Development Update July 2026
Four systems complete, a full pedestal avionics stack, an EFB that plans your flight, and a working weather radar.
Over the last nine weeks the AFL 737 MAX went from "electrical system nearly done" to a flyable systems platform. Four aircraft systems reached functional completion - electrical, master caution, inertial reference and hydraulics - a complete pedestal radio and avionics stack was built from nothing, the weather radar went from a blank pedestal to a working navigation display overlay, and the EFB grew into a tool that fetches a real dispatch flight plan and draws a live moving map. This is a longer read than usual, because there is a lot to show.
Airfoillabs Team
Electrical System: Complete, and Watching Over Itself
The electrical rebuild we described in the last update is finished. The system now covers the full distribution: three generators, ground power, two batteries, three transformer rectifier units, the complete standby power subsystem with its static inverter and feed relays, the battery bus relay logic, the hot battery bus, and the ground service bus. On top of it sits a live AC/DC metering panel with real readouts for every selector position, modeled load values across all sources and buses, and the small touches that make it feel physical - per-column warm-up stagger and eased sample-and-hold needle behavior.
With the buses alive, the aircraft can now tell you when something is wrong. The Master Warning and Caution System is up: the master caution lamps, the six-pack annunciators and the overhead caution lights, with press-to-test and recall working the way you expect. The important part is what drives them - fault detection is wired to actual component state, not scripted triggers. BAT DISCHARGE comes from real net battery current, TR UNIT from the actual rectifier state, STANDBY PWR OFF from the standby subsystem itself. If a light is on, something underneath genuinely caused it.
Hydraulics and the Inertial Reference System
The hydraulic system followed the same philosophy as the electrical rebuild: a kit of reusable components - tanks, lines, pumps, shut-off valves, shuttle valves, the power transfer unit, consumers - assembled into System A, System B and the standby system, all solved by a generalized network solver that simulates leaks and fire shutoff behavior. Both engine-driven and electric pumps are in, the PTU and its control valve work, consumers from ground spoilers to gear transfer to the leading edge devices are fed from the right places, and the forward overhead pump switches now drive it all - the system is operable from the cockpit, not just from a test page. The EFB hydraulic synoptic was developed in lock-step as the verification surface, and went through seven revisions: tank levels, flow brightening, PTU state, valve positions and reservoir air pressurization.
The Inertial Reference System was implemented in five planned phases over four days: the power model, the full alignment state machine with motion detection, position initialisation and validation, an error model with adaptive noise behavior, and the complete ISDU interface - display pages, keypad entry and the TEST sequence. It runs standalone for now; wiring its outputs into the FMS position initialisation comes once the navigation backend stabilises.
The Pedestal Comes Alive: Radios, NAV, ADF, Transponder
The largest single arc of the period: roughly 3,350 new lines of avionics logic across four panel programs, all sharing one architecture and one persistence layer, each panel built on the previous one as a structural precedent. The compounding effect is real - the first system of the period took four days; the transponder went from an empty folder to four verified phases in a single day.
Radio Tuning Panels - all three stations. Captain, first officer and observer panels, each with its own power feed and radio set. Full five-state behavior from dark panel through self test to normal operation, VHF 1 and 2 tuned through the X-Plane COM radios so external tuning flows through the same path, VHF 3 with the 8.33 kHz channel table, HF with AM/USB modes, the offside tuning light with its proper diode-OR logic, and physical lamp brightness for all eight lamps following the shared cockpit lighting law.
VHF NAV control panels - both sides. The standby-entry experience got particular attention and was re-cut twice until it behaved convincingly: the keypad acts as a filter, not a validator - a digit that could never produce a legal frequency is swallowed silently; ERR is a latch raised only when a transfer is refused; untyped cells show underscore placeholders; CLR works as a backspace; and the standby window keeps per-mode frequency memory across VOR, ILS and GLS. Two-way binding means externally driven tuning - hardware, third-party tools, X-Plane's own commands - is adopted cleanly.
Dual ADF. Both receivers simulated, with a five-step power resolver covering OFF, ANT, ADF, tone routing and TEST, and a per-digit mechanical frequency drum with wrap and no carry, driven by six concentric tuning knobs.
Transponder and TCAS panel. One control head driving two logical transponder units with the antenna transfer relay modeled, an octal per-digit code stepper, a mode resolver with silent degrade when the TCAS bus is dead, IDENT gating, self test that hands control to the simulator for the duration (we measured X-Plane's own test at about 12.3 seconds rather than assuming it), and per-airframe persistence.
The EFB Becomes a Dispatch Tool
The EFB entered this period as a synoptic viewer. It leaves it as something a pilot would actually open before a flight.
