Saturday, October 13, 2018


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 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 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:


  1. Drawings (c) by Kim Simmelink