Tailhook Topics: August 2010

4 July 2023: Illustrations of the bomb bay loading options:http://tailhooktopics.blogspot.com/2023/07/grumman-s2f-bomb-bay.html

Steve Ginter has an S2F-1 monograph in work; it should be available later this year. See his Naval Fighters web site HERE. If you can find Fall 2007 (#8) issue of Aerospace Modeler Magazine, it included a build article on the 1/48th Collect-Aire S2F and details on the S2F.

The nickname "Stoof" was derived from its original designation, S2F. The originally approved name was Sentinel. This was changed to Tracker when the COD (Trader) and AEW (Tracer) versions were named.

Designations Pre/Post 1962:

S2F-1 S-2A

S2F-1S S-2B

S2F-2 S-2C

S2F-3 S-2D

S2F-3S S-2E

S2F-1S1 S-2F (A very rare instance of a prior designation being reused in the post-1962 lexicon)

The S2F-1 has long been represented in 1/72nd scale by the excellent Hasegawa kit. Kinetic has now released a 1/48th scale "S2F"kit which represents the S-2E/G.

Once upon a time (that's me as a pre-teen, between my brother John Gregory and a naval aviator, John Brandenberg, who let us take a close look as his VS-21 S2F-1 in 1956 or thereabouts.

Short version of the differences between the Stoofs:

1. There were three fuselages, the S2F-1, the S2F-2 (S2F-1 with a bigger bomb bay), and the S2F-3. The S2F-3 center fuselage was longer than the -1's by 18 inches, 14 forward of the wing and 4 aft. The pilot compartment was increased in length by six inches by moving the aft bulkhead aft without changing the location of the window, which resulted in an increase in the length of the equipment operator's work space of eight inches. Note: the S2F-3 cabin was not widened externally as has been reported; there was an increase in internal width of three inches in the upper portion of the compartment accomplished by changing the fuselage skin in that area from skin/stringer construction to a honeycomb panel. The cabin window was also enlarged and it appears to have been relocated a bit farther forward.*

* As near as I can determine from pictures compared to a Grumman forward fuselage drawing, this is the size and location of the S2F-3 (S-2D and subsequent) crew compartment window:

2. There were two horizontal stabilizers, the original S2F-1 and a bigger version on the S2F-2/3 to offset the bigger bomb load and longer fuselage respectively. The S2F-3 had a greater wingspan/aspect ratio by virtue of the addition of rounded wingtips.

3. The big radome over the cockpit appeared early in S2F-1 production and was also on the S2F-2; it was deleted from the S2F-3. (The antennas were moved to the rounded wing tips.)

4. The aft end of the nacelles changed, first to add a "parrot beak" or "hawk's bill" fairing during S2F-1 production and then to cut the beak/bill off for the S2F-3 (S-2D)for more sonobuoy capacity. The two larger holes in the S2F-1/2 sonobuoy dispenser were for the SSQ-1 directional sonobuoy but it proved unsatisfactory in service so the bigger holes did not have the store retention clips.

S2F-1s (S-2As) with BuNos 129XXX and 133XXX and all S2F-2s (S-2Cs) were built with the small nacelle that faired into the upper surface of the wing at the trailing edge. All later S2F-1s (136XXX and higher) were built with an aft nacelle which extended over the top of the trailing edge of the wing and above and aft of the opening in the rear of the nacelle. The Canadian S2Fs had the early aft nacelle.* The Japanese S2Fs had the beak/bill.

Note that early S2Fs had a different main gear wheel hub as on this VS-21 S2F-2. They also had a smaller "head" on the extendible Magnetic Anomaly Detector located at the tail of the airplane.

Note that the pilot’s overhead hatch in the picture above is solid (no clear Plexiglas). Based on a quick review of a lot of pictures, it would appear that the hatch was solid on at least half of the first S2F-1s (and all S2F-2s) at initial delivery. The survivors, for the most part, eventually got clear hatches (the problem, identified early on in Navy trials, was that there was inadequate visibility into the turn with the solid hatch). My guess at the moment is that all S2Fs painted overall blue had solid hatches and there were even some early ones in the gray/white color scheme with solid hatches.

5. The original cockpit of the S2F-1 and -2 had the control columns extending out from the instrument panel and the pilot sat in a bucket seat on a seat-pack type parachute, strapped in with a conventional seat belt and shoulder harness.

With the S2F-3, the control columns were relocated to be between the pilots and the instrument panel and the seat was changed to one with a back-pack type parachute and a restraint system requiring a torso harness.

This excellent picture of an S2F-3 in flight test at Grumman illustrates the differences between it and the earlier S2Fs:

Note the increased distance between the cockpit window and the red propeller warning stripe compared to the lead photograph, the bigger crew compartment window, the rounded wingtips that housed the antennas that had been in the strut-mounted "pod" over the cockpit, and the increased span horizontal tail. The retro-smoke marker located on the lower right fuselage between the cabin door and the dust bin radome was rmoved. (It was reinstated on the S-2G.)

The forward angled probe under the fuselage was the barrier pickup. It was added early during S2F-1 production after a barrier crash. See my Navy aircraft history blog entry Here. It was no longer necessary after the U.S. Navy completed its switchover to angle-deck carrier. My impression is that it was no longer installed at some point during S-2E production.

