Biplane

Note: Size: a Stearman-class trainer, 9.0 m upper wingspan (8.3 m lower), about 8.1 m from spinner to rudder (8.4 m bounding box with the propeller disc) and 2.77 m tall at the upper wing, sitting tail-down at 11° on its two main tyres and tail wheel, all resting on y = 0 on flat facets. The nose faces +Z and the origin is at the bottom centre of the footprint. The airframe pitch is baked into the geometry, so the 'airframe' node and its parts sit at identity; only the propeller (on the pitched crank axis) and the hinge frames carry rotations. The GLB has 2,272 triangles in 25 meshes (merged per part and colour) and one 6 s clip 'scene-motion': the propeller turns six whole revolutions, the rudder sweeps once, the ailerons roll twice and the elevators nod once, each about its hinge line. Airframe and gear never move. Every material is named exactly after an Airfield kit palette colour; the default era uses 7 of the 12 (sky blue, signal orange, hangar white, hangar white light, soot black, mid grey, dark wood). The exporter writes one material per mesh, so names repeat: recolour by name. era (the kit's 'Era') steps the scheme: below 0.3 a 1920s barnstormer (grass green dark fuselage, hangar white dark linen wings, dark wood struts and prop, a wooden tail skid instead of the tail wheel); 0.3–0.7 a 1940s trainer (the default, with an orange cheatline); 0.7 and above a restored airshow ship (metal prop, orange spinner, blue wheel spats, white cheatline). wingSpan, stagger and controlSweep reshape the wings and the loop amplitude. Params are baked into the GLB at their defaults and only change the model when the scene is rebuilt in the viewer; three-check passes at both param extremes. glb-lint reports 0 errors; its warnings are expected heuristics (non-indexed flat-shaded geometry, per-part material duplicates, overlapping nested parts, 'detached' wings and control surfaces that hang on struts or hinges rather than touching a sibling mesh, and height vs a 1 m reference). plan-check rejects only the hyphenated library part ids (its regex allows no hyphen); the same plan with the slug de-hyphenated passes. The viewer's staging ground and light rig are not in the GLB.