load factor. This means that an aircraft with a normal  unaccelerated stalling speed of 50 knots can be stalled at 100  knots by inducing a load factor of 4 Gs. If it were possible  for this aircraft to withstand a load factor of nine, it could  be stalled at a speed of 150 knots. A pilot should be aware  of the following:  Figures 5-53  and  5-54  show that banking an aircraft greater  than 72° in a steep turn produces a load factor of 3, and the  stalling speed is increased significantly. If this turn is made  in an aircraft with a normal unaccelerated stalling speed of  45 knots, the airspeed must be kept greater than 75 knots to  prevent inducing a stall. A similar effect is experienced in a  quick pull up or any maneuver producing load factors above  1 G. This sudden, unexpected loss of control, particularly in  a steep turn or abrupt application of the back elevator control  near the ground, has caused many accidents.  Since the load factor is squared as the stalling speed doubles,  tremendous loads may be imposed on structures by stalling  an aircraft at relatively high airspeeds.  The following information primarily applies to fixed-wing  airplanes. The maximum speed at which an airplane may  be stalled safely is now determined for all new designs.  Since the leverage in the control system varies with different  aircraft (some types employ “balanced” control surfaces while  others do not), the pressure exerted by the pilot on the controls  cannot be accepted as an index of the load factors produced  in different aircraft. In most cases, load factors can be judged  by the experienced pilot from the feel of seat pressure. Load  factors can also be measured by an instrument called an  “accelerometer,” but this instrument is not common in general  This speed is called the “design maneuvering speed” (V$_{A}$),  which is the speed below which you can move a single  flight control, one time, to its full deflection, for one axis  of airplane rotation only (pitch, roll or yaw), in smooth  air, without risk of damage to the airplane. V$_{A }$ must be  entered in the FAA-approved Airplane Flight Manual/  Pilot’s Operating Handbook (AFM/POH) of all recently  designed airplanes. For older general aviation airplanes,  this speed is approximately 1.7 times the normal stalling  speed. Thus, an older airplane that normally stalls at 60  knots must never be stalled at above 102 knots (60 knots  ×  1.7 = 102 knots). An airplane with a normal stalling speed  of 60 knots stalled at 102 knots undergoes a load factor  equal to the square of the increase in speed, or 2.89 Gs (1.7  × 1.7 = 2.89 Gs). (The above figures are approximations to  be considered as a guide, and are not the exact answers to  any set of problems. The design maneuvering speed should  be determined from the particular airplane’s operating  limitations provided by the manufacturer.) Operating at or  below design maneuvering speed does not provide structural  protection against multiple full control inputs in one axis or  full control inputs in more than one axis at the same time.  • The danger of inadvertently stalling the aircraft by  increasing the load factor, as in a steep turn or spiral;  • When intentionally stalling an aircraft above its  design maneuvering speed, a tremendous load factor  is imposed.  Figure 5-54.  Load factor changes stall speed.  5-35  Ratio of acceleration V to unaccelerated V s s 5  4  3  2  1  0  40 40  50 50  60 60  70 70  80 80  100 120 150 Unaccelerated stall speed 0  1  2  3  4  5  6  7  8  20  40 60  80 100 120 140 160 180 200 220 240 260  “G” Load  Accelerated stall speed 