bdx — Elite Aerosports BDX (standard 2.65 m sport jet)

1. Intent and configuration summary

Provisional parametric reconstruction of the standard Elite Aerosports EA BDX RC sport turbine jet, initialized for future use as the canonical aero-design source behind the Elodin rc-jet example (per the BDX handoff document). Configuration: single-turbine sport jet; pointed nose; faired canopy blending into a dorsal spine; deep mid-body with flat belly and strong aft upsweep to a high exhaust; low-mid trapezoidal wing with modest LE sweep and near-straight trailing edge; conventional swept horizontal tail mounted high on the tail cone; one large, heavily raked centerline fin blended into the dorsal spine. Excluded variants: BDXL, BDXs, IND/UAS.

This bundle is a geometry checkpoint, not a validated flight-dynamics model. Every value below carries a provenance class following the handoff's convention: A manufacturer-supported, B independent corroboration, C engineering derivation, D placeholder.

2. Sources and view classification

PNG conversion record: all .webp sources decoded with Pillow, EXIF orientation applied (none present), converted to RGB PNG. sketch-top.png and sketch-side.png are crops of the two primary sub-views from the livery sheet; overlapping pixels of the sheet's central logo text were replaced with the local background gray (documented scrub, 418 px / 40 px). Both outputs verified to start with the PNG signature 89 50 4E 47 0D 0A 1A 0A. No usable front view was supplied, so sketch-front.png does not exist and section curvature is inferred (see §7).

Variant caveat: the orthographic sheet and two photos depict the BDXL, the stretched family variant; the handoff scopes this concept to the standard BDX. Family lines are shared (confirmed against bdx-2), so the sheet is used for shape ratios only, anchored to standard-BDX absolute span/length, and every sheet-derived ratio carries a widened tolerance for variant drift.

3. Requirement record

4. Coordinate, scale, and rectification method

• Convention: x/L = 0 at nose tip, x/L = 1 at tail; positive y centerline → right wingtip; vertical datum z = 0 at the nose tip center, positive up. All station z_offset_m values, wing.z_root_m, htail.z_m, and vtail.z_root_m share this datum.
• The livery sheet was segmented by background subtraction (saturation > 38 or value < 118/ > 226 against the smooth gray gradient), connected components labeled, and interior holes filled. Each of the four panels has its own scale; every measurement is normalized by that panel's own nose-to-tail pixel length before conversion to meters with L = 2.80 m (class A).
• Panel lengths: top view 342 px, bottom view 333 px, side views 415/414 px.
• Edges (wing/stab LE and TE) are least-squares line fits over the straight segments of the silhouette boundary; left/right semi-span fits agreed to 0.1° on wing LE sweep.
• Not rectified: the sheet is treated as orthographic as drawn (bootstrap — approximate agent image-space measurement, no four-point control or grid scale available). Oblique photos/renders were used only as qualitative cross-checks, never for numbers.

5. Measurement and inference record

Scale: 1 px(top) = 8.19 mm, 1 px(side) = 6.75 mm at L = 2.80 m. Base pixel uncertainty ±2 px plus variant drift is folded into the stated tolerances.

Planform (top view trace, sketch-top.png)

Side profile (side view trace, sketch-side.png)

Fuselage loft at shared stations — widths from top view, heights and centerline offsets from side view (z datum: nose tip center, up positive):

Other side-view items:

Inferences beyond the sketch (not visible/derivable from views)

Unit conversions shown: 104 in = 2.6416 ≈ 2.65 m; 110 in = 2.794 ≈ 2.80 m; 40–42 lb = 18.14–19.05 kg; 200 mph = 89.408 m/s = 173.8 kt; 6.0 L × 0.80 kg/L = 4.8 kg; 0.12 kg/(N·h) × 200 N = 24 kg/h = 0.006667 kg/s.

6. Template defaults retained (dotted paths, rationale)

• engine.thrust_lapse_*, engine.tsfc_part_*, engine.tsfc_mach_k, engine.min_throttle, engine.fuel_density_kg_m3 — solver calibration constants; a sketch proves nothing about them (skill rule: do not retune from a sketch).
• fuselage.nose_fine_ratio, fuselage.tail_fine_ratio — legacy once explicit stations are active; kept at template values.
• wing.t_over_c: 0.12 — surrogate thickness (BD-5 heritage is 12%, but the BDX section is unpublished); htail.t_over_c: 0.10, vtail.t_over_c: 0.07 typical thin tail surfaces (0.07 chosen below template's 0.10 for the thin blended fin; still a class-D assumption).
• mission.safety_factor: 1.5, mission.reserve_fuel_fraction: 0.08 — template defaults; no BDX data.
• mission.cl_max: 1.2 declared on section basis (class C): conservative against published NACA 0012/2412 section maxima at Re 0.5–1.5×10⁶; the schema's documented 0.9 × cos(quarter-sweep) conversion yields aircraft CLmax ≈ 1.06. Replaces the template's aircraft-basis 1.2 (class D), which overstated the corner-case lift target and pushed the +6 g structures load solve past the 12° linear-VLM honesty domain. No BDX stall measurement exists either way; stall claims remain assumption-labeled.
• structures.* — full template block including Al7050 material: the real airframe is composite sandwich with carbon tubes, but no laminate schedule is published, so the calibrated aluminum wingbox surrogate is retained deliberately (handoff §19). Do not present structural margins as BDX truth.
• mass.landing_gear_fraction: 0.035, mass.contingency_fraction: 0.08 — template defaults.
• solver.* — template numerical controls, including np_shift_mac: 0.04305 and cm_washout_per_deg: 0.00362 (calibrated at the template's 32° sweep reference; the balance model scales across this concept's envelope).

