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William Bihrle was born in New York City on August 10, 1925 to parents of German descent. He attended one of the specialized science high schools in the city before graduating and entering the accelerated engineering program at Rensselaer Polytechnic Institute (RPI) in 1942. At the height of World War II, the engineering programs at the time were administered throughout the year so the students could graduate in three years to support the war effort. Bill graduated in 1945 at the conclusion of the war with his degree in aeronautical engineering and joined the Navy. His naval duties included support of aircraft maintenance where he initially worked on WWII Navy fighters such as the F4U-Corsair, and others.
Following his Navy service, he returned to New York and started his aeronautical career with employment in the burgeoning Long Island aeronautical industry. Starting with Columbia Aircraft in Valley Stream, he quickly established his expertise in the new aerodynamic specialty of flight dynamics, a capability that led to his employment at the world renowned National Advisory Committee for Aeronautics (NACA) facility at Langley field in Hampton, Virginia. His flight dynamics expertise became especially important at this time in the evolution of NACA following the war, as the need to improve the stability and handling qualities of aircraft became a widely recognized issue resulting from the deployment of many dangerously difficult to fly aircraft during the war. This proficiency led to Bill’s many lectures both within NACA and the industry, as well as directing his increasing interest in the study of aircraft behavior in slow speed flight. At slow speeds, aircraft can experience stalls, the condition that occurs as the aircraft slows below a speed in which the wings can produce sufficient lift to continue flight. The behavior of the aircraft in the stall and beyond, known as fully departed flight, was a particular danger to virtually all contemporary military and civil aircraft and was the leading source of aircraft related deaths. Technical analysis of these behaviors, effectively unexamined up until this point, was just beginning at NACA, and Bill was very quickly involved in the development of analytical techniques to probe these characteristics.
Much of the initial NACA work attempted to provide empirical guidelines for aircraft development to avoid such adverse characteristics as the stall and spin (where the aircraft can enter a potentially unrecoverable rapidly descending spinning motion, popularly referred to at the time as the “death spiral”). While this approach was primarily based on observation of the behavior of various aircraft designs and their weight distribution, Bill attempted to analyze the fundamental aerodynamics of these motions using a more scientific approach. Attempting to extend and further develop a testing methodology initiated in the 1930s, Bill developed a test methodology that allowed the acquisition of the forces and moments acting on a model of a given aircraft during the imposition of spinning motions. Called a rotary balance, this apparatus enabled the specific aerodynamic characteristics of an aircraft in a spin. While his initial attempts at characterizing these data led to the first successful measurement of these aerodynamic behaviors as a result of significant improvements over earlier efforts, the productivity of the test apparatus was significantly limited by the available data measurement technology of the 1950s, and the apparatus was not capable of cost effectively supporting the acquisition of the large quantities of test data needed to fully analyze the stall and spin aerodynamics in production testing.
Commitment to family matters led to Bill leaving NACA and returning to Long Island where he began employment at the Republic aircraft company in Farmingdale, New York. He rose through the ranks at Republic, ultimately serving as the Chief Engineer on the aircraft development program that resulted in the Republic F-105 aircraft. That aircraft, also known as the Thunderchief, was designed as a high-speed penetrator and fighter bomber, capable of carrying a greater payload that the U.S. bombers of WWII at speeds up to twice the speed of sound. The F-105 (known affectionately as the “Thud” by its pilots) ultimately served extensively in the early part of the Vietnam war before being retired.
While Bill had accomplished significant technical achievement during his tenure at Republic, dissatisfaction with the management changes that occurred during the early 70’s led to his leaving to start his own consulting company. His technical expertise in the flight dynamics discipline was widely recognized, with his participation in a wide range of national and international symposia and lectures. This recognition supported his decision to pursue the consultancy. However, within a year, the practical realities of supporting a growing family led to his decision to return to the second major airframe manufacturer on Long Island, Grumman Aircraft.
Bill’s tenure at Grumman was marked by the return to the analysis of stall and post stall aerodynamics, in this case the behavior of the F-14 aircraft. Bill worked as an engineering specialist within the Grumman engineering office, supporting the analysis of the adverse characteristics exhibited by the F-14 during the spin. In addition, his reputation also led to additional flight dynamics related research contracts for Grumman with a variety of government agencies including NASA, the Air Force Research Lab as well as the Naval Air Warfare Center.
Many of these research programs focused on improvements in the handling qualities of contemporary aircraft, as well as addressing the continuing problems related to aircraft stall and departure. These programs, as well as his work related to the F-14 spin problem, led him to reconsider the analytical work that he had begun during his time at NACA in the 50s. Bill decided to leave Grumman and re-start his old company, Bihrle Applied Research in Jericho, New York.
After some initial contracts with NASA (the renamed NACA), Bill proposed to NASA Langley that the old rotary balance facility that he had developed in the late 40’s be re-established, utilizing modern data acquisition technology that would make the acquisitions and analysis of the rotary balance test significantly more practical. With a growing group of engineers, Bill was able to establish the first practical and productive test capability in the world, a test capability that provided new insight into the driving aerodynamic forces and moments that produced the stall and post stall behaviors. The analysis and application of these data have led to reliable predictive methods and simulation capabilities that, prior to this work, were not considered possible.
This capability has significantly advanced the design, piloting techniques, control system development and training of most aircraft developed since the seventies. As a direct consequence of these efforts, rotary balance testing, spin mode predictions, and large-angle database development from the resulting data have become standard practice during the development of new air vehicles throughout the industry, utilized by government agencies and airframe manufacturers alike. The company that has evolved from this genesis has grown to an internationally recognized entity that provides development support to virtually every major (and many smaller) airframe developers, as well as many government agencies, both nationally and internationally.
From its headquarters outside of NASA Langley in Hampton Virginia, to its wholly-owned research facility that houses a Large Amplitude, Multi-Purpose (LAMP) wind tunnel facility in Neuburg an der Donau, Germany, Bill’s company, Bihrle Applied Research Inc. still pursues his fundamental goal – MAKING FLIGHT SAFER.