Early World War II USN Paint and Markings

In the 1920 and 1930s, the U.S. Navy painted and marked its aircraft in a riot of color, starting with the upper side of the top or only wing being a bright yellow, the better to see the airplane in the event that it had to be ditched in the sea.

In the end, the markings indicated what carrier the airplane was flying from, which of the three-plane sections it was assigned to, and which plane it was in a section. Diagonal stripes on the wing provided a reference for the wingmen in flying formation. For more, see http://www.researcheratlarge.com/Aircraft/YellowWings/index.html

This marking of each airplane in accordance with its position in each section was reasonably practical at the time because the airplanes were relatively simple at the time and therefore close to 100% available. However, the high visibility and detailed marking would be a liability in wartime.

As a result, in 1940 the Navy decided to transition to a more subdued paint scheme and markings, first (and briefly) to an all-aluminum paint scheme and then to all-gray one at the end of 1940. I can't be sure, but this picture taken in March 1941 of an early F4F in test at NACA Langley looks like it is painted in the aluminum scheme:

Note that the national insignia is in four locations on the wings and there isn't one on the side of the fuselage, only "U.S.Navy."

This is a simplified timeline of the various paint and marking configurations through 1943*:

A:

Overall light gray, four-place insignia including the fuselage, white unit (VF-71) and airplane number markings

B:

Blue gray over light gray, four-place insignia including the fuselage, white unit (VS-2 and VF-2) and airplane number markings

C:

For a few months after Pearl Harbor, the powers that be thought that blue-on-blue ("own goal") incidents might be minimized by increasing the size of the markings and adding tail stripes and another pair of national insignias to the wings. One unintended consequence was that the red circle in the US national insignia was even more likely to be taken for the Japanese "meatball." Carrier captains were not enthusiastic about the visibility of the markings either so canvas covers were devised to cover them when the aircraft were parked on deck.

Note that the side markings are black on this airplane and the squadron number has been omitted.

D: The six-place configuration of the national insignia was retained but all red was deleted:

E: With the introduction of the reduced visual signature tri-color scheme, the number of national insignia was once again reduced to four.

Note that this is the Norfolk repaint of the original paint scheme (see http://tailspintopics.blogspot.com/2010/01/ww-ii-color-scheme-anomaly.html). I don't have an explanation for the brilliant white side markings that include the squadron number other than VF-17 hadn't arrived in the war zone yet. There was not only no reason to conceal the airplane identification but some benefit to doing so (increasing the likelihood of joining up on the right section leader and being dissuaded from buzzing, or flathatting as it was known then).

F: For some reason, the lesson about not having red markings in the Pacific theater was forgotten and the national insignia was briefly changed in mid-1943 to add a red surround along with white bars.

 G: The red was replaced by blue:

Note that compliance with the directives shown on the timeline above was delayed by months in some instances. Except for deletion of red markings, which might have begun to occur even before authorization, there was usually no urgency to comply not to mention capability to do so. Repaint would be accomplished at the next overhaul, which might be a year or more in the future. Production changeover also required time for the manufacturer to create the necessary documentation, receive approval for it, and implement it, preferably after using up existing inventory of parts painted in the old scheme. Exceptions were therefore not uncommon. For example, in this widely published picture of Jim Thatch and Butch O'Hare reportedly taken in April 1942, the national insignia is missing from the upper right wing. This suggests that when the change to larger and six-place insignia and to add rudder stripes was dictated four months earlier, the squadron painted on the stripes (and subsequently deleted the squadron number from the fuselage) but didn't bother to add the additional national insignia or increase the size of the existing ones.

Scott Tait asked about the validity of six-place national insignia with a white bar, no surround. As it happens, at least VMF-222's Corsairs in the Solomons were marked that way. Whether they didn't have blue-gray paint to mark out two of the insignia, didn't want to add red to the insignia, etc. is not known to me. Note also that this particular insignia and arrangement also skips step E, going directly from D to an approximation of F/G.

* There is a similar post on this subject on my U.S Navy Aircraft History blog: http://thanlont.blogspot.com/2011/06/brief-f4u-corsair-oriented-history-of.html

Are You Going to Believe Me or Your Lying Eyes? II

It is well known that the major external differences between the A4D-1 and A4D-2 Skyhawks were the inflight refueling probe and the externally ribbed rudder. Also the vortex generator arrangement but that was much more subtle.

