# Aero QA Geometry

> QA checklist for OpenVSP geometry work in open-air. Use when editing or reviewing src/openair/geometry/**, geometry.json, .vsp3/STL exports, packing, or anything touching the OpenVSP Python API.

- Skill: `elodin-sys/aero-qa-geometry` (Agent Skill)
- Install (CLI): `npx skillmds@latest add elodin-sys/aero-qa-geometry`
- Raw SKILL.md: https://api.skillmd.com/api/skills/elodin-sys/aero-qa-geometry/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: elodin-sys (https://skillmd.com/u/elodin-sys)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/elodin-sys/aero-qa-geometry

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# Geometry QA

Read `docs/guidebook/01-openvsp.md` and execute its "Check your work" list.

Non-negotiables for this repo:

- OpenVSP setters fail silently: any new `SetParmVal` needs read-back
  coverage in `build_openvsp_model`'s verification block, and errors must be
  drained via `vsp.ErrorMgrSingleton.getInstance()` (module-level error
  functions do not exist).
- Read-back proves values, never choices: a wrong rotation axis reads back
  "correctly" while the exported mesh is garbage (audit F14). The stage `ok`
  therefore requires `readback.matches_spec`, `stl_bbox.ok`, AND
  `mesh_checks.ok` (per-component extents, fin verticality, attachment,
  computed whole-model height — all measured from the exported STL).
- Always open `threeview.png`: it is rendered from the exported mesh, not the
  spec. If you change the builder, look at it before trusting any number.
- Set wing driver groups before planform parms; pin `Sweep_Location` to 0 for
  LE sweep; `Update()` before any read-back or export.
- A `wing.sections` reproduction needs one driver group per panel, exact
  per-section read-back, and a reopened-VSP3 check. OpenVSP 3.51 retains a
  stale aggregate area after XSec insertion unless `TotalSpan` is nudged and
  restored; without that recomputation the saved wing rescales on reopen.
  Require `geometry.json .wing.planform_mode == "sections"`,
  `.openvsp.readback.wing_sections.matches`, and the true section polygon in
  `.planform.planform_xy`.
- MassProp `Total_Mass` is unitless volume-proxy unless densities were set —
  never quote it as kilograms.
- Fin roots: `geometry.json .openvsp.fin_attach.mode` must match
  `vtail.root_attachment`. In `measured` mode the selected y/z must equal the
  spec exactly and read-back must verify both mirrored fins. If the visible
  root is outside the core body, require a source-measured
  `fuselage.fairings` loft plus derived `vtail*_root` extensions:
  actual-transform `fairings_match`, `vtail_root_extensions_match`, zero
  signed extension-tip junction gap, buried LE/mid/TE eccentricities ≤0.8,
  `fin_*_attached`, and `fairing_*_contained` (≥95% at least 2 mm inside the
  independent body/wing solids) must all pass after VSP3 reopen. The
  attachment verdict uses the authoritative
  body/fairing section at root x and a 10 mm or 0.2%-length proximity floor;
  never restore the old ±0.12 m bounding slab / 60 mm floor. Extensions are
  reproduction-only. Fairings and root extensions are loft-only and must be
  absent from VSPAERO lifting sets.
- Packing: payload bay must clear the engine compartment front
  (`L - 0.20 - engine_length - 0.05`) and fuel volume must fit wing tanks +
  fuselage leftover (`packing_report`).
- Reference model (guidebook chapter 13): when
  `designs/<concept>/reference/reference.json` exists, `geometry.json` carries
  `reference_fidelity` (gating: body p95 surface deviation and top/side
  silhouette IoU; disclosed: whole-aircraft and wing/fin p95, station and
  planform deltas; `reference_sha256`) and the phase directory holds
  `reference_overlay.png`. For `sketch.treatment: reproduction` the stage
  `ok` and the Geometry-truth gate require `reference_fidelity.ok`; otherwise
  it is disclosed evidence. Open the overlay. Any departure must trace to a
  documented unrepresentable feature in the brief, never to measurement error.
  For a sectioned wing, the disclosed exposed-wing p95 is model-to-reference
  outside the scan-derived body exclusion; pair it with silhouette
  reference-only area so omitted geometry cannot hide. Retain full component
  p95 as buried carry-through disclosure. The reference is measured design
  input — not validation truth.