Fix aircraft sinking into the runway in FS2004 by diagnosing aircraft.cfg contact points, static height, duplicate AFCADs and scenery elevation conflicts.
Aircraft sink into the runway in FS2004 (FS9) because either the aircraft’s wheel contact points do not match its visible landing gear, or the airport’s visual runway does not match the physical ground surface. Test a stock aircraft at the same airport: the result tells you whether to fix aircraft.cfg or the scenery.
Is the aircraft or the airport causing the problem?
The quickest diagnosis is to test the affected aircraft at a default airport, then load an unmodified stock aircraft at the problem runway.
| What happens | Likely cause | What needs attention |
|---|---|---|
| One aircraft sinks at every airport | Incorrect contact points, the wrong configuration or a mismatched model | The aircraft’s aircraft.cfg and model files |
| Every aircraft sinks at one airport | Duplicate airport data, an elevation conflict or an unhardened visual surface | The scenery installation and Scenery Library |
| Only one variant or livery sinks | Its model= entry selects different geometry, or it is installed in a separate aircraft folder | That variant’s [fltsim.x] entry and files |
| The aircraft starts underground, then jumps into place | Incorrect initial static height or pitch | static_cg_height and static_pitch |
| The aircraft falls through a raised runway, roof or deck | The visible object has no matching hardened platform | The scenery model, not the aircraft |
Use a known stock aeroplane as the control. If the original installation has been modified, our list of aircraft supplied with FS2004 identifies suitable test aircraft.
How do I correct FS2004 aircraft contact points?
Correct the landing-gear coordinates in the aircraft’s [contact_points] section, changing one dimension at a time and testing after every edit.
- Back up the configuration. Copy
Flight Simulator 9\Aircraft\...\aircraft.cfgto a safe location before editing it. - Confirm that the files belong together. A configuration made for a different model or undercarriage variant will place the physical wheels in the wrong positions. AI models converted for player use are especially prone to this; our guide to making FS2004 AI aircraft flyable covers the related model and ground-handling checks.
- Find the wheel entries. A line normally follows the structure
point.N = type, longitudinal, lateral, vertical, .... The coordinates are in feet relative to the aircraft reference datum. Wheel points normally use type1as the first value. - Identify each wheel by its position. Do not assume that
point.0must be the nosewheel. Main wheels usually have similar longitudinal values and opposite lateral values, while a nosewheel or tailwheel is normally close to the centreline. - Adjust the vertical coordinate. This is the fourth value when the type is counted as the first. Making it slightly more negative moves the physical wheel point farther below the datum and raises the visible aircraft. If the aircraft floats above the runway, move the value slightly towards zero instead.
- Keep paired gear symmetrical. Apply the same vertical change to the left and right main wheels. Change only the nosewheel or tailwheel when that end alone is buried, but expect this to alter the parked pitch.
- Reload and test. Select another aircraft and return to the edited one, or restart FS2004. Check the stance while parked, during taxi and after a normal landing.
Work in small increments. Large changes can make the aircraft appear correct while parked but cause bouncing, excessive gear loads or an unrealistic touchdown attitude.
Do not use wheel radius, suspension compression or damping as general ride-height controls. Those values affect wheel and strut behaviour; the vertical coordinate is the primary correction when the whole aircraft sits too low. Our field-by-field guide to FS2004 contact-point values explains the remaining entries and how to correct individual gear positions.
If extreme coordinates are needed to align the wheels, stop and verify the model. The visual gear animation may belong to another variant or may have been exported incorrectly; contact-point edits cannot repair defective model geometry.
Should I change static_cg_height or static_pitch?
Use static_cg_height and static_pitch to correct the aircraft’s initial ground placement, not to conceal incorrect wheel contact points.
These values are the main suspects when an aircraft loads underground or at the wrong angle and then snaps into the correct position once the ground physics settles. Correct the wheel points first, then make the static values agree with the resulting parked height and attitude.
Why are my aircraft.cfg changes being ignored?
Edits are usually ignored because FS2004 is loading another copy of the aircraft, Windows has redirected the saved file, or the aircraft has not been reloaded.
- Protected installation folder: An FS2004 installation under
Program Filesmay prevent direct changes or leave a redirected copy under the Windows VirtualStore location. - Wrong aircraft folder: Similar packages can contain duplicate aircraft titles or separate folders for different variants. Verify that the selected
[fltsim.x]entry belongs to the file being edited. - Incorrect file extension: Make sure the editor did not save the file as
aircraft.cfg.txt. - Read-only file: Remove the read-only attribute before saving, then confirm that the file’s modification time changed.
- Cached configuration: Switch to another aircraft and back. If the change still does not appear, close and restart FS2004.
Why does the aircraft sink at only one airport?
If every aircraft sinks at one airport, the visible runway and FS2004’s physical ground surface are at different heights.
- Duplicate AFCAD or airport BGL files: Two files may define the same airport with different reference elevations, runways or aprons.
- Scenery priority conflict: Part of an older airport can remain active while a higher-priority package supplies the visible buildings and surfaces.
- Mesh or flatten conflict: Terrain mesh and airport flatten data can place the surrounding ground above or below the intended runway.
- Missing hardened surface: A raised runway, rooftop helipad or deck may be visible without a platform that can support an aircraft.
- Files from another simulator: FSX airport files should not be mixed into an FS2004 installation, even when parts of the scenery appear to display.
Temporarily disable duplicate or older airport files one at a time, preferably by moving them outside an active scenery folder rather than deleting them. Keep the intended airport above older overlapping scenery in the Scenery Library, restart FS2004 and repeat the stock-aircraft test.
Do not lower an aircraft’s contact points to compensate for one faulty airport. That merely transfers the problem to every correctly built runway.
What should I check with SunSkyJet scenery?
Treat sinking at a SunSkyJet airport as a scenery conflict only when stock and add-on aircraft both fail at that location but sit correctly elsewhere.
SunSkyJet is associated with add-on airport scenery, so first check the package documentation for its intended simulator and installation order. If the archive provides separate FS2004 and FSX content, install only the FS2004 files. Do not combine an older airport release, a replacement AFCAD and a later package unless its instructions specifically require them together.
Search the active scenery folders for other files covering the same airport, then disable the suspected duplicate and restart FS2004. If aircraft fall through a raised visual surface to the terrain beneath it, the required hardened platform is missing or not loading; changing aircraft.cfg cannot fix that.
Why does the aircraft bounce after changing contact points?
Bouncing means the revised support points, static placement or landing-gear suspension values no longer agree.
- Restore the backup and repeat the vertical adjustment in smaller increments.
- Keep left and right main-gear coordinates identical apart from their lateral positions.
- Check that the wheel points align with the visible tyres when the undercarriage is fully extended.
- Do not alter compression or damping values unless the strut itself is behaving incorrectly.
- If bouncing occurs only after touchdown, test at a normal descent rate; a hard landing or malformed suspension is different from an aircraft that is already buried while parked.