F-84G Thunderjet Tailpipe (Ejector)


The jet age brought with it many engineering challenges. Heat generated by jet engine exhaust required development of new materials and techniques to cope with and disipate the heat generated. Republic engineers struggled to develop appropriate tailpipes, called ejectors in their documents. Although later production models were relatively consistent as to the ejectors fitted, at least within production blocks if not a model series, the first Thunderjets were subject to a series of changes in ejector design as Republic engineers sought to find materials and designs to solve overheating in areas of the aft fuselage. These changes did not necessarily show up externally, except for a number of variations in the length and sometimes shape of the ejector nozzle. My thanks to Byron Calomiris, who was one of the Republic employees who worked on the first XP-84, including helping with fabrication on the early ejectors, and who provided me with the above information.

As material and design changes were made to the Thunderjet, so to were materials and design changes made to the engines used. Both the "learning curve" and the engine upgrades affected ejector designs used on production aircraft. Generally, over the production life of the Thunderjet, the ejectors progressed from a simple "straight out" oval section with little compound curve that extended past the base of the rudder (up through C-model), to a "curved in" oval section that had a substantial compound curve that also extended past the base of the rudder (D/E-models), to a "curved in" round section that ended flush with the base of the rudder (G-models). The interior of the ejectors also became more complex during this transition, with the D/E and G models having fairly complex multiple wall construction with corregated (louvered) air passages. The taillight installations and the ventral fin fairing shape also changed to accomodate the changes in ejector shape and length. All of these changes are quite subtle, and become obvious only on close inspection.

I measured the ejector nozzle dimensions on a P-84C and an F-84E. Both are oval cross section. The C-model ejector measures 24-5/8" high by 19-5/8" wide by 28-7/8" long, and is fairly straight in side section with no taillights at the top. The E-model ejector measures 24" high by 19-1/2" wide by 28-3/8" long, is more curved in side section and has the taillights side by side at the top. Both extend beyond the base of the rudder. I have not had opportunity to measure the nozzle on an F-84G. Photos show them as round (as do the illustrations on this page) and the taillights are stacked above the nozzle, not side by side as on the E-model. My guess is the diameter is about 20 to 21".

Illustrations from the Republic archives courtesy of E.J. Boss

Go to page with large image of this illustration Go to page with large image of this illustration

Above: F-84G Ejector Installation.

Left: F-84G Aft Fuselage Assembly.


Contents Copyright 1997-1999 Bruce Craig -- All Rights Reserved


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