TM 1-1520-240-BD Stringer   -   A   long   light   structural   member   used   as longitudinal members in an airframe. Structure    -     An     assembly     of     connected     structural elements. Structure,  Nonessential   -   Structure   whose   function   is only to enhance aerodynamics or to protect and provide access  to  internally  housed  components.    Except  for secondary  damage  that  may  be  caused  by  a  structure separating  from  the  aircraft  in  flight,  failure  or  loss  of nonessential  structure  will  have  no  significant  effect  on the performance or short-term reliability of the aircraft. Structure,  Primary  -  Structure  that  is  essential  to  the airworthiness   of   the   aircraft,   failure   or   loss   of   which, alone    or    in    combination    with    other    failures,    could severely degrade the flight safety, ballistic survivability, and/or crashworthiness of the aircraft. Structure, Secondary - Structure that is essential to the functional  performance  of  the  aircraft,  failure  or  loss  of which, alone or in combination with other failures, could degrade the mission capability of the aircraft. Structures  Category  -  One  of  four  classifications  which describe  the  contribution  of  a  structural  component  to the airworthiness and mission capability of the aircraft. Structural   Component   -   A   structural   element   or   an assembly of structural elements (door, stabilator, etc.). Structural Element - One of the constituent parts of the airframe (frame, beam panel, etc.) Structural Member A structural element. Tension - The force tending to increase the dimension of a body in the direction of the force. Torsion - The internal movement of a body subjected to twisting force. Triage  -  The  sorting  out  and  classification  of  casualties of war or other disaster to determine priority of need and proper place of treatment. Type  I  Repair  Deferment  -  100  flight-hour  deferment' unrestricted operating envelope. Type  II  Repair  Deferment  -  One-time  flight  defermentv restricted operating envelope. Web  -  Principal  vertical  member  of  a  beam,  spar,  or other    primary    structure    running    length    of    wing    or fuselage. Wounds   -   Damage   caused   by   ballistic   impacts   and penetrations. SECTION II.  ACRONYMS AND ABBREVIATIONS Acft - Aircraft AC - Alternating current ACM/BDR - Aircraft combat maintenance/battle-damage repair AL - Alumel Amps - Amperes AN - Air Force-Navy AP - Armor piercing API - Armor pierdng incendiary APU - Auxiliary power unit ATT - Attitude AVIM - Aviation intermediate maintenance AVUM - Aviation unit maintenance BD - Battle-damage BDR - Battle-damage repair B.L. - Butt line C - Celsius CB (zone) - Cabin CD - Damage depth CL - Damage length CN Constantan CP (zone) Cockpit CR Chromel CRT Cathode-Ray tube Glossary-3