# correctairspeed

Convert airspeeds between equivalent airspeed (EAS), calibrated airspeed (CAS), or true airspeed (TAS)

## Description

example

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 then 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.

## Examples

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Convert three airspeeds from true airspeed to equivalent airspeed at 1000 meters using method 'TableLookup'.

ain = [25.7222; 10.2889; 3.0867];
as = correctairspeed(ain,336.4,89874.6,'TAS','CAS','TableLookup')
as = 3×1

24.5077
9.8024
2.9407

Convert airspeeds from true airspeed to equivalent airspeed at 1000 meters and 0 meters.

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 = 3×1

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 = 946.2572

## Input Arguments

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Input airspeed, specified as a floating-point array of size m-by-1, in meters per second. All values in the array must have the same airspeed conversion factor.

Data Types: double

Speeds of sound, specified as a floating-point array of size m-by-1 in meters per second.

Data Types: double

Air pressures, specified as a floating-point array of size m-by-1, in pascal.

Data Types: double

Input airspeed type, specified as one of these.

Airspeed TypeDescription

'TAS'

True airspeed

'CAS'

Calibrated airspeed

'EAS'

Equivalent airspeed

Data Types: char | string

Output airspeed type, specified as one of these.

Airspeed TypeDescription

'TAS'

True airspeed

'CAS'

Calibrated airspeed

'EAS'

Equivalent airspeed

Data Types: char | string

Airspeed conversion method, specified as one of these.

Conversion MethodDescription

'TableLookup'

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.

#### Dependencies

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).

Data Types: char | string

## Output Arguments

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Output airspeed, returned as a floating-point array of size m-by-1, in meters per second.

## Limitations

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

## References

[1] Lowry, J.T. Performance of Light Aircraft. Washington, DC: AIAA Education Series, 1999.

[2] Pratt & Whitney Aircraft. Aeronautical Vestpocket Handbook. United Technologies, August 1986.

[3] Gracey, William. Measurement of Aircraft Speed and Altitude. Washington, DC: NASA Reference Publication 1046, 1980.

## Version History

Introduced in R2006b