Saturday, October 13, 2018

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 only carried two on each launcher - inboard and lower stations)
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


6 comments:

  1. Hi
    Amazing site with amazing topics! :D

    After reading this great article, I was wondering a couple of things:

    1) Sidewinder carriage was almost always possible ( unless, I think, there was a Maverick or an ARM missile on the same pylon , or something with wings so big that the Sidewnder's rails would be in the way ), but was it always possible to use them before dropping what was on the pylon?

    For example, I've saw that the IAF Phantoms did carry Sidwinder only on a rail under which there was no bomb installed on the TER( weird loadout with a sidewinder and two bombs, one on the lower point and one on the Sidewinder opposite ).

    It *seems* like the sidewinder's wings would collide with the bomb on the TER if launched before the bombs were dropped, but I have absolutely no info on that ... Do you have any info ?


    2) I've seen some photos of a ter with 2 MK-83 ( 1000 lbs ) , I guess the TER is able to handle it but at a reduced g factor, correct?
    Since the limit should be 750 lbs for each weapon installed.

    3) The rail seems to be installed at an angle ... that angle should be the angle of attack ( or better, the opposite of the angle ) at which the Phantom would have flown for most of the time, correct? Probably the AoA for the cruise speed, to minimize the drag , correct?


    Again, great site, ad thanks for everything :D

    ReplyDelete
  2. Hi
    Amazing site with amazing topics! :D

    After reading this great article, I was wondering a couple of things:

    1) Sidewinder carriage was almost always possible ( unless, I think, there was a Maverick or an ARM missile on the same pylon , or something with wings so big that the Sidewnder's rails would be in the way ), but was it always possible to use them before dropping what was on the pylon?

    For example, I've saw that the IAF Phantoms did carry Sidwinder only on a rail under which there was no bomb installed on the TER( weird loadout with a sidewinder and two bombs, one on the lower point and one on the Sidewinder opposite ).

    It *seems* like the sidewinder's wings would collide with the bomb on the TER if launched before the bombs were dropped, but I have absolutely no info on that ... Do you have any info ?


    2) I've seen some photos of a ter with 2 MK-83 ( 1000 lbs ) , I guess the TER is able to handle it but at a reduced g factor, correct?
    Since the limit should be 750 lbs for each weapon installed.

    3) The rail seems to be installed at an angle ... that angle should be the angle of attack ( or better, the opposite of the angle ) at which the Phantom would have flown for most of the time, correct? Probably the AoA for the cruise speed, to minimize the drag , correct?


    Again, great site, ad thanks for everything :D

    ReplyDelete
    Replies
    1. I wasn't a weapons troop, so I am by no means a definitive source. I was a crew chief, and I know in my years working on the F-4Ds at RAF Woodbridge, I don't remember launching a bird without the sidewinder rails. But we also rarely carried TERs. We mainly carried SUU-21 practice bomb dispensers, Mavericks, a few times LGBs, and of course nuke shapes. During exercises we would carry Mk.82 concrete bombs, but that was also rather rare and I don't remember if they used TERs. A weapons troop could tell us if the TER ordinance and the sidewinders used the same wiring harness which could be a reason they didn't carry both. But I just don't remember ever seeing the sidewinder rails removed in my two years on the F-4D.
      2. Yes as far as I know.
      3. Yes it is at an angle. I really need to look back in my notes, I know I found what that angle was, but in my old age I don't remember. As I recall the F-4 flew at a slightly nose up attitude, so the rail was mounted slightly pointed down.
      The rails were mounted with spacers (standoffs) which created a bit of distance between the pylon and LAU-7. There were at least three different types that I have seen and there may be more. There was a large rectangular standoff, there were two round standoffs, and there were some that were merely arms which spaced out the rail and lowered it a bit. I will have to do some research on my material and do an blog on that.

      Delete
  3. Ok, I know in Europe in the 70s we flew with sidewinder rails (with spacers) almost all of the time. In fact I don't recall ever seeing one removed except for maintenance. But I wasn't a weapons troop so I could be wrong on this. And we flew with Mavericks and LGB and TERS.
    I have never seen a picture of a plane equipped with ordinance on the inboard pylon loaded with sidewinders during Vietnam War. It could have happened but probably was very rare. But in these cases it could have been just a weight issue, because to get the most out of the mission they wanted the max amount of AG ordinance.
    Yes when the plane was on the ground the sidewinder rail was clearly at a slight angle. Somewhere in my notes I have what this angle was. I think the F-4 flew with a slightly nose up attitude in cruise, but I am not sure of this not being a pilot.

    ReplyDelete
    Replies
    1. Thanks for the info.
      So, ok, sidewinder rails were almost always there, great piece of information!
      What do you mean with "spacers" ? Is it something on the sidewinder launcher or something on the pylon between the pylon itself and the TER?

      Also, 3 Mavericks seems to be too huge to be fitted with the sidewinder rail too ( but I'm just guessing here ) .

      The weight argument is indeed very good ... maybe Phantoms CAN load sidewinders, but won't because they won't need them for an air to ground ...
      That's the main issue for us modellers and enthusiast: to be able to find a realistic loadout and understand the "why".

      I've also found a great site ( well, for us modellers ) that wrote about the same argument, but it too wasn't able to sort the issue out ...
      http://thecombatworkshop.blogspot.com/2018/01/usaf-f-4s-and-their-perplexing-lack-of.html

      What puzzles me is that the Israeli Phantoms were loaded in a such strange way, with 2 bombs and 1 sidewinder on the pylon ( to avoid bombs and sidewinder one on top of another ) and even come out with a fuselage adapter to load and launch a sidewinder from one of the two front fuselage sparrow launchers (the other being used by an ECM pod ).

      The weight argument does not hold for the Israelis F-4 , even if it holds for everything else...
      I've also read that USAF had more planes, and so they can afford to dedicate a plane for ground attack only, while USN can not and so USN had phantoms with bombs and sidewinders ...
      And we did saw pictures of phantoms with bombs and sidewinders, but only USN phantoms ...

      I don't know, this still is an open question, I think ...


      Anyway, MANY MANY thanks for the reply,and GREAT SITE! Keep it up! :D

      Delete
  4. Note the dagger-not-saber wingpylons. Silly Aussies cut the wrong part off the sprue! :-]

    https://www.vintageleatherjackets.org/attachments/69-7211c-jpg.32474/

    ReplyDelete

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