Tractrix for AutoCAD manual

Version 1.0.0 previewAutoCAD 2025+Preview

Tractrix for AutoCAD runs airside manoeuvre simulations on the polylines of your drawing and draws the results on dedicated TX-* layers. It is a thin client of the OpenAirside engine, which runs on your computer or in Tractrix Cloud.

Preview

Command names and layer names follow the tractrix/1 protocol and are stable in intent, but prompts and dialogs may change before 1.0. Report problems on the Downloads (account required).

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Installation

Requirements

AutoCAD 2025 or later, or an AutoCAD-based vertical of the same release, on 64-bit Windows 10 or 11. The add-in targets .NET 8.
AutoCAD LT and AutoCAD for Mac do not load .NET add-ins and are not supported.
Local engine: bundled with the add-in, nothing else to install. Cloud engine: a Tractrix Cloud API token.

Run the installer

Close AutoCAD.
Download the installer from the download centre and check its SHA-256 checksum.
Run the installer. It installs the add-in for your Windows user.
Start AutoCAD. A Tractrix ribbon tab appears. If AutoCAD asks whether to load the add-in, choose Always load.
Type TXLIBRARY to confirm that the engine responds.

Local and cloud engine

Choose the engine in TXSETTINGS. Both give identical results: they are the same engine.

Local engine (default)

The add-in starts tractrix-engine run for each simulation and exchanges one JSON request and response through standard input and output. Nothing leaves your computer. The engine is found, in this order:

the engine path set in TXSETTINGS;
the TRACTRIX_ENGINE environment variable;
%ProgramData%\Tractrix\engine\tractrix-engine.exe;
the engine folder next to the add-in;
every folder on PATH.

If none is found, the command stops with an engine not found message that lists the places searched. See engine not found.

Cloud engine

In Tractrix Cloud, create an API token under Organisation → API tokens and copy it (it starts with tx_ and is shown only once).
In TXSETTINGS choose Cloud, enter the Cloud address from your invitation, and paste the token.
Requests are sent over HTTPS to POST /api/v1/simulate. Each simulation counts towards your organisation's monthly runs.

The token is encrypted with Windows data protection for your user and stored in %AppData%\Tractrix\settings.json. It is never written to the drawing, and it cannot be read by another Windows user or on another computer.

Workflow

Draw the path as lines, arcs or polylines in the direction of travel. Pieces are joined automatically when their ends touch within the join tolerance; the first piece selected sets the direction.
Run a command and select the path (lines, arcs, polylines or splines). The command line then shows the current options, for example Aircraft=A320 Tracking=Cockpit Standard=ICAO Context=Taxiway …. Type an option keyword to change it, Dialog to edit everything in a form, or press Enter to run. Options are remembered for the next run.
If you switched on paVement or Obstacles, select the pavement outlines (closed polylines) and obstacles.
Review the results on the TX-* layers and in the results palette (TXRESULTS). Issues are drawn and, by default, labelled where they occur.
Report with TXREPORT.

Commands

TXPATH — aircraft path

task aircraft_path

Simulates one aircraft, or several for a group path (comma-separated ICAO types), along the selected path. Options: Aircraft; Tracking (Cockpit — the default —, Nosegear, or cUstom with a distance ahead of the main gear); Standard (ICAO, FAA, EASA); conteXt (Taxiway, taxiLane, Stand); sPeed (default 15 km/h); Clearance override; steering Limit override; paVement and Obstacles checks; rEverse the direction; Dialog. Draws envelopes, tracks, footprints and issues.

TXPUSHBACK — pushback and towing

task pushback

Select the main-gear path from the stand. Pushback (the main gear follows the path in reverse) or forward tow (the tug leads). Options: Aircraft, Mode (Pushback, Tow), tUg (default the generic towbarless tug), towBar with its length, towing Limit (default 60°), sPeed (default 5 km/h), Standard, conteXt (default Stand), Clearance, paVement, Obstacles, rEverse. Nose-wheel angles beyond the towing limit are drawn as issues.

TXTURN — turning radii and 180° turn

task turning

Options: Aircraft (several to compare) and Steer angle (0 = maximum). Then pick the start of the 180° turn (main-gear centre) and its heading, or choose Tableonly for the radii alone. Computes R1–R6 and the minimum 180° pavement width; the radii are written as a table on TX-TABLE.

TXJETBLAST — jet blast contours

task jet_blast

Pick one or more positions, each with a heading. Options: Aircraft; Thrust (idle, breakaway — the default —, takeoff, Ground = idle + breakaway, or All); Velocities (default 56 and 35 km/h); rEference — the picked point is the main gear or the nose; Intake hazard areas (on by default). Each velocity goes on its own layer, TX-JETBLAST-56 for 56 km/h. Contours are indicative; see the methodology.

