By Tommy H. Thomason

Wednesday, September 29, 2010

XF2D-1/F2H-1/F2H-2 Fuel System

Today I read an article in an English modeling magazine by a well-known aviation history author who repeated the error that the F2H-2 fuselage was longer than the F2H-1's, whereas the length increase actually occurred between the XF2D-1 and the F2D-1 (F2H-1). I decided to fix that on Wikipedia as a public service. In the process of doing so, I also fact-checked statements about the fuel capacities of the three airplanes. That's when I discovered that I had only resolved part of the length error that continues to be promulgated.

At the time of the XF2D-1 mockup review, its Standard Aircraft Characteristics (SAC) chart dated 1 May 1945  lists the fuel capacity as 510 gallons internal plus a 345 gallon external tank. Unfortunately, there were no drawings on this SAC chart. However, the length was given as 38' 9.5". The external tank was probably similar to the one provided for the FD-1 (FH-1) as shown here in November 1948.

A month later, an addendum page was added providing the "effect of mock-up changes on XF2D-1 preliminary data sheets dated 1 May 1945": "Subsequent to the distribution of the XF2D-1 data sheets, mock-up board recommendations revised the fuel system to eliminate the external droppable tank and provide instead an increase in internal protected fuel capacity from 510 to 847 gallons."

The XF2D-1 SAC chart dated 1 June 1946 shows an overall length of 38' 11.5", an increase of only two inches. The total internal-fuel capacity shown is the required 848 gallons, including the two tanks in the stub wings that presumably was 90 gallons of the more than 300-gallon increase required. I would guess that the fuselage was deepened from the mock-up configuration to provide most of the rest.

Note that there are three large fuselage tanks, again similar to the FD/FH fuel system configuration.

According to the SAC charts, the F2H-1 internal fuel capacity was increased by only 29 gallons over that of the XF2D-1. What's a little confusing is that the 1 April 1948 F2H-1 SAC chart page for Armament & Tanks is identical to the one above for the XF2D, almost certainly an error in compiling the SAC chart since the correct fuel quantity of 877 gallons is listed on its Page 1. (Each tank has a small but different capacity, with the largest difference being the aft tank at 223 gallons instead of 198.) Another oddity is that this SAC chart lists 200-gallon tip tanks for the F2H-1, whereas it's clear from the Pilot's Handbook for the F2H-1 dated 1 October 1949 and the F2H-2 SAC dated 1 November 1949 that the F2H-1 did not have provisions for tip tanks. Note that the F2H-2 SAC page for Armament & Tanks once again uses the XF2D artwork although it has been updated to show the -2 tip tanks and label each fuselage fuel tank with its correct volume without changing the size or shape of the tanks from the original XF2D illustration.
Not withstanding all that, the revelation to me is that the increase in fuel system capacity does not account for all or even most of the fuselage length increase ahead of the engine inlets between the prototype XF2D and the production F2D (F2H). A net increase of 31 gallons in the three fuselage tanks (the wing stub tanks were reduced in capacity by one gallon each) requires a net increase in length of the tanks of only about five inches, not 12. The remainder may have resulted from the need for additional interior volume for equipment and/or the desire to increase the fineness ratio of the fuselage and canopy to reduce drag. A center-of-gravity correction can't be ruled out, either.

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