The enclosed programs, AIRDATA.BAS, and DENSALT.BAS were written by R. G. Gross, of Santa Cruz, CA. Together with his earlier program, published variously as WINDRFT and DRFTRNGL, they have the makings of a sophisticated flight planning program. The latter program, given the expected wind direction and velocity, will accurately predict the heading required to maintain a given course, as well as the groundspeed, given the true airspeed. The program AIRDATA.BAS, given either Calibrated Airspeed or Mach number along with observed temperature, will accurately compute True Airspeed. In addition to the latter, if CAS is given, the program will compute the Mach number. Conversely, if Mach is given, it will also compute the CAS. The program corrects for compressibility effects in the airspeed indicating system, and will also, if so commanded, correct for air friction errors in Outside Air Temperature indicating systems. For the latter function, a HELP function is provided, giving a very brief explanation of the differences in OAT indicating systems, and steps required to modify the program for standard correction of same. The program DENSALT is intended to compute Density Altitude for the purpose of Take-off performance calculation. Given Pressure altitude and Temperature in either C. or F., the program will accurately compute the existing Density Altitude. The limits of both programs are approximately 45,000 feet msl, and Mach 1.000. Potential users must be cautioned that the writer can make no guarantee of the above accuracies, and can accept no responsibility for conse- quences of use of the programs. Written or printed data output by a computer has an aura of exceptional credibility, whether or not it may be correct. In cases of limited performance, whether it regards range, or other products of True Air Speed, or Take-off, climb, and landing performance, it is imperative that any aircraft operator carefully consult the FAA approved aircraft operating manual. Numerous REM statements have been added to the programs, to assist the user in extracting pertinent portions of the program for his own use. This material is intended for the use of anyone for his own non-com- mercial purposes. R.G.G 1-13-87