THE F-4 INBOARD PYLONS

Recently a discussion on The F-4 Phantom II Group on Facebook caught my attention and I thought I would take the opportunity to outline the differences between the Navy and Air Force inboard pylons on the F-4.

First, we need to understand that the pylons used were originally designed for different purposes.

THE NAVY PYLON

The Navy versions of the F-4, as well as both Navy and Air Force RF-4s (and some early F-4Cs), utilize the LAU-17/A as their inboard pylon.  As the nomenclature suggests, its primary purpose is as a launcher not as a weapons pylon

LAU-17/A pylon

The LAU-17/A was designed to carry and launch an AIM-7 Sparrow III missile so that the F-4 could carry a total of 6 (4 on fuselage semi-submerged stations and one on each inboard pylons).

LAU-17A pylon with an AIM-7 Sparrow III Missile

When the AIM-7 wasn't carried, the inboard pylon could also be fitted with a launcher rail on each side to carry and launch the AIM-9 Sidewinder missile. The AERO-3/A/B allowed the LAU-17/A pylon to carry an AIM-9B missile only.  The LAU-7/A launcher rail allowed the LAU-17/A pylon to carry either the AIM-9B, AIM-9D, and subsequent Sidewinder missile. The launcher rail consists of a power supply for the electrical requirements of the missile, a mechanism which retains the missile during flight and releases the missile when fired, a nitrogen receiver assembly to provide coolant for the missile seeker head, and safety elements to keep the missile from accidentally firing during loading/unloading and during catapult launch and arrestment. (Note: Don't confuse the LAU-7/A launcher rail with the AERO-7A which was the launcher for the AIM-7 on the semi-recessed fuselage stations).

LAU-17/A pylon with the AERO 3/A/B or LAU-7/A launcher rail installed

AIM-9B Sidewinder on the AERO-3/A/B launcher rail
AIM-9D used the LAU-7/A launcher rail

As the F-4 began to perform air-to-ground missions an adapter was fitted to the inboard LAU-17/A pylons to allow the carriage of air-to-ground weapons.

LAU-17/A pylon with an adapter fitted

From this adapter, a wide variety of single weapons could be hung.  To carry more than one weapon on each pylon a TER (Triple Ejector Rack) could be installed  so that three weapons could be attached (up to 750lb. each.) Someone asked if the F-4 could carry a MER (Multiple Ejector Rack) on the inboard pylons. The answer is "No," MERs could only be carried on the centerline or outboard stations.

LAU-17/A pylon with adapter and TER fitted

When the adapter was fitted, the pylon cold also carry sidewinder rails as well.

THE AIR FORCE PYLON

The Air Force inboard pylon was sometimes called the MAU-12 pylon which refers to the Ejector Rack which was in the pylon.

MAU-12 pylon

Pylon with MAU-12 ejector rack removed for illustration

The ejector rack allowed the carriage of a single bomb, missile launcher or other weapons on the pylon. This pylon does not support the AIM-7 Sparrow III missile. But much like the Navy's LAU-17/A it could be fitted with a pair of AERO-3/B or LAU-7/A missile rails for the AIM-9 Sidewinder.  
The AIM-4D was used in combat in South-East Asia by some F-4D Phantoms, which were equipped with special LAU-42/A launchers for this purpose. However, it became soon apparent that the AIM-4D was ill-suited for the close-range dogfights encountered over Vietnam, and only 5 kills were achieved with the Falcon. The main problem of the missile was seeker cooling. The limited amount of onboard nitrogen coolant meant that the seeker could not be pre-cooled for any length of time, which in turn meant that it had to be cooled more or less shortly before firing, i.e. when close-range combat had already started. This cooling, however, took up to 5 seconds which is like an eternity in a dogfight, so that most targets were out of reach again when the missile was finally ready. Moreover, when the coolant was exhausted after several aborted launches, the Falcon was just useless dead weight, which had to be brought back to base for servicing. Another problem of the Falcon was the lack of a proximity fuze, which made it effectively a hit-to-kill missile. The AIM-4D was gradually withdrawn from use beginning in 1969, and by 1973, the AIM-4D was no longer operational with the USAF.

