is certificated. The maximum safe load factors (limit load  factors) specified for aircraft in the various categories are:  slower the ROT. This compensates for added centrifugal  force, allowing the load factor to remain the same.  $^{1 }$For aircraft with gross weight of more than 4,000 pounds,  the limit load factor is reduced. To the limit loads given  above, a safety factor of 50 percent is added.  There is an upward graduation in load factor with the  increasing severity of maneuvers. The category system  provides for maximum utility of an aircraft. If normal  operation alone is intended, the required load factor (and  consequently the weight of the aircraft) is less than if the  aircraft is to be employed in training or acrobatic maneuvers  as they result in higher maneuvering loads.  Aircraft that do not have the category placard are designs that  were constructed under earlier engineering requirements in  which no operational restrictions were specifically given to  the pilots. For aircraft of this type (up to weights of about  4,000 pounds), the required strength is comparable to present- day utility category aircraft, and the same types of operation  are permissible. For aircraft of this type over 4,000 pounds,  the load factors decrease with weight. These aircraft should  be regarded as being comparable to the normal category  aircraft designed under the category system, and they should  be operated accordingly.  At a constant altitude, during a coordinated turn in any  aircraft, the load factor is the result of two forces: centrifugal  force and weight.  [Figure 5-52]  For any given bank angle,  the ROT varies with the airspeed—the higher the speed, the  A study of this effect has revealed that an aircraft’s stalling  speed increases in proportion to the square root of the  Any aircraft, within the limits of its structure, may be stalled  at any airspeed. When a sufficiently high AOA is imposed,  the smooth flow of air over an airfoil breaks up and separates,  producing an abrupt change of flight characteristics and a  sudden loss of lift, which results in a stall.  For a coordinated, constant altitude turn, the approximate  maximum bank for the average general aviation aircraft is 60°.  This bank and its resultant necessary power setting reach the  limit of this type of aircraft. An additional 10° bank increases  the load factor by approximately 1 G, bringing it close to the  yield point established for these aircraft.  [Figure 5-54]  It should be noted how rapidly the line denoting load factor  rises as it approaches the 90° bank line, which it never quite  reaches because a 90° banked, constant altitude turn is not  mathematically possible. An aircraft may be banked to 90°  in a coordinated turn if not trying to hold altitude. An aircraft  that can be held in a 90° banked slipping turn is capable of  straight knife-edged flight. At slightly more than 80°, the  load factor exceeds the limit of 6 Gs, the limit load factor of  an acrobatic aircraft.  Figure 5-53  reveals an important fact about turns—the load  factor increases at a terrific rate after a bank has reached  45° or 50°. The load factor for any aircraft in a coordinated  level turn at 60° bank is 2 Gs. The load factor in an 80° bank  is 5.76 Gs. The wing must produce lift equal to these load  factors if altitude is to be maintained.  Load Factors and Stalling Speeds  Load Factors in Steep Turns  Figure 5-53.  Angle of bank changes load factor in level flight.  Figure 5-52.  Two forces cause load factor during turns.  Load factor = 2 Gs  Centrifugal  force = 1.73 Gs  Gravity = 1G  6 0 °$_{5}$ 0 ° 4 0 ° 3 0 °  2 0 °  1 0 °  7 6 5  4  3  2  1  0  0°  10°  20°  30°  40°  50°  60°  70°  80°  90°  Load factor (G units)  Bank angle  CATEGORY  LIMIT LOAD FACTOR  Normal 1  3.8 to  – 1.52  Utility (mild acrobatics,  4.4 to  – 1.76  including spins)  Acrobatic  6.0 to  – 3.00  5-34 