Tuesday, August 25, 2015

AIM-95 Agile Missile

Lt_Ayers_and_prototype_AIM-95_1970 Since we have been talking about the AIM-82 and AIM-95, here is some additional info from Ron Hinkel via Mark Nankivil on how the AIM-9L took over the AIM-82/95 role:

“AIM-9L Background #1 - Way Back
In following the recent postings about Sidewinders, and the Aim-9L in particular, it is time I share what I know on how that came about. What I know and think about this subject comes from my assignment as Air Weapons Officer at Naval Weapons Station, China Lake from the fall of 1973 to summer 1976. Air weapons included Air-to-Air and Air-to-Ground. Naturally, Sidewinder projects fell under air-to-air, so I can tell you today that I was there when it was being decided as to what the off-boresight limit and other parameters were to be developed in that missile. IMHO, as good as the -9L was, we, the Navy, gave up too much all-aspect air-to-air weapons capability to accommodate the USAF's lack of success. I'll let you judge later.
Recall the environment of the times; early 70's. Navy performance with F-8s and F-4's getting some Mig kills. AF frustrations with guys in the saddle only to have their Sidewinders go stupid or miss when they should have hit. This was the era of Pirate and the others teaching Navy tactics to them and the start of Top Gun. Now comes a big thrust by USAF brass to stop the embarrassment. Their arguments were that they needed a better Sidewinder, bought so many more missiles than the Navy, and for that they should be given a larger say as to what the next version would be. So they threw money at the project and DoD accepted, even giving them project Management control. The PM at China Lake for the AIM-9L was a LTCOL USAF. I know because I got to shoot one of the development missiles that did not kill the target. The recorded data showed the missile launch to be right in the designed test parameters, but that a circuit failed some where in the weapon system. Obviously, that flaw was fixed as your reported good results in the fleet show.

AIM-9L Background #2 - The Off-Boresight Battle
ACEVAL/AIMVAL Did any of you participate in this 1974-75 Air Farce forced "flyoff to determine what off-boresight capability the next joint missle should have?" In my duty as Air Weapons Officer, I was the Navy operational tech rep to the initial planning and evaluation with NAVWEPSCEN China Lake as the technical folks. China Lake and I were pushing for the 45 degree capability already proven available to our satisfaction and originally planned for the -9L by the Navy. The AF whose mentality at the time, if you recall, was based upon an F-4 with a gun pod, of course, disputed this. That, of course, turned it into a real fighter that could stay with the Migs. What they really wanted was an AIM-9B with minimal off-boresight, but one that worked. So the flyoff went on and the result was a compromise. I think that the AIM-9L off-boresight was set at one half of the 45 degrees and a head on capability was also required. That also had some effect on lowering the off-boresight angle because it was perceived that you had to be closer to head on for the missile performance to catch the guy if he turned away at launch. That does make sense, but I say perceived in that I don't recall if there was any real engineering quality data gathered during these flights to support the operational portion of this decision. Help us if you know something different out there. Technically, you have to remember that all Sidewinders, including the -9L, were fin controlled. That reduced all Sidewinder turning ability two ways. The missile had to go forward for a while to pick up speed before it could turn and the size of the fins were limited because the missile had to fit on the aircraft.

