Source: https://guthlabs.ai/docs/instruments/airspeed-converter-ias-cas-tas-eas/
instrument / verified-clean
# Airspeed Converter (IAS/CAS/TAS/EAS)
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Thermodynamics, Fluids & Aero
**Tranche**: tranche-6
**Evidence ID**: t6-065
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The instrument should expose the exact atmosphere model, altitude units/reference, temperature-deviation convention, IAS/CAS error assumptions, and the precise compressible EAS definition before implementation. As written, the concept is plausible but mathematically underspecified, so the verdict is NEEDS_REVIEW.
### Formula and scope findings
- The specification does not define the IAS-to-CAS correction, so CAS cannot generally be computed from IAS without an instrument/position-error model; the vectors below explicitly assume IAS=CAS.
- TAS=CAS/sqrt(sigma) is only an incompressible or low-Mach approximation. For compressible flow, CAS must first be converted to impact pressure using the standard-sea-level isentropic relation, then local Mach number and TAS must be computed.
- The compressible correction is not stated mathematically. A standard model is qc/p=(1+(gamma-1)M^2/2)^(gamma/(gamma-1))-1, with CAS defined from qc at standard sea-level pressure.
- EAS is not explicitly defined. The vectors use EAS=TAS*sqrt(rho/rho0), equivalently EAS=sqrt(2q/rho0), which is the standard dynamic-pressure definition; this differs from CAS at appreciable Mach number.
- The ISA table, atmosphere-layer equations, altitude reference, and treatment of temperature deviation are unspecified.
### Unit assumptions
- Altitude is geometric altitude in metres unless otherwise stated; one vector explicitly supplies 10000 ft converted to 3048 m.
- Airspeeds are knots indicated by the input and output labels; 1 kt=0.514444 m/s.
- Standard constants: gamma=1.4, R=287.05 J/(kg K), T0=288.15 K, p0=101325 Pa, rho0=1.225 kg/m^3.
- For the simplified vectors, pressure is the ISA pressure at altitude and actual temperature is T_ISA plus the stated temperature deviation; sigma=rho/rho0=(p/p0)/(T/T0).
- For the compressible vector, CAS is converted to impact pressure at standard sea level, then the same impact pressure is used at the local ISA static pressure. No position error, humidity, wind, or compressibility correction to the pitot instrument is included.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
A temperature deviation of -288.15 K at sea level makes the absolute temperature exactly zero, causing the density denominator R*T to vanish. The converter should reject the input; any numeric output would be erroneous.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"input_type": "CAS",
"CAS_kt": 100,
"altitude_m": 0,
"temperature_deviation_K": 0,
"model": "incompressible approximation",
"assumptions": "IAS=CAS; sigma=1"
},
"expected_outputs": {
"CAS_kt": 100,
"EAS_kt": 100,
"TAS_kt": 100,
"density_ratio_sigma": 1
},
"working": "At sea level, sigma=rho/rho0=1. EAS=TAS*sqrt(sigma)=100*sqrt(1)=100 kt. TAS=CAS/sqrt(sigma)=100/sqrt(1)=100 kt. Therefore CAS=100 kt, EAS=100 kt, TAS=100 kt."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche6/tranche6-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`