Date:22 Feb 99 03:30:25From:David Lednicer <dave@amiwest.com>Organization:Analytical Methods, Inc.References:1 2

View raw article or MIME structure

> On 1/17/99 2:37 AM, Scott (scott@golfmike.demon.co.uk) said: > Can anyone tell me how to work out TAS for IAS? According to the Pratt & Whitney handbook, to get from IAS, you first correct for airspeed position error - this gives Calibrated Air Speed (CAS). Then, you apply compressibility corrections to get Equivalent Air Speed (EAS). Finally, you apply a density correction to get True Air Speed (TAS). The CAS to EAS to TAS correction is necessary due to how airspeed indicators work. They measure the difference between total pressure and static pressure, to get dynamic pressure. They then assume density to be a constant to produce airspeed. However, density changes with Mach number (hence EAS) and altitude (hence TAS). To make the corrections, you need to know local sonic velocity, altitude and temperature. ------------------------------------------------------------------- David Lednicer | "Applied Computational Fluid Dynamics" Analytical Methods, Inc. | email: dave@amiwest.com 2133 152nd Ave NE | tel: (206) 643-9090 Redmond, WA 98052 USA | fax: (206) 746-1299