Chance Vought XF5U
| Chance Vought XF5U | |
|---|---|
|
|
| Type: | Fighter prototype |
| Design country: | |
| Manufacturer: | |
| First flight: |
only roll attempts |
| Number of pieces: |
1 ( Bureau Number 33958) |
The Chance Vought XF5U (factory designation VS-315) was the prototype of a planned extremely short take-off (ESTOL) fighter aircraft from the American manufacturer Chance Vought from the 1940s. The unofficial nickname Flying Flapjack (flying pancake) comes from the unusual structural design with an approximately circular wing. The development of the XF5U was based on the results of the test vehicle Chance Vought V-173 . After the V-173 was unofficially referred to as the "Zimmer Skimmer" (after its designer Charles H. Zimmerman ), the XF5U was also known as the "Skimmer".
history
Even before the first flight of the V-173, the US Navy placed an order with Chance Vought on September 17, 1942, to build an XF5U-1 prototype fighter based on the V-173. The V-173 served as a test aircraft in over 200 flights, but the step to test the vertical take-off capability was not taken; this would have required a fundamental redesign of the machine. The order included the construction of a break cell and a prototype for flight tests. The responsible designer was EJ Greenwood. A wooden dummy could be inspected on June 7, 1943, using three-blade propellers with a diameter of 4.88 m, which were later exchanged for a four-blade version.
The construction of the XF5U-1 in Stratford was completed on June 25, 1945, but at the time of the preparations for the first engine test runs the war ended and further development work was continued only to a very limited extent. Until 1947, propellers from the Chance Vought F4U were used as a substitute . In addition to overheating problems of the engine, the heavy and complex gear units were the biggest problem. Even in the first test runs, two gearboxes failed one after the other, so that it was concluded that flights of over 90 minutes would not be possible with them. Probably there was also a brief take-off during the taxiing tests, but a real flight did not take place. Last but not least, the development of the first jet aircraft, together with the development problems mentioned, caused further development to cease and the aircraft was scrapped shortly afterwards.
construction
The XF5U was slightly larger than the V-173 and, in contrast to this, an all-metal construction with a weight five times greater; the cell had Vought's own Metalite planking. The drive was also much more powerful with two Pratt & Whitney R-2000 twin-radial engines . The design with nearly circular wing lowest possible extension was maintained, as well as the development goal of the highest possible speed and low landing speed. In an expansion stage with more powerful engines, the F5U should be able to take off vertically and then reach a top speed of 800 km / h (500 mph).
As with the V-173, the plan of the wings was approximately circular, but had a straight leading edge because of the large propellers attached to the outer ends. Normally, wings with such a low aspect ratio are not suitable for achieving high speeds due to the strong tip vortices. In the case of the V-173 and XF5U, however, the propellers located far outwards generate a high-energy counter-vortex, which rotated in the opposite direction to the edge vortex of the wing and should maintain the higher pressure below it. The wing, which was kept so small, was intended to increase structural stability on the one hand and enable high maneuverability on the other. The high-energy vortices also ensure sufficient lift at low speeds with a high angle of attack. The ratio of top speed to landing speed should be improved from the usual ratio of 4: 1 to 10: 1 with these design features.
The original concept envisaged a design without a horizontal stabilizer, instead two ailevators (now called elevons ) in the middle at the end of the fuselage should take over this function. However, wind tunnel tests showed that their effectiveness would be inadequate, especially at low speeds and high angles of attack . Instead, a flying-tail elevator, which is now common in almost all supersonic aircraft, was used for the first time on the V-173 , which was then also used on the XF5U-1. While this was still arrowed on the V-173, an unarrowed version was used for the XF5U. With the retractable chassis, the XF5U had a ground angle of 18.7 °. The performance specifications called for a top speed of 500 mph (800 km / h), a landing speed of 40 mph (64 km / h) and a range of 1000 miles (1600 km). It should be possible to carry either two additional tanks or two 1000 lb bombs (454 kg) at external load stations. Originally six 0.50 cal. Machine guns and later four 20 mm cannons were planned as armament.
The drive consisted of two double radial engines Pratt & Whitney R-2000-7 Twin Wasp, which were installed in the wings. Fan wheels in the leading edge of the wing were used to cool the engine. Between the two engines there was a transfer gear and connecting shafts to synchronize the speeds and to distribute the power to both propellers if one engine failed. In addition, a gearbox was needed to divert the power flow from the engines to the propellers. For simple practical implementation of the flapping joints in the four-blade propeller, two two-blade propellers were arranged one above the other. With a sufficiently high engine power, the lift force should exceed the aircraft weight, so that a vertical take-off option was even considered. The propellers intended for the fighter plane should have flapping joints similar to those used on helicopters. An ejector seat was also planned so as not to collide with the very large propellers in the event of an emergency exit.
Technical specifications
| Parameter | Data (calculated) |
|---|---|
| crew | 1 |
| length | 8.72 m |
| Wingspan (width) | 9.91 m above the elevons 11.07 m above the propeller tips |
| height | 4.51 m |
| Wing area | 44.13 m 2 |
| Empty mass | 6356 kg |
| Max. Takeoff mass | 7628 kg |
| Top speed | 800 km / h at 8800 m |
| Rate of climb | |
| Engines | 2 × Pratt & Whitney R-2000 -7 Twin Wasp with 1350 PS (993 kW) each |
See also
literature
- Art Schoeni: The flying pancakes, Part 1. In: Airplane Monthly November 1975, pp. 566-571.
- Art Schoeni: The flying pancakes, Part 2. In: Airplane Monthly December 1975, pp. 624-627.
- Bill Norton: US Experimental & Prototype Aircraft Projects. Specialty Press, 2008, ISBN 978-1-58007-109-3 , pp. 165-168.
Web links
