27. Editing and Creating Airplanes

The airplane editor in SeligSIM is effectively two editors in one. The first is a “traditional” sim editor that lets you tune basic parameters like power, drag, etc. The second method uses the Scaling Wizard™ that can automatically scale up or down an airplane to create a new airplane. These two methods are usually combined when creating a new airplane size. Some of the airplanes in FS One were created this way - scaling up/down stock airplanes and then making additional edits to some of the traditional defining parameters. For example, the Hangar 9 Ultra Stick Lite 120 in its stock form in the simulator has a wing span of 76 inches. But by using the Scaling Wizard features in FS One, the stock airplane has been scaled over a range to create eight new sizes (new airplanes) as listed in the table below.

When the Scaling Wizard is used, it automatically scales the physics properties to the size you set.

Ultra Stick Lite 120 (stock size) and Scaled Variants
Name	Span (inch)	Weight	Engine
Ultra Stick Lite 120 (stock)	76	10 lb	Saito 180
Ultra Stick Lite (scaled variant)	39	22 oz	Electric Mini
Ultra Stick Lite (scaled variant)	50	60 oz	Electric 25e
Ultra Stick Lite (scaled variant)	58	5 lb	40 Size Glow
Ultra Stick Lite (scaled variant)	6	6 lb	60 Size Glow
Ultra Stick Lite (scaled variant)	100	23 lb	Gas
Ultra Stick Lite (scaled variant)	125	45 lb	Gas
Ultra Stick Lite (scaled variant)	150 (12.5 ft)	77 lb	Giant Gas
Ultra Stick Lite (scaled variant)	200 (16.7 ft)	182 lb	Giant Gas

27.1. Roadmap

The remainder of this chapter steps through an example of creating a newly sized airplane and then, as may be desired, refining it in additional steps, each increasing in detail.

Scaling Parts 1 and 2 below use the Scaling Wizard to create a newly sized airplane from a stock airplane. The actual Scaling Wizard on the editor page are the last two tabs: Scaling Size/Wgt and Scaling Propulsion. If you are going to scale an airplane up or down, start with Scaling Parts 1 and 2 below. Otherwise skip to the Airplane Editor section.

After the Scaling Wizard example with Parts 1 and 2, the basic Airplane Editor features are discussed. If you are not going to resize a stock airplane with the Scaling Wizard or use some of its features, then just start with this last section.

27.2. Make a Copy to Edit

The first thing to do is to make a copy of an airplane in order to make changes to it. Select an airplane from the selection list, and then click Copy and give it a new name. Then you can click Edit to customize your copy. The new airplane will be added to the bottom of the list of airplanes.

27.3. Scaling Wizard - Part 1

As an example of using the Scaling Wizard, this section shows how to make a copy of the Four-Star 60 and scale it. It has a stock wing span of 71 inch. Using the Scaling Wizard, the size of the airplane will be doubled and ready to fly in the sim - all in a matter of seconds.

Click Copy and give the Four-Star 60 a new name. It will be named “Big-Four-Star-60” as shown below. Next, click Edit to customize the size.

The first screen in the editor is shown below. It lets you enter more name details and a description. The name is edited to be “Big Four-Star 60”, including mention of being 200% scale. The description is added.

To scale up the size, click on Scaling Size/Weight which is on the left side (second tab from the bottom). The screen will look like this:

The default settings will leave the airplane unchanged - original scale being 100%. To double the size, set the Airplane Size to be 200% scale as shown below. Your changes are saved automatically.

No other changes are needed. The Scaling Wizard will automatically scale up the weight, motor, propeller, etc. The double-sized airplane is ready to test fly with that one change!

The screen shot below shows the original scale Four-Star 60 (yellow version) and the new one that is double sized at a wing span of 142 inch (11.8 ft, 3.6 m).

When running SeligSIM, pressing / shows the Scaling Wizard Data on-screen (upper left). An airplane this large would weigh around 60 lbs (27 kg), require a motor with approximately 16 hp, and according to the Cost Multiplier the double-sized Four-Star 60 would cost about 8 times the original airplane. If the original airplane ready-to-fly were to cost around $500 (in year 2022 dollars), then the double-sized variant would cost around $2,000. Performance-wise, the mid-throttle cruise speed is around 75 mph. Also, it has enough power to slightly climb in a hover - which is slightly more performance than the original scale. If that is too much power, adjustments to the power can be made by clicking on Scaling Propulsion (next section, Part II).

