In order to maximize stealth potential and aerodynamic performance, internal weapons bays are increasingly common on military aircraft and are particularly key for coming generations of UCAVs. Wind tunnel testing of store release problems therefore generally requires the ordinance to be mounted to its own sting strut from underneath, such that it can be placed in, and "dropped" from, the bay. Interference from this strut can disrupt the forces and moments obtained, and thus an investigation has been conducted into the extent of this interference, looking at the sting arm length and the geometry of the connection to the store as variables over a sweep of angles of attack. Original small-scale transonic wind tunnel testing was conducted, against which a numerical approach was validated, allowing investigations to conclude that the specific geometry of the sting at the attachment point had a much greater influence than any other geometric parameters, with non-linear interference observed through a range of angles of incidence.

Internal weapons bays are becoming increasingly common on aircraft for reasons of stealth and aerodynamic performance, and will be even more prevalent on coming generations of unmanned combat aerial vehicles (UCAVs). Wind tunnel testing of store releases to assess forces and moments for safety and clearance must be conducted with a store mounted to an angled strut rather than a conventional rear sting, to allow the full range of motion as the store ''drops'' from inside the aircraft. Interference from this strut can disrupt the flowfields and thus the reliability of moments obtained, and therefore an investigation was conducted to quantify the potential extent of discrepancies; original small-scale transonic wind tunnel testing was undertaken in a limited program which was supported by extensive numerical work. It was concluded that the precise geometry of the strut/store interface was of critical importance, with a typical design producing non-linear interference at high angles of attack. A simple improved design is proposed -making use of a blended interface and a more appropriate supercritical aerofoil strut cross section -yielding marked improvements in force and moment predictions.