Thermodynamic Modeling for the Analysis of Non-Stabilized Flight Test Temperature Data

Temperature is the result of underlying thermodynamically independent heat transfer modes of conduction, convection and radiation. Flight test methods have evolved to collect targeted data in support of most engineering disciplines – flight mechanics, aerodynamics, performance, dynamics – but little has changed in the field of thermal analysis, which relies mainly on stabilized temperature data requiring extended ground and flight test conditions. Traditional methods are time consuming and may result in imprecise extrapolation of steady-state temperatures. Temperature response is an exponential time decay function with time constant and asymptotic values defined by material properties, compartment volume, and heat transfer mode. A generalized heat transfer block diagram and matrix state space model presents each heat transfer mode in a multi-zonal system of helicopter compartments. The model is defined via system identification tests that isolate the heat transfer effects – electrical heating, passive cooling, solar radiation, and airspeed effects. The resultant model can be used with time-variant standardized hot day solar radiation and ambient temperature profiles to yield temperature versus time profiles for direct comparison with equipment qualification criteria. This methodology is the basis for more efficient and more accurate results than current evaluation techniques.