NAWWEPS DO-BOT-BO  STABILITY AND CONTROL  attack is capable of producing pro-spin mo-  ments of considerable magnitude which con-  tribute to the self-sustaining nature of the  spin.  Also, the large distributed mass of the  fuselage in rolling-yawing rotation contributes  to inertia moments which flatten the spin and  place the aircraft at extreme angles of attack.  excessive  angles of attack. Of course, a low  speed airplane could be: designed to be spin-  proof by making it stallproof.  By limiting  the amount of control deflection, the airplane  may not have the longitudinal control power  to trim to maximum lift angle of attack.  Such  a provision may be possible for certain light  planes and commercial aircraft but would  create an unrealistic and impractical limita-  tion on the utility of a military airplane.  The spin recovery of the modern high speed  airplane involves principles which are similar  to those of the spin recovery of the conven-  tional airplane. However, the nature of the  spin for the modern configuration may involve  specific differences in technique necessary to  reduce the sideslip and angle of attack. The  use of opposite rudder to control the sideslip  and effect  recovery will depend on the effective-  ness of the rudder when the airplane is in the  spin.  At high positive angles of attack and  high sideslip the rudder effectiveness  may be  reduced and additional anti-spin moments must  be provided for rapid recovery. The deflection  of ailerons into the spin reduces the autorota-  tion rolling moment and can produce adverse  yaw to aid the rudder yawing moment in  effecting recovery.  The modern high speed airplane configura-  tion is typified by low aspect ratio, swept wing  planforms with relatively large yaw and pitch  inertia.  The aerodynamic characteristics of  such a configuration are shown in figure 4.32.  The lift curve (C, versus U) is quite shallow at  high angles of attack and maximum lift is not  clearly defined. When this type of airplane is  provided a rolling motion at high angles of  attack, relatively small changes in C, take  place. When this effect is combined with the  relatively short span of this type airplane, it is  apparent that the wing autorotation contribu-  tion will be quite weak and will not be a pre-  dominating pro-spin moment. The relatively  large changes in drag coefficient with rolling  motion imply .a predominance of yaw for the  spin of the high speed airplane configuration.  There may be many other specific differences  in the technique necessary to effect spin re-  covery . The effectiveness  of the rudder during  recovery may be altered by the position of  elevators or horizontal tail.  Generally, full  aft stick may be necessary  during the initial  phase of recovery to increase the effectiveness  of the rudder. The use of power during the  spin recovery of a propeller powered airplane  may or may not aid recovery depending on the  specific airplane and the particular nature of  the slipstream effects. The use of power during  the spin recovery of a jet powered airplane  induces no significant or helpful flow but does  offer the possibility of a severe compressor  stall and adverse gyroscopic moments. Since  the airplane is at high angle of attack and  sideslip, the flow at the inlet may be very  poor and the staI1 limits considerably reduced.  These items serve to point out possible dif-  ferences  in technique required for various con-  figurations.  The spin recovery specific for  Actually, various other factors contribute  to the predominating yaw tendency for the  spin of the modern airplane configuration.  The static directional stability deteriorates at  high angles of attack and may be so weak that  extemely large yaw displacements result.  In  certain instances, very high angles of attack  may bring such a decay in directional stability  that a “slice”  or extreme yaw displacement  takes place before a true spin is apparent. At  these high angles of attack, the adverse yaw  due to roll and aileron deflection can be very  strong and create large yaw displacements of  the airplane prior to realizing a stall.  The aircraft with the relatively large, long  fuselage can exhibit a significant moment con-  tribution from the fuselage alone.  The cross  flow pattern on the fuselage at high angles of  31.1 