Find why FS2004 aircraft sink into runways and fix bad aircraft.cfg contact points, airport elevation conflicts and unhardened scenery.
Aircraft sink into the runway in FS2004 when the wheel contact points in aircraft.cfg do not match the model’s visible gear, or when an add-on airport’s runway elevation differs from its hardened surface. If one aircraft sinks everywhere, fix the aircraft; if every aircraft sinks at one airport, fix the scenery.
Is the aircraft or airport causing the problem?
The fault follows either the aircraft or the airport, so test the same aeroplane at a default airport and then test a stock aeroplane at the affected runway.
| What happens | Likely cause | Where to fix it |
|---|---|---|
| One aircraft sinks at every airport | Incorrect contact points or mismatched model and configuration | The aircraft’s aircraft.cfg or installation |
| Every aircraft sinks at one airport | Duplicate airport files, elevation conflict or an unhardened surface | The scenery package or Scenery Library order |
| The aircraft is buried only when first loaded, then settles correctly | Incorrect static height or pitch | static_cg_height and static_pitch |
| Wheels sink only into a raised visual runway or deck | The visible model lacks a matching hardened platform | The scenery model |
Use a known stock aircraft as the control; our reference list of aircraft supplied with FS2004 will help if the original installation has been heavily modified.
How do I correct FS2004 aircraft contact points?
Correct the wheel support coordinates in the aircraft’s aircraft.cfg, making small changes and testing the parked attitude after each edit.
- Back up the configuration. Copy
FS2004\Aircraft\aircraft-folder\aircraft.cfgbefore changing anything. - Confirm the model and configuration match. Different undercarriage variants can require different contact points. If the package has mixed files from several versions, reinstall it using our FS2004 add-on installation procedure before attempting manual corrections.
- Open the contact-point section. Wheel entries appear as numbered lines with a structure resembling
point.N = type, longitudinal, lateral, vertical, .... The coordinates are measured in feet relative to the aircraft reference datum, not in metres. - Identify the landing-gear entries. Wheel contact points normally use type
1. Do not alter scrape, float or auxiliary points simply because they appear in the same section. - Adjust the vertical coordinate. The fourth value after the equals sign is the vertical position. Making it slightly more negative moves the support point farther below the datum and raises the visible aircraft relative to the runway. Work in small increments rather than changing several feet at once.
- Preserve the aircraft’s stance. Apply the same change to both main wheels so the aircraft does not lean. Adjust only the nose or tail-wheel point when that end alone is buried. Changing the relationship between the main and nose or tail gear also changes the parked pitch.
- Reload and test. Select another aircraft and return to the edited one, or restart FS2004. Check it while parked, taxiing and landing because a configuration that looks correct while stationary may still bounce or trigger excessive gear loads.
Do not use wheel radius as a general ride-height control. That value should correspond to the wheel geometry and affects wheel behaviour; the vertical contact coordinate is the primary correction for a model sitting too low.
The static_cg_height and static_pitch values should agree with the corrected parked attitude. They are most suspect when the aircraft starts partly underground but jumps to the proper position as soon as the ground physics settles. They should not be used to conceal badly positioned wheel points.
Why are my aircraft.cfg changes being ignored?
FS2004 may still be using an unchanged copy of the file, particularly when it is installed in a protected Windows folder. Check that the file is not read-only, save it with its original name and extension, and watch for a second virtualised copy created by Windows. The aircraft must also be reloaded before revised contact points take effect.
Why does the aircraft sink at only one airport?
When every aircraft sinks at one location, the airport’s visible runway and physical ground surface are at different elevations.
- Duplicate airport files: Two AFCAD or airport-layout files may define the same airport at different elevations.
- Scenery priority: An older airport file can override part of a newer package while leaving its visual models active.
- Mesh or flatten conflict: Terrain mesh and airport flatten data can place the ground above or below the intended runway level.
- Unhardened visual surface: A raised runway, helipad, rooftop or carrier deck may be visible without having a matching platform that supports the aircraft.
Disable duplicate or recently installed airport and terrain files one at a time, then reload the location. Do not lower an aircraft’s contact points to compensate for one faulty airport; that will make the aeroplane sit incorrectly everywhere else.
Why does the aircraft bounce after changing contact points?
Bouncing usually means the revised support points, strut compression or static parked position disagree with one another.
- Revert to the backup and repeat the vertical adjustment in smaller steps.
- Keep left and right main-gear coordinates identical apart from their lateral signs.
- Avoid changing compression and damping values unless the gear strut itself is behaving incorrectly.
- Check that the support points align with the wheels when the undercarriage is fully extended.
For a home-built aeroplane, contact-point placement must be considered alongside the exported model and its gear animation. Our FS2004 aircraft-building overview explains how the model and configuration files fit together.