A4D-1 Rudder Development

One of the most notable differentiators between the A4D-1 and -2 is the rudder. On the -1, it had a smooth exterior surface. On the -2, longitudinal stiffening ribs were riveted to either side of a central panel. The change was made because of rudder flutter that had been experienced early on in A4D-1 flight test. Recently, someone inquired as to how the A4D-1 was released for service with a rudder flutter problem and by chance, someone else asked about a feature on the A4D-1 rudder that I hadn't paid  attention to before. It turns out that the feature was the answer to the question.

In passing, I also noted another rudder detail change from the XA4D-1 to the production A4D-1. The X and early production Skyhawks had a rudder trim tab with an actuating rod on the left side of the rudder.

The original solution to the rudder flutter problem was the addition of a dash pot-type damper just above the center rudder hinge. Note that the trim tab is still part of the design.

The dash pot allowed the pilot to move the rudder but "stiffened" it at high frequencies to preclude flutter.

The rudder trim tab was deleted on A4D-1s delivered to operational squadrons.

When the rudder flutter problem was solved aerodynamically with the so-called tadpole rudder, the damper was deleted.

Note the addition of a ground-adjustable trim tab.

NEW Airfix 1/72 A-4B/4P Modeling Notes

27 October 2025: This is a replacement link for an excellent build article on the 2011 Airfix A-4B/P kit: https://www.tapatalk.com/groups/airfixtributeforum/airfix-1-72-douglas-a4b-4p-skyhawk-a03029-t47356.html

26 October 2025: For the beginning of a build article of the original Airfix A4D kit, click HERE 

21 June 2014: I added a comment on the detail on the upper fuselage between the canopy and the dorsal fin here: http://tailspintopics.blogspot.com/2014/06/more-modeling-notes-on-172nd-airfix-4b.html

21 November 2012: I added some detail on the landing gear sponson features here: http://tailspintopics.blogspot.com/2012/11/the-dirty-underside-of-a4d.html

15 September 2012: I forget that you might have gotten here by a web search or reference link and so might not have scrolled through the blog and seen the other Skyhawk stuff:

Nose Shape: http://tailspintopics.blogspot.com/2012/11/airfix-172-a4d-2-overall-size-and-shape.html

A4D-1 Rudder http://tailspintopics.blogspot.com/2012/08/a4d-1-rudder-development.html

Fuel Tanks http://tailspintopics.blogspot.com/2012/07/douglas-low-drag-external-fuel-tanks.html

1/48th Cockpit http://tailspintopics.blogspot.com/2012/09/fitting-in.html

7 August 2012: One point that I might not have made clear is that the external configuration of the J65-powered Skyhawks changed over time as product improvements were incorporated at overhaul. Airframe change dates aren't much help because it might take a few years before an airplane went into overhaul after a modification was approved. The A4D-1 in the New England Air Museum is an example.

Note that it still has the fuselage vortex generators that were removed from some A4D-1s.

3 August 2012: Thanks to Peter Collins, we now know the difference between the early and late oil vent on the right side of the J65-powered A4Ds.

 Note that the round vent is located in the center of an oval panel that matches the one on the early vent.

I also added some information on the early and late wing tip lights.

2 August 2012: Added detail on differences
1 August 2012: I don't know if it's represented on the kit, but the A4D-1 and -2 had a small hole in the nose for avionics cooling:

Note: Because this is a picture of an A4D-1, there is no angle of attack sensor on the fuselage. There was however, a box on the upper right side of the landing gear strut containing lenses and a light to provide angle of attack information to the LSO at night. Scroll down to the bottom of the page for a picture and link.

The Scooter is one of my favorite airplanes so I was particularly pleased when Airfix issued a new kit of it in my scale.

 Picture from the Hannants web site

I haven't gotten it yet so this is a work in progress based on the posts of others. I also am not an expert on the A-4P so I'll confine myself to discussing the U.S. Navy Skyhawks.

