How can we help?

The QGIS plugin doesn't load

Symptom: no Tractrix menu or toolbar, or no Tractrix provider in the Processing Toolbox.

1. Check the QGIS version under Help → About: 3.34 or later is required.
2. Open Plugins → Manage and Install Plugins → Installed and make sure Tractrix for QGIS (OpenAirside) is ticked.
3. If you built the ZIP yourself, it must contain the openairside/ folder at its top level, with metadata.txt inside it — not the whole repository.
4. Open View → Panels → Log Messages and look at the Python error and Plugins tabs. Copy any traceback into your bug report.
5. If the Processing Toolbox is missing entirely, enable the core Processing plugin.

"Engine not found" in AutoCAD or Revit

Symptom: a TX command stops with "The Tractrix engine (tractrix-engine) was not found" and a list of searched paths.

With the local engine, the add-in looks for tractrix-engine in: the path set in TXSETTINGS; the TRACTRIX_ENGINE environment variable; %ProgramData%\Tractrix\engine\; the add-in's engine folder; and PATH.

1. Reinstall the add-in: the installer places the bundled engine in the add-in's engine folder.
2. If antivirus software quarantined tractrix-engine.exe, restore it and add an exception.
3. If you installed the engine with pip, set its full path in TXSETTINGS or in TRACTRIX_ENGINE.
4. Or switch TXSETTINGS to the cloud engine.

Steering exceedance explained

Symptom: an issue of kind steering_limit, with a value above the limit.

To follow your line, the nose wheel would have to turn further than the aircraft's maximum steering angle. The engine computes the angle from how quickly the heading changes along the path, δ = arctan(L dθ/ds), and marks the worst point. It usually means the curve is too tight for that aircraft, or the line has a kink.

1. Check the line for a sharp vertex or a short zig-zag from digitising; replace corners with arcs of a realistic radius.
2. Compare with the aircraft's minimum turning radius from Turning radii and 180° turn.
3. Check steer_source in the library: if a default limit (60° or 65°) was used, look up the manufacturer's value and enter it as an override.
4. For pushback, the limit is the towing limit, not the aircraft's steering limit.

Edge-margin breach explained

Symptom: an issue of kind edge_margin, or a negative minimum edge margin.

An outer main-gear tyre comes closer to the pavement edge than the wheel-to-edge clearance of the standard — 3 m for an A320 under ICAO, for example. A negative value means the tyre leaves the pavement. In a turn this is usually the main gear tracking inside the curve: the pavement needs a fillet.

1. Check that the right tracking point is used: cockpit for taxiway design.
2. Check the pavement layer covers the whole route and is a valid polygon.
3. Run Taxiway fillet / required pavement to draw the pavement the aircraft needs.
4. The check starts once the tracking point is on the line, so the first metres are not tested.

CRS and geographic input

Symptom: results in the wrong place or the wrong size, or envelopes of a few centimetres.

• QGIS: layers in a geographic CRS (degrees, e.g. EPSG:4326) are computed in the local UTM zone and the outputs are written in that UTM CRS. QGIS reprojects them on the fly; for exact work use a projected metre CRS for the whole project.
• A projected CRS in feet is treated as non-metric and also computed in UTM.
• CAD: set the drawing units (INSUNITS). A unitless drawing uses the metres per unit setting.
• Cloud: GeoJSON must be in planar metres; DXF units are read from $INSUNITS, and a DXF without units is read as metres, with a warning.

Cloud sign-in and token problems

Symptom: cannot sign in, verification link expired, or the API returns 401, 402, 403 or 503.

• Verification link expired (after 24 hours): request a new one from the sign-in page. Password-reset links last 60 minutes.
• Too many attempts: sign-in is rate-limited; wait a minute and try again.
• 401: the token is wrong, revoked or expired. Create a new one; tokens start with tx_. Check it with GET /api/v1/whoami.
• 403 "Viewers cannot run simulations": ask an admin for the member role.
• 402: the organisation reached a plan limit; the message names it.
• 503 busy: retry after the number of seconds in Retry-After. 504: the simulation took longer than 30 s; shorten the path or use a web run.
• In CAD, a token saved on another computer or Windows account cannot be decrypted: paste it again in TXSETTINGS.