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Charles Zimmerman and his "Skimmer"

Flight JournalApr 2005   by Gudaitis, Frank

IN NOVEMBER 1942, a strange object was seen in the sky over Bridgeport, Connecticut. Astonished residents (including me) saw their first flying saucer. It was actually a Chance Vought V-173-a prototype of the XF5U-1, which was the U.S. Navy's most radical fighter. The aircraft had the potential to be flown, under control, at speeds of from less than 20 to 500mph.

The V-173 was the product of a brilliant original thinker-Charles Norton Zimmerman. A farm boy from Olathe, Kansas, in the mid-1920s, he worked his way through school to earn an engineering degree. Like many young men of his generation, he was very interested in aviation, and his long-range goal was to develop safer, heavier-than-air flying machines.

Toward this end, in 1929, he joined the research staff of the National Advisory Committee for Aeronautics, Langley Memorial Laboratory. He was eventually responsible for designing the laboratory's famous flight and free-spin wind tunnels.

As early as 1933, Zimmerman's expertments revealed that in some applications, low aspect ratio wing designs were more efficient than the widely accepted, conventional, long, narrow wings. Zimmerman's concept of controlling the wing vortices with propellers was the key to the project's success, and it was tested on the V-173.

The V-173 was made of wood covered with fabric. Two air-cooled 80hp Continental engines each drove a large, three-blade propeller. The wingspan was 23 feet 4 inches, and the wing area was 427 square feet. The airfoil sections were symmetrical NACA 0015 forms without dihedral or wing twist.

Before the V-173 was flight-tested, the full-size aircraft was put through its paces in the Langley Field wind tunnel. Vought's chief test pilot, Boone Guyton, Richard Burroughs and several Navy pilots flew it for a total of 131 hours. It also made several forced landings because of mechanical problems, but there was little damage because it flew so slowly. Following numerous successful V-173 test flights in 1943, the design work on the XF5U-1 full-power Navy fighter was begun.

In planform, size and configuration, the XF5U-1 was identical to the V-173 prototype. The differences between the two lay in engine power and weight The V-173 weighed 2,250 pounds and-had 160hp. The XF5U-1 weighed five times as much and was powered by two Pratt & Whitney R-2000-7 air-cooled radial engines, each capable of 1,600hp. Propeller feathering could be adjusted by the pilot, and the articulation self-adjusted through 20, 1-degree arc positions.

The XF5U-1 was designed to carry bombs or belly tanks on pylons under its wing. Its armament consisted of six, 20mm cannon, and its top speed was calculated to be around 500mpb with a range of approximately 1,000 miles.

By March 1948, the work had been completed, but when further test were canceled, the Navy ordered Vought to destroy this remarkable aircraft and all the drawings and photographs pertaining to it! Fortunately, some photos and drawings did survive. The official explanation of the Navy's seemingly irrational decision to destroy all traces of the XF5U-1 was that it could now operate jet aircraft from its carriers. It considered propeller-driven fighters to be obsolete.

Although it can't be substantiated, a more logical rationale for the destruction of the XF5U-1 might be found by taking a closer look at the official explanation. After the end of WW II but before the conflict in Korea, Congress was understandably reluctant to spend more money on the military. The Navy was seeking appropriations for additional carriers. If the honorable gentlemen on the hill were to learn that the Navy had a high-performance fighter that could be flown off any small vessel, why would any new aircraft carriers be needed?

We can only empathize with Charles Zimmerman and imagine what he must have felt as he watched 15 years of pioneering work destroyed by a wrecking crew's steel ball. The real loss, however, is discovered in the realization that more than half a century ago, we were offered a new, potentially safer, form of flying.

After the "Skimmer" program was ended, Charles Zimmerman returned to the Langley Research Center in Virginia and was eventually appointed director of aeronautics at NASA headquarters.

One of Zimmerman's most intriguing theories was that of the vector flight principle. Canadian engineer Lewis McCarty adopted it to design and build one of the world"s simplest helicopters. With the DeLackner Aircraft Co., he built and successfully flew a number of very unusual rotary-wing aircraft.

Luckily, the V 173 was spared the fate of the XF5U-1 and is now in the possession of the National Air Museum. Plans are in the works for a group of Vought retirees in Dallas, Texas, to restore this rare old bird.

Before he died in 1996, Charles Zimmerman's lifetime achievements were recognized when he was made a Fellow of the American Institute of Aeronautics and Astronautics; he was also awarded the Wright Bothers Medal.

-Frank Gudaitis

Copyright Air Age Publishing Apr 2005
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