Air to air weapons effectiveness
Posted by picard578 on June 15, 2013
Measures of effectiveness
To determine effectiveness of weapons, first we must determine what are measures of that effectiveness. Weapons are designed to kill, and to preferably kill opponent before he can kill you. But opponent wants to do the same thing, so he will try to survive – which means prevent you from killing him, and kill you. Best way to achieve advantage is by surprise; further, weapons should be as resistant to countermeasures as possible.
Historically, engagements were always between flights and squadrons, more rarely entire wings. This means target saturation. It also means that pilot is always in danger of getting killed by somebody even as he tracks the target; resultantly, time required for tracking the enemy should be reduced to minimum. But even side with inferior weapons was able to win if it has superior personnell or superior numbers as Germans have proven in France in 1940 and USSR in 1941/2. But once USSR learned from mistakes, and adjusted both training and tactics correspondingly, its numerical superiority decided the war.
Thus most important aspect of weapon is how it affects user’s skill. Second is how many weapons can be sent to and supported in fight; only third is combat capability of weapon itself. Further, more expensive weapon is not necessarily more effective even when numbers are ignored. More on it here. As for aircraft weapons, their primary function is to kill enemy quickly, reliably and at minimal danger to the user.
AIM-7 Sparrow was thoroughly tested by USAF, and in R&D tests it achieved Pk of 80-90%, with operational tests resulting in Pk of 50-60%. In Vietnam, Pk dropped to 8-10%, with many US pilots firing entire AIM-7 loadout, from visual range and from perfect tail position, only to watch all missiles miss.
AIM-9B achieved 15% Pk, which increased to 19% for USN AIM-9D. USAF used AIM-9E and J which scored Pk of around 20% less than B and D models, 12% – 15% Pk. Soviet copy of AIM-9B missile, Atoll, achieved 12% Pk. Radar-guided missiles fared worse. AIM-7D achieved Pk of 8%, which increased to 10% for AIM-7E. AIM-7E2, introduced in last year of the war to correct AIM-7Es fusing problems, achieved Pk of 8%. Despite having long spin-up time, M61 20 mm rotary cannon achieved Pk of 26%.
Out-of-envelope launches only resulted in 7% of non-kills, and 46% of attempts were failures to launch or guide, compared to 30-37% failure rate of AIM-9.
In Indo-Pakistani war of 1971, Pakistani gun- and Sidewinder- -armed F-86s achieved 6:1 exchange ratio against Indian MiG-21s, Sn-7s and Hunters. Subsonic Folland Gnat, smallest fighter in the world, managed to kill several F-86s without suffering losses.
Immediately after the 1973 Arab-Israeli war, claims were made than 1/3 of Israeli 251 air-to-air kills were due to Sparrow, and that Sparrow achieved Pk of 50%. As it turned out by 1978, only 12 Sparrows were fired, achieving either none or a single kill, with majority of Israeli pilots refusing to carry Sparrow at all. Only 4 of these firings were made from beyond visual range, and a single kill made might have been from beyond average visual range (5 nm) despite the fact that Israel does not claim it as a BVR kill. As many large fighters are visible well beyond 5 nm (up to 15 nm if engine smokes heavily) it is possible that kill in question was a visual-range one. Out of remaining kills, 2/3 were made with IR missiles and 1/3 with guns, according to statistics avaliable; Israelis however credited 2/3 of their air-to-air kills in both wars to guns or to guns aided by initial missile launch. Syrian pilots hated MiG-23 and considered it a worse fighter than MiG-21. Israeli general Hod stated that in 1973 war radar was “essentially useless” and that only one or no kills were made by radar-guided missiles.
In Bekaa Valley in 1982, 8 kills were with guns, 54 with IR missiles and 12 with radar-guided missiles; more than half of kills were made by “multirole” F-16 despite it being primarly tasked with bombing missions. All radar-guided missile kills except one were from visual range. Total of 5 BVR shots were made, making data range very low. It is known however that Syrian pilots were rather incompetent, with Israel winning 73-0 victory. After the war, Israeli General Mordecai Hod had stated that. had Israelis swapped planes with the enemy, outcome would have been the same.
In Falklands war, British have achieved 19 kills in 26 launches, for a Pk of 73%. Harriers themselves saw little fighting after first day, and almost all kills were against bomb-loaded aircraft. Further, Harriers used only IR missiles, majority of which were fired from rear hemisphere, thus achieving surprise. Argentine pilots did not try to outmaneuver missiles – even when they did notice they were being fired at, they used Vietnam war tactics which did not work with all-aspect missiles used by Harriers. At the same time, all Argentine radar-guided BVR Matra missiles missed.
During entire Cold War, only 3 or 4 air-to-air kills were made from beyond visual range out of 60 – 61 shots made at beyond visual range, for Pk of 5 – 6,6 %. All BVR kills were carefully staged outside combat.
Combat results from 1991 and 2003 invasions of Iraq and 1999 war in Yugoslavia are used to prove that AIM-120 can achieve BVR dominance. Yet these are misleading even if actual statistics are true.
Serbian MiG-29s were suffering from lack of spares since 1996, and resources were spent on riot police instead of maintaining aircraft; their pilots were flying 20 hours annually. To put this into perspective, US pilots even at worst of times flew more than 10 hours per month. Systems on MiG-29s were malfunctioning; on most aircraft, neither radar nor RWR functioned. Despite that, some pilots managed to evade several BVR missiles. One MiG-29 shootdown attributed to AIM-120 could also be a case of Serbian SAM engaging in fratricide; that would make AIM-120 performance as 5 kills in 13 launches, a Pk of 0,38.
