by Tommy H. Thomason

Wednesday, January 27, 2016

Grumman A-6B Iron Hand

29 January 2016: Still refining and correcting...

Thanks to Mick Roth and Rick Morgan, who generously provided most of the information and many of the illustrations for this post and then patiently answered my questions. However, this is still a work in progress and subject to their review (and comments from others for that matter).

The escalating air battle during the Vietnam War resulting in the introduction of the big SA-2 Guideline surface-to-air missile (SAM) by the North Vietnamese.
Various counters to it were successively employed by the Air Force and the Navy including electronic warning, evasive maneuvers, jamming, and anti-radiation missiles (ARM). The latter was the most satisfying, because—if successful—it resulted in the destruction of the SAM-site radar. However, the original ARM (the Shrike, which was based on the Sparrow air-to-air missile) had less range than the SAM, making an attack on a SAM site too much of a fair fight.

The solution was the repurposing of the U.S. Navy's big ship-based SAM, the RIM-66/SM-1 Standard Missile, from anti-aircraft to anti SAM-site radar.

Since it was a bit big (pushing 1,400 lbs) for the little A4D Skyhawk then being used for the Iron Hand missions, the resulting AGM-78 Standard ARM missile was to be carried by modified Grumman Intruders, designated A-6B. As the mission equipment, tactics, and missile evolved to be more effective, the A-6Bs were continuously updated. From a modelers standpoint, there were four different configurations (see for a more detailed and less informal description of airplane and missile).

Mod 0 Early: As shown on the following picture of a test-bed NA-6A, the main external configuration feature was the addition of APS-107A/B* elongated-diamond homing antennas on each side of the upper part of the radome and the lower side of each engine nacelle along with wing and stabilizer tip antennas. Several other small antennas are also circled. The BDA (Bomb Damage Assessment) aft antenna and right side ER-142 DF antenna wouldn't be visible in this picture; the forward BDA antenna and the left side ER-142 antenna could be hidden behind the crew ladder.  Note the LAU-77A/A adapter on the outboard pylon (it is missing the DECM boom that would be on the A-6Bs) that was used to configure it to carry the Standard ARM missile

* The APS-107B was part of the Mod 0 Update. It allowed the employment of the AGM-78B/C/D missiles in addition to the AGM-78A. There was no external change from a modelers standpoint

The APS-107A/B homing antenna:

Forward fuselage antennas:
 There was also an aft BDA stub antenna under the aft fuselage.

Forward facing wingtip antenna:
Mick Roth

Rearward facing stabilator-tip antenna.
The combination of the wing and stabilizer-tip antennas provided 360-degree warning coverage.

Mod 0 Late: The major change was the replacement of the APS-107B with the ALR-55 and the ER-142 with the ALR-57, which was identified as the Mod O/1 Update.
US Navy photo via Tony Thornborough annotated by Mick Roth

The system changes did not affect the external antenna configuration or location with the exception of the Mod O and O Update diamond antennas when the APS-107 system was replaced. These might have been left in place, removed and covered by a blanking plate, or in at least one instance, the engine nacelle antennas were left in place and a radome without antennas installed.

Here the antennas have been removed and covered with a blanking plate.

The most obvious difference between the Mod 0 cockpit and that of an A-6A bomber's was the addition of a row of threat warning lights at the top of the instrument panel, a radar warning instrument for both the pilot and the bombardier/navigator, and the replacement of the B/N's attack-radar control stick (that radar had been removed) with a missile control panel.

Mod 1: This version featured a radome festooned with small antennas and a rudder modified with even more that covered the aft quadrant:
Bruce Trombecky via Mick Roth

The bottom of the rudder was modified to add a bulge that terminated in a faceted antenna mount/fairing; the position light was raised up over it.

The Mod 1 had a different wingtip antenna mount/fairing with an aft antenna added to provide 360-degree coverage without the need for an antenna on the stabilator tip.

 Mick Roth

 Photos from Squadron/Signal A-6 Walk Around, Mick Roth captions

The B/N center console reverted back to one more similar to the standard A-6 bomber's, However, the hand controller (slew stick) was only used for Standard ARM and APS-118 functions since the APQ-112 attack radar had been removed from Mod 0 and Mod 1 A-6Bs.

 There were only five Mod 1 A-6Bs: 149955, 151591, 151820, and 152616/7

PAT/ARM: These final versions of the A-6B were only distinguishable from the basic A-6A by the BDA (Battle Damage Assessment) antennas that were retained. They also got back their all-weather attack radar capability. Only three were so modified: 155628/29/30
Masumi Wada as annotated by Mick Roth

 The AGM-78:
National Museum of the United States Air Force

At some point after 1971, the A-6B ejection seats would have been changed from the GRU-5 to the GRU-7:
The major difference is the parachute housing, which changed from a metal "sugar scoop" to a plastic container.

Obscuro provides a 1/72 conversion for the A-6B Mod 1. See HERE. Unfortunately, it does not include the rudder modification but that's no hill for a stepper. Note that the pedestal provided was for the Mod 0 cockpit, not the Mod 1

Darren Roberts (Steel Beach Accessories) is planning to offer 1/48 and 1/32 A-6B conversions.

AGM-78 missiles are available from Eduard in 1/72 and 1/48. They are also reportedly included in the Hasegawa 1/48th Weapon Set and F-4G Wild Weasel kit. A 1/32 AGM-78 is available from AMS Resins but you have to contact Harold directly.

