text: The trim of the powered control system is 
  essentially any device to produce zero control 
  force for a given control surface deflection. 
  One system may trim off bungee force at a 
  given stick position while another system may 
  trim by returning the stick to neutral position. 
  Flight at high supersonic Mach numbers 
  might require a great variety of devices in the 
  longitudinal control system. The deteriora- 
  tion of pitch damping with Mach-number may 
  require 
  that dynamic stability be obtained 
  synthetically by pitch dampers in the control 
  to 
  system. The response of 
  longitudinal control may be adversely affected 
  by flight at high dynamic pressures. In such 
  conditions of flight stick forces must be ade- 
  quate to prevent an induced oscillation. Stick 
  forces must relate the transients of flight as 
  well as the steady state conditions. Such a 
  to control system forces may be 
  contribution 
  provided by a pitching acceleration bobweight 
  and a control system viscous damper. 
  
  where 
  
  The yaw angle of an airplane relates the dis- 
  placement of the airplane centerline from some 
  reference azimuth. and is assigned the short- 
  ,hand notation I& (psi). A positive yaw angle 
  occurs when the nose of the airplane is dis- 
  placed to the right of the azimuth direction. 
  The definition of sideslip angle involves a sig- 
  nificant difference. Sides&p angle relates the 
  displacement of the airplane centerline from 
  the relative wind rather than some reference 
  azimuth., Sideslip angle is’provided the short- 
  hand notation p (beta) and is positive when 
  ihe rela&e wind is displaced to the right of 
  the,airplane centerline. Figure 4.22 illustrates 
  the definitions of sideslip and yaw angles. 