Calculate equivalent airspeed (EAS), calibrated airspeed (CAS), or true airspeed (TAS) from each other
Flight Parameters
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)
Specifies the input and output units:
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 |
Specify the airspeed input type:
| True airspeed |
| Equivalent airspeed |
| Calibrated airspeed |
Specify the airspeed output type:
Velocity Input | Velocity Output |
---|---|
| EAS (equivalent airspeed) |
CAS (calibrated airspeed) | |
| TAS (true airspeed) |
CAS (calibrated airspeed) | |
| TAS (true airspeed) |
EAS (equivalent airspeed) |
Specify a method for computing the conversion factor. The block might generate associated lookup table data depending on the setting of the Subsonic airspeeds only check box.
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, use 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 to EAS
.
Conversion with Airspeed input set to
EAS
and Airspeed
output set to TAS
.
Conversion with block input airspeed is greater than five times the speed of sound at sea level (approximately 1700 m/s).
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
.
Specify action to take in case of out-of-range input, where airspeed is greater than Mach 1. This parameter displays if the Subsonic airspeeds only check box is selected.
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. |
Input | Dimension Type | Description |
---|---|---|
TAS/EAS/CAS | double | Contains the selected airspeed in the selected units. |
a | double | Contains the speed of sound in the selected units. |
P0 | double | Contains the static pressure in the selected units. |
Output | Dimension Type | Description |
---|---|---|
TAS/EAS/CAS | double | Contains the selected airspeed in the selected units. |
This block assumes that the air flow is compressible dry air with constant specific heat ratio, γ.
See the aeroblk_indicated
model
and the aeroblk_calibrated
model
for examples of this block.
Lowry, J. T., Performance of Light Aircraft, AIAA Education Series, Washington, DC, 1999.
Aeronautical Vestpocket Handbook, United Technologies Pratt & Whitney, August, 1986.
Gracey, William, Measurement of Aircraft Speed and Altitude, NASA Reference Publication 1046, 1980.
COESA Atmosphere Model, ISA Atmosphere Model, Lapse Rate Model, Non-Standard Day 210C, Non-Standard Day 310