As for Iraq, situation was similar with its air force in both wars, with pilots usually failling to take any evasive action once radar lock occured. Thus it is logical that USAF success rate would be similar, and it was. In Desert Storm, 41 USAF aerial victories were achieved with anywhere between 5 and 16 kills made at beyond visual range. 2 kills were made with guns, 10 with IR missiles and 24 with radar-guided missiles. 88 AIM-7 shots were made, giving a Pk of 0,27. Out of 24 AIM-7 kills, at least 9 were from visual range. For F-15Cs, 12 AIM-9 launches resulted in 8 kills (Pk 67%), and 67 AIM-7 launches resulted in 23 kills (Pk 34%). It should be noted that F-16s made 36 AIM-9 launches, of which at least 20 were accidental due to poor control stick ergonomy, and made 0 kills. US Navy F-14s and F-18s fired 21 AIM-7s for one kill (Pk 4,8%), and 38 AIM-9s for two kills (Pk 5,3%). As it can be seen, Pk for missiles fired by multirole F-16s and F-18s (0% and 5%) was far lower than that of missiles fired by singlerole F-15s (67% WVRAAM and 34% BVRAAM), suggesting that pilot training is the primary factor in missile performance. Relative Pk of IR WVRAAM and RF BVRAAM fired by air superiority aircraft stayed same as in Vietnam, with IR WVRAAM Pk twice that of RF BVRAAM.
Between Desert Storm and Allied Force, USAF achieved 3 kills with AIM-9 and 3 with AIM-7, with at least one AIM-7 kills being visual range. Further, on Jaunary 5th 1999, two MiG-25s (equipped with radars for a change, which they used to illuminate US fighters) violated southern “no-fly” zone, and succeeded at evading 3 AIM-7, 1 AIM-120 and 2 AIM-54 missiles, all fired by US fighters from beyond visual range.
These results immediately point to AIM-7s operational tests, when it achieved 50% to 60% Pk against non-maneuvering drone targets.
Problem in using radar-guided BVR missiles against capable opponent is that surprise was always one of dominant factors in air-to-air combat. But radar is an active sensor, and thus warns the opponent of one’s presence.
Further, kills have to be made in as short amount of time as possible. Times for launching and guiding weapon that are longer than 3 and 5 seconds become exponentially more lethal to the pilot, and USN TopGun school teaches (or at least taught) that in one-versus-many and many-versus-many engagements one should never pursue the steady state maneuver or same path for more than 7 seconds.
Time from firing opportunity to breakaway is 3 – 6 seconds for gun, 5 – 7 seconds for IR missile and 10 – 15 seconds for radar-guided missile. Radar-guided missile’s time increases if target is maneuvering or using ECM. Missile’s problems, however, are somewhat reduced by off-bore capability, which means that attacking fighter can maneuver while attempting to gain a lock.
Another problem is suceptibility to countermeasures. Already-fired missiles can be evaded by hard maneuvers, and both gun and missile firing solutions can be defeated by maneuvers. IR missiles’ lock on can be defeated by aircraft flying out of seeker’s field of view, whereas with radar guided missiles, it is possible to avoid or break radar lock (“beam turn” and “doppler turn”), as well as prevent or delay radar lock with jamming. For most of these counters, target must be aware that it is being targeted, which makes fully-passive IR missiles inherently superior to radar-guided ones.
But even greater problem than missiles’ relative ineffectiveness is its impact on user’s skill and on number of aircraft that can be put into the air. Aircraft that rely on BVR combat are more complex than dogfighters, which makes them more expensive for same weight as well as less reliable. Fighters with BVR focus are also larger and heavier than WVR fighters, which results in even higher cost and worse dogfighting performance. BVR-centric F-4E cost 3 times as much per flight hour as F-5E, and F-15 costs 4 times as much per flight hour as F-16. Stealth fighters are even worse: F-22 costs 12 times as much per flight hour as JAS-39.
During Six Day war all shootdowns achieved by Israeli were by cannon. It dropped to 70% during Attrition War, 30% during Yom Kippur war, and 7% in Lebanon Interdiction in 1972. During 1982, only 4 shootdowns scored by British fighters were by gun, and US only scored 2 during Desert Storm.
But one should not assume that gun is outdated. During Vietnam war, cannon-armed aircraft performed far better than missile-only aircraft. Of F-105Ds 27,5 kills, only 2 were by missile. Cannon-armed F-8 achieved best kills:loss ratio of all US aircraft in Vietnam, 6:1 as opposed to average score that was 2,15:1 for USAF and 2,75:1 for USN.
In total, F-100 achieved 1 victory with cannon; F-105 achieved 31 victory, of which 3 were by AIM-9 and 28 by cannon. F-4 achieved 156 victories, of which 67 with AIM-7, 70 with AIM-9 and 17 with cannon. F-8 achieved 19 victories, of which 14 were by AIM-9 and 5 with cannon. A-7 achieved 1 victory with cannon. Total is 52 victories with cannon, 87 with AIM-9 and 67 with AIM-7.
In air combat, length of burst is rarely greater than 1 or 1,5 seconds as longer bursts have no application, with standard being 0,5 s. Gattling guns require 0,3 to 0,6 seconds to achieve full rate of fire, while revolver cannons require 0,05 seconds to achieve full rate of fire. Result is that in 0,5 second burst, GIAT-30 achieves 8 MJ of energy, M61A2 ~4,3 MJ, M61A1 ~3,6 MJ, BK-27 ~4,9 MJ, and GAU-12U just above 6 MJ. Combination of heavy and destructive shell, relatively high rate of fire and high muzzle velocity makes GIAT-30 best fighter cannon in the world. Revolver cannons in general are more suited for ACM application than rotary cannons because of ACM requirement of using short bursts while maintaining high rate of fire.