Downloaded from https://www.everyspec.com MIti-STD-810D 19 July 1983 The temperature of the external surface “ofthe store tends to beoome that”of the boundary layer air, due to high convective heat transfer at flight speeds. Boundary layer air temperature ia primarily a function of flight speed and altitude. An expression relating this temperature to flight conditions ia: Tr = Th ( ~) , + r(k-l)M2 Where: Tr = adiabiatic recovery temperature (Kelvin) Th = ambient air temperature (Kelvin) as a function of altitude R= recovery faator k= ratio of specific heats (1.4 for air) ,..
* M= Mach number When the expression.within the brackets, the aerodynamic heating ‘factor,ia friction along a,store with a aircraft,velocity alone. The evaluated for atmospheric air brought to rest”by cylindrical surface, it reduces to a function of equation for a store with a cylindrical surface ia: Tr = Th (1 + 0.174 142)” Higher Mach number flights tend.to oocur at “higher,thus oolder, altitudes and. there is a corresponding tendency for the velocity-dependent heating effeet to oanoel the effect of decreasing temperature with altitude.
When the above expression is evaluated for normal mieaion profiles, flown in a standard atmosphere, of the time the akin temperature will be w$thin the temperature band -150C to 350C. Temperature patterna at points deep within the store will depart considerably from the corresponding akin temperature patterns, due to thermal lag in conduction from the skin end internal heating sources’such as electrical or electronic components. A thermal model of the”store can be generated to calculate internal temperature patterns. ..
An additional therml parauibterneeded to satisfy miesion conditions is that of climatio departure’from the standard atcxmphere, which depends on the global and seasonal variations of atmospheric temperatures (the Th in the TR fOrMUla above). ... I-2.2.3 Experimental evidence has shown that captive flight vibrations are due“largely to aero-acoustic loads (reference 3). This acoustic forcing function, typically consisting of broad-bend random noise, .ismodified as it is transmitted through the store struottire’ to the component. When there is sufficient transmission of frequencies causing resonances of the unit or ita components-or structural mechanisms, a vibration”failure can occur.
Environmental testing, using a reverberant acoustic chamber, tries to duplicate the directional,’epatial aid spectral distributions of vibration expected throughout the etore during captive flight. METHOD 523.0 19 July 1983 523.0-2