cooled" sensor and much better maneuverability. Unfortunately, the launch sequence was designed for the 101, 102 and 106 armament system. Integrating it on the Phantom was a bitch, although the thing did prove to be more accurate than the 'winder or Sparrow.

For example: The ADC birds cooled the sensor when the rails extended, without any special pilot switch actions. So we had "x" seconds to fire or the thing wasn't cooled. The Phantom installation required the pilot or GIB to command cooling prior to launch. The AIM-4 also locked on before launch or wouldn't go, best I remember. When we were evaluated on inspections, the weapon simulator would show if the thing had actually "seen" the target.

later,

Gums sends ..."

He is probably the best public source of historical experience for F-101 and F-102. (edit: He did not fly F-106)
 
Last edited:
Scott Kenny said:
Prox fuze is fixable, just takes money. If you could talk the USAF into the cheap option, you steal the Sidewinder prox fuze. Downside is that Sidewinder is a Navy program and the USN is the enemy (of the USAF budget).
Click to expand...
Erm, no. Not that simple.

First of all, installing the Sidewinder fuze won't work. It's basically a section of Sidewinder's body, to install it on Falcon it would need to be comoletely reworked.

Second - the Falcon warhead is SMALL. Adding proximity fuze would inevitably force to reduce its even more. So you would have proximity fuze, but with warhead so small, that its close burst would not be much different from direct hit.


Scott Kenny said:
So I suspect that even the F-102 or F-106 squadrons would struggle with IR Falcons, but the radar Falcons would be fine.
Click to expand...
The IR Falcons of internally-carried versions - not the externally-carried AIM-4D, that F-4 used in Vietnam - have no fire control differences from SARH ones. The seeker was pre-locked on target by plane FCS, using data from plane radar. The missile was launched with seeker already cooled and "tracking".
 
Last edited:
Dilandu said:
It's basically a section of Sidewinder's body, to install it on Falcon it would need to be completely reworked.
Click to expand...
Indeed.

Sidewinder is narrower than Falcon, so it seems like it should be an easy lengthening job (install a fuselage plug and put the prox fuze in). However, that lengthening and adding of weight potentially has major knock-on effects on the missile's response to manoeuvre demands, especially for a missile as small and light as Falcon is.

So no, you can't jury-rig it in the field and yes, you do actually have to recertify the whole missile. And while you're doing that, you might as well design a better proximity fuze to start with, maybe put in a bigger warhead, a better motor... and thus you're right back where you started with XAIM-4H before it was cancelled.
 
pathology_doc said:
So no, you can't jury-rig it in the field and yes, you do actually have to recertify the whole missile. And while you're doing that, you might as well design a better proximity fuze to start with, maybe put in a bigger warhead, a better motor... and thus you're right back where you started with XAIM-4H before it was cancelled.
Click to expand...
Exactly. Especially considering that Sidewinder's fuze would likely be far too long-range for AIM-4 small warhead - it could trigger the detonation at the distance too big to cause any damage. And since its pre-digital technology, the only way to change setting (since Sidewinder did not have such option planned) would be to re-wire the whole fuze.
 
Dilandu said:
The IR Falcons of internally-carried versions - not the externally-carried AIM-4D, that F-4 used in Vietnam - have no fire control differences from SARH ones. The seeker was pre-locked on target by plane FCS, using data from plane radar. The missile was launched with seeker already cooled and "tracking".
Click to expand...
Without SAGE ground controllers, however.
 
Scott Kenny said:
Without SAGE ground controllers, however.
Click to expand...
SAGE was an advantage to a single-seat aircraft, but GCI still provided voice. The difference in implementation between GCI and SAGE was digital versus voice. SAGE still relied on GCI controllers to put the information in. Neither underperforming GCI nor lack of SAGE explains misses because it still comes down to pilot operating the system correctly. What was described about Falcon use during the Vietnam War literally made the case that a majority of the misfires were pilot errors and the majority of misses (was again) pilot errors. They likely did not want to use them, especially anyone that was already familiar with the Sidewinder's growl.
 