TXGSE — ground vehicle path

task vehicle_path

Swept path of a ground support vehicle or train whose front axle follows the path. Options: veHicle, sPeed (default 15 km/h), Clearance (default 0.5 m), paVement, Obstacles, rEverse. Steering-lock exceedances and jack-knife (articulation above 90°) are drawn as issues.

TXLIBRARY — libraries

task library

Browse and search the 388 aircraft and 14 vehicles, with dimensions, codes and the source of each steering limit. The aircraft or vehicle you choose becomes the default for the next command.

TXSETTINGS — settings

Engine (local or cloud), engine path, Cloud address and token, time-out (default 120 s), default standard (ICAO), footprint spacing (10 m), whether to draw footprints, poses and issue labels, label height (1.5 m), chord tolerance for arcs (0.05 m), join tolerance (0.05 m), and metres per unit for unitless drawings (1.0). Settings are per Windows user.

TXRESULTS — results palette

Opens the palette with the summary of the latest run: pass or fail per check, maximum steering angle, minimum edge margin, conflicts, notes — or the error message if a run failed.

TXCLEAR — remove results

Choose Run to pick one result to erase, or All to erase every Tractrix result in the drawing (after confirmation). Your own geometry is never touched. TX-* layers are kept; use PURGE to remove empty ones.

TXREPORT — report

Saves the runs stored in the drawing as a self-contained HTML report or as a CSV table (the file dialog offers both; the default name is <drawing> – Tractrix report.html): inputs, engine version, summary figures, issues and notes, including what geometry was estimated.

TXRERUN — run again

Pick a Tractrix result and run its stored request again — for example after changing engine, or on a new engine version — replacing that result. To change the path or options, run the original command again.

Each run is stored in the drawing as a group named TX_… that carries its request and summary, so results, reports and re-runs survive saving and reopening the DWG.

Stand design and taxiway fillets are in the engine (protocol v1.1) and will be added as commands in a later preview.

Layers

Every result goes on a layer whose name starts with TX-. Layers are created on first use with true colours from the Tractrix palette, the nearest ACI colour, lineweight, linetype and transparency.

**Table 1** TX layers.
Layer	Contents	Style
TX-ENVELOPE	Swept envelope	Blue, filled, 70 % transparent
TX-CLEARANCE	Clearance envelope	Violet, dashed
TX-SWATH-MAINGEAR	Main-gear swath	Navy, filled
TX-SWATH-NOSEGEAR	Nose-gear swath	Teal, filled
TX-SWATH-ENGINE	Engine swath	Amber ink, filled
TX-ENVELOPE-TUG	Tug and towbar envelope	Slate, filled
TX-TRACK-NOSEGEAR	Nose-gear track	Teal
TX-TRACK-COCKPIT	Cockpit (pilot eye) track	Blue, centre line
TX-TRACK-MAINGEAR	Outer main-gear tyre tracks	Navy
TX-TRACK-WINGTIP	Wingtip tracks	Amber
TX-TRACK-TAIL	Tail track	Slate, dashed
TX-TRACK-ENGINE	Engine tracks	Amber ink, hidden
TX-TRACK	Other tracks	Teal
TX-FOOTPRINT	Footprints along the path	Slate, thin
TX-POSE	Reference-point poses (off by default)	Slate
TX-ISSUE	Issues: steering, edge margin, conflicts	Red, filled, heavy
TX-STAND-CLEARANCE	Stand clearance zone	Violet, dashed
TX-STOPBAR	Stop bar	Amber ink, heavy
TX-PAVEMENT-REQUIRED	Required pavement	Green, filled
TX-FILLET	Taxiway fillet	Green, filled
TX-JETBLAST-<v>	Jet blast contour at <v> km/h, e.g. TX-JETBLAST-56	Graded, filled
TX-JETBLAST-INTAKE	Engine intake hazard area	Red, dashed
TX-LABEL	Labels	Graphite
TX-TABLE	Result tables	Graphite
TX-OTHER	Results without a dedicated layer	Slate

Units and coordinates

The engine works in metres. The add-in reads the drawing units (INSUNITS) and converts coordinates to metres before sending, and back when drawing.
For a unitless drawing (INSUNITS = 0) it uses the metres per unit setting, 1.0 by default. Set INSUNITS in the drawing to avoid surprises.
Arcs and curves are tessellated with the chord tolerance (0.05 m by default).
Headings are degrees clockwise from the drawing's +Y axis.

Troubleshooting

Engine not found
Steering exceedance explained
Edge-margin breach explained
Cloud token rejected
"The selected curves cannot be joined": the pieces do not touch within the join tolerance. Close the gap, or increase the join tolerance in TXSETTINGS.