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Aviation History
1947
1947 - 0526.PDF
FLIGHT APRIL IOTH, 1947 PHANTOM DEVELOPMENT lation in the fuselage would have been ideal, but this meant a loss in aerodynamic efficiency as the air intake ducts would have to be either very long or curved. In addition, as the fuselage was to be quite small, it would have necessitated carrying most of the fuel in the wings ; this would have involved complicating the wing structure to provide large unobstructed tank bays, making the tanks themselves in awkward shapes and almost doubl- ing the amount of fuel system '' plumbing,'' all of which was bad from the production angle. So McDonnells finally chose a position for the engines for which they must have had a secret preference all the time—enlarged wing fillets. They had used the same idea in their XP-67 twin-engined fighter, to house fuel and ammunition, and had found that it offered many aerodynamic advantages. The weight was kept well inboard and, by careful design, the structure weighed les^ and offered less drag than an enlarged fuse- lage or bulged wing. The problem of housing the main undercarriage wheels when retracted also ceased to offer any headaches, even with outer wings of thin aerofoil sec- tion . Fillet Behaviour There was at first some doubt as to how these fillets would affect airflow at high Mach numbers. Again wind- tunnel models provided the answer, and it was found that, provided the air intake ducts in the leading edge of the fillets were carefully designed, they still offered very definite advantages over nose, "elephant ear" or under-wing in- takes. Tests in the N.A.C.A. tunnel showed that over the fillet the critical Mach number was considerably better than over the basic wing. The most apparent explanation for this is that, as the air enters the leading edge at the fillet, this in effect splits the one thick wing into two aerodynamic- ally thin ones, added to which the maximum depth line of the aerofoil section sweeps back at the fillet so giving a better "laminai flow" effect. All of which is most satis- factory and, naturally, the extra depth of the inboard portion ot the wing gives the whole wing additional rigidity. Much time was spent in evolving the best possible inlet duct; the result is a nice-looking and aerodynamically good intake that may well provide inspiration for future jet- fighter designs. Once the engine installation was all settled, the rest of the design work was quite simple. The centre fuselage Air Commodore Whittle in the cockpit of a Phantom. Withhim is Mr. James S. McDonnell, President of the manufacturing company A typical American gun installation (four grouped 0.5m.Brownings) characterizes the Phantom. and fillets were made as a single very strong unit, the nose and tail portions of the fuselage being simple monocoque structures, and the wings were designed to fold backwards immediately outboard of the fillets. A tricycle under- carriage was an obvious choice as, apart from all the usual advantages claimed for this arrangement, there were con- siderable misgivings about the effect of jet exhaust upon the wooden flight decks of carriers. The wide track of the main wheels was considered necessary for landing-on, and a deck-landing arrester hook was fitted under the rear fuselage. The four 'point-fives " were mounted in the nose of the fuselage, the installation being very similar to that of the Messerschmitt 262 jet-fighter. This has the advantage of bringing their line of fire close to the pilot's line of sight and also makes them easily accessible from ground level for servicing operations. As usual with jet-fighters, it was possible to put the cockpit well forward of the wing, giving an excellent field of view through the now cus- tomary "bubble" canopy. Aft of the cockpit were fitted the three large self-sealing fuel tanks, separated from the pilot by substantial armour plate and firewalls. The tail unit remained fairly orthodox although the tailplane was given a small dihedral to clear the jet exhaust. First Flight on One Engine By January, 1945, the last drawings had been finished, the last airfrarre parts made and assembled. Finally, the whole machine was given a very smooth high-gloss finish and was ready for its first flight, but . . . only one engine was ready for installation. McDonnells had such con- fidence in.theu XFD-i, however, that, after a few ground runs and taxying tests, they decided to make the first flight on just the one engine. This test was completely successful and showed that, because its engines were so close inboard, the XFD-i had an almost negligible yawing movement on one engine—a fact that could easily save pilot's life if an engine got shot up in action or failed du ing take-off. Soon the second engine was installed and the serious test- flight programme began. Meanwhile the fighter had acquired the name of Phantom and the engine the designa- tion Westinghouse 19B. It soon proved itself capable of speeds well over 500 m.p.h., combined with low-speed fly- ing characteristics comparable with those of any conven- tional carrier-based fighter. Its cruising range proved better than 1,000 miles and its service ceiling over 35,000 feet. McDonnells and the U.S. Navy had a fighter to be proud of. Then came the day, July zist, 1946, when the prototype made its first landings and take-offs from the Franklin D. Roosevelt. The rest of the story is still being written. N.B.—In describing the Phantom's armament installa- tion as being '' very similar to that of the Messerschmitt 262 '' Mr. Taylor is referring only to the disposition of the guns. The Messerschmitt, of course, with its four 30 mm high-capacity, low-velocity MK108 guns, was greatly superior in fire power.—-Ed.
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