 But here is A4D-1 BuNo 137821 with an inflight refueling probe:

(The little pods on the stores stations are intended to house four 2.75-inch folding-fin rockets; they were the original armament for the F4D Skyray. I don't know why they were being carried here. Increased weight, space for instrumentation?)

Here is the first production A4D-2 BuNo 142082 with the solid -1 rudder and rudder damper on the middle rudder hinge:

 (It also has the -1 vortex generator arrangement on the fuselage and wing.)

Here is A4D-2 BuNo 142095 with the externally ribbed rudder but it doesn't have the inflight refueling probe:

(Also note the slight mismatch of the nose cone and forward fuselage as indicated by the edge of the dark gull gray anti-glare panel and the then-standard 150-gallon tanks.)

These, of course, are extreme examples of flight test and very early production airplanes but they illustrate why model kit manufacturers might have trouble getting every configuration detail right.

J79 Exhaust Nozzles

There are two different J79 afterburner nozzles, "short" and "long." The -8 engine in the F-4B/N, almost all of the Blue Angels F-4Js, A3J-1s, and some RA-5Cs; and the -15 in the F-4C/D have the short nozzle. The -10 engine in the F-4J/S (except for most of the Blue Angels F-4Js) and some RA-5Cs; and the -17 in the F-4E have the long nozzle.

Dave Aungst created a good visual differentiation of the two nozzles from kit parts:



I'll refer to the "non-moving ring" as the "collar." However, it turns out that the ring/collar does move. Also, although his illustration leaves the impression that the -8 engine is notably shorter than the -10, the engines are about the same length.*

Since these two parts are for F-4 Phantom kits, the difference in length of the afterburners shown above is primarily the result of a small difference in the airframe structure if it's represented correctly on the kit: a short versus wide end to the fuselage structure at the opening for the afterburner nozzle. Note that the some of the difference relative to the "step" in the heat-resistant panels in the pictures below may be caused by the angle from which each picture was taken but according to a pretty-good McDonnell lines drawing, the aft end of the -10/17 nozzle does extend 1.28" aft of the -8/15 nozzle's. (The difference in the width of the sheet metal at the forward end of the nozzle is about 3".)

The location of the end of the nozzle relative to the airframe is very inconsistent on static display F-4s and RA-5Cs. This appears to be more common than I would have thought, and even occurs on the same aircraft.

(Picture by John B.)

Some static display airplanes also have the nozzles closed down, which makes the -8/15 nozzle very different in appearance (and much shorter) and the -10/17, a bit shorter. However, the nozzle was only in this position when the engine was running and not in afterburner.

A closed-down -8/15 nozzle is rare (actually, very unlikely) on flightworthy F-4s and RA-5Cs when they are shutdown.

The gray rectangle on the -8/15 drawing is the location of the exposed portion of the -10/17 nozzle. The forward exposed end of the -10/17 nozzle is farther forward as shown in the photos above. Also note the movement of the collar when the -8/15 nozzle closes down for non-afterburning operation. The movement of the collar into and out of the fuselage opening results in some "polishing" of it.

 Craig Kaston Photo

The interior of the two different nozzles is very different (the one on the left is in a museum aircraft and appears to be located much farther forward than it should be, not to mention a screen has been installed to keep birds and critters out):


The -8/15 nozzle has longitudinal ribs on the inside of the petals whereas the -10/17 nozzle has a relatively smooth inner surface. The difference in ejectors is depicted in a Rockwell International maintenance publication:

The presence of the -8 versus the -10 in the RA-5C is much less obvious than shown above in most pictures because the collar is in the shadow of the horizontal stabilizer. As with the F-4, it appears to me that the end of both nozzles is very close to the same location relative to the airframe fairing above the nozzle. (Again, static display airplanes, particularly the RA-5C at the Pima Museum, can't be trusted in this regard.) According to Craig Kaston's research, the -10 was installed in RA-5C BuNos 156608-156643 and the same airframe change (AFC-328) was used to modify nine existing RA-5Cs of early vintage: 146702, 149276, 149287, 149298-9, 149301. 150824, 150831, and 151630. The incorporation of the change is apparent by the difference in the sides of the engine inlet and the extension of the wing inboard leading edge to the front of the inlet.

*A now defunct GE webpage listed the -8 and -10 as having exactly the same length. It may be that the -10 engine was installed slightly farther aft to help resolve a forward cg problem. One stated but perhaps apocryphal reason for the Navy F-4s not getting a nose-mounted gun like the Air Force F-4E is that it would have moved the empty cg too far forward in light of the Navy's requirement for relatively low-speed takeoffs and landings.

