Simulating New Designs in X-Plane 12

[Radicaldude1234]

Oh, I can feel eyes rolling already...since this topic comes up every 2-3 years or so.

I'm not going to go into how X-Plane works, which you can find here: How X-Plane Works, but I'm hoping to share my learning on how to put some of my designs into the sim and to hear input from others who might also have experience.

Some preliminary observations:

What X-Plane is not good at:

• Being a primary/only design tool:
  • I mean, it's possible to fiddle around with values to get an airplane to fly well in the sim. But for God's sake, don't take the aerodynamic parameters and run with them without doing some actual calculations...
• Exploring the edges of the flight envelope, especially post-stall behavior
  • The sim does not calculate actual flow separation.
  • The 2D airfoil flow separation is simulated by a Coefficient of Lift drop at the anticipated critical angle-of-attack. This is an "eyeballed" but computationally efficient way of approximating a stall for "game" purposes.
• Simulating actual control forces
  • The variation in the way different joysticks behave, including spring forces, control curves, and even force feedback.

What is X-Plane good for:

• Seeing your design fly!
  • I find this a huge motivator to keep designing
• General stability trends
  • Good for finding positive/neutral/negative stability tendencies
  • Control axis coupling, especially Dutch-Roll
• Very rough cruise performance
  • I'd say you can get within ±15% of actual performance if you input correct information
• Functional Test of actual normal operations
  • Flying approaches, pattern behavior.
  • Can get more out of it if you model the actual cockpit.

What I do before replicating the design in X-Plane:

1. Create a generalized aircraft layout including component locations
2. Run airfoils and planform in XFLR5
3. Also input preliminary values into a Performance/Stability Excel spreadsheet I've created. Some of the stability stuff can be found HERE
4. Create CAD model of the aircraft Outer Mode Line

To create the model, I use the X-Plane included Plane Maker to create an aerodynamic model. You can actually stop here and just use this model in-game.



If I want more eye-candy, I can export the model from CAD and import it into Blender 3D for import. This is purely a visual overlay and X-Plane will use the model above for aerodynamics. I'm still learning how to animate and create the cockpit model right now.



After that, it's in the sim!



How does this one fly?

Didn't have any unexpected behavior:

• The large tail surfaces give the desired control authority. A LOT of weather vaning from the large vertical stab, but compensated by the equally large rudder.
• Max speed comes out to ~190kts on 250HP and ~210 on 300hp at 3000' MSL. It's a small airframe, but the thick wings designed for maneuvering do it no favors in the drag department.
• Climb comes out to ~2000fpm at 110kts.
• Stall behavior is mild due to positive pitch static and dynamic stability, forward CG, and wingtip washout. Stalls at ~55kts with full flaps.

To Do:

• Figure out how to animate components. This is for visuals only.
• Learn how to model the cockpit. Just to fine tune the cockpit ergonomics.

 

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[llemon]

 

[ScaleBirdsPaul]

 

[Radicaldude1234]

 

[Laromin]

 

[Radicaldude1234]