Pylon with AERO-3/B or LAU-7/A missile rail installed

AIM-9 Sidewinder installed on LAU-7/A

To carry more than one weapon on this inboard station a TER could be installed which increased the load to 3 weapons of 750 lb. each.  Several other adapter rails could be installed for different missiles as well.

Inboard pylon with single Mk82 practice bomb

Inboard pylon with TER for carrying three weapons

AGM-45 Shrike on LAU-34 launcher adapter

AGM-65 Maverick on a LAU-88 triple rail launcher (although the Phantom often only carried two on each launcher - inboard and lower stations. In Vietnam they would carry 3, and the IDF/AF would carry 3 when the range to their targets was short.)

As with the Navy's LAU-17/A, the Air Force could also install AERO-3/B Sidewinder rails on the pylon with some of the air-to-ground weapons installed.  Unlike the LAU-17/A the Air Force inner pylon could not be jettisoned.

For an interesting take on a modification of the Air Force inboard pylon found on Israeli and Turkish F-4s for carrying the Popeye missile see this post:  https://phantomphacts.blogspot.com/2013/10/israeli-mods-to-f-4-pylons.html

References:

1. Drawings (c) by Kim Simmelink
2. 
   

USAF F-4 Wild Weasel Aircraft before the F-4G

As the air war in Vietnam heated up, and the Soviet Union started supplying the North Vietnamese armed forces with better air defenses, the US Air Force realized the need for what became known as Wild Weasel aircraft to help suppress the SAMs.  Their first attempt was the F-100F Wild Weasel I aircraft.  While the F-100F was successful in suppressing SAM activity, it had one glaring weakness - speed.  The F-105s that were carrying out the bombing campaign found themselves flying very slow so they didn't out-distance the F-100s that were providing them protection.

A newer airframe was needed, one that could keep pace with the fighter-bomber formations without affecting their performance.  The two airframes that were available at the time were the F-105 Thunderchief and the F-4 Phantom II.  So the US Air Force initiated parallel programs fitting the Wild Weasel electronic suites into both aircraft.  This decision was based on the fact that there were a finite number of F-105s available as production had been closed on that aircraft, but the F-4 was still in production and could make up for combat loses with new aircraft.  This decision was to prove to be a very wise one.

(E)F-4C Wild Weasel IV

The first flight of a Weasel EF-105F took place on 15 January 1966, with the first flight of a Weasel F-4C expected to take place six months later in July of the same year.  But the F-4C conversion was very protracted and was beset by one problem after another.  The first problem was simply one of space.  While the F-105 and F-4 were roughly the same size, the F-105 was a single-engine aircraft where the F-4 with its two engines needed more real estate for fuel lines, control lines, and electronics just to operate. In short, the Phantom was a jam-packed aircraft and simply could not handle the added electronics and wiring required to properly install Wild Weasel equipment without some major revisions.

The (E)F-4C Wild Weasel went through several versions during development.  The first - Wild Weasel IV-A was a pod mounted system in the starboard rear missile well.  All of the Sparrow launch equipment and wiring were removed and replaced with the necessary electronics and wiring for the Wild Weasel mission.  Itek/ATI APR-25 and -26 RHAW  equipment was installed and a IR-133 Panoramic Receiver was put in the pod.  Sounds nice, but it didn't work, there was high interference coming from someplace and it gave either erratic displays or no display at all.  For a year the engineers beat their collective head against the wall, trying to understanding how the same system that worked well in the F-100F and EF-105F resulted in nothing but problems on the F-4.  Finally, Mr. C.K. Bullock the brain-child of the Wild Weasel I system installed in the F-100F was brought in as a consultant and he spotted the problem right away. The F-100 and F-105 both used a low-capacitance coaxial cable to carry the video information to the RHAW scopes to match the low-capacitance wiring of the of the aircraft. The F-4, on the other hand, used high-capacitance wiring on its systems so they had used high-capacitance wiring to incorporate the Wild Weasel installation.  The equipment wasn't designed for that.

With this problem solved, McDonnell began flight tests of the Wild Weasel 4, but further problems with vibration in the pod caused erratic displays, again delaying the program. Meanwhile, EF-105F Weasels were already in combat and were achieving a lot of success. It became obvious to McDonnell Engineers that somehow the system would have to be mounted internally.