For one of the build posts, see Drewe Manton's web site http://drewemanton.com/models/2012-07-27-a4b-800s/a4b-build-800s/vma324_a4b.html

Airfix based its new Skyhawk kit (it also produced a much simpler and not very accurate A4D-1 kit decades ago) on the A-4B displayed on Intrepid, which is now a floating museum docked on the Hudson at New York City. It therefore represents one that has been through rework and modification several times.

For example, here are some differences annotated on a picture published by "Ajay" as part of his build post in 72nd Aircraft:

Note that the scoop on the aft fuselage was not on early A4D-1s or 2s. It appears to have been added during A4D-2N production over one of the existing vents to improve cooling in the aft fuselage. It appears to have been retrofitted to A-4As and Bs beginning in 1965 on a quick review of pictures in Steve Ginters Naval Fighters Number Fifty. Also see Naval Fighters Number Forty-Nine for many, many photographs and illustration of the A-4A and B.

The kit also has the radar altimeter fairing under the left wing tip. This was added during A4D-2N production and retrofitted to some A4D-2s, including the one on the Intrepid. However, it may have to be removed depending on the specific A4D-2 being represented. For this and some other details on the differences between the A4D-2 (A-4B) and A4D-2N (A-4C), see http://tailspintopics.blogspot.com/2010/07/a4d-skyhawk.html. Note that the A4D-2N (A-4C) had a nine-inch longer nose to accommodate a terrain avoidance radar.

The major omission is the oil vent port on the left side of the fuselage. It was a significant feature in no small part because of the oil streak emanating from it.

This vent was originally  rectangular with rounded corners on the A4D-1 and -2 as shown above. At some point, at least on the -2 and possibly in conjunction with the addition of the air scoop over the small rectangular flush intake on the side of the fuselage, it became round. The feature is present on the  Skyhawk displayed on Intrepid that Airfix used as a reference but wasn't included on the kit.

Cropped from Peter Roan picture HERE

The missing upper rectangular openings just aft of the fuselage break (these provided access to the bolts that attached the aft fuselage to the mid fuselage) could be represented with paint or a decal for simplicity of construction...

I don't know whether the blade antenna aft of the canopy in the kit and on the Intrepid Skyhawk is representative of a later version or not, but the early antenna was clearly different:

 
The kit has a representation of a later version of the Douglas ejection seat, the main external difference being the addition of a vertical slot/channel in the headrest for the "head knocker" used to arm the later seat. It had better ejection performance and was introduced with the A4D-2N (A-4C) in early 1960. It was retrofitted to A4D-1s and 2s.

This is a very early seat being lifted by Ed Heinemann himself to demonstrate its light weight:

Note that the ejection handle should be housed slightly and stick straight out, not be slightly extended and drooped.  For this display, the seat is missing the seat cushion, backpack parachute, seat belt, and shoulder harness as shown in the Escapac seat picture above. The shoulder harness straps (to which the parachute straps were attached) are very short because they were to be connected by the pilot to fittings on the pilot's torso harness, not the seat belt. The early seat can be created from the kit seat by filling in the head-knocker slot (there should still be a depression in the headrest that accommodates the back of the pilot's helmet) and cutting back the sides.

Another picture of the early headrest:

Note: The blade antenna normally mounted behind the canopy was installed under the nose of this aircraft.

The external wing tanks may be undersized and according to the pictures, have a constant cross section where they should be bulged. See http://tailspintopics.blogspot.com/2012/07/douglas-low-drag-external-fuel-tanks.html for more on the Skyhawk tanks, sources for accurate tanks, and a link to Douglas external tanks drawings.

There were early and later main landing gear wheel hubs. Some A-4s had the early hubs through at least through 1970. The kit reportedly has the early hubs.

Another feature on the early Skyhawks that changed over time was the wingtip light. On the A4D-1 and at least the early A4D-2s, they were flush and inboard of the tip. The early formation and position lights were the same color. The formation lights were subsequently deleted and the position lights relocated to the edge of the wing tip: the aft light was a conventional filament one with a colored lens when dim lights were desired and the forward one was a colored gas-discharge light illuminated on the Bright setting. The "Fuselage" lights (there was also one on top of the fuselage; it was subsequently replaced by a red anticollision light with another added to the bottom of the left main landing gear fairing) were used for signaling at night.

