by Tommy H. Thomason

Friday, October 28, 2016

North American FJ-4/4B Fury Notes

 27 January 2017: In response to a question about the tail bumper;
Unlike most tail bumpers, the FJ-4's was very narrow - basically a blade - and not retractable. There was a fixed guard in front of the bumper, which could pivot to absorb the shock of a tail-low touchdown. There was almost certainly a damper involved, since the bumper is always extended except on museum examples (see second picture) where the damper is missing or inoperative. There was a tie-down hole in the bumper.


23 January 2017: Some notes on and pictures of the 1/72 Emhar kit can be found here:
http://www.britmodeller.com/forums/index.php?/topic/235015791-emhar-fj-4-fury-172/

 October 2016: Updated to revise the horizontal tail discussion and correct other details.

In the process of preparing an information package requested by a kit maker, I revisited a question raised several years ago, the size and shape of the horizontal stabilizer. The problem is a fundamental inconsistency among the drawings and data available to me, which include the excellent North American FJ-4 four-view drawings, the FJ-4/4B Standard Aircraft Characteristics (SAC) charts, two NACA spin tunnel test reports, and a couple of measurements of an actual FJ-4B stabilizer by Jim Robbins. Thanks to FJ-4 maintenance manual data provided by Frank Truchi, a volunteer at the National Naval Aviation Museum, I can confirm that the NAA drawing of the horizontal tail is correct except for the span and the location of the elevator.


Note that the FJ-4 empennage was subjected to development changes.

The original FJ-4 horizontal tail was swept at 35° at the 25% chord. At some point in flight test, the sweep was changed to 35° at the leading edge, probably to reduce the overall length of the airplane, an important consideration from the standpoint of compact parking on aircraft carrier flight and hangar decks. The span was subsequently reduced by 18 inches on each side for production due to structural problems found in flight test.

In the process of reviewing the documentation I have, I discovered a detail that I wasn't aware of before. The major change between the FJ-3 and the FJ-4 was the wing. The new one provided more area to lift more weight, much of which was fuel. The knock on the FJ-3 was that performance suffered when it was carrying external tanks and endurance suffered when it was not. As a result, the FJ-4 was to have the same internal fuel capacity when clean (no external tanks) as the FJ-3 configured with external tanks. The ailerons were also to be moved inboard to avoid weight that would otherwise have been needed to stiffen the wing torsionally, which didn't leave much trailing edge available for flaps. As a result, the FJ-4 had narrow-chord leading edge flaps to further increase camber and a panel hinged to the bottom of the flap to scoop air into the slot between the leading edge of the flap and the aft spar of the wing.

This panel isn't shown on the NAA drawing bottom view.

One tidbit about the FJ-3 versus the FJ-4 that I'd forgotten was the increase in tread. This didn't result from the main landing gear struts being relocated more outboard: the wheels were simply located on the outboard side of the strut rather than the inboard side.

The FJ-4 had excellent handling qualities, eliminated the FJ-2/3's gunnery inaccuracy that resulted from the excessive downward angle of their cannon, and was almost certainly one of the best jet fighters from a performance and maneuverability standpoint that didn't have an afterburner.  Unfortunately, fighters with afterburners had an innate interception and air-to-air combat advantage so the Navy gave all the FJ-4s to the Marine Corps, which was happy to have them until Vought produced more F8U Crusaders than the Navy needed.

However, that wasn't the end of the FJ-4. The Bureau of Aeronautics decided that Douglas' Ed Heinemann wasn't paying proper attention to its concerns about the A4D Skyhawk program so it contracted with North American for an attack variant of the FJ-4.
Note the spoilers added to the upper surface of the wing for increased roll-control power required for the asymmetric loading of the heavy nuclear weapon that was the raison d'etre for the A4D/FJ-4B. Most descriptions of the FJ-4B state that these were located forward of the flaps, which I had presumed to be correct since that is where they would normally be.

It turns out that they were on the upper surface of the flaps as shown in the SAC drawing above. Note the open spoiler on this FJ-4B's damaged flap.
They are also evident in this FJ-4B walkaround photo taken by Fotios Rouch (for the complete set, see http://www.aircraftresourcecenter.com/awa01/401-500/awa463-FJ-4-Rouch/00.shtm).

For an FJ-4B configuration with the left-hand cannon removed, see: http://tailspintopics.blogspot.com/2012/03/modelers-guide-to-sabre-fury.html

For some detail under the canopy see http://tailhooktopics.blogspot.com/2012/12/fj-4-detail-under-canopy.html. Note that the FJ-4B was in service long enough to be retrofitted with the Martin-Baker ejection seat.

For an excellent set of annotated photos with configuration and other information, see this Phil Friddell post: http://tailhooktopics.blogspot.com/2012/12/fj-4-detail-under-canopy.html

For a summary of all the different FJ Furies, see http://tailspintopics.blogspot.com/2009/10/fj-fury.html

And, of course, there's great information and drawings in Steve Ginter's FJ-4/4B monograph, Naval Fighters Number Twenty Five, which is regrettably out of print.

Tuesday, October 18, 2016

Grumman AF-2W Guardian Redux

In a 25 May 2015 post to a Special Hobby 1/48 AF Guardian thread on Britmodeler (HERE), "Homebee" noted that there appeared to be two different radomes for the AF-2W. To my chagrin, I must report that I hadn't notice the difference before I tripped over his unanswered post yesterday.

Here is an early AF-2W in Grumman flight test (it is configured with an ejection seat):

Here is a Navy Reserve AF-2W:

My post on the AF Guardian (HERE) failed to note that. I overlooked the obvious yet again.
The interface of the radome with the fuselage on the early version is smoothly faired between the bomb bay opening and the radome. The later interface (possibly an added sheet-metal fairing) is flat sided and appears to terminate abruptly. Unfortunately, I don't have a good picture of the aft end of the later radome.



I have no idea when or why the change occurred. It appears to have been a production change as evidenced by this picture of BuNo 124783 on the Grumman flight line.