Thanks to Craig Kaston for his observation of the -8/15 collar position and photo and to Mark Nankivil for the pretty good McDonnell drawing that I used to depict the nozzle position.

Are You Going to Believe Me or Your Lying Eyes?

I've tried to make three-view drawings from photographs and failed. Photography experts can tell you why; all I want to do is illustrate the pitfalls.

This is an example of a pretty-good drawing compared to a pretty-good picture, which means it was taken from the side at pretty much a right angle. (Hopefully, the height versus width of the picture, which I took off the interweb as-is, wasn't changed in the process of getting it out of the camera and onto the web.)

What I did was match the tip of the radome and the bottom aft edge of the rudder of the picture with the outline drawing (traced very closely on Illustrator from a McDonnell lines drawing that might not be "exact" in shape but should be very close in terms of the locations of significant features like the position of the wing leading edge versus the tip of the radome and the trailing edge of the rudder).

Note that details on the forward fuselage in the picture shift aft including the location of the wing leading edge. The fuselage appears to be deeper in the photo with the length matched to the drawing but that sort of makes sense to me and can be corrected for to some extent by increasing the length to height ratio of the picture in the middle but keeping it the same at the right side. (Otherwise the vertical fin would not be tall enough.) Note that this slightly affects the angles of non-vertical and non-horizontal lines.

Another problem not illustrated above is that objects closer to the camera appear bigger than they really are with respect to those farther away, the difference being dependent on the camera lens used and the distance from the subject.

These effects are minimized but not eliminated by taking a picture from far, far away using a telephoto lenses.

The good news is that you can rely on the shape and relationship of small areas that are the same distance from the camera. For example, whereas the inlet ramp is way out of position in the full side view as shown above, if you zoom in on just it and resize the picture slightly, the ramp matches the pretty-good drawing very closely. Another trick is to locate something with respect to the centerline of the airplane that is way off to one side of the picture like the tips of the stabilators by drawing a line between them and finding its midpoint. Of course, that means that both the left and right side of the something in question has to be visible.

My conclusion is that you can refine a pretty-good drawing with the judicious use of pictures but you have to start with a pretty-good drawing in the first place or be able to make measurements of the key features of the subject, which is not as easy as it sound, also speaking from experience...

Cockpit Confusion

In response to a request for a picture of the F7U-3 cockpit, I did some research and while I'm still not sure what it looked like, I did come across some interesting stuff. To me, at least.

First, cockpits of airplanes changed over time so a picture may not be representative of the airplane being modeled. What's worse, some cockpit photos are of airplanes in flight test with switches and instruments that have been added for purposes of the test. For example, this is the instrument panel of an early F7U, BuNo 128452, used for spin test.

Clearly the stuff that's up on the glare shield is test equipment. The two prominent T handles on the left side are for spin chute deployment and jettison. The location of any instrument in this picture can't be relied on for an operational cockpit but you can note that the instrument panel was curved, meaning each instrument and switch was roughly equidistant from the pilot.

This is the instrument panel of early production F7U-3s, BuNos 128467-78. Note that the cover marked "glass" protects the lens that projects the gun aiming image on the windscreen.

The "dark" instrument that looks like a radar screen is really the artificial horizon. F7Us, apparently including the -3M (more on that later), did not have visual-assist radars.

This is a photo taken by Don Hinton of the cockpit of F7U-3 BuNo 129554 at the Museum of Flight Restoration Center at Paine Field in Everett, Washington. The cockpit appears to be pretty stock. It appears that the artificial horizon and the directional gyro on the far right of the instrument do protrude out from the panel.

This is a picture of the same cockpit from a slightly different angle, now with a dummy sitting on the ejection seat. Unfortunately, I don't know who the photographer was.

The next picture is really confusing. It is BuNo 129590, which was an F7U-3 as far as I know. It has the F7U-3 gunsight. However, it also has the "zero reader" (it looks like an ILS indicator) and a range indicator immediately above it that I associate with the F7U-3M cockpit. The big ammeter mounted to the bottom of the glare shield doesn't appear to belong in an operational cockpit. I think the thing blocking the gun sight projection lens is a camera to record the image. My guess is that this picture shouldn't be relied on as representative of an operational F7U-3.