Thursday, January 21, 2016

Photo Panthers: F9F-2P vs. F9F-5P

To start with, the F9F-2 and F9F-5 were similar but different in detail. The -5 had an eight-inch plug in the forward fuselage ahead of the engine inlet, a somewhat larger vertical tail, and other more subtle changes. See

However, although the -2P and -5P have very different noses, most published pictures and illustrations that are identified as being of -2Ps are actually -5Ps.

The -2P was a depot-level kludge to convert a fighter for the photo-reconnaissance mission. (The F2H-2P was a few months away from operational use and a jet photo-reconnaissance capability was needed in Korea.) The existing nose cone was modified by blocking off the gun ports and adding a flush clear panel in its upper left side. The armament was removed and replaced with a platform for an oblique camera. The nose cone slid forward for access to this camera.

The gun sight was removed and replaced with a camera control panel.

On at least some F9F-2Ps, a camera window was also added on the underside of the nose cone for a downward facing camera,

The nose cone had to be removed for access to this camera.

The F9F-5P, on the other hand, was a bespoke photo-reconnaissance jet procured from Grumman. It had a 12-inch longer nose. Only the front part slid forward. The aft section was accessed by a sideward-hinged door.

The F9F-5P had a flat-panel windows on each side of the nose and two downward-facing windows under the nose. There were various combinations of cameras that could be installed.
The pilot was provided with a large viewfinder in lieu of the gun sight to be able to accurately position the airplane for pictures of the terrain and objects of interest directly below it. There was a small clear panel for the periscope aft of the downward facing windows. There was also one just forward of them in the sliding section for a small movie camera.

Wednesday, January 13, 2016

F4H/F-4 Phantom Ram Air Inlet Mysteries

28 January 2016: Corrections and additions.

 At the base of the leading edge of the vertical fin of the F4H/F-4 Phantom, there is a ram air inlet.

In the illustration of the original inlet above, two ducts lead downward from it, but didn't show where they went after that. Presumably, it is for cooling air for something, probably the aft fuselage and also to insure that fuel vapors don't build up there. An early Phantom illustration is of no help (the horizontal line goes from the fuselage fuel tanks to the fuel vent at the aft end of the fuselage).
I had thought that duct might have gone down to the louvers just above the afterburner on each side of the fuselage, although the air vented from them was more likely from the engine compartment.

The best guess now is that the air was piped down to the interior of what appears to be double-walled side panels aft of the engine tailpipes and exited through a large slot on either side of the aft end of the tailhook.
In a McAir inboard profile, it's referred to as a "blast cone cooling air duct". The pilots were told that the inlet was for "aft compartment cooling",

Still unanswered is why the configuration of the inlet changed over time.

For the F-4A/B/C and probably the D, it was a simple inlet almost flush with the top of the fuselage as shown in the first illustration with what appears to be a very shallow boundary-layer-removal slot at the bottom of the opening that dumps the slow moving air into the aft fuselage. (This is F-4A BuNo 145310 currently being refurbished for flight.)
Craig Kaston Photo

Then with the J/E/F, a horizontal splitter was added in front of the opening. Below the horizontal splitter, a curved wedge was provided to move the slow-moving air in the fuselage boundary layer outboard of the fin.

But wait, there's more: On the K/M, the Spey-powered Phantoms, the lower side of the inlet curves inboard so that the horizontal splitter extends slightly outboard of it for a short distance aft of the inlet.
Iain Ogilvie

That little exterior curve does more closely match the shape of the internal ducting. (Note that the internal louvers have disappeared with the introduction of the horizontal splitter.)
Bill Spidle

So: Why the ongoing "improvements"? There couldn't have been a great deal of benefit because it appears that the Bs were never retrofitted with the later inlet, not even on the Bee Line when they became Ns. It's possible that with the introduction of the Spey, the cooling being provided was marginal, necessitating a tweak in the inlet to reduce duct losses.

F-4 Phantom Outboard Pylon and MER

A recent post on a modeling website describing an F-4 Phantom build stated that the inboard bombs had been left off the MER on the outboard pylons because of an interference with the main landing gear doors. Knowledgeable respondents pointed out that the MER was angled outboard for just that reason. That was news to me, although as it turned out, it shouldn't have been.

The MER (Multiple Ejection Rack) was the end result of a Marine A-4 pilot wanting to make the Skyhawk more than a one-trick pony. His relatively crude creation allowed him to carry several more bombs. However, it came into being after the F-4 outboard pylon location became established and as it turned out, was a bit too close to the landing gear doors. The solution was to angle the pylon outboard. As usual, the Navy and the Air Force, although forced to have a common designation for the Phantom, elected different solutions.
The Navy MER was mounted on an adapter to the original outboard fuel tank pylon*, which was mounted vertically.

The Air Force pylon was angled outboard starting at the lower wing surface, allowing a slightly smaller angle outboard to provide the same clearance.

* See

Tuesday, January 5, 2016

Grumman S2F/S-2 Monograph

If you're building an S2F/S-2 model or just interested in early carrier-based antisubmarine warfare or the S2F itself, you'll want to buy this monograph and won't be disappointed. It's at the printer now. Steve Ginter should have it on his website soon (