Development Update 07/27/2025
Engine displays, display unit architecture, and the integrated standby flight display take shape.
This is our latest development update for the 737 MAX project. This report provides a comprehensive overview of our recent progress, with a particular focus on the aircraft's complex display systems. Our development philosophy is rooted in a dual approach: meticulously replicating the observable elements a pilot sees and interacts with, while simultaneously building the deep, underlying systems architecture that drives them.
Airfoillabs Team
Engine Display System Development
A significant portion of our recent work has been dedicated to a comprehensive rework of the engine display indications. This work moves the simulation beyond a generic representation to one that reflects the specific operational modes and logic of the 737 MAX's CFM LEAP-1B engines. The annunciations are not static text; they are the final output of the Thrust Management Computer's (TMC) simulated logic, which continuously evaluates FMS inputs, atmospheric data, and aircraft configuration to provide accurate, real-time information.
The following Thrust Mode Annunciations are now logically implemented. These are critical for procedural flying and confirming the autothrottle's status. Each mode corresponds to a specific phase of flight or operational need, a technique used by airlines to optimize performance and reduce engine wear.
TO, TO 1, TO 2: full power and fixed derated takeoff thrust modes
D-TO, D-TO 1, D-TO 2: assumed temperature reduced thrust takeoffs, including combination derates
TO B: takeoff bump thrust, where applicable
CLB, CLB 1, CLB 2: full and derated climb thrust modes, essential for efficient climb profiles
CRZ: the economy or long-range cruise thrust mode calculated by the FMS
G/A: go-around mode, commanding the necessary thrust for a missed approach
CON: continuous thrust, used in engine-out scenarios or other non-normals
MAN: indicates manual N1 setting by the pilot
---: displayed when the FMC is not computing a thrust limit
Additionally, the following critical indications are being implemented. These indicators are part of an interconnected system, providing vital cues about engine health and configuration.
Engine Parameters: Total Air Temperature, Selected Temperature for assumed temp takeoffs, Reference N1 Bugs, N1 Command Sectors, digital N1/EGT Readouts, and dynamic N1/EGT Indications. The N1 and EGT Redlines and EGT Amber Bands are now rendered dynamically based on operational limits.
System Alerts & Limits: the Autothrottle Limit (A/T LIM) now appears when the autothrottle enters a protection mode (e.g., to prevent overspeed). The Thermal Anti-Ice (TAI) indication is tied to the pneumatic anti-ice system; its activation correctly adjusts the N1 limits and is reflected in EGT, a crucial system interdependency. The Thrust Reverser (REV) and Engine Fail (ENG FAIL) alerts are also fully integrated.
Display Unit and Electrical Logic Architecture
Progress continues on the foundational electrical and data logic for the Display Units (DUs). We are simulating this from the ground up, treating the electrical system as a network of buses, generators, and switches. The DUs act as clients of this network, meaning their behavior is dictated entirely by the state of their assigned power source. This architecture is fundamental for creating a truly robust simulation, enabling realistic cold-and-dark startups and the accurate replication of non-normal procedures.
Current implementation work includes:
Electrical Power Sources: the DUs are now correctly mapped to their respective power sources, including the DC Standby Bus and DC Bus 2. This means a DU will correctly power down if its associated bus fails and will power on via the standby system during specific non-normal events, as in the real aircraft.
Display Switching Logic: logic for the Overhead Displays Source Panel and the Main Panel's PFD/MFD selector is being implemented. This functionality is vital for IFR flight, as it allows the crew to maintain primary flight and navigation data in the event of a screen failure, directly replicating a critical non-normal checklist procedure.
Display Processor Computers (DPCs): the logic for DPC 1 and DPC 2 is being coded to correctly prioritize, process, and display data from other aircraft systems. This is a precursor to simulating more subtle failures, such as data flags or invalid readouts.
Brightness and Contrast: independent BRT/CONTRAST logic for all six main display units is functional, allowing for individual adjustment by both Captain and FO.
Failure Logic Framework: the groundwork is in place to begin implementing specific DU failure modes, which will be triggered by the electrical system simulation or via a dedicated failure menu.
Display Unit Logic Preview
Cockpit Interaction and Fidelity
Our philosophy is that every interactive element should not only look correct but also behave correctly.
3D Modeling & Texturing: we have completed accuracy passes on the EFIS, landing gear, and main instrument panels. This involves refining high-polygon models and using a full Physically Based Rendering (PBR) workflow to ensure materials like brushed aluminum, matte plastics, and backlit panel text react realistically to X-Plane's lighting engine.
Animations & Manipulators: switch and knob animations have been tuned to match the correct travel distance and rotation angles. The click-spots and manipulator logic are being carefully defined to provide an intuitive experience for users in both traditional 2D and VR environments.
Watch the cockpit interaction preview · Animations preview 1 · Animations preview 2 · Animations preview 3
Integrated Standby Flight Display (ISFD) Development
Development has commenced on the ISFD. This unit functions as a critical "last line of defense," providing attitude, altitude, airspeed, and heading information independent of the main display system. We are simulating it as such, with its own (virtual) internal power source and inertial sensors.
The 3D model, manipulators, and animations for the unit are finalized.
The base attitude display is functional.
A key part of this task is the development of a custom, pixel-perfect font. The legibility of these backup instruments is critical, and standard simulator fonts do not accurately capture the specific stroke weight and spacing of the real unit's display. This custom development is necessary to achieve the required level of authenticity.
Current and Forward-Looking Development Plan
Systems Integration and Logic Hardening: the immediate next phase is to connect these various components. This involves ensuring the EFIS panel commands correctly interface with the DPCs, which in turn must request data from the IRS and FMS, all while respecting the state of the electrical system. We will be rigorously testing edge cases and logical priorities.
Electrical System Expansion: beyond the displays, we will be expanding the electrical simulation to the entire overhead panel, including bus transfer switches, generator controls, and battery management. The goal is a full electrical flow simulation for a complete cold-and-dark startup.
Flight Model and Performance Validation: with the core engine parameters established, we will begin a rigorous tuning pass. This involves validating takeoff and landing performance against published performance data, matching climb profiles (time, fuel, distance), and ensuring cruise fuel flow is accurate within a small margin of error.
Failure Model Implementation: with the foundational systems solidifying, we can begin the systematic implementation of the failure model, guided by real-world non-normal procedures - starting with DU failures, electrical bus faults, and sensor data discrepancies.
Thank you for your continued interest in our project. We will provide another update when we have more progress to share.
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
