when the ship is descending without power at the rate of  250 ft. per minute.  This pressure, while inadequate for  normal flight, is sufficient to permit satisfactory hand› ling of the ship during landing operations.  Instructions for starting the blower for airships  K-3 thru K-98 are given on  p~ _ ge  44.  During flight, it may bec.ome necessary to adjust the  relative inflation of the two ballonets •in order to change  the trim of the ship.  This is done by operating the air  valves and dampers manually.  In trimming the ship in this manner, it may be well to  consider air as ordinary ballast, the effect of transferring  air being the same as that of transferring any ballast.  In emergency cases where a large amount of gas has been  lost, such as when the ship is descending after having over› shot its pressure height, and the ballonets, even when fully  inflated, cannot keep up the. pressure of the envelope, it  may become necessary to blow air into the gas.  This may be done by untying the sleeve connecting the  air chamber to the envelope.  This sleeve is located above  -38- (k) Blowing Air Into The Gas  (j) Shifting Air 