McDonnell engineers began working feverishly on Project Wild Weasel IV-C, the reengineering effort to make room in the F-4C for the Wild Weasel components. Finally, in June of 1968, almost two years after the scheduled deployment of at least four (E)F-4C Weasels, the installation of the electronics in their new internal spaces was begun!  The new installation worked as advertised and the first operational (E)F-4C Wild Weasel was delivered to the 67th TFS based at Kadena AB, ROK on October of 1969. 

By this time is seemed that the Vietnam War was winding down and the EF-105Fs seemed to have things well in hand, so the (E)F-4Cs were not needed. But, the 67th TFS (E)F-4Cs would get a crack at combat. Because of the North Vietnamese Easter Offensive in 1972, President Nixon ordered a full resumption of bombing military targets in North Vietnam. Many more aircraft were committed to LINEBACKER operations than before and the sole Wild Weasel EF-105F unit in SEA could not handle the increased mission load. In October of 1972, the 67th TFS was alerted for combat duty and was sent TDY to Korat, Thailand, just in time for the LINEBACKER II maximum effort in December. The (E)F-4Cs performed admirably while flying over 460 missions

(E)F-4C Wild Weasel IV-C of the 67th TFS

The Wild Weasel (E)F-4C could be distinguished from a standard fighter only by the additional antennas on the aircraft. Around the nose at forty-live degree positions, were the four diamond-shaped homing antennas for the ER-142. Under the nose is a short blade antenna for the APR-26, and the two small stub Omni antennas directly in front of the nose gear wheel well are for the ER-142. Above the wing/fuselage juncture the raised square patch with a six-inch black circle is the ER-142 direction finding antenna. The antennas for the APR-25are found inside the chin fairing under the radome, and in a fairing on the trailing edge of the vertical fin. The rear cockpit was extensively modified with the upper right corner of the rear instrument panel being taken up with RHAW scopes and Threat Display Panels.

Thirty-six (E)F-4Cs were eventually modified to Wild Weasel IV-C specifications, twelve were assigned to the 67th TFS, Kadena AB, Okinawa, Japan; twelve to the 81st TFS, Spangdalem, West Germany; with the final twelve were assigned to the 35th TFW at George AFB, California - the new home of the Wild Weasels.

The (E)F-4C Wild Weasel was a very successful conversion once all the bugs were ironed out.  But not every weapon system is flawless.  The one glaring weakness with the (E)F-4C was the lack of the ability to use the AGM-78 Standard ARM missile.

(E)F-4C Wild Weasel IV-C of the 81st TFS

 

(E)F-4D Wild Weasel IV-B

There were two F-4Ds modified for the Wild Weasel mission under Project Wild Weasel IV-B. Both aircraft (65-657 and 65-660), were used to test the Bendix APS-107 Radar Homing and Warning (RHAW) system with an ER-142 panoramic receiver. Although the APS-107 gear was more sophisticated and accurate than the APR-25/-26 units and finally gave the (E)F-4 the ability to use the AGM-78 Standard ARM, it proved unreliable and erratic under combat conditions - at least for the Wild Weasel mission.

Several standard F-4Ds were used to test other programs relative to the Wild Weasel mission. One aircraft (65-0644) was used to test the AGM-78 Standard ARM missile, and several F-4Ds were used to perfect the AGM-65 Maverick missile.

(E)F-4D Wild Weasel V Test Platform

 At least two F-4Ds (66-7635 and 66-7647) were modified and equipped with the new McDonnell-Douglas designed APR-38 Warning and Attack System, the basis of the entire F-4G program. 

Originally, the F-4G program had originally been slated for installation in ninety F-4Ds, but the Air Force opted for the more modem F-4E.  This decision was made because the F-4E had much more internal volume available (especially once the gun was removed) and it was considered the cheaper option because the F-4E aircraft were much more up to date than the F-4Ds which would have to be brought up to the current state of the art. This was apparent in testing the (E)F-4D test aircraft which had to carry much of the electronics in a special canoe fairing which took the place of the port/forward missile launcher because of the lack of space.

The (E)F-4D Wild Weasel aircraft never progressed farther than a test platform for the Wild Weasel V electronics, so none entered active service in any USAF squadrons. 

(E)F-4D Wild Weasel Testbed

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References:

1. Drawings (c) by Kim Simmelink
2. Wild Weasel - The SAM Suppression Story, by Larry Davis

Revisions:

10/27/2013 - Original Post