Early F-4Ds had an important alteration in their secondary air-to-air armament. While the AIM-7 Sparrow was retained, AIM-9 Sidewinder wiring was removed and replaced with equipment for the Hughes AlM-4D Falcon missile.
In late May 1967, the first F-4D Phantom II aircraft began arriving at Ubon to equip the 555th TFS. This new D-model placed a much greater emphasis on improved bombing capability.
Block 26z-33ag aircraft were the first to feature a fully operational F-4D avionics suite. This included replacing the basic, manually depressed sight of the F-4C with the General Electric (GE) AN/ASCU-22 lead computing optical sight set (LCOSS). These jets were also equipped with wiring for GE’s SUU-23/A gun pod. Although this new variant was primarily developed to enhance tactical bombing performance, it ultimately proved to be the most successful MiG killer of the Vietnam War, achieving 44 confirmed kills.
As Peter E. Davies notes in his book USAF F-4 Phantom II MiG Killers 1965–68, the early F-4D also featured a major change to its secondary air-to-air weapons. The AIM-7 Sparrow was kept, but the wiring for the AIM-9 Sidewinder was removed and replaced with systems to support the Hughes AIM-4D Falcon. The Falcons were carried in pairs on ‘slant two’ LAU-42 launchers, which incorporated piping for gaseous nitrogen to cool the missiles’ infrared seeker heads. This setup was evaluated at Eglin AFB in late 1965 during Project Dancing Falcon, and, at least in theory, the missile offered better detection capability than the AIM-9B, along with a larger acquisition envelope.
Air Defense Command had been using the Falcon since it reached Initial Operational Capability (IOC) in 1956, making it the world’s first fully guided air-to-air missile, with development efforts dating back to 1947. The USAF’s decision to adopt it as its primary close-range dogfighting missile was heavily influenced by inter-service rivalry, as the AIM-9 program was largely driven by the US Navy. According to Brig. Gen. Robin Olds,
`The word was that the Air Force, in a fit of righteousness, wanted an air-to-air missile they could call their own. The powers in Systems Command must have tired of having to kowtow to the Navy in testing and improving the AIM-9. They wanted a missile of their own devising and picked the existing AIM-4 as a solution. What a farce!’
His views stemmed from hard-earned experience with a missile system that exhibited serious technical flaws from the very beginning. Chief among these was the relatively long cooling time (at least 4.2 seconds) required for the Falcon’s seeker head, which prevented the AIM-4 from achieving a rapid lock-on and launch in the midst of a dogfight. Once its liquid nitrogen coolant was depleted, the missile became unusable.
The USAF’s Red Baron report characterized the AIM-4’s firing sequence as the most complicated of any air-to-air missile in service. Another serious drawback was the lack of a proximity fuse—unlike the AIM-9B, which meant that the missile’s small 7.5-pound warhead had to score a direct hit to destroy a target. Due to its poor combat record with the 8th TFW, development of a planned AIM-4H version was ultimately canceled.
The US Navy, for its part, proceeded with the development of an upgraded Sidewinder, the AIM-9D, which achieved a significantly higher hit probability than the AIM-9B. Although the AIM-9B had some moderate success when used on the F-4C, there was a clear need for a more capable missile. Maj. Gen. Dick Pascoe, who had flown with both the early Sidewinder and the Falcon in combat, was thoroughly familiar with the limitations of each weapon.
‘On my 6 January 1967 mission, I was able to maintain a position of advantage behind the second element of MiG-21s after I had shot the leader down. However, even though I fired three AIM-9s during the turning engagement, none found the target due to the weapon’s limitations. To address this generally recognized deficiency, a decision was taken to adapt existing AIM-4s to the F-4 as a potentially enhanced dogfighting weapon. Having flown the AIM-4-equipped F-102, I was familiar with the Falcon’s characteristics and limitations. Unfortunately, the AIM-4 was declared unfit (at Ubon) before I was able to convince the 8th TFW of its merits.
`While the Falcon’s flight dynamics were better than the AIM-9’s, the arming and firing process was more complex—certainly in a dogfight environment. The AIM-4 was a hit-to-kill weapon, and to achieve the required accuracy, it used nitrogen to supercool the seeker head before launch. This design is effective but adds a degree of complexity to the missile launch sequence. In the all-weather interceptor application, the added complexity was managed by the weapons system. However, in the F-4D application, the pilot had to decide to fire the weapon 90 seconds prior to it actually leaving the aircraft, as he had to push a button to discharge the nitrogen and then fire the missile within a lapse time of between two to three minutes after the nitrogen had been discharged! Not an easy task to complete in a 6g turning fight.’
Like Robin Olds, fellow ‘Wolfpack’ MiG-killer Brig. Gen. David Williams also disliked the AIM-4.
`Pilots much preferred to employ the Sidewinder because it was more reliable, required less cockpit procedure, and incorporated a proximity fuse. The AIM-4 was a hit-to-kill missile, and the pilot had to go through a “Mickey Mouse” (“hit the tit” twice) cockpit procedure to cool the missile’s seeker head, uncage the gyro, and then secure a “high tone” IR signal from the seeker’s head before he could launch the missile. As a consequence, we tended to rely more on the Sparrow because we appreciated its proximity fuse and the missile’s reliability.’
The ‘Wolfpack’s’ first combat action using AIM-4D-armed Phantom IIs occurred on 2 June 1967. A MiGCAP formation made up of two F-4Cs carrying Sidewinders and two F-4Ds tried to pick off MiG-17s flying in a defensive ‘wheel’ of eight aircraft. During the engagement, two Falcons, four Sparrows, and three Sidewinders were launched—but not a single missile hit its target.
A second chance came three days later, during the air battle in which Pascoe and his ‘GIB,’ 1Lt (later Capt) Norm Wells, scored their second kill. Once again, the MiGCAP formation combined both F-4Cs and F-4Ds. Maj. Gen. Pascoe recalled,
‘It was decided to fly the AIM-4s in positions 1 and 3 and the AIM-9s in positions 2 and 4 in each flight. That mix was intended to back up the Falcons with Sidewinders in the event that the Falcons didn’t perform up to expectations. In my case, that was how it worked out. After Col. Olds had either fired or “stepped through” his AIM-4s, I downed a MiG-17, hitting it with both of the AIM-9s that I fired. The result was that the AIM-4 was declared unfit for combat in engagements requiring visual acquisition, another of the many lessons learned in the South-East Asia conflict, which have led to the array of devastating weapons systems available to out-fighting forces today.’
The Falcon’s failure during the June 1967 missions ultimately led to changes. By mid-January 1968, the 8th TFW’s MiGCAP setup was revised with the introduction of a dedicated ‘Fast CAP’ flight tasked solely with countering MiG-21s. These F-4s carried AIM-9s instead of AIM-4s, a 600-gallon centerline tank in place of the gun pod, and a single ECM pod.
Going back to the 5 June 1967 mission, Col. Olds’ first two shots from ‘Chicago 01’ as he broke into a MiG defensive ‘wheel’ were AIM-4s, launched exactly according to the book. One missile failed to guide, and the other failed to leave the rail. Abandoning the AIM-4s, he then fired all four of his AIM-7s in boresight mode, but none of them tracked properly either. As a result, Col. Olds was deprived of his fifth victory and the status of jet ace.
USAF F-4 Phantom II MiG Killers 1965-68 is published by Osprey Publishing and is available to order here.
Photo by U.S. Air Force
