of attack beyond that giving the ma-ximum lift, the dynamic lift nat  ..  urally decreases.  At the same time the downward thrust on the eleva› tors is increased.  The gain in the upward component of the propeller  thrust at reversing speed or below will not compensate for the loss  in lift just described and the airship will be under the action of a  greater resultant downward force than at the start.  f.  The opposite effect to that described in  c  above occurs when an  airship is trimmed tail heavy and the elevator is depressed.  In this  case the whole airship will rise.  g.  It  might appear that reverse control would be a source of great  annoyance to the pilot.  This is not the case when the phenomenon is  properly understood.  I n fact, many maneuvers are executed by in› telligent use of reverse control, for example, heavy take-off.  This is  described in paragraph 37.  37. Application of dynamic control to operation of air› ships.-a. The three major maneuvers in airship operation which  are assisted by dynamic control are- These operations are fully covered in TM 1-310 and are discussed but  briefly here to bring out the aerodynamic principles involved therein.  b.  As soon as the take-off is completed and the obstacles in the imme› diate foreground cleared, the pilot climbs to the altitude at which he  desires to cruise.  He then trims the airship so that with the controls  in neutral the algebraic sum of the vertical forces is zero.  Since the  airship is almost never in static equilibrium, one of two situations will  prevail, static heaviness or lightness.  52  FIGURE 24.-Fl!gbt at constant altitude (airship statically heray, trimmed tail heavy,  •elevators neutral).  AIR CORPS  TM 1-320  36-37  Ls  (1) Flight at constant altitude.  (2) Take-off.  (3)  L anding~ 