If you do use the Scaling Wizard, change the weight with the Scaling Wizard Size/Wgt tab. Do not use the Mass tab.

Tip: Make Small Airplanes Indestructible

The software does not limit the amount of scaling (up or down). However, the math might. If you make an airplane small and light, it is advisable to make the airplane and propeller indestructible in Options | General. Otherwise, the breakable-parts math calculations can “blow up” - the simulator will crash.

If you scale down an airplane, initially avoid a wing span less than 12 inch span and a weight less than 5 grams. Also, you may want to turn off exhaust smoke because the smoke puffs are not scaled down. If you scale down and do not see the airplane when you start a Flight Session, then restart the sim and increase the airplane size and test again. Another problem with super tiny airplanes is that the ground reaction calculations can become unstable, and you will not see the airplane as it bounces and zooms off into oblivion at startup (math “blowing up”). Again, just restart and try increasing the size and/or weight.

If you make the airplane enormous, again you might want to make the airplane indestructible because otherwise the airplane can break apart rather easily (it may seem). That latter might be an example of taking the Alpha 40 trainer up to a ridiculous wingspan of, say, 300 ft, which is actually allowable (no limits) and more than the wingspan of a Boeing 747 jet. You would have to press the F5 view to actually see the airplane completely at startup.

Airplane Physics Scaling - Background Theory

SeligSIM uses fundamental scaling laws to automatically scale an airplane. The mathematical development begins with what is traditionally called the square-cube law and then builds off of that to scale motor power, propeller properties, mass properties, landing gear characteristics, and everything that goes into the physics calculations in the simulator.

27.4. Scaling Wizard - Part 2

For this Four-Star 60 scaling example, beyond the basic 200% scaling, finer adjustments can be made if desired. The auto-scaling for weight and propulsion/prop can be tweaked or overridden on the Scaling Size/Weight and Scaling Propulsion tabs.

First, supposed you wanted to get the example airplane (in step 1) down to 55 lbs to be below the AMA “Large Model Airplanes” category, which applies if your airplane weighs over 55 lbs. On the first scaling tab, you can override the auto-scaled weight and directly input the 55 lb weight as shown below (or something a bit smaller to be below 55 lbs). With that new weight, at runtime, the new auto-scaled power (press / ) is 13.8 hp. The medium throttle cruise speed is around 70 mph.

Other options (see screen shot) would be to leave the weight auto-scaled, but check the box for Increased realism. This accounts for the fact that as airplanes get larger, the materials change from balsa, to hardwood, to metal (including composites!), to unobtainium. In other words, simple scaling can leave an airplane too light vs what might actually be true (typically) in real life. The other check box lets you instead just add your own multiplier on the auto-scaled weight. More options let you add some weight directly (e.g., a payload weight at the c.g., hardly affecting the moments of inertia). Alternatively, you can set the wing loading, e.g., if you know an actual wing loading value from a real airplane for the size you have created.

The Scaling Propulsion tab (below) lets you make more fine grain adjustments vs using the auto-scaled values. As engines increase in size, the power drops off relative to a perfect scaling. Cooling and strength of materials are the main drivers. Check the Increased realism box to take this effect into account. Alternatively, more options give you more direct control over the motor. Note that the direct RPM input options still scales the power (internally), so any RPM you specify here may not be what you actually see when you fly in the simulator, but it will be close. For the propeller, it is recommended that the auto-scale option be used, but you can test the optional adjustment features. If you select Increased realism for the propeller, it increases the propeller weight which thereby increases the propeller moments of inertia and thereby gyroscopic effects and decreases propeller RPM acceleration with the application of power. (Note that changing the propeller diameter affects the propeller physics and not the visual size of the propeller graphics model on your airplane when you fly. Also it does not change the propeller collision contact points for breakable parts calculations.)

27.5. Airplane Editor

Whether you scale up/down an airplane (Parts 1 and 2 above) or not, the other tabs on the main edit page give you more options to customized your airplane. The screen shots below for each tab continue with the Four-Star 60 data.

