text: is cti~n&zti~e during cyclic stressing, the useful 
  service life of the aircraft must be anticipated 
  the gross effect of service loads. 
  to predict 
  Then, the primary structure is required to 
  sustain the typical load spectrum rhrough the 
  anticipated service life without 
  the occurrence 
  of fatigue failure. To prove this capability 
  of the structure, various major components 
  must be subjected to an accelerated fatigue 
  test to verify the resistance to repeated loads. 
  The design of a highly stressed or long life 
  structure emphasizes the problems of fatigue. 
  Great care must be taken during design and 
  manufacture to minimize stress concentrations 
  which enhance fatigue. When the aircraft 
  enters service operation, care must be taken in 
  the maintenance of components to insure proper 
  adjustment, torquing, inspection, etc., as proper 
  maintenance is a necessity for achieving full 
  service life. Also, the structure must not be 
  subjected to a load spectrum more severe than 
  was considered in design or fatigue failures 
  may occur within 
  the anticipated service life. 
  With this additional factor in mind, any pilot 
  should have all the more respect for the oper- 
  ating strength 
  overstress 
  causes a high rate of fatigue damage. 