Startup and Actor Initialization

Overview

When the FMGC application starts, frmMain_Load executes a 9-step boot sequence: loading INI configuration, verifying database connectivity, registering encoding support, configuring the INET client module ID, creating the Akka.NET actor system, wiring the BITE diagnostic target, building the diagnostics menu, resolving actor references, and starting BroadcastRCV server discovery. The actor system creates all 12 actors inside FmgcSupervisor.PreStart and wires their inter-actor references via typed messages — but database preloading is deferred until after the INET connection to ASTServer is established. This ensures that the startup progress pages (SEQ 1-6) are visible on the MCDU display as databases load. The post-connection initialization chain is: INetClient1.Connected → InetConnected → StartPreload → SEQ 1-4 → PreloadComplete → SEQ 5-6 → auto-navigate to STATUS.

Startup Sequence

Step Details

Step	Method / Call	Notes
1	NLog auto-config	`NLog.config` in project root; rolling file + console targets
2	`IniConfiguration.Load(iniPath)`	`iniPath = Application.StartupPath & "\FMGC.ini"`; custom INI parser with case-insensitive lookup
3	`TestPerfDbConnection()`	Opens and immediately closes `FMGCPERF1.MDB`; logs warning if not found (non-fatal)
4	`System.Text.Encoding.RegisterProvider(CodePagesEncodingProvider.Instance)`	Required before any ARINC 429 encoding; must precede INetActor startup
5	`INetClient1.SetModuleID(55, "FMGC")`	Module ID 55 is the FMGC identity on the INET register bus; must be called before `Init`
6	`ActorSystem.Create("FMGC")` + `ActorOf(FmgcSupervisor)`	Props.Create lambda passes `frmMain` and `_config` to FmgcSupervisor constructor
6b	`BiteNLogTarget` registered	Added to NLog configuration at runtime; routes Warn/Error/Fatal to frmBITE via `NLog.LogManager.ReconfigExistingLoggers()`
6c	`BuildDiagnosticsMenu()`	Creates a MenuStrip with Diagnostics > Side View / Map View / BITE entries
7	`ActorSelection("/user/FmgcSupervisor/INetActor").ResolveOne(TimeSpan.FromSeconds(5))`	Synchronous `.Result`; 5-second timeout; INetActor is created early in `PreStart` so resolution is near-instant. Note: FlightPlanActor refs are resolved lazily on first diagnostic button use (not at startup) because `PreStart` blocks during synchronous OPCAMI DB read — actors created after that point don't exist yet when `frmMain_Load` runs.

FmgcSupervisor.PreStart Wiring

FmgcSupervisor.PreStart creates all 13 actors then sends wiring messages to establish inter-actor references. All wiring is complete before the first KernelTick fires (the tick timer starts at TimeSpan.Zero initial delay, but actor mailboxes process in order, so wiring messages arrive before external messages). Note: NavDbActor is created but does not preload databases in PreStart — preloading is deferred until StartPreload is received after the INET connection is established (see Post-Connection Initialization Chain).