MadRat said:
What was described about Falcon use during the Vietnam War literally made the case that a majority of the misfires were pilot errors and the majority of misses (was again) pilot errors.
Click to expand...

Unlike ADC pilots the F-4C/D pilots in South Vietnam weren't trained in how to use AIM-4Ds including their strengths and weaknesses, acquisition and launch envelopes plus limited GN2 to cool their seekers. F-4 pilots derisively referred to the AIM-4D as the "Hughes Arrow".​
 
Last edited:
Dilandu said:
And since its pre-digital technology, the only way to change setting (since Sidewinder did not have such option planned) would be to re-wire the whole fuze.
Click to expand...
I suspect the detonation distance could be tuned fairly easily with a resistor in the right place. It was designed to be simple after all.

More likely, they would adapt their own proximity fuze from the AIM-26.
 
pathology_doc said:
Indeed.

Sidewinder is narrower than Falcon, so it seems like it should be an easy lengthening job (install a fuselage plug and put the prox fuze in). However, that lengthening and adding of weight potentially has major knock-on effects on the missile's response to manoeuvre demands, especially for a missile as small and light as Falcon is.

So no, you can't jury-rig it in the field and yes, you do actually have to recertify the whole missile. And while you're doing that, you might as well design a better proximity fuze to start with, maybe put in a bigger warhead, a better motor... and thus you're right back where you started with XAIM-4H before it was cancelled.
Click to expand...
No, this would not be a field fix. It'd be a Hughes-developed-at-USAF-insistence fix.

There was already a difference in length between the SARH and IR Falcons. Adding a couple of inches to both should not matter much. Or rather, adding a couple of inches to the SARH Falcons, since we're already at 1970 and the AIM-4H finally has a prox fuze.


pathology_doc said:
I suspect the detonation distance [of the Sidewinder prox fuze] could be tuned fairly easily with a resistor in the right place. It was designed to be simple after all.
Click to expand...
Exactly.

Remember, Sidewinder is basically APKWS for 5" rockets.


pathology_doc said:
More likely, they would adapt their own proximity fuze from the AIM-26.
Click to expand...
Or however the AIM-4H got its prox fuze.
 
MadRat said:
SAGE was an advantage to a single-seat aircraft, but GCI still provided voice. The difference in implementation between GCI and SAGE was digital versus voice. SAGE still relied on GCI controllers to put the information in. Neither underperforming GCI nor lack of SAGE explains misses because it still comes down to pilot operating the system correctly. What was described about Falcon use during the Vietnam War literally made the case that a majority of the misfires were pilot errors and the majority of misses (was again) pilot errors. They likely did not want to use them, especially anyone that was already familiar with the Sidewinder's growl.
Click to expand...
Having SAGE or GCI in Vietnam would have gotten the F-102/106 pilots pointed in the right direction, but the problem was the ROEs.

When you "must" have positive Visual ID of the target you're de facto in a dogfight and 2 minutes of cooling is very likely not enough. Even if the pilots were operating the system correctly in the F-4s.

But the SARH Falcons would at least not had that problem. So I think F-102s or 106s would have been better with the SARH Falcons than with the IR Falcons.
 
Scott Kenny said:
There was already a difference in length between the SARH and IR Falcons. Adding a couple of inches to both should not matter much.
Click to expand...
It really isn't as simple as that. If you add weight and length:
1) The centre of gravity moves relative to the centre of pressure (which the length change will itself move).
2) The pitching moment changes, which means that the relations the autopilot has wired in with regard to control response per unit input will no longer be correct.

It's possible that there's enough imprecision in the system anyway that such changes fall within acceptable bounds. But they might not.
 
I'd say one interesting (but rather fundamental) consequence (for which Aim-4 cancellation is only partially responsible) is that for decades, almost entire world designs fighter aircraft around weapons, rather than fighter weapons to fit into aircraft.

Almost no exceptions, which is all more interesting since in US case, bay is to a significant extent informed by AMRAAM, which itself was developed to match F-16...
 
Ainen said:
I'd say one interesting (but rather fundamental) consequence (for which Aim-4 cancellation is only partially responsible) is that for decades, almost entire world designs fighter aircraft around weapons, rather than fighter weapons to fit into aircraft.

