Lift Coefficient / Lift Force Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Thermodynamics, Fluids & Aero

Tranche

tranche-5

Evidence ID

t5-033

Ledger rows

1

No ledger note is attached.

Review findings

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.

Formula and scope findings

• 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.

Unit assumptions

• 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.

Boundary hardening

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.

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": {
    "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."
}

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-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json