The major changes to convert the kit to an A4D-1 are easy: remove the inflight refueling probe and fuselage fairing and modify the rudder (or replace it) so it has a flat surface rather than external stiffeners. The hard part is the different configuration of the vortex generators. For that and some more detail on the A4D-1, see http://tailspintopics.blogspot.com/2011/01/a4d-1-vortex-generators.html

The nose landing gear was slightly different:

 Note: Early A4D-2s might have the early angle of attack indicator and fork or the early angle of attack indicator and the later fork.

For a description of the early angle of attack indication to the LSO, see http://thanlont.blogspot.com/2012/04/night-carrier-landings-in-beginning.html

Douglas Low-Drag External Fuel Tanks Redux

I provided dimensioned drawings of the 150, 300, and 400-gallon Douglas low-drag external tanks here: http://tailspintopics.blogspot.com/2011/07/douglas-low-drag-external-fuel-tanks.html

The tanks and fins were standardized but the number and location of the fins varied with the specific location on a particular type.

The 150-gallon tank was common on the A4D-1 and early A4D-2s.

Because the tanks were very similar in shape, you have to look carefully to see which one is installed. In the case of the A4D, the clues are a somewhat smaller diameter relative to the airframe and more obviously, how far the tank extends behind the wing trailing edge and to a lesser degree, ahead of the wing leading edge.

Here is an example of a single 400-gallon tank on an A-4 and one with two 300-gallon tanks. Note that the 300-gallon tanks do not have fins, which is not unusual, but the forward location of the national insignia on an A-4E is.

I've seen questions about which kits have accurate external tanks so I did a quick survey of some of the 1/72 kits in my stash, comparing their 300-gallon tanks to the drawing. In rough order of acceptability:

Esci A-4 (A4D): Excellent

Hasegawa A-1 (AD): Almost perfect. Rounding the nose a bit provides almost exact length; the fins are a bit small but not objectionably so.

Tamiya F4D: Very slightly oversized, rounding the nose would be appropriate.

Airfix F4D: Very slightly oversized.

Airfix S-3: Basic size and shape okay; the fins need to be cut down. (The basic shape of the airframe is also better than the Hasegawa kit, e.g. the engine nacelles aren't circular.)

Hasegawa EA-6B: Basic tank okay but fins slightly undersized.

Fujimi A-6: Length okay but diameter a bit undersized and too tapered; fins good.

Hasegawa S-3: Too short by about 13" and forward edge of fin angled downward too sharply.

Fujimi A-7: Too short by about 31" and terrible fins

Airfix AD: Somewhat undersized (too tapered/conical) and fins too small.

Hasegawa A-4: Definitely undersized; could be sectioned to create the 150-gallon tank.

Matchbox F3D: 150-gallon size but forward part of tank is too tapered, conical.

Hasegawa F9F-8: 150-gallon size but too small in maximum diameter; taper down in diameter from mid section both forward and aft is too conical; and the fins are not correct.

Alex provided some additional notes on tanks from other kits:

Fujimi A-4E/F kit # F24: L = 77.5mm, D = 8.7mm.
Overall shape appears to be correct.

Hasegawa AV-8B kit # D19: L = 85mm, D = 10.4mm.
Definitely oversized.

Academy OV-10A kit # 1665: L = 54mm, D = 7mm.
Too small even for a 150-gallon tank.

Sword F3D-2 kit # 72072, 300-gallon tank: L = 77.5mm, D = 8.5mm.
Overall shape appears to be correct.

Sword F3D-2 kit # 72072, 150-gallon tank: L = 61mm, D = 7.3mm.
Apparently undersized.

For some aftermarket options, see http://tailspintopics.blogspot.com/2013/08/things-under-wings-douglas-low-drag.html

Comments, additions, and corrections welcome.

Sea Blue vs. Insignia Blue

I usually stay away from color stuff because it's not one of my areas of expertise and it's fraught with potential for error, which I prefer to avoid. This post is therefore for discussion purposes, not to provide a definitive color statement.

