Mechanical Standards
The mechanical conventions for panels and mounts. Some of this is settled (screws, gauge sizes); panel-level dimensions are still being worked out and are marked TBD — don't invent them.
Screws
| Screw | Use | Clearance |
|---|---|---|
| M2 | PCB mounts, small standoffs | — |
| M3 | Placards, light rings, small brackets | — |
| M4 | Instrument bezels, gauge mounts | Ø4.3–4.5 mm |
| M5 | Panel-to-subpanel, corner mounts | Ø5.3–5.5 mm |
Gauges
| Gauge | Size | Drive |
|---|---|---|
| LOX gauge | 2-5/8″ (~67 mm) | — |
| Radar altimeter | 3-1/8″ (~100 mm with bezel) | — |
| Cabin pressure | — | X27.589 Switec stepper, shaft-through-PCB mount |
Switches & controls
- Toggle switches: 12 mm standard; ~6 mm on the ECM modules.
Panel dimensions, cutouts, bezels, light rings
Dzus rail mounting — MIL-F-25173A
Left/right console panels mount on standard Dzus rails (MIL-F-25173A — see
docs/References/). The width and mounting pattern are now settled:
| Dimension | Value |
|---|---|
| Panel width — global default for L/R console panels | 146.05 mm (5¾″) |
| Mounting-stud centers, left ↔ right | 136.525 mm (5⅜″) — 4.7625 mm (3⁄16″) inboard of each edge |
| Vertical fastener pitch (rail receptacle grid) | 9.525 mm (3⁄8″); ≥ 2 studs/side |
| Panel height | N × 9.525 mm ("Dzus units"), per panel |
| Stud rows, from the panel's own top edge | outermost at 1.5 × pitch; every row at a half-integer multiple |
| Panel thickness | 1.59 mm (1⁄16″) aluminum |
Work from the exact inch fractions, not the rounded millimetres: the inset is exactly half a
pitch, so the stud span is panel width − pitch = 146.05 − 9.525 = 136.525 mm. Rounding the
inset to 4.76 does not close against a 146.05 panel.
Where the stud rows go
The outermost stud sits 1.5 pitch units from each end of the panel (e = 1.5) — the
convention these panels are built to, verified against the A-4's Doppler panel, which has an
independent height. So a panel of N units carries its outer studs (N − 3) × 9.525 mm apart.
Because e is a half-integer and panel heights are whole units, every stud in a stack lands at
(k + 0.5) × 9.525 mm from the top of the stack. Any additional row must therefore also be at a
half-integer position (2.5, 4.5, 6.5 …); a row at a whole unit misses the rail by half a pitch.
Across a joint the spacing is always (N − 1.5) → (N + 1.5) = 3 pitch = 28.575 mm, whatever
the two panels' heights, and panels butt with no gap.
Worked example — a 6-unit panel (57.15 mm): rows at 1.5 and 4.5, i.e. 14.2875 and
42.8625 mm from the top edge, both rails at x = 4.7625 and 141.2875 mm. That is the
136.525 × 28.575 mm pattern the APN-153 panel uses.
Fastener — quarter-turn stud + receptacle strip:
- Stud: head Ø .375″ (9.53 mm) · body Ø .257″ (6.53 mm) · panel hole ~.26″ (6.6 mm) · .050″ screwdriver slot · 1⁄16″-panel grip · quarter-turn lock (85–135°). Detail design per MIL-F-25173A Fig 2 — no single mandated stud P/N; use any conforming quarter-turn stud (Dzus / Southco / Skybolt), chosen by head style + grip.
- Receptacle strip (the rail): Dzus
PR 3½-L(or equal), cut to length · .051″ music-wire spring · aluminum · cadmium plated.
Exceptions (non-standard width — measured individually): throttle quadrant, lighting panel, and any panel not on the standard Dzus rail.
Per-panel cutouts / bezels / light rings
TBD — driven by the CAD models
Switch/gauge cutout templates, bezel profiles, and light-ring geometry come from the Fusion/FreeCAD panel models, which are early-stage. These are documented per panel as they are modelled. CAD tooling is still under evaluation — see CAD Workflow.
Board-level placement
Mechanical placement on the PCB itself — LEDs on the front face, everything else on the back, through-hole connectors accessible from the panel side — is part of the PCB Design Rules.