Source: https://guthlabs.ai/docs/instruments/lift-coefficient-lift-force-calculator/mechanism/

instrument mechanism / verified-clean

# Lift Coefficient / Lift Force Calculator mechanism

The inspectable method record for Lift Coefficient / Lift Force Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The lift-force equation is correct under standard steady-flow aerodynamic assumptions. Verdict is NEEDS_REVIEW because the required-Cl output formula and the altitude-to-density implementation are not explicitly specified, and the density data source is absent.

- The lift-force formula L = ½ρV²ClS is standard and correct for steady aerodynamic lift when ρ is in kg/m³, V in m/s, S in m², and L is in newtons.

- The claimed output 'required Cl for level flight given weight' has no formula in the spec. It should explicitly use Cl_required = W/(½ρV²S), where W is force in newtons.

- The altitude-adjusted density calculation is underspecified: the spec references an ISA density table but provides neither the table, interpolation rule, altitude input definition, nor an alternative ISA formula.

## Units and conventions

- ρ is air density in kg/m³.

- V must be in m/s before applying the formula; if entered in km/h, convert using V_m/s = V_km/h ÷ 3.6.

- S is wing planform area in m².

- Cl is dimensionless.

- Lift force L and weight W are in newtons.

- For level-flight Cl, required weight must be supplied as a force in newtons, not as mass in kilograms.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "Cl": 0.5,
    "S_m2": 16,
    "V_mps": 50,
    "rho_kg_m3": 1.225,
    "weight_N": 12000
  },
  "expected_outputs": {
    "lift_N": 12250,
    "required_Cl": 0.4897959184
  },
  "working": "Dynamic pressure q = ½ρV² = ½ × 1.225 × 50² = 0.6125 × 2500 = 1531.25 Pa. Lift L = q × Cl × S = 1531.25 × 0.5 × 16 = 1531.25 × 8 = 12250 N. Required Cl = W/(qS) = 12000/(1531.25 × 16) = 12000/24500 = 0.4897959184."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

Required-Cl calculations divide by zero when V=0 or S=0 and must reject the input rather than emit a numeric result. The specification also provides no genuine formula branch, so signed negative velocity handling and the sign convention for lift and Cl remain ambiguous.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/lift-coefficient-lift-force-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/lift-coefficient-lift-force-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/lift-coefficient-lift-force-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`