Ideal Airspeed Correction
Calculate equivalent airspeed (EAS), calibrated airspeed (CAS), or true airspeed (TAS) from each other
Libraries:
Aerospace Blockset /
Flight Parameters
Description
The Ideal Airspeed Correction block calculates one of these airspeeds from one of the other two airspeeds:
Equivalent airspeed (EAS)
Calibrated airspeed (CAS)
True airspeed (TAS)
Examples
Lightweight Airplane Design
Address the technical and process challenges of aircraft design using the design of a lightweight aircraft.
True Airspeed from Indicated Airspeed Calculation
Compute the indicated airspeed from true airspeed using the Ideal Airspeed Correction block.
Limitations
This block assumes that the air flow is compressible dry air with constant specific heat ratio, γ
Ports
Input
TAS — True input airspeed
scalar
True input airspeed, specified as a scalar, in the units specified by the Units parameter.
Dependencies
To enable this port, set Airspeed input to
TAS
.
Data Types: double
EAS — Equivalent input airspeed
scalar
Equivalent input airspeed, specified as a scalar, in the units specified by the Units parameter.
Dependencies
To enable this port, set Airspeed input to
EAS
.
Data Types: double
CAS — Calibrated input airspeed
scalar
Calibrated input airspeed, specified as a scalar, in the units specified by the Units parameter.
Dependencies
To enable this port, set Airspeed input to
EAS
.
Data Types: double
a — Speed of sound
scalar
Speed of sound, specified as a scalar, in the units specified by the Units parameter.
Data Types: double
P0 — Static pressure
scalar
Static pressure, specified as a scalar, in the units specified by the Units parameter.
Data Types: double
Output
EAS — Equivalent output airspeed
scalar
Equivalent output airspeed, returned as a scalar, in the units specified by the Units parameter.
Dependencies
To enable this port, set Airspeed input to
TAS
or CAS
and Airspeed output to
EAS
.
Data Types: double
CAS — Calibrated output airspeed
scalar
Calibrated output airspeed, returned as a scalar, in the units specified by the Units parameter.
Dependencies
To enable this port, set Airspeed input to
TAS
or EAS
and Airspeed output to
CAS
.
Data Types: double
TAS — True output airspeed
scalar
True output airspeed, returned as a scalar, in the units specified by the Units parameter.
Dependencies
To enable this port, set Airspeed input to
CAS
or EAS
and Airspeed output to
TAS
.
Data Types: double
Parameters
Units — Units
Metric (MKS)
(default) | English (Velocity in ft/s)
| English (Velocity in kts)
Input and output units, specified as:
Units | Airspeed Input | Speed of Sound | Air Pressure | Airspeed Output |
---|---|---|---|---|
| Meters per second | Meters per second | Pascal | Meters per second |
| Feet per second | Feet per second | Pound force per square inch | Feet per second |
| Knots | Knots | Pound force per square inch | Knots |
Programmatic Use
Block Parameter:
units |
Type: character vector |
Values: 'Metric
(MKS)' | 'English' |
Default: 'Metric
(MKS)' |
Airspeed input — Airspeed input type
TAS
(default) | EAS
| CAS
Airspeed input type, specified as:
| True airspeed |
| Equivalent airspeed |
| Calibrated airspeed |
Programmatic Use
Block Parameter:
vel_in |
Type: character vector |
Values:
'TAS' | 'EAS' |
'CAS' |
Default:
'TAS' |
Airspeed output — Airspeed output type
EAS
(default) | CAS
| TAS
Airspeed output type, specified as:
Airspeed Input | Airspeed Output |
---|---|
| EAS (equivalent airspeed) |
CAS (calibrated airspeed) | |
| TAS (true airspeed) |
CAS (calibrated airspeed) | |
| TAS (true airspeed) |
EAS (equivalent airspeed) |
Programmatic Use
Block Parameter: vel_out_tas ,
vel_out_cas , vel_out_eas ,
depending on the input velocity type, vel_in . For
more information, see the airspeed output type table. |
Type: character vector |
Values: 'EAS' |
'CAS' 'TAS' |
Default:
'EAS' |
Method — Method for computing conversion factor
Table Lookup
(default) | Equation
Method for computing the conversion factor, specified as:
Table Lookup
| (Default) Generate output airspeed by looking up or estimating table values based on block inputs. If the Subsonic airspeeds only check box is selected, the Ideal Airspeed Correction block generates code that includes subsonic (Mach < 1) lookup table data. If the Subsonic airspeeds
only check box is cleared, the
Ideal Airspeed Correction block
generates code that includes all (Mach < 5) lookup
table data. Beyond Mach 5, the block uses the
The
Using the |
Equation
| Compute output airspeed directly using block input values. Calculations involving supersonic airspeeds (greater than Mach 1) require an iterative computation. If the function does not find a solution within 30 iterations, it displays an error message. The block does not include lookup table data in generated code. |
The Ideal Airspeed Correction block automatically uses the
Equation
method for any of these
instances:
Conversion with Airspeed input set to
TAS
and Airspeed output set toEAS
.Conversion with Airspeed input set to
EAS
and Airspeed output set toTAS
.Conversion when block input airspeed is greater than five times the speed of sound at sea level (approximately 1700 m/s).
Programmatic Use
Block Parameter:
method |
Type: character vector |
Values: 'Table
Lookup' | 'Equation' |
Default: 'Table
Lookup' |
Subsonic airspeeds only — Use with subsonic airspeed
off
(default) | on
Select this check box to use this block only with subsonic airspeed (airspeeds less than Mach 1) applications. Selecting this check box may improve performance.
The block generates code as follows:
If this check box is selected, the Ideal Airspeed Correction block generates code that includes subsonic (Mach < 1) lookup table data if Method is set to
Table Lookup
.Selecting this check box displays the Action for out-of-range input parameter.
If this check box is cleared, the Ideal Airspeed Correction block generates code that includes all (Mach < 5) lookup table data if Method is set to
Table Lookup
.
Programmatic Use
Block Parameter: SubOnly |
Type: character vector |
Values: 'off' |
'on' |
Default: 'off' |
Action for out-of-range input — Out-of-range block behavior
None (default) | Warning
| Error
Out-of-range block behavior, where airspeed is greater than Mach 1, specified as follows.
Value | Description |
---|---|
| Does not display warning or error. |
| Displays warning and indicates that the airspeed is greater than Mach 1. |
| Displays error and indicates that the airspeed is greater than Mach 1. |
Dependencies
This parameter is enabled only if the Subsonic airspeeds only check box is selected.
Programmatic Use
Block Parameter:
action |
Type: character vector |
Values:
'None' | 'Warning' |
'Error' |
Default:
'None' |
References
[1] Lowry, J. T., Performance of Light Aircraft, AIAA Education Series, Washington, DC, 1999.
[2] Aeronautical Vestpocket Handbook, United Technologies Pratt & Whitney, August, 1986.
[3] Gracey, William, Measurement of Aircraft Speed and Altitude, NASA Reference Publication 1046, 1980.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
Version History
Introduced before R2006a
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