Almost no exceptions, which is all more interesting since in US case, bay is to a significant extent informed by AMRAAM, which itself was developed to match F-16...
Click to expand...
I dunno, weapons bays were going out of style in the late 1950s.
 
Ainen said:
I'd say one interesting (but rather fundamental) consequence (for which Aim-4 cancellation is only partially responsible) is that for decades, almost entire world designs fighter aircraft around weapons, rather than fighter weapons to fit into aircraft.
Click to expand...
There were no alternatives, frankly. 1950s - 1960s technology was bulky and demanding; building the fighter around the weapon system was essentially the only available solution. The AIM-9 Sidewinder was essentially the first truly crossplatform weapon outside this paradigm, but it was rather limited in performance.
 
Dilandu said:
There were no alternatives, frankly. 1950s - 1960s technology was bulky and demanding; building the fighter around the weapon system was essentially the only available solution. The AIM-9 Sidewinder was essentially the first truly crossplatform weapon outside this paradigm, but it was rather limited in performance.
Click to expand...
Sort of yes, but all Hughes AAMs were visibly short, i.e. they were meant for internal carriage. It doesn't necessarily makes them worse for bulky technology - as internal/conformal weapon can afford to be fatter.

Arguably that was part of their downfall, when one by one, Valkirye got canned, F-106A soundly lost to navy Phantom, and YF-12B was axed together with any hope of new USAF interceptor.
Dilandu said:
Weapon bays on fighters were a specific USAF gimmick; as far as I know, no one else fielded interceptors with such weapon arrangement.
Click to expand...
And when USAF got the chance, they immediately introduced them again. :)
 
Dilandu said:
Weapon bays on fighters were a specific USAF gimmick; as far as I know, no one else fielded interceptors with such weapon arrangement.
Click to expand...
I mean even on small attack/strike/bombers. Buccaneer went to Jaguar and Tornado, F-111 went to Strike Eagle, and all the older birds that I'm weak on.
 
Dilandu said:
Weapon bays on fighters were a specific USAF gimmick; as far as I know, no one else fielded interceptors with such weapon arrangement.
Click to expand...
The weapons bays were a luxury for big increases in aerodynamic performances with secondary benefit of protecting payloads from wear and tear from being exposed to the slipstream. Interceptors that used them required additional sophistication when bulk numbers were desired. Technical implementation was requiring better technology to break through production limitations. Weapon technologies increased the survival of ordnance faster than advancement of airframe technologies. Modern production of stealth airframes makes implementation more critical than ever. That's why they are so popular today.
 
Dilandu said:
But for completely different reason. And immediately started to complian, that weapon loads did not fit inside)
Click to expand...
Self-inflicted problem, they did not specify that the F-22 should have bays deep enough to hold 2000lb weapons. As-is, it can hold 1000lb weapons just fine. Allegedly learned that lesson for F-35.
 
Scott Kenny said:
Self-inflicted problem, they did not specify that the F-22 should have bays deep enough to hold 2000lb weapons. As-is, it can hold 1000lb weapons just fine. Allegedly learned that lesson for F-35.
Click to expand...
There are layout problems with every arrangement(1- or 2- engined); deeper bay takes different arrangement, coming with different set of compromises. F-22 ultimately does the thing it was designed for in the most straightforward way; proposal with too many ideas lost.
 
Dilandu said:
The AIM-9 Sidewinder was essentially the first truly crossplatform weapon outside this paradigm, but it was rather limited in performance.
Click to expand...

Aside from being very simple for an AAM the AIM-9 wasn't designed for any one particular fighter jet, this is also why the AIM-9C (The only SARH variant) didn't last long (It was designed specifically for the F-8D/E).
 
NMaude said:
this is also why the AIM-9C (The only SARH variant) didn't last long (It was designed specifically for the F-8D/E).
Click to expand...
Ron Westrum notes this in his book about the Sidewinder's development and history. His opinion on AIM-9C's downfall echoes somewhat my thinking about weapon systems, in that they can sometimes be too tightly developed for further growth. In this case it wasn't so much being tied to the aircraft as tied to the radar it carried, and when the radar went out of service, the missile followed (although some of them got converted to SideARM and saw their moment of glory in 1991).