Actor Creation Order

#	Actor	Path	Created via
1	KernelActor	`/user/FmgcSupervisor/KernelActor`	`Context.ActorOf(Of KernelActor)("KernelActor")`
2	TrajectoryActor	`/user/FmgcSupervisor/TrajectoryActor`	`Context.ActorOf(Of Trajectory.TrajectoryActor)("TrajectoryActor")`
3	McduCaptainActor	`/user/FmgcSupervisor/McduCaptainActor`	`Context.ActorOf(Props.Create(Of Mcdu.McduActor)(McduSide.Captain), "McduCaptainActor")`
4	McduFoActor	`/user/FmgcSupervisor/McduFoActor`	`Context.ActorOf(Props.Create(Of Mcdu.McduActor)(McduSide.FirstOfficer), "McduFoActor")`
5	GuidanceActor	`/user/FmgcSupervisor/GuidanceActor`	`Context.ActorOf(Of Guidance.GuidanceActor)("GuidanceActor")`
6	INetActor	`/user/FmgcSupervisor/INetActor`	`Context.ActorOf(Of Inet.INetActor)("INetActor")`
7	NavDbActor	`/user/FmgcSupervisor/NavDbActor`	`Props.Create(Of NavDb.NavDbActor)(astnavPath, userdataPath)`
8	PrimaryFlightPlanActor	`/user/FmgcSupervisor/PrimaryFlightPlanActor`	`Props.Create(Of FlightPlan.FlightPlanActor)("PrimaryPlan")`
9	SecondaryFlightPlanActor	`/user/FmgcSupervisor/SecondaryFlightPlanActor`	`Props.Create(Of FlightPlan.FlightPlanActor)("SecondaryPlan")`
10	AcarsActor	`/user/FmgcSupervisor/AcarsActor`	`Props.Create(Of Acars.AcarsActor)(acarsDbPath, metarPath, inetActor)`
11	UserdataActor	`/user/FmgcSupervisor/UserdataActor`	`Props.Create(Of Userdata.UserdataActor)(userdataPath)`
12	SimBriefActor	`/user/FmgcSupervisor/SimBriefActor`	`Context.ActorOf(Of SimBrief.SimBriefActor)("SimBriefActor")`
13	TmpyActor	`/user/FmgcSupervisor/TmpyActor`	`Context.ActorOf(Of Mcdu.TmpyActor)("TmpyActor")`

Post-Connection Initialization Chain

Database preloading and startup page display are deferred until after INetClient1 connects to ASTServer. This ensures the MCDU display is live and can render the startup progress pages as each database loads. Without this ordering, SEQ 1-6 messages would be published before the INET transport is active and the startup pages would never be visible.

Message Chain

#	Event / Message	From	To	What Happens
1	`INetClient1.Connected`	ASTServer	frmMain	INET connection established; frmMain tells FmgcSupervisor
2	`InetConnected`	frmMain	FmgcSupervisor	FmgcSupervisor sends `StartPreload` to NavDbActor
3	`StartPreload`	FmgcSupervisor	NavDbActor	NavDbActor begins preloading databases
4	`StartupProgress(1)`	NavDbActor	EventStream	Airports loading — McduActors render START-UP page
5	`StartupProgress(2)`	NavDbActor	EventStream	Navaids loading
6	`StartupProgress(3)`	NavDbActor	EventStream	Waypoints loading
7	`StartupProgress(4)`	NavDbActor	EventStream	User waypoints loading
8	`PreloadComplete` (with `AiracInfo`)	NavDbActor	FmgcSupervisor	All databases loaded; carries AIRAC cycle data; FmgcSupervisor sends `CallCreateRoute("8999")` to INetActor (first subscribe — VB6 line 4067)
9	Register 8999 (first)	ASTServer	FmgcSupervisor (via EventStream)	Routing-complete signal received; FmgcSupervisor publishes SEQ 5, sends `DataTX 2281=1` and `2607=0`, then fires ~97 bulk `CallCreateRoutes` in exact VB6 order (lines 5165-5293) with `"8999"` as the last route
10	`StartupProgress(5)`	FmgcSupervisor	EventStream	SERVER DATA receiving — McduActors render startup progress. MCDU keypresses are discarded while on Startup page.
11	Register 8999 (second)	ASTServer	FmgcSupervisor (via EventStream)	All register subscriptions confirmed routed; FmgcSupervisor publishes SEQ 6, merges OPCAMI + AIRAC into complete `StatusSnapshot`, sends `SetStatusData` to both McduActors
12	`StartupProgress(6)`	FmgcSupervisor	EventStream	Startup complete
13	Auto-navigate	McduActor	—	Both MCDUs switch from START-UP to STATUS page