(From the National Museum of Naval Aviation)

Speaking of the F7U-3M, it appears to me that its AERO 10E Armament Control System (APQ-51 plus Mk16 MOD 4 Armament Fire Control System) as incorporated in the Sparrow I-armed Cutlass did not include a radar scope for its APQ-51, per se. In lieu of a radar scope, the pilot was given two gauges, one showing the direction of the object that Fire Control System had locked on to and the other, the range to the object in yards as well as a light that indicated a lock on had occurred:

My current guess is that when the Armament Control System locked on something, the pilot could point the airplane at whatever it was using the zero reader (the instrument just to the right of the turn-and-bank indicator), and more precisely aim the radar beam using a different gun sight from the one provided in the F7U-3. Or the pilot used the gun sight to be sure the radar was locked on to something that needed to be shot down and/or aim it at something he wanted to shoot down. I don't know.

The BIS Service Acceptance Trials report noted that the armament system would lock on to the bullet stream when the guns were fired (as indicated by the illumination of the lock-on light and the rapidly increasing range) if it wasn't already locked on to something.

As background, the Sparrow I missile was a beam-rider. It had rearward-oriented antennas that detected where the airplane's radar beam was pointed and "rode the beam" toward the target, so to speak. The shortcoming was the beam got wider the farther it was from the antenna. That meant that it wasn't accurate enough at distances over a couple of miles to get the missile, which was gyrating from side to side and up and down to stay in the beam,  close enough to the target to detect it and detonate the warhead. Aiming at the target through the gunsight might have been necessary to improve the accuracy by refining the lock on. In any event, riding the beam by looking backwards at where it was pointed meant the Sparrow I was only likely to be effective in visual conditions at relatively short ranges.

The Sparrow III, on the other hand, homed in on the radar beam being reflected from the target, which meant that its guidance was getting more and more accurate the closer it got to the target. That made the missile pretty effective as long as the target didn't start maneuvering to evade it.

This is a picture taken in July 1955 of the instrument panel of "YF7U-3M", BuNo 129700, in test at Point Mugu. Note the ammeter on the top of the glare shield and the zero reader to the right of the stick grip with the radar range indicator above the zero reader (the picture of the range to target and zero reader instruments above was cropped from this one). And that there is no visual-assist radar scope. (The instrument behind the stick grip is almost certainly the turn-and-bank indicator.)

(National Archives 80G-669514)

This is a picture of the bench test setup for the "APQ-51 gun sight" for the Point Mugu tests.

(National Archive 80G-669163 cropped)

That's a little confusing because this is a picture taken by Don Hinton of the Cutlass in the National Naval Aviation Museum at Pensacola marked as F7U-3M BuNo 129655. (Why the cautious wording? Because it doesn't have the pylons on the outboard wing panels and 129655 is listed as an F7U-3.) Note that the gun sight is very different from the one pictured above and is also not correct for an F7U-3M as noted by Laurent in his comment on this post. Other instruments are missing or mislocated, e.g. the artificial horizon, so this clearly isn't a stock operational cockpit of an F7U-3, much less an F7U-3M.

It is however, sensationally documented. See http://www.navalaviationmuseum.org/nnam/virtualtour/#MUSEUM/COCKPITS/F7U/F7U. I noted, however, the throttle for the right engine is for an F8U Crusader as indicated by the marking, "Cruise Droop" with an arrow, so modeler, beware.

One thing that I think we can rely on is that some F7U-3 cockpits were pretty much black except for the bottom of the control column and the rudder pedals:

And the ejection seat:

S2F Cockpit Overhead Hatches

For a riveting discussion of a small mystery about the S2F Cockpit Overhead Hatches with pictures, see http://tailhooktopics.blogspot.com/2012/12/s2f-overhead-hatch.html

Tailhook Topics Drafts (http://tailhooktopics.blogspot.com/) is a blog I use to respond to specific questions. My intention is to incorporate the material in Tailhook Topics posts when appropriate. Someday.

You Can't Tell the Phantoms Without a Score Card

This is a summary of the various U.S. Navy Phantom models and the configuration differences. It is by no means complete and not necessarily accurate although not for lack of good intentions and research. If nothing else, it will provide an indication of how varied the detailed configuration could be for a given letter designation. Also, for the time being, it's a work in progress...

