Balloon Inflation Balloons should be inflated slowly, with helium. A 10-gram balloon should take 3/4 to 1 minute to fill, and a 30-gram balloon should take 2 l/2 to 3 minutes to fill. This slow inflation rate allows the balloons to stretch properly during filling. The  balloons  are  inflated  by  using  the  ML-575/UM universal balloon balance set (fig. 2-45). Refer to the technical  data  supplied  with  the  set  for  detailed information. The 10-gram balloons, attached to the inflation nozzle weighted to 45 grams, are inflated to neutral buoyancy. This yields 45-grams of free lift. The 30-gram  balloons  are  inflated  to  139-gram  free  lift. Chemical lights and balloon-tying cords are added to the  inflation  nozzle  during  inflation,  but  are  not calculated in the weighting figures. Determination of Cloud Height You must always request permission from the Officer of the Deck (OOD) and the Air Boss aboard a carrier, or from the air traffic controller at an air station, to release a ceiling balloon.  After  clearance  is  received, the ceiling balloon is released and the ascension is timed. Cloud height is determined by the elapsed time, in minutes and seconds, that the balloon takes to enter into the cloud base. Consider the point of entry as midway between the time the balloon first begins to fade and the time of complete disappearance for layers aloft. Use the point at which the balloon disappears to estimate vertical visibility. Use the standard ascension rate tables in either NAVMETOCCOMINST 3141.2 or NAVMETOCCOMINST  3144.1  to  determine  the height. So far, we have covered most of the equipment used in surface aviation weather observations. We have mentioned a few of the calculators used to compute Figure 2-45.—ML-575/UM universal balloon balance set. observational  data,  such  as  the  psychrometric  computer and the true wind computer. Now let’s discuss the various  types  of  calculators  used observations. Q41. Q42. Q43. Q44. Q45. Q46. Q47. Q48. Q49. Q50. REVIEW  QUESTIONS What  are  the  three  main  parts 507/GMQ-13 Cloud Height Set? in  surface of  the  ML- When you use the ML-507/GMQ-13, how are cloud heights determined? What data must be computedfor each individual RO-546/GMQ-13 GIFFT recorder? When is the correction factor of the GIFFT recorder not applied? What instrument is used in conjunction with the ML-121 Ceiling Light Projector to obtain cloud heights? What  publication  contains  instructions  for  using the shipboard clinometer? How are cloud heights determined when using a clinometer? Under  what  conditions  should  red  ceiling balloons be used to measure cloud heights? Why should larger, 30-gram balloons be used in high wind conditions vice 10-gram balloons? How is cloud height determined when you use ceiling  balloons? CALCULATORS LEARNING OBJECTIVE: Explain the care and use of four types of hand-held calculators. In the 1930’s and 1940’s, the military first made serious attempts to study the weather and apply it operationally. Much of the data, such as dew-point temperature  and  relative  humidity,  had  to  be  determined from printed tables (such as those available in the Smithsonian Meteorological Tables) or calculated manually. In the ensuing decades, as meteorology became  more  of  a  precise  science,  many  paper nomograms  and  metal  or  plastic  calculators  were developed to make the calculations easier. These nomograms and calculators helped free the user from bulky   printed   tables.   Although   the   built-in computational  power  of  the  ASOS  and  SMOOS perform  many  of  these  calculations,  we  include  this section on the proper use and care of the most frequently 2-35