correctairspeed

Convert from one of other two airspeeds to equivalent airspeed (EAS), calibrated airspeed (CAS), or true airspeed (TAS)

Syntax

outputAirpseed = correctairspeed(inputAirspeed, speedOfSound, pressure0, inputAirspeedType, outputAirspeedType)
outputAirpseed = correctairspeed(inputAirspeed, speedOfSound, pressure0, inputAirspeedType, outputAirspeedType, method)

Description

outputAirpseed = correctairspeed(inputAirspeed, speedOfSound, pressure0, inputAirspeedType, outputAirspeedType) computes the conversion factor from specified input airspeed to specified output airspeed using speed of sound and static pressure. The function applies the conversion factor to the input airspeed to produce the output in the desired airspeed.

outputAirpseed = correctairspeed(inputAirspeed, speedOfSound, pressure0, inputAirspeedType, outputAirspeedType, method) uses the specified method to compute the conversion factor.

Input Arguments

inputAirspeed

Floating-point array of size m-by-1 of airspeeds in meters per second. All values must have the same airspeed conversions from inputAirspeedType to outputAirspeedType.

speedOfSound

Floating-point array of size m-by-1 of speeds of sound, in meters per second.

pressure0

Floating-point array of size m-by-1 of static air pressures, in pascal.

inputAirspeedType

Input airspeed, specified as a string. Supported airspeeds are:

'TAS'True airspeed
'CAS'Calibrated airspeed
'EAS'Equivalent airspeed

outputAirspeedType

Output airspeed, specified as a string. Supported airspeeds are:

'TAS'True airspeed
'CAS'Calibrated airspeed
'EAS'Equivalent airspeed

method

Specify a method, as a string, for computing the conversion factor.

'TableLookup'

(Default) Generate output airspeed by looking up or estimating table values based on inputs inputAirspeed, speedOfSound, and pressure0.

The 'TableLookup' method is not recommended for either of these instances:

  • speedOfSound less than 200 m/s or greater than 350 m/s.

  • pressure0 less than 1000 Pa or greater than 106,500 Pa.

Using the 'TableLookup' method in these instances causes inaccuracies.

'Equation'

Compute output airspeed directly using input values inputAirspeed, speedOfSound, and pressure0.

Calculations involving supersonic airspeeds (greater than Mach 1) require an iterative computation. If the function does not conclude within 30 iterations, it displays an error message.

The correctairspeed function automatically uses the 'Equation' method for any of these instances:

  • Conversion with inputAirspeedType set to 'TAS' and outputAirspeedType set to 'EAS'.

  • Conversion with inputAirspeedType set to 'EAS' and outputAirspeedType set to 'TAS'.

  • Conversion with inputAirspeed is greater than five times the speed of sound at sea level (approximately 1700 m/s).

Output Arguments

outputAirpseed

Floating-point array of size m-by-1 of airspeeds in meters per second.

Examples

Convert three airspeeds from true airspeed ('TAS') to equivalent airspeed ('EAS') at 1,000 ms using the 'TableLookup' method:

ain = [25.7222; 10.2889; 3.0867];
as = correctairspeed(ain,336.4,89874.6,'TAS','CAS','TableLookup')
as =

   24.5077
    9.8024
    2.9407

Convert airspeeds from calibrated airspeed ('CAS') to equivalent airspeed ('EAS') at 1,000 m and 0 m using the 'Equation' method:

ain = [25.7222; 10.2889; 3.0867];
sos = [336.4; 340.3; 340.3];
P0 = [ 89874.6; 101325; 101325];
as = correctairspeed(ain,sos,P0,'CAS','EAS','Equation')
as =

   25.7199
   10.2889
    3.0867

Convert airspeed from true airspeed ('TAS') to equivalent airspeed ('EAS') at 15,000 meters. Use the atmoscoesa function to first calculate the speed of sound (sos) and static air pressure (P0):

ain = 376.25;
[~, sos, P0, ~] = atmoscoesa(15000);
as = correctairspeed( ain, sos, P0, 'EAS', 'TAS')
as =

  149.6042

Limitations

This function assumes that air flow is compressible dry air with constant specific heat ratio (gamma).

References

Lowry, J.T., Performance of Light Aircraft, AIAA Education Series, Washington, D.C., 1999

Aeronautical Vestpocket Handbook, United Technologies Pratt & Whitney, August1986

Gracey, William, Measurement of Aircraft Speed and Altitude, NASA Reference Publication 1046, 1980.

Introduced in R2006b