AIM-9L Background #3 - The Problem of Off-Boresight Capability
The issue of off-boresight capability was not, IMHO, fully understood completely by even the good guy Navy operators in the ACEVAL/AIMVAL decision loop. Frustrated as we were at China Lake at the time that was somewhat understandable because the whole thing was a humongous political football. And, its awful hard to see how really close the technology is to what you want without having at least some of the system in your hands trying it operationally. Then, having to fight for it in a David and Goliath scenario. They were in a tough position. Eventually, Navy Washington showed us all the real decision. They wanted the Air Force's money, so we were all told to sit down and shut up which we did. It has become even more understandable from your comments about the uncertainty and flux in training, tactics, Top Gun, etc. going on in the fleet.
The problem with off-boresight capability is that it goes against the grain of our training, our weapons to date, and our inherent instinct to best the other guy. We need to show him we are superior to him by getting behind him in the perfect firing so that he can't get away and blasting him out of the sky. Funny, when you think about it. How gallant is slipping up behind some unawares guy just motoring back to base and letting him have it. Not necessarily superior because it was Smiling Jack and he had the performance aircraft to kick your ass, if he had seen you. Further, I don't recall hearing any WWII ace say something like, "I got 123 kills, really 140, but I don't count those where the guy obviously didn't see me."
Yes, those individual kills win battles, especially a lot of them. But wars are won by attrition. That is reducing the number of enemy aircraft faster than he does yours. If I recall correctly, top gun was created in order to improve the kill ratio of Navy F-8s and F-4s to third world Migs. It is particularly important when one side or both have a fixed or limited supply of assets to draw from. IMHO, in the case of an aircraft carrier, a lot faster. What off-boresight capability gives you is a lesser need both air space and aircraft performance wise to be in the position to achieve your kills and very much less exposure to your being in position to be killed.
AIM-9L Background #4 - The Off-Boresight Capability we could Have Had (Agile)
I turned up at China Lake Naval Weapons Center as the newly appointed Air Weapons Officer and Agile Project Pilot in October 1973. The AIM-95 Agile was an air-to-air missile being developed as an advanced replacement for the AIM-9 Sidewinder short-range air-to-air missile. The Navy intended it for the F-14. The US Air Force was developing the AIM-82 missile to equip the F-15 Eagle at the same time. Since both missiles were more or less identical in their role, it was decided to abandon the AIM-82 in favor of the Agile.
The Agile was equipped with a sophisticated, high tech (at the time), Gallium-arsenide infrared band seeker by Hughes. The seeker head had a large off-boresight capability (0 to +/- 165 degrees practical) lock-on capability. The pilot targeted it by using a Helmet Mounted Sight (HMS). A solid-state missile rocket engine was used to provide the go power. Control was achieved by thrust vectoring giving it superior turning capability over the Sidewinder. This combination of greatly improved IR sensor, large off-boresight acquisition and thrust vectoring control would allow Agile to be fired at targets which were not directly ahead•thus making it far easier to achieve a firing position. Did it ever,
I must have flown 20 or 30 test flights with the Agile seeker on F-4s. It was amazing in its ability to detect targets and lock on and track the target aircraft to all angles. Hughes did a fantastic job. The helmet mounted sight to acquire targets worked beautifully. I could climb, dive, stay level, roll inverted, zoom climb or dive, keep my speed up approaching the target or slow to simulate 1 vs. 1 turning and that seeker would lock on as soon as I put the sight on it and pressed the button. What made it even more outstanding was its ability to discriminate the target with a high sun caused hot white cloud background? I easily acquired the target aircraft at off-boresight angles of 0 to about 170 degrees. Now don't restrict your visualization of this to the plane of the wings. You have the whole half cone above you, and you could look down; essentially, wherever you could look you could acquire and shoot a launch and leave Agile. The easier acquisitions occurred when you didn't have to stretch your neck to make them; like between 30 degrees off the nose to about 135 degrees. Tactics, oh yeah! How about this idea? You are about to enter a many on many situation in deuce formation. You both keep the speed up or accelerate, if necessary. You pull up through the fur ball shoot two on the way up. Pull over the top, and shoot two on the way down and run like hell. Eight kills without not much chance of your getting hit. I mean it was going to be that good, I think.
The official line is: The AIM-95A was developed to a point where flight tests were carried out including test firing at China Lake (Not true, to my knowledge) and inclusion in the ACEVAL/AIMVAL Joint Test & Evaluation conducted with both the F-14 and F-15 at Nellis AFB in 1975-78. AIMVAL analysis results indicating limited utility of higher high boresight capability and high cost resulted in opinion that it was no longer regarded as affordable and the project was cancelled in 1975. Instead both the Air Force and Navy developed an improved version of the Sidewinder for use. Although this was intended to be an interim solution, in fact the AIM-9 continues in service today.
The Soviet Union did embark on development of an advanced high boresight SRM with thrust vectoring and subsequently fielded the AA-11/R-73 Archer on the MiG-29 in 1985. NATO learned about their performance due to the German reunification and efforts began to match or exceed the R-73's performance with the IRIS-T, AIM-9X and MICA IR programs.
Author's Note:  "If these used thrust vectoring it was Agile again. If not, how could they compete?"
Ron Hinkel
2 August 2015”

Wikipedia has a good write-up on the AIM-95 here

Another good article on AIM-82/95 is here


Anonymous said...

The Air Force wanted a whole bunch small cheap missiles that could be fired in salvos in a dogfight. The Navy needed a few big missiles that could defend a bomber in one shot without the bomber deviating from the course to the target too much. Politicians unrealistically wanted one missile that could do both jobs.

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