The short version#
- Same as Zibo, proven: systems, engine indications, autopilot and autothrottle, LNAV, VNAV, autoland, TCAS logic, GPWS logic, the FMS, the displays' layout and symbols.
- Different because MSFS is not X-Plane: the flight model, the traffic, the weather, the terrain, the navigation data, the radio signals, how the hardware throttle and the stick reach the aircraft.
- Closer to the real 737 than Zibo: the ILS receivers (false glideslopes, noise, bends, back course, DME lock-on).
- Behind Zibo for now: sound, the EFB, fire detection, the HUD, terrain look-ahead.
Side by side#
| Subject | Real 737-800 | Zibo in X-Plane 12 | This aircraft in MSFS 2024 | Mark |
|---|---|---|---|---|
| Flight model | The aircraft | X-Plane's flight model with LevelUp's airfoils and geometry | MSFS's flight model. Masses, CG and geometry from LevelUp's file, aerodynamic tables tuned to public 737-800 figures | Ours |
| Engine indications | CFM56-7B | Zibo's CFM56 tables (N1, N2, EGT, fuel flow, start) | The same tables, compared value by value | Zibo, verified |
| Engine thrust | CFM56-7B26 | Zibo's engine model on X-Plane | MSFS's turbine engine, with its N1, thrust and fuel-flow tables generated from Zibo's model. Reverse, spool time and fuel flow at altitude are estimates | Ours |
| Hot start | The EEC protects the engine on the ground | The EEC aborts a ground hot start at about 711 °C | The same. Can be switched off as an option | Zibo, verified |
| Systems (electrics, APU, air, hydraulics, fuel, gear, brakes) | The aircraft's systems | Zibo's logic | Zibo's logic, translated and compared with the original | Zibo, verified |
| APU overspeed failure | — | The APU trips at once | N1 runs up past 100 % and the ECU trips at 107 %, about 3.7 s (owner's choice) | Ours |
| IRS alignment | 5 to 17 minutes depending on latitude | ALIGN TIME option: real, short, long | The same three, plus instant | Zibo, verified |
| Autopilot and autothrottle logic | Collins AFDS | Zibo's AFDS and A/T | Zibo's, translated. Every mode compared with the original | Zibo, verified |
| Autopilot servo | Servos on the control cables | X-Plane's servos | Our own servo on MSFS's elevator and ailerons. Zibo's commands, tuned for MSFS's aircraft | Ours |
| Autoland | CAT III dual channel, FLARE, ROLLOUT | Zibo's | Zibo's, flown closed-loop in the oracle | Zibo, verified |
| Throttle levers and autothrottle | The A/T servo moves the levers. The pilot can hold or move them against it | X-Plane keeps the joystick axis apart from the levers the A/T moves | MSFS has one throttle. Three modes to choose from: last mover, follow the A/T, always the hardware | Ours |
| Manual reversion (no hydraulics) | Cables only. Heavy, slow controls | X-Plane loads the controls | MSFS cannot load the stick, so its authority is cut to 60 % and its rate to 0.8 of full travel per second | Approximation |
| FMS | Smiths / GE FMC | Zibo's FMS (Lua scripts) | The same Lua scripts, running unchanged inside the aircraft | Zibo, running |
| Navigation data | The airline's AIRAC cycle | X-Plane's or Navigraph's files | MSFS's own database, converted to what Zibo's FMS expects. Procedures are fetched when an airport is first entered | Ours |
| LNAV and VNAV | FMC guidance | Zibo's path and speed calculation | Zibo's, compared with the original | Zibo, verified |
| ILS signal | Real beams: false glideslopes at 6° and 9°, noise outside the service volume, bends, a back course | X-Plane's radios | MSFS's perfect beam plus a receiver model that adds all of those. On by default, can be switched off | Ours |
| DME | A few seconds to lock on, memory through short losses | X-Plane's | 2 to 4 s to lock on, holds the last distance for 8 s | Ours |
| Displays | Honeywell display units | X-Plane PANEL_3D instruments with Zibo's bitmaps | Zibo's PANEL_3D and bitmaps, interpreted. Positions, sizes and fonts match X-Plane's render | Zibo, verified |
| TCAS logic | TCAS II | Zibo's | Zibo's. Identical on 2,543 frames | Zibo, verified |
| TCAS traffic | Transponders of nearby aircraft | X-Plane's AI and multiplayer | MSFS's AI and multiplayer within 40 nm, 18 slots, airborne aircraft first | Ours |
| Coordinated RA | Both aircraft agree who climbs | — | Not modelled. MSFS's AI does not manoeuvre | Not done |
| GPWS | EGPWS modes 1 to 7 | Zibo's GPWS | Zibo's. Identical on 13,785 frames. No voices yet | Zibo, verified |
| Terrain display | EGPWS terrain database, coloured against the aircraft's altitude | The TerrainRadar plugin by another author. Zibo only reads it | MSFS's terrain map in the EGPWS colours: red above +2,000 ft, yellow +1,000 to +2,000, green below | Ours |
| Terrain look-ahead, peak numbers | Yes | From the TerrainRadar plugin | Not yet. MSFS gives an aircraft no terrain heights | Not done |
| Weather radar | Antenna with tilt and gain, multiscan, turbulence detection | X-Plane's radar, set from Zibo's radar panel | MSFS's weather radar layer in the 737's colours. Zibo's panel logic | Zibo, translated |
| Radar gain, tilt, turbulence | Real beam geometry against the cloud | X-Plane's | Gain scales the colour thresholds. Auto mode shows the heaviest cores in magenta. The ALT knob fades returns. MSFS gives no cloud heights | Approximation |
| Lightning | Not shown by the 737's radar | — | Not shown | — |
| Transponder | Mode S | Zibo's knob and TCAS test | The same. MSFS's transponder state follows, so ATC and traffic see it | Zibo, verified |
| Cockpit controls | Hands | X-Plane manipulators, left and right click | MSFS-style: wheel, click, drag. Left button only, because MSFS looks around with the right one | Ours |
| Sound | — | LevelUp's FMOD sound set | None yet | Not done |
| EFB | Varies by airline | Zibo's tablet: options, ground services, loading | Not rewritten. Options are L:vars | Not done |
| Fire detection | Engine, APU, cargo | Zibo's | Not rewritten | Not done |
| HUD (HGS) | Optional | Zibo's | Not drawn | Not done |
A dash means the documents do not say. The real 737 column is general knowledge about the type, for orientation. It is not taken from the project's measurements.
Why the flight model is not Zibo's#
X-Plane computes forces from the shape of the aircraft and its airfoils. MSFS uses its own model with coefficient tables. There is no way to carry one into the other, so the flight model is rebuilt:
- Exact, from LevelUp's
.acf: geometry, masses, CG, gear, tanks, engine positions. - Tuned to public 737-800 figures: lift, drag, stability, control power. For example cruise at FL350 and Mach 0.785 near 85 % N1, and VREF at flaps 40 near 145 kt at 65 t.
- From Zibo's engine model: the N1 schedule, thrust and fuel-flow tables of MSFS's engine, so that the thrust MSFS makes agrees with the N1 the cockpit shows.
Details: Flight model tuning.
Compared with Zibo's own pictures#
The PFD and ND were laid over X-Plane's own render of Zibo's panel. Positions, sizes and fonts match. The differences are the values (the two pictures are different moments) and the horizon's blue and brown: X-Plane's preview was made with an older Zibo whose horizon bitmap was more saturated. This project uses the current Zibo's bitmap.