Toward the end of World War II, the complex Navy camouflage scheme for carrier-based aircraft was gradually replaced with an overall Sea Blue color. However, the national insignia was retained intact. This provided examples that directly compare Sea Blue and Insignia Blue. (Note that the colors may not have been accurately depicted in the original that I scanned, much less on your computer screen.)

It was eventually suggested, probably by Grumman, that the Insignia Blue surround of the national insignia was redundant and should be eliminated on all-blue airplanes. It was reportedly deleted well before the official authorization to do so was issued in June 1946.

A red bar was added in January 1947 to reinstate all the colors of the U.S. flag.*

 (This F4U would appear to have spent some time ashore in its recent past...)

I like the color in the picture immediately above but it appears to be lighter and bluer than Sea Blue color chips from Elliott, et al. Here are the current Federal Standard colors (Insignia Blue = 15044; gloss Sea Blue = 15042) according to Colorserver:
http://www.colorserver.net/showcolor.asp?fs=15044+15042

The sea-blue story is complicated by the fact that according to Dana Bell, "There were two completely different versions of ANA 623 Glossy Sea Blue. Citing the instability of the original pigments, in 1947 BuAer reformulated the color and issued new color chips. Modelers have been arguing about this for years, not realizing that some of us have the early chip (on heavy card stock) and others the newer chip (on a metal plate). The newer chip is indeed darker and is also a bit greener."

The new blue paint was also notably tougher and faded less. Note the difference between the two Corsair pictures above.

*Note that action with respect to authorization often occurred in due course. How else to explain this F4U national insignia that still has the Insignia Blue surround and also the red bar?

The picture is obviously too green; here is an auto correction, which looks about right:

 

That the bar is faded may be indicative of it being added in the field with paint at hand.

My impression is that Grumman painted overall-blue F6Fs with paint that didn't fade as dramatically.

Markings: A Cautionary Example

Two F4Ds, same squadron, possibly deployed but maybe not:

My guess is the Skyray at the top of the picture was a replacement aircraft that hadn't been completely marked by the squadron yet. (The presence and absence of the in-flight refueling probe isn't a marking thing but is a similar issue with respect to the configuration of a particular aircraft.) The difference in location of the squadron identification was particularly interesting. It appears three times in the picture (the angle it was taken from puts the marking on the right side of the lower airplane out of view) and each is in a different position longitudinally. The anti-glare panel color probably depended on when the airplane had gone through overhaul. I can't explain the difference in national insignia orientation. I think that at the time it was supposed to be angled.

Note that national insignia orientation wasn't as hard and fast as you might think as exemplified by this letter in the May 1949 Naval Aviation News:

Chris Paulson posted a comment with a link to a couple of F9F-5 pictures from his father's collection. I've cropped and added them to this post for your convenience.

Note the "20" on the nose that's angled nose down relative to the national insignia:

It's a bit subtle, but the placement, size, stroke weight, etc. of the "AE" on the vertical fin and rudder varies:

One of the Panthers is unpainted. See http://thanlont.blogspot.com/2009/12/it-seemed-like-good-idea-at-time-vii.html for the explanation.

WF (E-1B) Update

I've added a brief description of the WF aerodynamic prototype and an inboard profile of the WF cabin from the mockup review to the Trader/Tracer post here: http://tailspintopics.blogspot.com/2010/11/trader-and-tracer.html

For more on the WF (E-1), also see here: http://thanlont.blogspot.com/2011/10/designation-story.html

WF (E-1) Wing Changes

In a response to a question from Mike Hazlewood (http://www.vagabonddecals.com/)about the changes between the S2F-1/2 wing and the WF (E-1), I created an illustration that depicts the difference. Note that the outboard end of the wing center section and the inboard end of the outboard wing was completely redesigned to incorporate the Grumman sto-wing concept.

I also reorganized the original blog post, http://tailspintopics.blogspot.com/2010/11/trader-and-tracer.html, in addition to incorporating this illustration.