Effects of targeting pod modification on F/A-18C Hornet weapons release

Abstract

This paper describes a study that investigated the efficacy of modifications to the trailing end of the externally mounted advanced targeting forward looking infrared pod (ATFLIR) on the store separation characteristics of the F/A-18C aircraft. Prior work by Godiksen suggests that the trailing end of the geometrically similar targeting forward looking infrared pod (TFLIR) is the likely source of shock waves that can adversely impact the trajectory of a recently released store. In our study five different modifications to the aft end of the ATFLIR were analysed using computational fluid dynamics (CFD). The two most promising designs, an ogive shape such as that used in artillery shells and rockets, and a simpler extended but truncated cone shape were then further investigated. The moments that these trailing shapes produced on an adjacent released store were compared. CFD analysis revealed that the simpler cone shape resulted in weaker shocks from the aft end of the pod with a resultant smaller adverse moment on the store. While there is an extensive history of using CFD to predict store separation behavior, results from our study should be compared with wind tunnel data in order to validate the CFD simulations. NOMENCLATURE 6-DOFsix-degree of freedom AOA angle-of-attack ATFLIR advanced targeting forward looking infrared pod C D drag coefficient CFD computational fluid dynamics

Litening Pod Modification to Improve Mk-83 Store Trajectories (Invited)

“…1 The TetrUSS flow solver, USM3d, has been used extensively in other store separation studies. [2][3][4][5][6][7][8][9][10] Geometry representing a symmetric half of an F/A-18C equipped with the Litening Pod and released Mk-83 JDAM was recreated using Rhino, a versatile Computer Aided Design (CAD) program compatible with TetrUSS. An unstructured threedimensional grid was then generated around the CAD model (associated surface grid shown in Fig.…”

Strut Effects on Store Freestream Aerodynamics

“…5,6 The TetrUSS flow solver, USM3d, has been used extensively in other store separation studies. [7][8][9][10][11][12][13][14][15] Geometry representing the Mk-82 and ARA strut was recreated using Rhino, a versatile Computer Aided Design (CAD) program compatible with TetrUSS. An unstructured three-dimensional grid was then generated around the CAD model (associated surface grid shown in Fig.…”

Reducing transonic wind tunnel sting interference effects for concealed store release testing

“…It is now relatively common for computational fluid dynamics (CFD) work, particularly using Reynolds-Averaged Navier-Stokes (RANS) modelling, to be involved in the process to both predict design problems in advance of physical testing and, increasingly, to plan and help interpret the tunnel data itself before scaling up to real-world Reynolds numbers to anticipate further issues. [1][2][3][4][5] Mounting an aircraft tunnel model to one sting, and the store from the rear to another, is not applicable for weapons bay work where the store is originally in the cavity when ejected, before crossing the highly turbulent shear layer and proceeding to clear the vicinity of the aircraft. An additional strut arm connecting to the middle of the store is one standard design approach (a very short rear sting and strut could interfere much more with the cavity flow), whereby the sting itself can be far from the store, reducing interference.…”

“…It is now relatively common for computational fluid dynamics (CFD) work, particularly using Reynolds-Averaged Navier–Stokes (RANS) modelling, to be involved in the process to both predict design problems in advance of physical testing and, increasingly, to plan and help interpret the tunnel data itself before scaling up to real-world Reynolds numbers to anticipate further issues. 1–5…”