airfoil-selectionlisted

# Airfoil Section Selection (aerodynamics/airfoil/airfoil-selection) Use when the task is airfoil section selection for a wing: scoring candidates by lift-to-drag ratio, filtering by thickness, and choosing the best qualified section. ## Domain quick reference - Classic airfoil data (NACA Report 824 and successors) supplies lift and drag coefficients per section. - The design condition defines the target lift coefficient and Reynolds number. - Thickness constrains the section: structural depth and internal volume come from the thickness ratio. - Selection maximizes lift-to-drag ratio among sections that meet the minimum thickness. ## Workflow 1. Collect candidate sections with cl, cd, and thickness at the design condition. 2. Score each with ld_ratio. 3. Filter with thickness_ok. 4. Select with select_airfoil. 5. Confirm the choice against the design lift condition. ## Pitfalls - Choosing by cl alone instead of lift-to-drag ratio. - Ignoring the thickness constraint until the structure is sized. - Comparing candidates at different Reynolds numbers. ## Behavior contract (gate 3) The scoring, filtering, and selection logic is exercised by the gate 3 contract test: scripts/test_airfoil_selection.py against scripts/airfoil_selection_logic.py (stdlib unittest, offline). Run: python3 scripts/test_airfoil_selection.py ## Compliance - NACA Report 824 is US government work (public domain); summary and physics values only, per standards-map.yaml. - compliance: S