This invention relates to bomb rack sway brace assemblies and in particular to elastic sway brace assemblies including sway bolts providing continuous bolt-to-store contact under the influence of internal compression springs.
Spray brace assemblies are employed on bomb racks to restrain roll, yaw and pitch of the bomb about a retaining hook and to provide a measure of longitudinal restraint. Conventional sway brace assemblies normally employ solid sway bolts and massive sway brace arms which depend from a section of the bomb rack designed for load acceptance. Thus conventional systems employ a rigid construction in the sense that when the solid sway bolts are torqued down to engage a hard-cased store the elastic deflection of either the brace arm or the store is minute. (Hard-cased stores are defined herein as those stores whose case thickness and arc configuration present a virtually unyielding surface.)
Theoretically, hard cased stores restrained by rigid sway brace assemblies will follow all aircraft maneuvers without change in position. However, conventional sway brace assemblies of rigid construction have certain inherent disadvantages. For example, after firm metal seating of the solid bolt with the hard-cased store, further application of torque unnecessarily increases the down hook load without significant additional restraining force. Actual field experience has demonstrated that down hook forces several times the store weight are achieved when the bolts are excessively torqued. In severe cases of excessive torque application, the hook has failed, that is, fractured. Even in the absence of immediate hook failure, excessive torque application produces unwarranted stress on the hook and creates microscopic fissures which are readily attacked by salt spray. The resultant corrosion contributes to premature hook failures.
A further drawback of the conventional sway brace assembly results from the fact that the frictional restraining force in the longitudinal direction is not always proportional to the normal force at the bolt-to-shore interface. Slight but repeated translation of the store along the hook-to-store lug interface can quickly reduce the longitudinal restraint of the bolts to near zero.
An additional drawback of the conventional sway brace assembly is the imposition of an unwanted weight penalty when soft-cased stores must be carried since strong points or saddles must be provided. (Soft-cased stores are defined herein as those stores whose arc configuration and case thickness present a yielding surface.) Lastly the massive sway brace arms of the conventional sway brace systems have been known to fracture during severe aircraft maneuvers because such massive structures are unable to elastically deform under the forces generated by such maneuvers.