TM 1-1520-240-BD CHAPTER 2 AIRFRAME SECTION I.  INTRODUCTION 2-1.  SCOPE. a. This   chapter   contains   methods   for   assessing battlefield  damage  to  the  primary  structure  of  the  CH- 47D    airframe,    classification    of    damage,    rules    for deferring  repair,  and  expedient  field  fixes  of  battlefield damaged airframe structures. b. Aircraft   structure   is   classified   as   primary   and secondary structure. (1)    The  primary  structure  is  the  basic  structure which  holds  the  aircraft  together.    Any  serious  damage to  any  element  of  the  primary  structure  will  restrict  the combat capability of the aircraft.  The primary structures for    each    major    airframe    subassembly    are    defined throughout this chapter. (2)      Secondary   structures   are   mounted   on   the primary  structure.    No  amount  of  structural  damage  to secondary structures will restrict combat capability from a  structural  safety  point  of  view;  however,  secondary structure may be required for aerodynamic reasons or to accomplish or support mission functions. 2-2.   ASSESSMENT  PROCFDURERS.    The  battlefield structural damage assessment consists of two steps:  an initial   assessment,   and   a   detailed   assessment.      The initial   assessment   is   a   quick   visual   assessment   to decide whether or not a detailed assessment should be made.  A detailed assessment involves the identification of  all  damage  to  primary  structural  elements,  possibly some cleanup and measurement of the damage and of the damaged elements.  This process requires damage measurement  and  determination  of  the  corresponding damage limits.  An overall view of all the aircraft zones used in damage assessment is shown in Figure 2-1. NOTE The standards contained herein allow  aircraft  to  be  flown  with  battle damage   substantially   in   excess   of peacetime limits. Under no circumstances  shall  this  manual  be used wholly or in part for peacetime maintenance of the aircraft. Assessment of aircraft battle damage requires  extreme  care  and  diligence and strict adherence to the instructions and standards contained  in  this  manual.    If  at  any stage    of    damage    assessment    the assessor  believes  that  oversights  or errors have been made, the assessment  shall  be  stopped  at  that point and TM 1-1520-240-BD repeated from    the    beginning.        Under    no circumstances shall the requirements     of     this     manual     be waived  or  circumvented  without  the express  approval  of  the  commander or his designated representative. WARNING · Battle    damaged    areas    should    be inspected  for  unexploded  ordnance before  attempting  repairs.    Disposal of  unexploded  ordnance  should  be accomplished by qualified EOD personnel. · Loaded  weapons,  or  weapons  being loaded or unloaded, shall be pointed in  a  direction  which  offers  the  least exposure to personnel or property in the event of accidental firing. Personnel     shall     remain     clear     of hazardous area of all loaded weapons. · Ground safety pins must be installed in    pilot    and    gunner    arming/firing handles   of   canopy   removal   system whenever   the   helicopter   is   on   the ground.  Pins should be installed by crew. 2-1