Why is my aircraft below the runway in Prepar3D?

An aircraft appears below the runway in Prepar3D when the simulator’s physical ground level does not match the visible runway, or when that aircraft’s landing-gear contact points are wrong. If every aircraft sinks at one airport, troubleshoot scenery and elevation conflicts; if one aircraft sinks everywhere, repair or reinstall that aircraft.

How can I tell whether the runway or aircraft is wrong?

The pattern of where the sinking occurs usually identifies the faulty layer before you touch any files.

A mistake we see constantly is editing aircraft.cfg before testing another aircraft. Do that comparison first. A small tyre contact patch entering the surface can be normal; rims, axles, landing-gear legs or the fuselage below the runway are not.

How do I fix a Prepar3D runway elevation conflict?

A runway elevation conflict is fixed by finding the duplicate or misplaced scenery layer, not by raising the aircraft.

1. Establish a clean comparison. Load a default Prepar3D aircraft at the affected airport, then try the same aircraft at a default airport. This separates an airport problem from an aircraft problem.
2. Disable suspect scenery one package at a time. Start with another version of the same airport, regional airport collections, compatibility layers and recently added mesh. Restart Prepar3D after each change; changing several packages together hides which one caused the fault.
3. Keep only one add-on airport definition active. Airport-layout BGL files, often informally called AFCAD files, can contain runway and reference-point elevations. Two active versions of the same airport may place the visible surface and physical ground at different heights.
4. Correct the scenery priority. The airport package and its required flatten or compatibility component normally need to take precedence over regional terrain mesh and older airport packages. Follow the package’s prescribed internal order where it supplies one.
5. Check for an obsolete elevation correction. Some installers place small altitude-adjustment BGL files in Scenery\World\scenery. Remove them through the original installer when possible. If manually testing an identified file, back it up and disable only that file; never delete unknown default BGL files in bulk.
6. Test the custom runway surface. Some add-on airports draw the runway as a custom ground polygon above the actual collision surface. If the aircraft sits correctly on the physical ground but disappears beneath the visible runway, reinstall the correct Prepar3D edition of the airport or disable its faulty ground-polygon component if the package provides that option.
7. Test terrain mesh last. Disable the relevant mesh area temporarily. If the airport becomes level, restore the airport’s flatten or move the airport package ahead of the mesh rather than altering the aircraft.

If the airport also has trenches, plateaus or aprons at different heights, follow our layer-by-layer checks for floating and sunken add-on airports. Because Prepar3D inherited much of the FSX scenery architecture, the same principles in our terrain-mesh and scenery-priority explanation apply when diagnosing mesh conflicts.

Changing mesh resolution, clearing the shader cache or increasing graphics settings will not repair conflicting airport elevations. Those settings do not determine the aircraft’s physical contact surface.

How do I fix one aircraft that sinks at every airport?

If one aircraft sinks at every airport, repair its package or correct its landing-gear contact points.

1. Restore the original aircraft files. Reinstall the Prepar3D-compatible package or use its repair option first, especially if the aircraft was converted from FSX or manually edited.
2. Back up aircraft.cfg. For an editable freeware aircraft, inspect its [contact_points] section. Do not modify protected or installer-managed aircraft files.
3. Check the gear contact positions. The longitudinal, lateral and vertical coordinates must correspond to the wheel locations relative to the model datum. Wheel radius and suspension values also affect where the aircraft settles. Landing-gear animation is visual; the contact points provide the physical support.
4. Do not copy values from another aircraft. Two visually similar models can use different datum positions, scales and gear geometry. Copied coordinates commonly place the wheels or fuselage underground.
5. Treat static placement values separately. static_cg_height and static_pitch influence initial ground placement and resting attitude, but they should not be used to conceal incorrectly positioned gear contact points.

If the gear has visibly collapsed, check failures, damage and the actual gear position before editing anything. That is a systems or damage problem rather than runway elevation.

Why does it happen only in saved flights, AI or multiplayer?

Saved scenarios, AI models and multiplayer sessions each store or display ground position differently, so isolate them separately.

• Saved scenario: If airport scenery changed after the scenario was saved, its stored altitude may no longer match the runway. Create a fresh scenario and choose the runway or parking position again.
• AI traffic: One AI model sinking at several airports has faulty contact points. All AI aircraft sinking at one airport points back to airport scenery.
• Multiplayer: Prepar3D users with different airport editions or elevation corrections can see the same transmitted aircraft position above or below their local runway. Matching the airport package, version and active elevation layers across computers resolves it.
• Camera-only effect: If the aircraft behaves normally and the problem appears only from certain low external angles, suspect a custom ground-polygon rendering issue rather than the flight model.