SimBrief integration is complete and accepted in-sim. Enter your pilot ID, press Fetch, and the EFB pulls your dispatch flight plan and presents it across five Flight Plan tabs: Dispatch (fuel, weights, crew), Weather, Navlog, Map, and the raw OFP document rendered verbatim. The parser handles SID/STAR identifiers, average wind and temperature deviation, tropopause, alternate runway and per-fix wind data. There are no timers and no polling anywhere - the Fetch button is the sole call site, in line with SimBrief's terms of service. Performance was verified against a 120-fix long-haul plan: a full navlog rebuild in about 4 milliseconds, with smooth scrolling in the cockpit.
The moving map is complete and was accepted on a live flight from Dublin to London Stansted. A new canvas renderer draws OpenStreetMap tiles with drag pan, cursor-anchored zoom, North-Up and Track-Up orientation, a live aircraft symbol with follow mode, the SimBrief route with zoom-dependent label decluttering, top-of-climb and top-of-descent markers, a next-waypoint strip, and a fading flight trail. The verification was genuinely adversarial: over two live legs we cross-checked 130 samples of the next-waypoint logic against an independently written reference implementation - zero mismatches - and exercised the disconnect handling with a real 20-second connection outage.
Alongside these, the ACF STATES page now applies aircraft state presets end to end through the electrical system, the Ground Services, Options and Settings pages gained tabbed subpages, and the in-sim window chrome was aligned to the brand palette.
Weather Radar, VNAV and the Platform
On Dominik's side, the weather radar went from a blank pedestal to a working end-to-end system in about a week: a new rendering library wrapped in a radar component, drawn into the navigation display beneath the map, with TEST/NORM modes, MAP/AUTO/MAN tilt, gain and range controls on a per-side pedestal panel, and the WXR and TERR pushbuttons toggling mutually exclusively on the EFIS panel. By the end of the period the sweep buffer covers the full circle and rotates with aircraft heading, and the ND's compass rose, tick lines and range arcs moved to contour-drawn variants.
VNAV work continued in parallel: a substantial LNAV and VNAV integration pass reworking the leg classes and flight-phase logic, ECON climb speed calculation, and a new magnetic variation model built from Navigraph data. The platform itself also moved forward - including a scripting refactor that, in fairness, briefly froze a set of annunciator lamps while the fault logic underneath kept running correctly. It was caught, understood and fixed within the window; the honest cost of platform work landing mid-flight.
Systems Status, and How We Work
Where each system stands at the end of the period:
Electrical system - complete. Full distribution including standby power, ground service and the live metering panel.
Master Warning and Caution - complete. Fault detection driven from real component state.
Inertial Reference System - complete (standalone). Full ISDU; FMS hookup follows as the nav backend matures.
Hydraulic system - complete. Systems A, B and standby; operable from the overhead panel.
Radio Tuning Panels (x3) - complete. All three stations, verified in-sim.
VHF NAV panels - in progress. Core behavior done; final QA sweep outstanding.
Dual ADF - in progress. Logic done and verified; display art binding and QA outstanding.
Transponder / TCAS panel - complete. All four phases landed in a single day.
EFB SimBrief integration - complete. Accepted in-sim; release housekeeping remains.
EFB moving map - complete. Accepted on a live flight, nothing outstanding.
Weather radar - in progress. Working end to end; electrical integration to follow.
VNAV - in progress. LNAV integration and ECON climb landed; approach work mid-arc.
A word on how we work, because the pace above is only interesting if it is repeatable. Every system now follows the same protocol: a design contract written before any code, one phase per working session, and a per-phase test guide executed in the running simulator with observed values recorded verbatim. We treat "it compiles" as meaning nothing - verification happens in the sim. That policy keeps paying for itself: this period alone it caught a wrongly documented dataref unit, measured the simulator's own transponder test timing instead of assuming it, and validated the moving map against an independent reference implementation. And where something is not finished - a test sequence stubbed, a lamp without cockpit art yet - it is written down as open, not rounded off to done.
What's Next
These are the threads we are pulling on, not promises with dates attached:
Fuel system - with electrical, hydraulics, IRS and the radio stack modeled, fuel is the natural next aircraft system.
Weather radar integration - electrical power gating and consolidation of the new renderer.
QA and cockpit art for the new panels - the NAV and ADF QA sweeps, plus display art for the ADF frequency windows and the first officer and observer stations.
EFB platform groundwork - exploring serving the EFB over a local address, which would open the door to nicer map handling down the road.
Continued VNAV and approach work - the climb logic and approach pages are mid-arc.
Radio audio - the tuning tones and static volume logic are a finished contract waiting for FMOD sound design to bind them.
Thank you for following along and for your patience - it genuinely keeps us going. We'll be back with more soon.
Clear skies,
Juraj, Airfoillabs
AFL 737 MAX is an independently developed add-on for X-Plane, not affiliated with or endorsed by any aircraft manufacturer. Full disclaimer
