In order to maximize stealth, most new military fighter/attack aircraft are designed to carry weapons internally. Associated wind tunnel testing of stores inside an internal bomb bay or cavity can be problematic due to the use of a sting or strut to place the simulated store in the desired position inside the internal cavity. Since aft mounted stings are usually not feasible, a strut mounted sting is typically used for determination of moments on a simulated store in an internal cavity. However, these strut devices can impact store freestream aerodynamics. A study was completed to see if computational fluid dynamics could be used to identify the potential impact on the strut on store aerodynamics. NomenclatureARA = Aircraft Research Association CAD = computer aided design CFD = computational fluid dynamics CPU = central processor unit GBU = guided bomb unit NICS = Navy Internal Carriage and Separation Ma = Mach number Mk-82 = 500 lb bomb TetrUSS = Tetrahedral Unstructured Software System D = cavity depth L = cavity length W = cavity width Z = distance below internal cavity upper surface α = angle of attack β = side slip angle Cm y = pitching moment coefficient

In this paper we discuss a Computational Fluid Dynamics (CFD) study to determine the impact of moving an air cooling intake scoop on theLitening external targeting pod mounted on an F/A-18C. Specifically, we investigated whether a change in the location of the Litening Pod cooling air intake scoop creates more favorable store separation characteristics for the Mk-83 1000 lb gravity bomb. Previous research has shown that small changes to the geometry of external targeting pods can change generated shock waves that may result in adverse moments on the smaller Mk-82 gravity bomb. These adverse moments can result in the released bomb striking the aircraft. The Litening Pod is mounted on the starboard side of the F/A-18C fuselage adjacent to a pylon carrying a Mk-83 bomb. The air scoop is an approximately rectangular inlet on the side of the Litening Pod that collects ram air to cool internal electronics. Rotating the Litening Pod air scoop away from the store may reduce shock wave interaction with the released store. Our CFD simulations show that rotation of the air scoop to the down side of the Litening Pod significantly reduces adverse moments on the released Mk-83 bomb. Visualizations of the generated shockwaves also indicate reduced interaction with the released store for the Litening Pod air scoop in the down instead of the side position. Nomenclature CAD = computer aided design CFD = computational fluid dynamics CPU = central processor unit F/A-18C = US Navy fighter attack aircraft JDAM = joint direct attack munition Ma = Mach number Mk-83 = 1000 lb bomb TetrUSS = Tetrahedral Unstructured Software System