Aerodynamics of Flight

7 6 5 4 3 2 1 0 –1 –2 –3 20 40 60 80 100 120 140 160 180 200 220 240 5-38 rotcaf daoL Structural damage Caution range Indicated airspeed (mph) Structural failure Maneuvering speed Accelerated stall Normal operating range Normal stall speed Level flight at 1 G Structural Damage Never exceed speed Figure 5-55. Typical Vg diagram. The other point of importance on the Vg diagram is the Rate of Turn intersection of the negative limit load factor and line of The rate of turn (ROT) is the number of degrees (expressed in maximum negative lift capability. Any airspeed greater than degrees per second) of heading change that an aircraft makes. this provides a negative lift capability sufficient to damage The ROT can be determined by taking the constant of 1,091, the aircraft; any airspeed less than this does not provide multiplying it by the tangent of any bank angle and dividing negative lift capability sufficient to damage the aircraft from that product by a given airspeed in knots as illustrated in excessive flight loads. Figure 5-55. If the airspeed is increased and the ROT desired is to be constant, the angle of bank must be increased, The limit airspeed (or redline speed) is a design reference point otherwise, the ROT decreases. Likewise, if the airspeed is for the aircraft—this aircraft is limited to 225 mph. If flight held constant, an aircraft’s ROT increases if the bank angle is attempted beyond the limit airspeed, structural damage or is increased. The formula in Figures 5-56 through 5-58 structural failure may result from a variety of phenomena. depicts the relationship between bank angle and airspeed as they affect the ROT. The aircraft in flight is limited to a regime of airspeeds and Gs that do not exceed the limit (or redline) speed, do NOTE: All airspeed discussed in this section is true airspeed not exceed the limit load factor, and cannot exceed the (TAS). maximum lift capability. The aircraft must be operated within this “envelope” to prevent structural damage and Airspeed significantly effects an aircraft’s ROT. If airspeed is ensure the anticipated service lift of the aircraft is obtained. increased, the ROT is reduced if using the same angle of bank The pilot must appreciate the Vg diagram as describing the used at the lower speed. Therefore, if airspeed is increased allowable combination of airspeeds and load factors for as illustrated in Figure 5-57, it can be inferred that the angle safe operation. Any maneuver, gust, or gust plus maneuver of bank must be increased in order to achieve the same ROT outside the structural envelope can cause structural damage achieved in Figure 5-58. and effectively shorten the service life of the aircraft.