7. Visible or known features not representable in the schema

• Flush side/belly inlets near the wing root (visible in bdx-1): no inlet component exists; internal-flow and inlet drag effects are absent.
• Canopy is modeled only as loft height/z-offset (no separate transparent component).
• Ventral strakes / aft belly fences hinted in bdx-side: not modeled.
• Landing gear, gear doors (visible in photos): not modeled.
• Exhaust pipe nub beyond the tail cone: folded into the last station.
• Blended fin-root fairing: the dorsal blend is represented as a plain trapezoid fin with a long root chord; the builder derives the fin attachment height from the body (≈ +0.26 m), slightly below the sheet's visual fin base (+0.34 m), so the rendered fin sits marginally lower than the livery art.
• Control surfaces (ailerons, elevator, rudder, flaps with published mm throws): geometry hinge data insufficient; flight_dynamics left disabled. Converting published throws to hinge angles is Priority-0 follow-up work per the handoff.
• No front view: cross-section curvature (super-ellipse powers) is inferred from photos; expect section-shape error until a front view or hardware measurement exists.
• Sheet depicts the BDXL variant; standard-BDX proportions may differ within the widened tolerances recorded above.

8. Geometry-checkpoint iteration log

• Iteration 1: initial authored bundle. All geometry gates passed (readback.matches_spec, stl_bbox.ok, mesh_checks.ok, packing.ok, empty error queue, shape fidelity ok). Visual mismatch: windshield/canopy rise too gradual — stations at 0.25/0.42 L interpolated the canopy top ~0.07 m low around 0.31 L versus the side trace.
• Iteration 2: source fix — replaced the 0.42 L station with the measured canopy-top station at 0.33 L (w 0.254, h 0.385, z +0.105); the 0.33→0.64 interpolation now reproduces the measured 0.405 m height at 0.42 L. All gates pass again (ok: true, readback match, STL bbox 2.80 × 2.65 × 0.746 m, 16/16 mesh checks, packing ok, empty error queue). Three-view windshield/canopy silhouette now within the recorded station tolerances; remaining known deviations are the documented fin-attachment height (builder-derived +0.26 m vs sheet +0.34 m) and the straight-trapezoid dorsal blend. Loop stopped at iteration 2 of 3.
• Iteration 3 (Studio review): user re-traced in Design Studio — station 3 moved from 0.25 L (h 0.256, z +0.040) to 0.223 L (h 0.330, z +0.077), sharpening the windshield break. The Studio save serialized the schema and dropped optional sketch-contract fields; treatment: inspiration, hard_scale: 3, fidelity_weight: 1, and the measured fin_* priors were restored from this brief's measurement record before the pre-MDO geometry checkpoint. No other value changed.
• Iteration 4 (structures-gate investigation): first full pipeline run passed 11/12 gates; the structures gate failed honestly — the ±g load case flies a corner condition targeting 79.2% of aircraft CLmax, and with the template-defaulted aircraft-basis CLmax 1.2 the +6 g solve required α = 12.45°, past the 12° linear-VLM domain (strength itself had large margin: failure index −0.92, tip deflection 4 mm). Fix: declare cl_max: 1.2 on section basis (see §6), lowering the corner-case target to CL ≈ 0.84 (α ≈ 11°) while preserving the +6 g/−3 g aerobatic requirement.

Sketch measurement worksheet

Generated by open-air Design Studio. Preserve source/inference notes in the brief above this section.

Rectification and scale

• top: source not supplied; control points not rectified (no four-point control set); fuselage 24.50 grid squares; 0.11429 m/grid square.
• side: source not supplied; control points not rectified (no four-point control set); fuselage 24.50 grid squares; 0.11429 m/grid square.
• front: source not supplied; control points not rectified (no four-point control set); fuselage 24.50 grid squares; 0.11429 m/grid square.

Measured geometry and tolerances

Fuselage stations

Inference record

Document every value inferred rather than directly traced (including hidden-view dimensions, airfoil, gauges, material, propulsion assumptions, and tolerances) in the narrative above.