fa18

A working model of a slice of the F/A-18C Hornet Stores Management System (SMS) — the avionics that track what weapons are hung on the jet, let the pilot select them, set how they come off, and command their release.

This is a personal learning project. The behavior being modeled is the SMS as it appears in DCS World (Digital Combat Simulator). The goal is to understand how the aircraft's systems actually work by re-implementing their logic from scratch — and to do it in Ada, the language traditionally used for real avionics software.

It is a subset of the real system: enough of the Stores page to be faithful to the state machine and release gating, and nothing that would make it a flight-rated training device. See Scope below.

What it models

The code implements the cockpit STORES page — the Digital Display Indicator (DDI) format the pilot uses to manage and employ weapons:

• Stations 1–9 with a per-station state machine (Empty → Loaded → Selected → Releasing, plus Jettison).
• A small weapon catalog: MK82 (bomb), AIM9 / AIM7 (missiles), TANK (fuel).
• Release modes — CCIP, CCRP, and RIPPLE (string quantity + ripple interval).
• The Master Arm safety interlock (SAFE / ARM / SIM) and the air-to-ground vs. air-to-air employment toggle.
• Release logic and gating — the pickle command, CCRP "release point reached" handoff, ripple burst sequencing, and selective jettison.
• DDI pushbutton dispatch — mapping the 20 physical bezel buttons to the events they raise in the current state.

The whole thing is built around a single total reducer:

function Apply (State : SMS_State; Event : Input_Event) return SMS_State;

Every state change flows through Apply. It never raises on bad input — an invalid event returns the state unchanged with an advisory message. That keeps the model easy to test and reason about.

Layout

Path	Purpose
src/sms.ads / src/sms.adb	Core: domain types, event model, the Apply reducer, release gating, pushbutton dispatch.
src/sms-render.ads / src/sms-render.adb	Pure text renderer for the STORES DDI page (State -> screen text, never mutates).
src/sms_demo.adb	Runnable walkthrough of the spec's worked example (load, select, ripple, arm, commit), plus A/A and jettison demos.
src/sms_tests.adb	Assertion-based tests against the spec's state machine, invariants, and gating. Exits non-zero on failure.
docs/sms-stores-page-spec.md	The normative specification this code implements.
fa18.gpr	GPRbuild project file.

The spec in docs/ is the source of truth. The data model (§8), input event model (§9), station state machine (§5), and release gating (§10) are treated as the normative contract; the Ada code implements them and the tests check them.

Building and running

Requires the GNAT Ada toolchain (gprbuild). On Debian/Ubuntu this is gnat + gprbuild; alternatively use Alire (alr).

# build both executables into ./bin
gprbuild -P fa18.gpr

# run the worked-example demo (renders the STORES page at each step)
./bin/sms_demo

# run the test suite (exits non-zero if anything fails)
./bin/sms_tests

Build artifacts land in obj/ and bin/ (both gitignored).

Scope

This is a functional proof-of-concept, not flight-rated software and not a training device. Deliberately out of scope: real CCIP/CCRP ballistics and navigation, radar / IR seeker / targeting-pod sensors, the full weapon catalog, true carriage and weight-and-balance limits, hardware/1553-bus integration, HUD and other DDI formats, and any airworthiness or live-arming behavior. The "LIVE" release is a logged event, not a hardware command. See §12 of the spec for the full list.