content_image/520943.jpg content_image/520950.jpg content_image/520942.jpg
(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- 

<img src='content_image/520943.jpg'>

The pilot may be called upon to fly a heavy airship on account of vari› ous reasons such as-- 

(a) Collection of moisture if rain is encountered. 

(b) Leakage in envelope. 

(c) Loss of superheat. 

(d) Heavy take-off. 

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 : 

[In pounds] 

<img src='content_image/520950.jpg'>

(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- 

<img src='content_image/520942.jpg'>

(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 

