AEROGRAPHER'S MATE 3 & 2 



speed, rate of climb, and fuel consumption, 

 but also plays an important role in determining 

 the length of runway necessary for takeoff. 



The Density Altitude Computer CP-718/UM 

 consists of two plastic or metal discs and one 

 cursor. The bottom disc contains the temperature 

 expressed in Celsius and Fahrenheit, while the 

 top disc contains the pressure density, moisture 

 correction, and dry bulb temperature scales. 

 On the cursor is found a wet bulb temperature 

 scale. 



The computer was primarily designed to 

 compute atmospheric density. It may, however, 

 also be used to interconvertthermometric scales, 

 pressure units, density ratio, vapor pressure, 

 specific humidity, etc. The operating instructions 

 are printed on the back of the computer. (See fig. 

 2-12.) 



MAINTENANCE 



The important points in regard to calcula- 

 tors, computers, and evaluators are the cleaning 



and storing of them. The pointers listed in 

 this section apply to all the computers in use in 

 the Naval Weather Service, such as the psy- 

 chrometric computer, true wind computer, mixing 

 ratio calculator, and the like. 



To remove accumulations of dirt, dust, and 

 lint from the spaces between the plates and 

 under the cursor, draw a piece of paper through 

 the space while applying a slight pressure to 

 the discs or cursor. If grease or gummy deposits 

 are present, moisten a blotter with soap and 

 water and proceed as above. Exposed surfaces 

 may be cleaned with a soft cloth, soap, and 

 water. Rinse thoroughly and dry. DO NOT USE 

 SOLVENTS. 



Plastic calculators, computers, and evaluators 

 should be returned to their original packaging 

 preparatory to storage or shipment. If the original 

 packaging is no longer available, an equivalent 

 method will suffice. The items should not be 

 stored in any atmosphere in which the tem- 

 perature exceeds 140° F. 



NOTE: Changes to all column numbers and 

 entries on NWSC Form 3140/8 were received too 

 late for inclusion in this manual. Where errors 

 in column numbers appear, refer to the U.S. 

 Navy Supplement to FMH #1, Chapter 13, Marine 

 Aviation Observations for the most recent ampli- 

 fying instructions. 



32 