11 December 2012: Added information and photographs on the F-4S provided by Jan Jacobs and Rick Morgan

F4H-1F (F-4A): The first 47 F4H-1s were redesignated F4H-1F (and subsequently F-4A) in May 1961. Although the more or less official reason was that these had the 5/10 degree inlet ramps and were powered by the J79-GE-2 engine (the F suffix indicated a engine change), I'm not sure that there weren't some retrofitted with -8 engines or that flew with the 10/14 degree ramps and/or -8 engines for test purposes. For sure, you can't tell an F-4A by the flat canopy (only the first 18 had it) and small radome. There were F-4As with the flat canopy and the big radome and the raised canopy and the big radome. See http://tailspintopics.blogspot.com/2012/11/f4h-1-large-and-small-radomes.html for a list of my posts on the F-4As, one of which includes a summary of the various configurations of the F-4As by Bureau Number.

F4H-1 (F-4B): The "real" F4H-1 production began with Block 6 (Block numbers were used to designate production configuration*), starting with Bureau Number 148363 .

There were only a handful of notable external changes to the F-4B (as it was redesignated in November 1962) during its service life. These included the low-speed lift improvements, the bulges on the top of the wings over the main landing gear struts, and the ECM stuff added during the course of the Vietnam War.

Although developed for the heavier F-4J, the low-speed lift improvement package that consisted of the drooped ailerons, slotted stabilator, and elimination of the inboard leading edge flap was of benefit to the F-4B as well. It was incorporated on the production line beginning with F-4B Block 26, the first of which was BuNo 152995 that first flew in March 1966.  It was retrofitted to most of the surviving earlier F-4Bs over time.  For more on this, see http://tailspintopics.blogspot.com/2011/09/f-4-flapstabilizer-change.html

The addition of the strengthened main landing gear was reportedly accomplished in conjunction with the lift improvements. However, according to the McDonnell Plane Captains Handbook dated January 1970, it wasn't installed on the production line until BuNo 153912, which was the last but three of the production F4Bs; those delivered before then were modified at the next overhaul. The longer stoke oleo required a fairing over the landing gear mounting point on the upper wing surface.

You're on your own with respect to the ECM configurations, external strengthening doublers, the USMC RF-4B, etc for the time being.

The F-4C/D/E were U.S. Air Force variants. The F-4F was delivered to the German Air Force. The F-4G designation was applied to two different F-4s, a dozen built for the Navy with a data link and automatic carrier landing system (see http://thanlont.blogspot.com/2011/07/look-no-hands.html) and subsequently designated as F-4Bs, and a U.S. Air Force version specialized for air defense suppression. F-4H (supposedly too similar to the original F4H) and F-4I ("I" could be confused for "1"?) were not used.

The F-4J was the Navy's next Phantom, which flew for the first time in June 1966. The major changes were the deletion of the infrared tracker under the radome, the bulged wings to accommodate the larger tires introduced with the Air Force F-4C, an additional fuselage fuel cell, and the incorporation of an improved radar and an uprated J79, the -10. As it happened, neither the radar nor the engine were available on schedule, so the first F-4Js were delivered with ballast in the nose and -8 engines. These were known as the lead-nosed Js; most were delivered to the Blue Angels. (As a result of attrition, the Blues eventually flew at least two Js with -10 engines.)

The J79-GE-10 had a notably different afterburner. See http://tailhooktopics.blogspot.com/2011/11/j79-afterburner-nozzles.html. As far as I know, the -10 was not retrofitted to any F-4B.

The F-4K and F-4M were the British Phantoms, powered by the Rolls Royce Spey engine instead of the J79. These had bigger inlets, a wider fuselage, a deeper fuselage under the afterburners, an additional auxiliary air door on the upper aft fuselage, all to accommodate the larger Spey engine. The F-4K also had an extra extendable section on the nose landing gear strut for launch from the smaller British carrier. See http://tailhooktopics.blogspot.com/2012/05/spey-powered-phantom-changes.html

For various reasons, not the least of which was attrition during the Vietnam War, the F-4Bs went through a service-life-extension program, becoming F-4Ns. In addition to replacement of the wiring and other product improvements and repairs, the Bee Line brought all the selected F-4Bs up to the latest basic configuration, including the lift improvements and the strengthened main landing gear. The first F-4N flew in June 1972.

Note that early Ns did not get the long ECM-associated fairings on the top of the nacelle inlets as shown above (the one on the J was about half that length for some reason), so it isn't a certain indication of an N. This N is an example of that:

The open door under the forward fuselage under the "2" in "207" deployed the automatic carrier landing system radar reflector, a feature introduced on the Navy F-4G. For more, see https://tailspintopics.blogspot.com/2017/08/f-4-phantom-acls-radar-reflector.html and http://thanlont.blogspot.com/2011/07/look-no-hands.html

Like ''I", "O" wasn't used for a modification letter and I don't know what the F-4P or R were to be.

