Estimate Of Effect Of Mer Structural Dynamics On Store Separation PDF Download

Structural flexibility has long been suspected as being a factor affecting the ejection phase dynamic response of stores. After hook opening, in-carriage loads, associated with a release store, and an ejection recoil force deflect the MER beam away from its initial position. This in turn leads to a lower ejection velocity, lower ejection pitch rate, and an induced rolling moment. A theoretical structural dynamic model is based upon "Bernoulli" pitch and yaw deflections and torsional rotation of the MER beam; wing, pylon, hanger, shoulder pad, and ejector unit deformations are neglected. Detailed development for the present report is confined to the pitch plan bending and store pitch dynamics case. For small pitch angles a linear set of kinematic and dynamic equations for the store ejection phase is obrained. Sample computations are given for two stores and constant aircraft pull-up rates. A 4-g pull-up produces the greatest structural deformations. However, the pull-up maneuver alone affects the ejection pitch rate and velocity to a greater extent than the structural deformation. A break even point occurs for small pull-up rates. For the pitch bending case, flexibiity probably accounts for no more than a 10% deviation from the rigid case. Flexibility affects the ejection angular rate more significantly.