The higher gross weight of the S2F-3 required power plant installation changes as well:

Compare the size of the crew compartment window, the location of the warning stripe, and the engine nacelle of this Reserve S2F-1 to the above:

The "plumbing" in the nose cap was also rearranged (note that early S2Fs did not have the taxi light):

The final U.S. Navy Tracker was the S-2G, which were modified S-2Es:

A folding antenna was added with an avionics upgrade where the barrier pickup had been. Note that extra sonobuoy dispenser scabbed onto the right side of the right nacelle (the 1/48th Kinetic kit has two but only one is needed) and the fuselage-mounted retro smoke marker system was reinstated. The S-2G was also operated by the Australians.

* The Canadian S2Fs were initially all but identical to the early production S2F-1s. However, the avionics suite underwent a series of improvements. For almost everything you need to know about the Canadian program, see This Excellent Website, identified to me by Robert St-Pierre, who also provided this picture of a CS2F landing on Bonaventure.

The "cans" on the CS2F wing tips contained passive ESM antennas, which presumably were incorporated in lieu of the similar S2F system located in the pod above the forward fuselage of the S2F-1/2.

Kinetic Kit Redux

Mike Belcher of Belcher Bits has done an evaluation of the Kinetic S-2E/G fuselage with an eye toward creating aftermarket decals and options for the CS2F. In the process, he has identified a problem with the length of the aft fuselage of the kit. See HERE.

Mike also offers a S-2E to early S2F-1 conversion kit consisting of new horizontal stabilizers, aft engine nacelle terminations and an instruction sheet, which is on line. Click HERE.

Modelers continue to note shortcomings with the kit's cockpit. It provides a relatively simple version of the later seats, the S2F-1/2 instrument panel and control wheels, (see above) and a rectangular opening to the cockpit rather than an opening with an arch at the top, and is missing the aft (folding section) of the center console. I assume that it's also missing the search light control stick that can be seen in the copilots side window.

In order to provide adequate access to (and from) the pilot and copilot seats, the aft section of the center console could be pivoted upwards against the instrument panel where it was retained by a latch on the glare shield. The following are pictures of an S2F-1 cockpit. One shows the arch at the top of the opening to the cockpit.

The S2F had a fixed slot in the outboard leading edge of the wing.

The slot opening was farther forward on the underside of the wing. Note that there was a deicing boot on the lower surface of the wing aft of the slot opening as well as one on the leading edge of the wing.

Another view of the slot and boot on the lower side of the wing.

Another question raised about the Kinetic kit is the location of the jury struts used to secure the wings when folded.

There were two very small permanent attach points on the centerline of the upper fuselage.

The wing-attach point for each strut was located inside a small door.

Note that the location of the attach point was different on the left and right wing.

The forward strut angled forward when installed:

For more pictures of the wing jury struts, among other things, click Here.

The Kinetic kit also omitted the search light reflector, etc. inside the searchlight housing. The light was mounted on a gimbal and aimed using a removable control handle mounted in the copilot's side window. (The picture of the gimbal has been rotated so you're looking down from above; it was lifted from this website.)

Click Here for pictures of the control handle (Note that the cockpit is an S2F-1 procedures trainer, not an S2F-3's.)

Click Here for a discussion of the difference in cockpit side windows between early and late airplanes.

Upper exhaust troughs:

Note: I've revised this entry in response to a lengthy comment that I have not posted because it contained minor errors, some of which were the result of my less than crystal clear statements in the original and verbally hand-waving the location of the exterior angle-of-attack indicator lights on the A4D-2N and subsequent. Since I'm not sure that I can delete a personal email address in a comment before posting it and some people may not want their email address made public, if someone wants a personal response to their question/comment, feel free to email me at tommythomason@sbcglobal.net

I've been busy writing a book for Specialty Press on the Scooter. The A-4A/B corresponds to the A4D-1 and -2; The A-4C was previously the A4D-2N and the A-4E, the A4D-5. Note also the inlet difference on the J52-powered A-4E/F. More to come.

The A4D-2N (A-4C) nose was lengthened to accommodate a terrain avoidance radar and an access door added on the right side. It was originally produced with a large dark radome. The pitot that was located in front of the windscreen was moved to the left and a total temperature added to its right.

For some reason, probably to reduce weight or improve avionics access, the original A4D-2N nose was modified to replace the large dark radome with one shaped the same but possibly made of different material. The area defined by a paint or a erosion resistant coating was smaller, usually with a distinctive slant. The change roughly corresponded to the designation change to A-4C in 1962. However, large dark radomes are seen on deployed A-4s through at least 1965 that had not yet been through overhaul after the change was implemented.

(For an update on the radome story see http://tailspintopics.blogspot.com/2012/10/skyhawk-details.html)

There were other detail improvements like the addition of a windshield wiper. Another detail external difference between the A4D-2 and -2N was the angle of attack sensor and the external angle of attack indication for the LSO. On the A4D-2, the angle of attack transducer was a small "peg" (left picture below) in approximately the same location as the A4D-2N's "weather vane" and the light display was mounted on the nose gear strut (center picture below).

On the A4D-2N, it was a large weather vane as shown here. (Note also the replacement radome that has not yet been painted to match the forward fuselage.)

The three-light external display was relocated from the nosewheel strut to the left wing's inboard leading edge. In the following picture, it is the dark window on the wing leading edge just above and on the inboard side of the forward end of the main landing gear fairing.

Another difference between the A4D-2 and the -2N initially was the radar altimeter, located in a pod under the left wing. It was added during A4D-2N production and retrofitted to A4D-2Ns and some A4D-2s.