text: Various control surface tab devices can be 
  utilized to modify control forces. Since the de- 
  flection of a tab is so powerful in creating hinge 
  moments on a control surface, the possible 
  application of tab devices is almost without 
  limit, 
  tab arrangement is 
  shown in figure 4.18 where a variable linkage 
  connects the tab and the control surface. Ex- 
  tension or contraction of this linkage will de- 
  flect the tab relative to the control surface and 
  create a certain change in hinge mon~ent coef- 
  ficient. The use of the trim tab will allow the 
  pilot to reduce the hinge moment to zero and 
  trim the control forces to zero for a given flight 
  condition. Of course, the trim tab should have 
  forces 
  adequate effectiveness so that control 
  can be trimmed out throughout the flight speed 
  range. 
  
  The basic trim 
  
  The bobweight is an effective device for im- 
  proving stick force stability. 
  As shown in 
  figure 4.17, the bobweight consists of an eccen- 
  tric mass attached 
  the control system 
  to 
  which-in 
  an increment of pull 
  to the 
  force identical 
  In fact, a bobweight added to 
  downspring. 
  the control system of an airplane produces an 
  effect identical to the downspring. The bob- 
  increase the airspeed stick force 
  weight will 
  gradient and increase the feel for airspeed. 