Experimental Study of an Air-to-Ground Store Release from a Jet-Fighter Weapons Bay in Transonic Flow Conditions

In this study, wind tunnel experiments are conducted to study the release of an air-to-ground store (AGS) model from a rectangular weapons bay (WB) that is part of a generic jet-fighter configuration in transonic flow conditions. A total of three WB configurations are investigated here: i) a 'clean' baseline rectangular WB, ii) a rectangular WB with two doors installed on the two side edges of the bay, and iii) a rectangular WB with one door installed on the outboard side edge of the bay. The pressure field and acoustic spectra within the bay are evaluated for each WB configuration, without and with an AGS placed within, in a range of angles of attack and sideslip angles of the aircraft. The release of an AGS model from the various WB configurations is investigated by measuring its aerodynamic forces and moments using two methods: i) placing the AGS at three different elevations from the ceiling of the bay (captive tests), and ii) performing grid Z-sweeps of the AGS out from the bay along a normal path. Results show that the flight conditions (alpha, beta) are the primary factor to affect the WB flow field, and, thus, the initial aerodynamic and acoustic conditions for the AGS release. Both door configurations reveal a distinct effect on the acoustic spectra within the WB, resulting in a significant augmentation of the second mode. Moreover, adding doors to the bay relaxes the dependency of the captive loads in flight conditions while increasing the maximum loads exerted on the AGS throughout its release. The insights provided here can improve our understanding of the various phenomena affecting store separation from bays and may serve as a basis to improve future designs of jet-fighters' WBs.