Mr. William Bihrle, after a distinguished career in
aerodynamics, flight dynamics and simulation at NACA Langley, Republic Aviation and Grumman Corporation, established Bihrle Applied
Research, Inc. (Bihrle) in 1973 as a consulting and wind tunnel testing firm. Bihrle began by supplying simulation database development and
wind tunnel testing and analytical services to the Government (US Navy and NASA). As part of their efforts under a NASA contract, Bihrle
developed the test techniques and the data acquisition and analytical tools needed to make the rotary balance apparatus in the NASA
Langley 20 foot vertical wind tunnel into the first viable tool for obtaining good quality, repeatable wind axis test data.
The
availability of these data allowed the demonstration that the rotational data set was both necessary and sufficient to predict a
configuration's steady state spin modes. The development of a spin prediction methodology by Bihrle has enabled the on line prediction of
aircraft spin modes as the wind tunnel data is acquired. This capability, along with the ability to identify the source of aerodynamic
characteristics using component rotary balance testing, has for the first time allowed developers and researchers to analyze and modify a
configurations post stall behavior early in the development cycle.
Further studies demonstrated that the rotational data, when used in a large-angle six degree-of-freedom simulation that properly
mechanized static, wind axis, and body axis dynamic data sources, could accurately simulate all possible aircraft motions, including
out-of-control motions in the post-stall region. Consequently, it was finally possible to simulate and analyze an air vehicles behavior
in post stall flight, as well as to evaluate control inputs and/or control system architectures' effectiveness in suppressing or
recovering from out of control motions.
As a direct consequence of Bihrle's efforts, rotary balance testing, spin mode predictions, and large-angle data base development from the
resulting data have become required efforts during the development of new air vehicles throughout the industry, utilized by government
agencies and airframe manufacturers. Over the past 29 years, Bihrle has successfully completed over 200 contracts for over 45 government and
commercial organizations covering engineering activities ranging from wind tunnel testing and analysis to flight test and simulation
studies. As a result of the success of these activities, Bihrle's engineering staff has become internationally recognized as leaders in the
fields of high angle-of-attack aerodynamics, dynamic data acquisition, novel wind tunnel test techniques, all aspects of simulation, and
simulation software development.
In the late 1980's, Bihrle designed and built a new, wholly-owned research facility that houses a Large Amplitude, Multi-Purpose (LAMP) wind tunnel that incorporates all of the capabilities that the years of collecting and
using dynamic data had shown were desirable. The LAMP facility's dynamic model support rig permits the acquisition of wind axis (rotary
balance) dynamic data, body axis (forced oscillation) dynamic data, and combinations of the two types of motion, as well as static
data.
For our in-house simulation efforts, Bihrle developed a PC based simulation environment that incorporates all of the tools we found
necessary to do our data base development and simulation and analysis tasks. Realizing that none of our customers had access to anything
that approached the capabilities of this tool suite, Bihrle developed the software into a commercial product, which we call D-Six. D-Six (is currently used by government agencies and industry in North America, Europe, and Asia.