Sparrow avoided this fate, since while not exactly a multi-platform missile in as broad a sense as the Sidewinder, it was never restricted to just one in-service airframe the way AIM-9C and AIM-54 were (F3H/F-3, F-4, F-14, F-15, F-16, F-18, Tornado, Viggen {indirectly via Skyflash} - did I miss any? Yeah, I did - Cutlass, albeit only in its primitive beam-riding form.).
 
Last edited:
I can't see why the F-4's fire-control system couldn't have been modified to illuminate a target for the AIM-9C.

Talking about radar guidance it occurred to me the other day that Hughes might've had better luck with its' XAIM-4H programme if it had also developed in parallel a SARH variant (Call I the XAIM-4J).
 
NMaude said:
I can't see why the F-4's fire-control system couldn't have been modified to illuminate a target for the AIM-9C.
Click to expand...
Short version? What's the point? The Phantom could already fire Sparrows, it had no need for radar guided Sidewinders. The Navy only developed them to give their Essex class carriers and their Crusaders some all weather capability when performing the Fleet Air Defense mission.
 
Last edited:
AIM-9Cs could've given limited all-weather ability to the likes of the F-5E/F Tiger for example or for other fighters that were too small to carry the AIM-7.
 
NMaude said:
AIM-9Cs could've given limited all-weather ability to the likes of the F-5E/F Tiger for example or for other fighters that were too small to carry the AIM-7.
Click to expand...
And they would be a rather nice addition to Chaparral SAM - only required a small illumination-only radar slaved to optical sight (yes, its my idea fix)
 
NMaude said:
AIM-9Cs could've given limited all-weather ability to the likes of the F-5E/F Tiger for example or for other fighters that were too small to carry the AIM-7.
Click to expand...
True, postulating their ability to fit the Crusader's system in their noses. Speaking of noses, the problem with a radome is that it isn't just weather protection for the radar. As the dish 'looks' through various angles, the radome's apparent thickness and refractive index change, and the signal can be distorted if it's not what the radar/radome combination is tuned for.

So even if you can gut the Tiger's nose and cram the radar and associated electronics in there, for the dish it will be like looking through an entirely different prescription of glasses, with equally serious consequences for the SARH illuminator beam.
Dilandu said:
And they would be a rather nice addition to Chaparral SAM - only required a small illumination-only radar slaved to optical sight (yes, its my idea fix)
Click to expand...
It's not that far from there to a hypothetical Chaparral Blindfire as electronics get smaller and lighter and the ability to fit such a system to a small DD or FF increases.
 
Dilandu said:
And they would be a rather nice addition to Chaparral SAM - only required a small illumination-only radar slaved to optical sight (yes, its my idea fix)
Click to expand...
That would have required a pretty big 400hz generator to power it. Because if I'm sticking an illumination radar on Chaparral, I'm going to push for an air search radar or two. possibly as simple as that on Phalanx CIWS.
 
Scott Kenny said:
That would have required a pretty big 400hz generator to power it. Because if I'm sticking an illumination radar on Chaparral, I'm going to push for an air search radar or two. possibly as simple as that on Phalanx CIWS.
Click to expand...
This would overcomplicate things a lot. Just use a simple radar, AN/VPS-2 style (the ranging-only radar on Vulcan gun), slaved to the optical sight. It would solve the main problem of early Chaparral models - inability to engage targets head-on. Any kind of search/track capability could be added on later models.
 
pathology_doc said:
Speaking of noses, the problem with a radome is that it isn't just weather protection for the radar. As the dish 'looks' through various angles, the radome's apparent thickness and refractive index change, and the signal can be distorted if it's not what the radar/radome combination is tuned for.

So even if you can gut the Tiger's nose and cram the radar and associated electronics in there, for the dish it will be like looking through an entirely different prescription of glasses, with equally serious consequences for the SARH illuminator beam.
Click to expand...

This is all taken into account when a radar is being designed.
 

Similar threads

Back
Top Bottom