Key Design Decisions

NavDbActor.PreStart does NOT preload. Unlike earlier implementations where PreStart called PreloadAll() synchronously, the actor now waits for a StartPreload message. This decouples actor creation from database I/O and allows the INET connection to be established first.
frmMain is the bridge. The INetClient1.Connected COM event fires on the UI thread. frmMain forwards it as a Tell to the actor system, bridging COM events into the Akka message flow.
McduActor guards keys during startup. While _activePage = Startup, all keystroke/scratchpad/CLR events are discarded (with keystroke ack still sent to prevent external MCDU freeze). Keypresses are only processed after auto-navigation to STATUS.
SEQ 5→6 is gated on register 8999. FmgcSupervisor subscribes to RegisterReceived on EventStream and filters for register 8999. The first 8999 triggers SEQ 5 and the bulk CreateRoute sequence; the second 8999 triggers SEQ 6. ASTServer sends registers in CreateRoute order, so receiving 8999 (requested last) proves all other registers have been routed. This replaces the earlier 1.5s timer delay.

OPCAMI Configuration Loading

FmgcSupervisor loads the OPCAMI configuration database during PreStart(). This provides aircraft-specific parameters (type, engine, performance thresholds, weight limits, speed limits, fuel settings). The SetStatusData message sends real values to both McduActors, replacing hardcoded defaults.

OpcamiData.ReadFromDatabase() opens OPCAMI.mdb via OleDb, reads all rows from the OPCAMI table, and maps ID-keyed values to 24 typed fields matching the VB6 OPCAMI_Type struct exactly (including /10 division for weight and factor fields). See Navigation Database Access — OPCAMI Configuration Database for the full field table.

Note: SetStatusData is sent twice — first during PreStart with OPCAMI-only data (acType, engType, idleFactor, perfFactor), then again when the second 8999 is received (inside the RegisterReceived handler) with the complete OPCAMI + AIRAC snapshot (adding activeDb, activeDbName, secondDb, secondDbName, databaseUpdateAvailable). The second message overwrites the first in each McduActor's _statusData field. See Navigation Database Access — AIRAC Cycle Information for the AIRAC data flow.

KernelActor.PreStart

KernelActor.PreStart is called by the Akka.NET framework immediately after the actor is created, before any messages are processed.

Key behaviours:

The timer key "kernel-tick" ensures that if PreStart is called again after an actor restart, the previous timer is cancelled and replaced. No duplicate ticks.
TimeSpan.Zero initial delay means the first KernelTick fires immediately — the computation cycle begins as soon as the actor is alive.
TrajectoryResult subscription enables KernelActor to cache the latest trajectory for inclusion in GuidanceInput on the next tick.
RegisterReceived subscription enables KernelActor to maintain the 18-field INET register cache (_cachedLatitude, _cachedLongitude, etc.) used to assemble AircraftState.

Supervision Strategy

FmgcSupervisor uses a OneForOneStrategy with Directive.Restart:

Protected Overrides Function SupervisorStrategy() As SupervisorStrategy
    Return New OneForOneStrategy(
        Function(ex)
            _Logger.Error(ex, "Actor failure — restarting: {0}", ex.Message)
            Return Directive.Restart
        End Function)
End Function

OneForOne means: if TrajectoryActor crashes, only TrajectoryActor restarts. All 11 other actors continue running without interruption. The Restart directive calls PostStop on the failed actor, creates a fresh instance, and calls PreStart — restoring the timer and EventStream subscriptions automatically.

Source Files

A320_FMGC/frmMain.vb — frmMain_Load 9-step boot sequence
A320_FMGC/Kernel/FmgcSupervisor.vb — PreStart actor creation and wiring, SupervisorStrategy
A320_FMGC/Kernel/KernelActor.vb — PreStart timer and EventStream subscriptions
A320_FMGC/Common/IniConfiguration.vb — INI file configuration loader
A320_FMGC/Common/OpcamiData.vb — OPCAMI configuration class; loaded during FmgcSupervisor.PreStart
A320_FMGC/Forms/frmBITE.vb — BITE diagnostics form; BiteNLogTarget registered at startup