TM 1-320  37  AIRSHIP AERODYNAMICS  (1) Figure 24 shows the case in which the airship is statica:Jly•heavy  and trimmed nose light.  In this case the equation of vertical forces  to give constant altitude flight with neutral controls becomes- The pilot may be called upon to fly a heavy airship on account of vari› ous reasons such as-- Most airships can carry about 10 percent. of their gross lift dynamically  at the surface of the earth.  Since the dynamic lift varies as the air  •density, it decreases with nltitude.  Table III shows results of some ex› periments on an Italian M type airship at- full speed :  (2) Figure 25 shows the case in which the airship is  fl.yin~  statically  light at constant altitude with controls in neutral.  In this case ’the  equation of the vertical forces becomes- (3) In the unusual case in which the airship is in perfect static  equilibrium, it will be necessary to trim the airship about 2° nose  heavy to overc6me the upturning moment  of  the propeller thrust. So  trimmed the airship will fly on an even keel at cruising speed.  The  motorized observation ba1loon, having only one ballonet, cannot be  trimmed for an individual flight.  An approximate 2° nose heavy  53  L0= W  +  L e  +  Lt  +  L8  W = £ 0+ L e+ L t+  L ~  (a)  Collection of moisture if rain is encountered.  (b)  Leakage in envelope.  (c)  Loss of superheat.  (d)  Heavy take-off.  TABLE  III.- Lijt of Italian M type at full speed  [In pounds]  Altitude, 3,000 feet  Altitude, 10,000 feet  Altitude, 16,500 feet  Angle of  I  I  <I)  I  I  I  I  !XI  1:1  0  1:1  0  ~  1:1  0  inclination in  ....  Q)Q)  !').~  1:1  ....  Q)Q)  ’"’fl) ....  Q)Q)  .... fl)  ~  ~  ~  :=l  o. ....  0.~-o  radiants  .....  ..... o. -~  ..... o. .._.a>  .....  ;..:::  ..... o. ._Cil  ....  oo .....  oo 0~  - o- 0  - Q3  0~  0  - 0 .....  0  .  <IS  Q)  .  Q)  .5  s  Q3  ....  -+">  <!:0. ....  -+">  .... 0. ....  -+">  +>o.  0  ~  0  ....  ....  0  - .....  ~  •- ......  •- • - •- •- •- E-<  H  H  H  E-.  H  H  H  E-.  H  H  ..:I  0.03- - - --- - - - 1, 224 330 60 834 I, 012 269 48 695 839 218 40 481  0.06 __ ___ ____  1, 855 612 125 1, 118 1, 542 495 101  946 1, 287 400 82 805  0.09_-------- 2, 290 810 200 1,  2801, 914 657 163  1,095 1, 608 530 130 948  0.12 ___ __ ____  2,497 913 290 1, 294’2, 101  742 235  1, 124 1, 778 599 189 99  0 