Highly Survivable Truss Type Tail Boom.
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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Highly redundant truss type structures, which are lightweight, have been analyzed by NASTRAN for replacement of the semimonocoque type tail boom. Analyses show that even with massive damage criterion imposed, the structure retains its integrity with level flight loads up to 130 knots. The truss presents itself as a structural challenge to Soviet AA threat of the 23mm and 30mm HEI rounds. Comparing the vulnerable semimonocoque configuration with the truss structure semimonocoques vulnerable area is nearly 100 of the present area the truss has a greatly reduced vulnerable area the joints are most vulnerable and their areas are small. The semimonocoque is blast sensitive to the AA threats mentioned because the detonation is confined and a large surface area is blown away the truss does not confine the blast, thus is less sensitive. Since the thin skin structure of the semimonocoque carries a great deal of load it is sensitive to crack propagation the russ is insensitive to crack propagation. Since the truss can be easily designed lightweight, the truss presents itself as a highly survivable competitive alternate for future Army helicopter. Author