NAVWEPS 00-ROT-80  OPERATING STRENGTH LIMITATIONS  THE V-B OR V-g DIAGRAM  due to the gust condition are higher.  This is  explained by the fact that essentially the  same lift change acts on the lighter mass.  The high  accelerations and inertia forces  magnify the impression of the magnitude of  turbulence. If this same airplane encounters  the gust condition at higher than ordinary  gross weight, the accelerations  due to the gust  condition are lower, i.e., the same lift change  acts on the gteatet mass. Since the pilot  primarily senses the degree of turbulence by  the resulting accelerations and inertia forces,  this effect can produce a very misleading  impression.  The operating flight strength limitations of  an airplane are presented in the form of a  V- ‘ -n or V-g diagram.  This chart usually is  included in the aircraft flight handbook in the  section dealing with  operating limitations.  A typical V-n diagram is shown in figure 5.3.  The V-n diagram presented in figure 5.3 is  intended to present the most important general  features of such a diagram and does not neces-  sarily represent the characteristics of any par-  ticular airplane.  Each airplane type has its  own particular V-n diagram with specific V ’ s  and n ’ s,  The effect of airspeed and altitude on the  gust load factor is important from the stand-  point of flying operations. The effect of alti-  tude is related by the term &, which would  related that an airplane flying at a given EAS  at 40,000 ft. (c=O.25) would experience a  gust load factor increment only one-half as  great as at sea level.  This effect results be-  cause the true airspeed is twice as great and  only one-half the change in angle of attack  occurs for a given gust velocity. The effect of  airspeed is illustrated by the linear variation  of gust increment with equivalent airspeed.  Such a variation emphasizes  the effect of gusts  at high flight speeds and the probability of  structural damage at excessive  speeds  in turbu-  lence.  The flight operating strength of an airplane  is presented  on a graph whose horizontal scale  is airspeed (V) and vertical scale is load factor  (n).  The presentation of the airplane strength  is contingent on four factors being known:  (I) the aircraft gross weight, (2) the configura-  tion of the aircraft (clean, external stores, flaps  and landing gear position, etc.), (3) symmetry  of loading (since a rolling pullout at high speed  can reduce the structural limits to approxi-  mately two-thirds of the symmetrical load  limits) and (4) the applicable altitude.  A  change in any one of these four factors can  cause  important changes in operating limits.  For the airplane shown, the positive limit  load factor is 7.5 and the, positive ultimate  load factor is Il.25 (7.5x1.5)-  For negative  lift flight conditions the negative ’ limit  load  factor is 3.0 and the negative ultimate load  factor is 4.5 (3.0x1.5).  The limrt airspeed is  stated as 575 knots while the wing level stall  speed is apparently 100 knots.  The operation of any aircraft is subject to  specific operating strength limitations.  A  single large overstress may cause structural  failure or damage severe enough to require  costly overhaul.  Less severe overstress re-  peated for sufficient time will  cause fatigue  cracking and require replacement of parts to  prevent subsequent  failure. A combat airplane  need not be operated in a manner like the “little  old lady from Pasadena” driving to church on  Sunday but each aircraft type has strength  capability only specific to the mission require-  ment.  Operating limitations must be given  due regard.  Figure 5.4 provides supplementary informa-  tion to illustrate the significance of the V-n  diagram of figure 5.3.  The lines of maximum  lift capa ’ bility are the first points of importance  on the’ V-n diagram.  The subject aircraft is  capable bf developing no more than one posi-  tive “g”  at 100 knots, the wing level stall speed  of the airplane.  Since the maximum load  faztor varies with the square of the aitspeed,  334 