The K-airships are designed for a maximum speed of  65 knots with an internal gas pressure of 1.5 inches of  water.  Since the automatic air valves, as .pointed out above,  are operated by the air pressure of the ballonets, the  corresponding gas pressure at which they open depends on the  gas inflation of the ship.  If, for instance, the ship is  85% gas inflated and the ballonets are more than half infle.ted,  it can be seen, by referring to the curve in Fig. VII that  the gas pressure in the envelope is about 0.32 inches of  water less than the air pressure in the ballonets.  The air  valve of the forward ballonet will open, therefore, at air  pressure of 1.5 inches of water, while the corresponding gas  pressure is .32 inches of water less than the setting of  th~  gas valve or 1.18 inches.  It will still be possible, however, to maintain the  recommended operating gas pressure of 1.5 inches of water  by opening the forward air damper and regulating the scoop  opening so as to produce air circulation through the air  damper and the partially opened air valve.  CAUTION:  The matter of the proper regulation of the air  scoops is of the utmost importance.  If the  scoops are opened too wide, excessive pressure  may be built up in the envelope causing loss of  gas.  If the scoops are not opened enough, the  gas pressure may drop to a dangerously low value  resulting  in  buckling of the envelope.  -28-