William Bihrle, Jr.

 
 

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 as a result of the deployment of many dangerously difficult to fly aircraft during the war. This proficiency led to many lectures both within NACA and the industry, as well as directing Bill’s increasing interest in the study of aircraft behavior in slow speed flight. At this condition, 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, in what’s called 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.

 

NACA and his early career...