Aircraft Parameters

Aircraft Parameters (CAN-FIX)

Every aircraft carries a set of numbers that make its instruments correct for that airframe and engine — the airspeed arcs, the redline, the green/yellow bands on the engine gauges, the fuel capacities, the electrical limits. This feature gives each aircraft a managed Aircraft Parameter Profile: those numbers, edited as validated forms, versioned, and delivered to the aircraft's FIX-Gateway.

It lives in the same web app as the panel editor (pyefis.aerocommons.org), under an Aircraft tab on each project.

Status: Phase A is built. You can create a profile, edit it with live validation, start from a template, import an existing file, and download a ready-to-install aircraft.ini — usable on the bench today. Automatic delivery to the aircraft over the device link is the next phase (Phase C).

Why this is separate from the panel editor

The panel editor deliberately leaves these numbers out. A V-speed or a gauge warning band is not a layout choice — it's a value in the aircraft's FIX database (the flight-data layer), which the instruments read at runtime. The same airspeed tape shows different arcs on a Cub and an RV because the data differs, not the layout. (This is pyEfis issue #64.)

So the boundary is clean:

• Panel editor → where instruments sit and how they look. → The Configurator
• Aircraft Parameters → the airframe/engine numbers those instruments display.

It's called the "CAN-FIX configurator" because these values belong to the CAN-FIX / FIX-database layer of the stack, not to any one display.

How the numbers are modelled

In FIX-Gateway, each quantity is a key (e.g. IAS for indicated airspeed, OILP1 for oil pressure) with a set of named aux slots hanging off it. V-speeds are aux slots on the airspeed key; warning/alarm bands are aux slots on each gauge key:

• IAS carries Vs, Vs0, Vfe, Vno, Vne, Va, Vx, Vy, …
• a gauge like OILP1 carries lowWarn, highWarn, lowAlarm, highAlarm, Min, Max.

The instruments derive their look from those: the airspeed tape draws white = Vs0…Vfe, green = Vs…Vno, yellow = Vno…Vne, red ≥ Vne; a gauge colours its bands from its warn/alarm slots. An unset slot simply means "no band" — leaving a value blank is always allowed.

The profile is just the set of those values for one aircraft, saved as a versioned record (append-only versions, one active at a time), belonging to the aircraft so all its devices share it.

What a profile covers

Group	Examples	Notes
Airspeeds	Vs, Vs0, Vfe, Vno, Vne, Va, Vx, Vy	Live white/green/yellow/red arc preview as you type; enter in kt / mph / kph (a C170B POH is in mph, European types in kph) and it's stored in the database's native units.
Engine (per engine)	tach, manifold pressure, oil pressure/temp	An engine-type provider decides which parameters exist (see below).
Cylinders (per engine)	CHT, EGT bands	Free-form cylinder count (4 and 6 common; radials run to 28, odd counts legal); one shared band set, expanded to every cylinder at compile.
Fuel	tank capacities + low warnings, fuel flow/pressure	1–4 tanks; each tank has a role and feed (see the fuel model below).
Electrical	volts, amps	12 V / 24 V presets.
Air / AOA	OAT, CAT, angle-of-attack references	AOA is a placeholder in Phase A, firmed up when the AOA sensor integration lands.

FIX-Gateway is the authority for what keys, aux slots, units, and sane ranges exist: it generates the parameter schema, and the web forms render from it. Add a key in FIX-Gateway, regenerate, and it appears in the UI — the form code hard-codes nothing.

The provider model (engines and fuel)

Two parts of an aircraft are too varied for a fixed form, so they're modelled as providers — the same pattern used elsewhere in the stack:

• Engine type — piston today (tach, MAP, oil, plus the cylinder group); turbine and electric/hybrid are reserved seams for later. Engine count is unbounded; each engine picks its type.
• Fuel system — real fuel systems are a topology, not a count. Each tank carries a role (main, aux, tip, header, transfer) and a feed edge (→ an engine, or → another tank for a transfer). That directed graph is the fuel system, recorded in the profile so later features (a fuel totalizer, an in-EFIS fuel page, an aircraft system diagram) can use it.

Validation

The forms mark V-speed and gauge-band ordering problems inline as you type, and blank still means "leave unset."

Saving checks the whole profile on the server, against these rules:

• V-speeds: Vs0 ≤ Vs < Vno < Vne ≤ Max, and Vs0 ≤ Vfe ≤ Vno.
• Every other gauge: Min ≤ lowAlarm ≤ lowWarn ≤ highWarn ≤ highAlarm ≤ Max.
• Every value is a number; the speed unit is kt, mph or kph, and the altimeter unit inHg or hPa.

Ordering is checked across blanks, so a gap cannot hide an inversion. A profile that breaks a rule is refused with HTTP 422, and the page shows not saved: followed by each broken rule. A malformed ownship identity (below) blocks both Save and Download until it is fixed.

Ownship identity

The Ownship identity card takes the aircraft's Registration (up to 10 letters, digits and hyphens; one starting with N must be a valid US N-number) and an optional ICAO address override (six hex digits, not 000000). It names the 24-bit address whose ADS-B reports are hidden from the traffic display as your own aircraft: the override if set, otherwise the address derived from a US N-number, otherwise none (only the receiver's own ownship report is filtered). Registrations from other states do not derive an address; enter the hex from the registration certificate or transponder. The identity is saved with the profile but is not yet sent to the aircraft: set the address the card shows as ownship_address in FIX-Gateway's stratux connection.

Templates and import

You don't start from a blank form. Phase A ships starter templates — Lycoming O-320 / O-360 and Continental O-470 engine groups, and a full Cessna 170B example — and you can import an existing init_data file (paste it in; it's parsed in FIX-Gateway's exact dialect).

Delivery to the aircraft

When published, the profile compiles to an aircraft.ini in FIX-Gateway's own init_data format, with a generated header (aircraft name, profile version, timestamp, and a hash of the source). FIX-Gateway loads layered init files at startup, later files overriding earlier ones, so the managed aircraft.ini is appended last — it overrides the shipped defaults without touching them.

• Today (Phase A): Download aircraft.ini and drop it into ~/makerplane/fixgw/config/init_data/ yourself (install instructions are in the file header). Immediately useful on the bench.
• Next (Phase C): the file rides the same device-pull pipeline as panel layouts (pair → token → verified pull → atomic swap), and applying it is a quick FIX-Gateway restart on the ground. This closes the last un-versioned piece of an aircraft's setup — the FIX-Gateway numbers — making it versioned and reproducible.

Looking ahead (recorded, not yet built)

• On real CAN-FIX nodes, some limits live in a node's own memory. The profile already records the CAN-FIX parameter ID next to each FIX key, so the same profile can drive node configuration later without rework — a hardware-gated exploration (Phase D).
• An aircraft system diagram — an IT-network-style view of tanks, feeds, engines, bus nodes, and devices — generated from the profile and device data the app already holds.

Design spec and decisions: docs/canfix_configurator.md.