The F-4S resulted from a service life extension program for the F-4J. It also featured the substitution of maneuver slats for the leading edge flaps. See http://tailspintopics.blogspot.com/2012/12/f-4s-wing.html

As it happened, according to Jan Jabobs, the first 43 F-4S conversions were completed without the maneuver slat modification that involved new outboard wing panels. These Phantoms were delivered to Marine Corps squadrons. Note that it does have the strip formation lights on the vertical fin and fuselage that were one of the external changes for the S configuration.

 Photo by Toshiki Kudo at Kadena, 12 September 1981

  At least one slat-less VMFA-251 F-4S had a suitable designation on the aft fuselage above the Bureau Number.

 Photo by Rick Morgan at Key West, 7 December 1980

The slat-less Ss were subsequently modified to the full S configuration shown here. Note the much shorter ECM antenna fairing on the engine inlet than present on the F-4N, another characteristic of the J/S. (Rick pointed out the cool way the squadron's crusader sword outlined the F-4S formation light on the vertical fin.)

Photo by Rick Morgan at Key West, 3 August 1980

At least a few F-4Ss with the slat modification also had the inboard leading edge flat reactivated. It was subsequently locked back up again.

I haven't addressed the various cockpit changes over time and don't intend to with the exception of the ejection seats. The first F-4s had the McDonnell-furnished ejection seat (an illustration is provided in one of those F-4A blogs referenced above) but it was soon replaced by the introduction of the Martin-Baker seat in almost all the Navy's fighters. (For more detail on the F4H seat change, see http://phantomphacts.blogspot.fr/2013/10/f4h-phantom-ii-ejection-seat-history.html.) The Mk 5 was installed in the Bs and the first Js. According to the June 1968 issue of Naval Aviation News, F-4Js began to be delivered with the Mk 7 in December 1967; the Mk 5s in the Bs and the earlier Js were modified to the Mk 7 configuration or replaced by Mk 7s. See http://thanlont.blogspot.com/2011/02/transition-to-martin-baker-ejection.html

*That letter that you sometimes see after the Bureau Number on Navy airplanes indicates the production block number, in this case "a" for Block 1. (BuNo 142259 was actually the very first Phantom; note that the designation is not YF4H-1 and "Navy" was still being included along with the designation and bureau number.)

The letter suffix wasn't much use for configuration definition after an airplane had gone through its first overhaul so it was rarely present thereafter.

Having a Problem?

Somehow a string of what amounts to gibberish (to me, anyway) got inserted into the middle of the text of "F-4S Wing". The only browser that couldn't seem to cope with it was Internet Explorer. I've fixed it both here and in a post (http://thanlont.blogspot.com/2012/11/and-now-for-something-completely.html) in my U.S. Navy Aircraft History blog. Since I don't have Explorer, if those of you who do have a hang, please let me know with a comment on http://ththomepage.blogspot.com/

F-4S Wing

The F-4S was an update to the F-4J, providing a service life extension as well as system and aerodynamic performance improvements.

The major external change was the substitution of slats for the leading edge flaps on the outboard inner wing and the outboard wing panel. These resulted in increased maneuverability due to notably higher angle of attack capability (in fact, a new angle of attack indicator was required with a higher upper range).

 

The maneuver-slat modification included a small fence just outboard of the wing fold area. The slat on the folding portion of the wing provided a permanent slot – it didn’t extend further but simply pivoted to increase the size of the slot. The inboard slat extended, moving forward via a parallelogram linkage; note that when retracted, it protruded below the lower surface of the wing.

Both the slats and the wing fence were different from the Air Force F-4E maneuver-slat modification.

The original wing configuration that was tested included reinstatement of the inboard flap extension that had been deleted on the F-4J, a change that was retrofitted to the B/N. See http://www.vmfa251.org/photos1970s/Pictures%20from%20the%201970s/album/slides/F4S_155872_nmna-file.html However, most photos of F-4Ss in service don't show the inboard flap extended when the trailing edge flaps are down, indicating that its activation was subsequently deleted.

To add to the confusion, the first 43 or so F-4Ss out of rework did not have the maneuver slats. See http://tailspintopics.blogspot.com/2012/12/you-cant-tell-phantoms-without-score.html