Create an FSX water runway and seaplane start in Airport Design Editor, compile the BGL, install it correctly, and fix common spawn problems.
To create a seaplane take-off location in FSX or FSX: Steam Edition, build an airport-facility BGL containing a water-surface runway and a matching water start. Place them over existing simulator water, compile the project, activate its scenery folder, then select the new airport and water runway in Free Flight.
A water runway is airport data rather than visible scenery. It tells FSX where the operating lane and spawn point are, but it does not turn land into water, reshape a shoreline or draw a strip on the surface.
Building the FSX water runway in Airport Design Editor
Airport Design Editor (ADE) is the most practical tool for creating a permanent, selectable seaplane base. Our step-by-step ADE airport and compiler setup explains the editor controls in more detail.
- Choose a clear water site. Check the position inside FSX rather than relying only on real-world maps. Leave enough open water for the intended aircraft, with clearance from shorelines, bridges, boats, piers and terrain.
- Create or load the airport. For a new base, assign an unused airport identifier, name and reference point. If the site belongs to an existing stock airport, load that airport into ADE and create a higher-priority modification; never overwrite a stock scenery BGL.
- Set the airport elevation. Use the water-surface elevation represented by FSX. Coastal water is normally close to sea level, but an elevated lake must not be assigned a zero elevation simply because it is water.
- Add the water runway. Draw the centreline along the intended take-off direction and set its surface to Water. Give it a realistic length and heading. Let ADE check runway numbering against the airport's magnetic variation rather than guessing from the true heading.
- Inspect or add the runway starts. Create a start of type Water at each end you want to use. Its runway number and designator must match that end of the water runway, and its heading must point along the departure lane. For example, a Runway 18 start belongs near the north end and faces south.
- Compile for FSX. Configure ADE with a valid FSX-compatible BglComp compiler and resolve any compile errors. FSX: Steam Edition uses the same airport-facility BGL format, although its installation path and available development tools may differ from boxed FSX.
- Install and test the BGL. Put it in a dedicated folder such as
<FSX>\Addon Scenery\My Water Base\scenery, activate that scenery area and restart FSX. In Free Flight, find the airport by its identifier and explicitly select the water runway.
The hand-written SDK equivalent is an airport record containing a <Runway surface="WATER"> element and a matching <Start type="WATER"> element, compiled with BglComp. ADE generates this structure while reducing the risk of mismatched coordinates, headings and runway identifiers.
Do I need both a water runway and a water start?
Use both for a dependable, named Free Flight location: the runway defines the operating lane, while the water start controls exactly where and in which direction the aircraft spawns.
An airport reference point alone is not a suitable take-off position. A parking spot is also different from a runway start; it can place the aircraft beside a dock, but it does not define the departure lane. You can compare your setup with these existing FSX water-runway locations to see how working facilities appear in the airport selector.
Why does the seaplane spawn in the wrong place?
Most bad spawns are caused by a mismatched start, incorrect elevation or a site that is not classified as water in FSX.
| Problem | Likely cause and fix |
|---|---|
| The airport is missing | Confirm that compilation produced a BGL, the file is inside an active scenery area's scenery folder, and the airport identifier is valid and unique. |
| The old airport layout appears | Another BGL for the same airport has higher scenery priority. Move the new scenery area above the conflicting entry and remove duplicate modification files. |
| The aircraft starts on shore | The water start may be missing, misplaced or assigned to the wrong runway end. Also make sure you selected the water runway rather than the airport's default position or a dock parking spot. |
| The aircraft drops, jumps or sits underwater | The airport or start elevation does not match the simulated water surface. Correct the elevation and check whether an add-on terrain mesh has changed the lake level. |
| The runway lies over dry ground | A facility BGL cannot create water. Move the runway over existing water or create separate terrain scenery containing the required water polygon and shoreline. |
| The aircraft faces the wrong way | Reverse the start heading or move it to the opposite end. Check that each start's number and designator match the corresponding runway end. |
Can I add docks, parking and fuel to the seaplane base?
Docks and fuel are optional scenery or airport features and do not replace the water runway or its starts. ADE can place library objects, a fuel trigger and Dock GA parking positions around the operating area.
Keep dock parking far enough from solid scenery that the aircraft's wings and floats will not intersect it. Taxi links are needed only for parking or AI operations, and FSX's AI floatplane handling is limited. A finished seaplane base with docks, fuel and compiled BGL files provides a useful example of how these elements can be packaged together.
Can I create a one-off water start without a BGL?
For a private one-off departure, slew the aircraft onto open water and save the flight instead of creating an airport BGL. Position the seaplane just above the surface, point it towards clear water, leave Slew Mode, let it settle, and then use FSX's Save Flight command.
A saved flight remembers that aircraft and position, but it does not add a searchable airport, runway selection, ATC facility or reusable scenery location. Use the BGL method when the water base needs to be permanent, selectable with different aircraft or distributed to other FSX users.