by Tommy H. Thomason

Thursday, November 29, 2012

F-4 Radome Redux

Thanks to Craig Kaston, we have a good view of the cross section of the F-4 fuselage at the parting line between the radome and the fuselage:
Crop of a Craig Kaston photograph of a QF-4S+ forward fuselage

Note the obvious flattening at the top of the parting line.

And the area between the windscreen and the parting line where the rain removal ducts are located is really flat:
 Craig Kaston photograph of the YF-4J now at China Lake



Saturday, November 24, 2012

F4H-1 Large and Small Radomes

Thanks to Mark Nankivil and Larry McCarley, I have a little more insight into the difference between the large and small radomes on the F4H. This is an overlay of McDonnell drawings of the forward fuselage:

Note that the radomes are located on the same center line (boresight). However, Larry McCarley (who has access to an F-4 at China Lake) pointed out that the top of the larger radome is slightly flattened at the parting line with the forward fuselage. (Note also that the parting line of the larger radome is not perpendicular to the radome center line like the smaller one is.) The flattening of the top of the radome was probably done to minimize the reduction in over-the-nose visibility with the new nose.

You'll note that the ramp extends farther forward on the F4H with the bigger radome. That is one of the differences in the ramp between the F-4A and the F-4B. The change resulted in a modification to the aft edge of the lowest kick-in step and the lower access panel.

One of these days, I plan to reorganize and combine all the posts that I've done on the early Phantom IIs. In the meantime, I think this is a comprehensive list of them:

http://tailspintopics.blogspot.com/2011/09/f-4-flapstabilizer-change.html

http://tailspintopics.blogspot.com/2009/11/early-phantom-iis.html

http://tailspintopics.blogspot.com/2011/05/early-phantom-iis-redux.html


Wednesday, November 21, 2012

The Dirty Underside of the A4D

One of the other differences between the early and late A4D-2s (See the preceding post and http://tailspintopics.blogspot.com/2012/07/new-airfix-172-4b4p-modeling-notes.html for much, much more) was the detail on the main landing gear sponsons (the fairing for the retracted main landing gear strut). The original A4D -1/2 simply had a small fuel vent on the right-hand sponson aft of the main landing gear well:
A closeup of that feature:

When the FAA implemented a civil requirement for anti-collision lights, a red light was added (and retrofitted) to the top of the fuselage and the left-hand sponson.

 If the airplane that you are building a model of has the red beacon on top of the fuselage, then it will have this beacon installation on the-left hand sponson.
At some point,  a fuel dump mast was added to the right sponson aft of the fuel vent.

The Airfix A4D-2 has all three of these features on its sponsons. Only the fuel vent was on Skyhawks from the beginning. The others were retrofits to the A4D-2.

Saturday, November 10, 2012

Airfix 1/72 A4D-2 Overall Size and Shape

A question has arisen as to whether the length of the Airfix 1/72nd A4D-2 is correct. One reviewer looked at the station diagram in Naval Fighter Number Forty-Nine, Douglas A-4A/B Skyhawk, and correctly calculated the overall length for the A4D shown as 39' 2".


He then noted that the Airfix kit was several scale inches shorter than this.

Unfortunately, this station diagram is for an A4D-2N (note the canted bulkhead in the nose) rather than an A4D-1/2, which have a nine-inch shorter nose.

Realizing that this isn't the correct length for an A4D-1/2 isn't helped by the fact that there are two basic overall lengths for the A4D-1/2, one parallel to the ground with the airplane in its normal stance and the other parallel to the fuselage reference plane (also known as the waterline):


Note that the length parallel to the ground is 39' 4 1/2", close enough to the A4D-2N waterline length to be confusing if that's the only length given in a table and without reference to a drawing.

As best I can tell, the Airfix kit is the correct length.

Compared to pretty good Douglas drawings, however, the rudder extends down a bit too much on the fin and the nose is definitely tilted down, suggesting a foreshortened A4D-2N nose. (I had thought the nose looked a little off when I first saw pictures of the kit and this tends to confirm that observation.)

For much more on the Airfix A4D kit and the Skyhawk in general, see http://tailspintopics.blogspot.com/2012/07/new-airfix-172-4b4p-modeling-notes.html

Friday, November 9, 2012

F7U-1 Cutlass

My long overdue monograph on the F7U-1 Cutlass for Steve Ginter's Naval Fighters series is finally done and at the printer.

It is available from Amazon: http://www.amazon.com/dp/0984611479, Sprue Brothers, Specialty Press, and Steve Ginter himself (http://www.ginterbooks.com/NAVAL/NAVAL.htm).

I guarantee that it has pictures and illustrations that you haven't seen before.

The F7U-1 was ahead of its time in many ways.
(Swept national insignia wasn't authorized until March 1955.)

Rogue markings were indicative of much more audacious decisions that resulted in F7U-1 development falling well behind schedule and the production program being terminated. I hope you agree that I've done its story justice.

Sunday, November 4, 2012

Things Under Wings - Radar

In early WW II, some U.S. Navy carrier-based torpedo and scout bombers were equipped with the ASB radar. These were identifiable by the presence of a Yagi array antennas under the left and right outboard wings.
These were individually aimed by the radar operator in directions of interest and the return could be interpreted for navigation (identification of harbors, coastal cities, and ships) and attack at night and from above the clouds. Ironically, the antenna was invented by a Japanese scientist before the war.

It took some training and skill to operate the ASB radar. It was replaced by the APS-4, which looks more like a conventional radar. It could be mounted on an existing bomb rack and jettisoned if needs be. Airplanes wired for the APS-4 received an "E" suffix indicating modified electronics. It is sometimes mistaken for a fuel tank or a bomb.


The APS-4 was replaced by the APS-19, a more capable radar, for most new applications beginning in 1946. (The TBM-3S conversions used for the interim ASW hunter/killer team were still equipped with the APS-4, however.) When provisions for the self-contained radar pod were standard, as in the Douglas AD-4, no E suffix was required. In general, when the APS-19 was installed in night fighters it was an integral part of the aircraft rather than carried as a pod. The Grumman F8F was an exception.


The APS-31 appears to have come in two different flavors from the standpoint of antenna size. The APS-31 or -31A carried by the Grumman AF-2S pod was similar to the APS-19 pod except that it had a longer and more pointed tail cone.
The APS-31B pod that was hard mounted (albeit removable) under the right wing of the AD-4N and AD-5N was much larger than the APS-31 or -31A on the AF-2S. The pylon was unique to and integral with the APS-31B radar and unlike the one it replaced, perpendicular to the wing surface instead of perpendicular to the ground.
 The AD-5Q could utilize both an APS-31C and an APS-19:
Rick Morgan noted that the airplane pictured above might have been taken when VAW-13 was involved in Operation Water Glass trying to intercept North Vietnamese aircraft dropping supplies in the south since the APS-19 had an air-to-air intercept mode.

The following illustration is based on drawings that aren't up to my usual standards and pictures. Better information would be appreciated. e.g., it appears that there may have been an AD-4N pod radome that wasn't quite as "blunt"as shown here.