During a supersonic run of a blowdown wind tunnel, temperature of air in the
test section drops which can affect planned measurements. Adverse thermal
effects include variations of the Mach and Reynolds numbers, variation of
airspeed, condensation of moisture on the model, change of characteristics of
the instrumentation in the model, et cetera. Available data on thermal
effects on instrumentation are pertaining primarily to long-run-duration wind
tunnel facilities. In order to characterize such influences on
instrumentation in the models, in short-run-duration blowdown wind tunnels,
temperature measurements were made in the wing-panel-balance and main-balance
spaces of two wind tunnel models tested in the T-38 wind tunnel. The
measurements showed that model-interior temperature in a run increased at the
beginning of the run, followed by a slower drop and, at the end of the run,
by a large temperature drop. Panel-force balance was affected much more than
the main balance. Ways of reducing the unwelcome thermal effects by
instrumentation design and test planning are discussed.