text: and magnitude. Neutral static longitudinal 
  limit of 
  stability usually defines the lower 
  the boundary 
  airplane stability since it ‘is 
  between stability and instability. 
  The air- 
  plane with neutral static stability’ may be 
  excessively responsive to controls and the 
  aircraft has no tendency to return to trim fol- 
  lowing a disturbance. The airplane with 
  negative sradc longitudinal 
  is in- 
  from any intended trim 
  herently divergent 
  condition. 
  If it is at all possible to fly the 
  aircraft, the aircraft. cannot be trimmed and 
  illogical control forces and deflections are rc- 
  quired to provide equilibrium with a change 
  of attitude and airspeed. 
  
  GENERAL CONSIDERATIONS. An air- 
  craft will exhibit positive static Iongitudinal 
  stability 
  if it tends to return to the trim angle 
  of attack when displaced by a gust or control 
  movement. The aircraft which is unstable will 
  continue to pitch 
  in the disturbed direction 
  until the displacement is resisted by opposing 
  control 
  is neutrally 
  stable, it tends to remain at any displacement 
  It is most necessary 
  to which it is disturbed. 
  to provide an airplane with positive staric 
  longitudinal stability. The stable airplane is 
  safe and easy to fly since the airplane seeks and 
  tends to maintain a trimmed condition of 
  flight. 
  that control deflec- 
  tions and control “feel” are logical in direction 
  
  stability 