This tutorial is to help new builders to build a replica fixed wing aircraft. With the most comprehensible way to make a replica fast. All the steps are based on the experiences I accumulated. I will take the M6A1 Japanese WWII fighter as an example.

The performance is based on these specifications:

• Scale
• Speed
• Acceleration
• Deceleration
• Empty weight
• Gross weight
• Glide performance
• Maneuverability

This post does not included with the elements below:
Rocket,Car,Ship,Airship,Hovercraft,Submarine,Helicopter,Rotorcraft.
VTOL,Fly-by-wire,Static instability,Flying wing,Dynamic swept wing,Vector thrust.

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Step 1

Find data (Important)

• Blueprints
• Length
• Wingspan
• Wing area
• Empty weight
• Gross weight
• Wing loading
• Cruise altitude
• Max speed

If you don’t have the wing loading, that’s ok.

Wing loading=Gross weight/Wing area (lbs/ft^2 or kg/m^2)

I recommend using Wikipedia to find the data.

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Step 2

Build the Fuselage

To make a replica, Scale is very important.
In Simpleplanes, length of 2=1Metre
e.g. To make a 5m-long-fuselage the block’s length is gonna be 10.

Make a support block with glass, it can support the aircraft before you make the landing gear.

The supporter glass's length and wide is aircraft’s Length and Wingspan.
Load the blueprint and adjust the scale. (This scale number is going to be use times, make sure to write it down)

Use 0.001 mass and 0 drag fuselage to build the fuselage. (VERY VERY IMPORTANT)

The mass of Shock,Piston, Rotors,Pylon,Detacher and wheels can not be 0 because the material strength of these parts are affect by mass. Also, the parts connected to those parts can either be 0 for the same reason.

These xml are very common as well.

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Step 3

Fuel

To make an accurate Empty weight, you need to know the fuel capacity first.

Gross weight-Empty weight=Fuel Weight

Fuel Weight (kg)*1.2438=Fuel Capacity (L)

Or

Fuel Weight (lbs)*0.149=Fuel Capacity (gal)

Add one Fuel Tank and scale it small.
Adjust the “fuel” and “capacity” to match the Fuel Capacity you just calculated.
Also, don’t forget to set the fuel tank’s drag to 0.

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Step 4

Mass & CoM

CoM is the Centre of Mass.

Change the mass scale of the fuel tank to match the aircraft’s weight to “Gross weight”.
The CoM’s position can be change easily due to almost all the weight is at the “fuel tank”, so you can just adjust the position of the fuel tank and the CoM will follow.

The position of CoM plays an very important role in the aircraft’s performance.

• To make a stable fixed wing aircraft, the CoM must be at the front of the CoL (Centre of Lift).
• To have a nice take off & landing performance the CoM should be at just above the support point when the aircraft is taking off or landing (Tricycle Landing Gear).

Examples:

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Step 5

Drag Point

Drag Point is a concept to describe how much drag your aircraft have.
The drag ratio can be change by rewriting the “dragScale” in overload.
The drag have a big differences between aircrafts due to the different size and shape.
Example: (for reference only)

The aircraft should have no drag now because the whole fuselage is made of 0 drag block.
After confirming the drag your aircraft have, it time to add them on it.
I usually add drag at both side of the wings’ leading edge.

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Step 6

Wing loading

Wing loading is the most important part of making a realistic performance aircraft.
The Wing area we talk about is the area of the wing including the main wing and the horizontal stabilizer. (Vertical stabilizer is not included because it does not generate lift)
Also, don’t forget to set the wing’s drag and mass to 0.

• Calculate the areas

Estimate the ratio between main wing and the horizontal stabilizer. I’ll take 4:1 to the M6A1.

Main wing area=4*Horizontal stabilizer area

Total Wing area=2*(Main wing area+Horizontal stabilizer area)

• Example:

M6A1’s total wing area=290ft^2

Main wing area=116ft^2

Horizontal stabilizer area=29ft^2

Start a new file to make the wings.

If you can’t make a perfect wing size manually, adjust the tipPosition in overload for fine-turning.

Save two wings as assembly and install them on the aircraft, you can move the main wing little bit closer or further to the CoM to make sure the CoM-CoL distance is fit.
Also, the main wing should be closer to the wingtip so the aileron will be more effective.

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Step 7

Propulsion

Add the vertical stabilizer. (Normally as big as one side of the horizontal stabilizers)

Nothing special, just adjust the powerMultiplier in overload and test out the max speed to match the data you found.
The engine will have a different thrust ratio at different altitudes, I usually test the aircraft at sea level or Cruise Altitude.
P.S. Trim the aircraft roughly during propulsion test to make sure the speed is tested in a straight flight.

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Step 8

Final stuffs

• Trim the aircraft by adjusting the angle (X-axis) of the horizontal stabilizer to make sure it fly straight at max speed.
  
• Adjust the control-surface size to have the aircraft a realistic maneuverability.

• Add “flap” input to the elevator.

  Example:Pitch*0.85+clamp01(-VTOL)*0.15

• Add the “airbrake”.

• Brake performance: Adjust the brakeTorque of the support wheels, set other wheels’ brakeTorque to 0.