Thunderjet Series Changes

About the Early/Late and Short/Long Thunderjets
By Bruce Craig, Webmaster

From prototype to final G-model, the Thunderjet progressed through a number of evolutionary changes. Some of those changes were very visible, others were not. Two kinds of changes were particularly visible, if not well documented, and both were significant enough that there has been a tendancy to divide the Thunderjet series into the "early" and the "late" models. The problem is, the two changes did not occur beginning with the same model, so it is appropriate to make clear what is "early" and what is "late."
These two changes were (a) landing gear shrink method changed from hydraulic to mechanical, and (b) lengthened fuselage. These changes were not the only significant changes made to the Thunderjet; indeed, there were others which are equally significant, if not more so. However, one change, the strengthened wing, was made at the same time as, and in conjunction with, the change from hydraulic to mechanical strut shrink method. The primary reasons the landing gear shrink method and the lengthened fuselage are significant as dividing lines, is because both were accompanied by other less obvious improvements and both are highly visible where the other changes were not particularly visible, if at all.
The landing gear shrink method was changed beginning with the D-model. As mentioned above, this change to the landing gear was done at the same time the wing structure was modified and thicker skins were used in order to strengthen the wings. Therefore, if this change is used as a definition, the "early" models are XP-84 to P-84C, and "late" models are F-84D/E/G.
The fuselage extension was added beginning with the E-model. I have seen two "reasons" expounded for making the extension. One, and the most stated, was "for the pilot's comfort" because the cockpit was cramped. This may have been a factor, but I seriously doubt it to be the main reason. McLaren, in his book, Republic F-84, a Photo Chronicle, states the reason was an attempt to correct a flight-instability problem. That reason is much more likely than for "pilot comfort" -- unless, of course, the pilot is uncomforable with flight-instability.
The dimension of the extension has been variously published to be either ten inches, twelve inches, or thirteen inches. As documented on this site in the Extension page, the correct dimension of the extension is fifteen inches. I have concluded, because of my own measurements of a C-model and an E-model, that this extension was distributed as follows: eight inches added to the length in the cockpit, four inches added aft of the cockpit at the equipment bay section, and three inches added aft of the canopy at the "fuselage splice." Also, as discussed more completely in the Extension page, the tailpipe (Republic uses the term "ejector") was changed from model to model, these changes included differences in length of the ejector, so measuring the length of a D- then an E- would not necessarily differ by fifteen inches (even though that amount was added to the fuselage) and an E- and a G- would not necessarily be the same length because the G- ejector was about two inches shorter than an E- ejector. I have concluded that the differences in published dimensions of the fuselage extension are due to the differences in lengths of the ejectors from model to model. If the fuselage extension change is used as a definition, the "early" models are XP-84 to F-84D, and "late" models are F-84E/G.
Clearly, using the landing-gear-change definition of "early" and "late" creates a conflict with the fuselage-extension definition of "early" and "late." I concluded it would be best to reference the landing gear change as "early" and "late" and the fuselage extension as the "short" and "long." Unfortunately, I didn't figure all this out until I was well into creating pages for this site -- I keep learning new things as I study the documentation I have (so far) obtained. So, despite my intention to be consistent, there are inconsitencies in my text because I have started lately to use the "early" and "late" to differentiate the landing gear changes (XP-84 to P-84C from F-84D/E/G), and the "short" and "long" to differentiate the fuselage extension changes (XP-84 to F-84D from F-84E/G).
So, keep the context of the specific subject in mind when you encounter the terms, and that these two changes are the significant occurances around which the "early" and "late" or "short" and "long" discussions revolve. Are you dizzy now!

XP-84-RE 45-59476

The second Thunderjet, XP-84-RE 45-59476, at Wright Field. Photo: USAF via Greg Spahr.

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