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Charles H. Zimmerman

Charles H. Zimmerman
Charles H. Zimmerman
Credit: NASA

Charles H. Zimmerman

Charles H. “Charlie” Zimmerman (1908 –1996) was an innovative designer of revolutionary research facilities, unconventional aircraft, and advanced flying vehicles. He was an expert in the field of stability and control of aircraft, as well as in flight dynamics. In addition to his aeronautical contributions, Zimmerman also participated in early studies that stimulated the NACA research on spaceflight. He became a participant in Project Mercury and led advanced studies of vertical takeoff and landing (VTOL) aircraft.

Zimmerman joined the staff of the NACA Langley Memorial Aeronautical Laboratory in 1929 after graduating from the University of Kansas with a bachelor of science degree in electrical engineering. He later received a master of science degree in aeronautical engineering from the University of Virginia in 1954.

His initial assignments at Langley in the 1930s consisted of wind-tunnel and analytical studies at the 5-Foot Vertical Wind Tunnel (which Zimmerman designed in 1929), to investigate aircraft spins, which had become a frequent factor in fatal airplane accidents. The facility could simulate the spinning motions of models affixed to a balance that measured air loads during the simulated spin. However, this testing approach proved to have numerous limitations, and Zimmerman was assigned the task of developing a more capable free-spinning 15-ft spin tunnel, in which hand-launched models were used to study the characteristics of spins and spin recovery in a much more efficient and informative manner. He provided the basic design of the facility and its operational procedures, which have been followed in Langley’s follow-on 20-ft Spin Tunnel operations to the present day. Also, in the early 1930s, Zimmerman continued his interest in the applications of free-flying models by designing a proof-of-concept 5-ft wind tunnel for studies of dynamic stability and control in conventional flight. The success of this facility in 1937 led to the design and construction of the larger Langley 12-Foot Free-Flight Tunnel in 1939. The free-flight testing technique was later transferred in 1958 to the Langley Full-Scale Tunnel, where it was used until the closure of that facility in 2009.

During 1933, Zimmerman’s research efforts focused on aircraft capable of extremely low-speed takeoff and landing operations, resulting in reduced runway requirements.  These efforts led him to concentrate on a radical new aircraft configuration. Results of his studies indicated that wings, having “flying saucer” shapes and powered by large propellers that immersed the wing in their wakes, could produce much more lift at low speeds than conventional wings. After conducting extensive wind-tunnel and free-flying model tests of the concept, Zimmerman left Langley in 1937, to join the Chance Vought Aircraft Division. At Chance Vought, he successfully advocated for a contract from the U.S. Navy for a proof-of-concept aircraft known as the V-173, which was later tested in the Langley Full-Scale Tunnel, and flown by pilots such as Charles Lindbergh, who praised the flying qualities of the design. Plans were set into motion to proceed to a refined high-speed propeller-driven fighter known as the Vought XF5U, intended to operate from small aircraft carriers for protection of the naval fleets in the Pacific from Kamikaze attacks. However, development issues arose that delayed the project until the end of the war, at which time the Navy lost interest in the concept. Despite an unsuccessful ending, the “Flying Pancake” or “Zimmer Skimmer” concept remains one of the most innovative ideas in aircraft design. The V-173 aircraft was acquired by the Smithsonian Institution and placed on long-term loan to the Vought Heritage Foundation for restoration, and the restored V-173  is currently on display at the Frontiers of Flight Museum in Dallas, Texas.

Zimmerman returned to the Langley Memorial Aeronautical Laboratory in 1946, and continued working in the area of stability and control. In the early 1950s, Zimmerman conceived and demonstrated the capabilities of a portable, individual air transportation concept – the flying platform. He proposed that the flying platform could be easily controlled by an individual by “kinesthetic control,” the ability to stand upright and steer by leaning toward the direction of intended motion. The concept was designed with military applications in mind. Operated by an individual soldier, the platform was designed to be used for easier travel over rough terrain, assisting in reconnaissance, or spotting land mines. Consisting of a circular, stand-on platform powered by ducted fans beneath the “pilot”, the concept was developed and demonstrated by Zimmerman and his colleague Paul Hill during flight tests at Langley and at the Wallops Flight Station. The revolutionary vehicle was flown on several occasions by volunteers having no experience in flying aircraft. Flights were achieved at speeds up to 17 knots and altitudes up to 12 feet. This exploratory concept stimulated considerable interest in the military services, resulting in several industrial contracts to further evaluate the flying platform concept. Unfortunately, the concept could not compete against emerging ideas for VTOL aircraft and was eventually discarded. Nonetheless, this is but one example of Zimmerman’s ability to think “out-of-the-box.”

Zimmerman was a key manager and technical lead for Langley’s research program on Vertical and Short Takeoff and Landing (V/STOL) aircraft configurations in the late 1950s and 1960s. He conceived and participated in evaluations of many novel concepts designed to permit helicopter-like operations for takeoff and landing or extremely short field requirements. He was also co-inventor of the unique “tilt-wing” configuration demonstrated years later during flight tests of the Ling-Temco-Vought XC-142 transport.

In 1953, at the dawn of the space age, Zimmerman joined a three-member NACA study group that called on the country to go forward with research for space flight. After heading a space study group in 1958, he became a division chief for NASA’s Project Mercury, in charge of logistics. He was named Director of Aeronautics at NASA Headquarters in 1962 and retired in 1967.

In 1956, Zimmerman was awarded the American Helicopter Society Klemin Award “for notable achievement in advancing the field of vertical flight aeronautics.”

Charles Zimmerman died May 5, 1996 at the age of 88 in Hampton, Virginia. He was survived by his wife of 64 years, Beatrice, and a son, Charles H. Jr., of Hampton;