Realize that if you are using the scaling features (Parts 1 and 2 above for Scaling Size/Wgt and Scaling Propulsion) to scale up/down an airplane, that process will scale up/down, as may be appropriate, the data in all of the other tabs automatically. So you would not want to “double up” on your edits and, say, select in this group (below) a motor suitable for a 200%-sized Four-Star discussed above. The motor in the Propulsion tab below will automatically be scaled up - again, if you are using the scaling features of Parts 1 and 2 above.

27.5.1. Aerodynamics

Factors and Offsets

The Aerodynamics tab includes several groups of data starting with Factors and Offsets. In total for all groups, there are around 130 editable parameters, giving you a wide degree control for aerodynamic customizations.

The first parameter in the Aerodynamics tab is the elevator trim angle, which can be gleaned from the basic Description and somewhat from the parameter name. For any parameter in the list, a description will be given. Some parameters not only have the basic Description, but also a popup Detailed Description. To change a value, enter your value in the New box and click Apply to see it take effect. Your changes are saved automatically after you click Apply.

Surface Deflections

Scrolling down the list shows the next group: Joystick (yellow heading below). This group lets you adjust maximum control surface deflections. The selected parameter (see below, “…mRudK”) controls the rudder maximum deflection (see the Description). If you wanted to change the maximum amount of rudder throw, you would change the 20 deg value to something else, say, 25 deg.

The maximum value that you input must be within the allowable max/min deflection for that control surface, which is defined in the next group, i.e., Control Surface Deflection Limits (cyan heading below). For this latter group, the min/max values cannot be edited because they represent the built-in limits consistent with the aerodynamic data tables for the airplane.

Note

It is possible to increase the maximum control surface throws using other approaches in the sim, but it is not recommended. One way is to increase the servo arm length (edit airplane servo settings). Another way it to edit the transmitter (edit transmitter settings). But those are both indirect methods and not recommended. By using the airplane edit approach here, you have easy, direct, and precise control over the maximum deflections in degrees! Whatever the case, the amount of deflection will always be forced to stay within the limits for the specific airplane (i.e., the “ControlSurfaceDeflectionLimits” data).

Other Aerodynamics Groups

Additional groups include:

• Super Trims: Set the trim increment that is applied if you use the Fine Trim keys on the keypad.

• Motor Data and Prop Data: Position the motor, change the propeller aerodynamic properties, and more.

• Aero Parts: Define, for example, g-load limits before parts break off inflight in addition to other parameters.

27.5.2. Mass

If you use the Scaling Wizard, change the weight with the Scaling Wizard Size/Wgt tab. Otherwise use the Mass tab to change weight as described here.

The Mass tab allows you to:

• Change the empty weight (the weight without fuel).

• Adjust the CG location. The convention is

  • Move forward (use a positive number)

  • Aft (negative)

  • Left (negative)

  • Right (positive)

  • Up (negative)

  • Down (positive)

• Note that the CG Location values are relative to the airplane datum, which is just a reference point on the airplane and usually very close if not on the center of gravity of the stock airplane. For example, suppose you want to test out moving the center of gravity forward 0.5 inch. In that case, add 0.5 to the value in the first box. Per below, for the Four-Star 60, the first box is zero, so enter 0.5 and then test fly.

• The last group Inertia Multiplier lets you scale the moments of inertia for (in order) roll, pitch, and yaw. Smaller numbers increase agility, and larger numbers just the opposite.

  • Ixx - Roll axis

  • Iyy - Pitch axis

  • Izz - Yaw axis

27.5.3. Propulsion

In the propulsion tab, you can select the Engine/Motor (electric or glow/gas) and the propeller. The values here are for the Four-Star 60 stock airplane. Data in this group will be appropriately scaled up/down if you are using the scaling features (Parts 1 and 2 above).

Important Note

If you are editing an airplane with a gas/glow engine, then only select an gas/glow engine if you make a change. Likewise, only select an electric motor if your stock airplane is electric. Presently (presently is September 2022), there is no way to convert a gas/glow engine to electric or vice versa. That ability has not been coded into the airplane editor menu.

27.5.4. Motor/Engine

This screen is similar to the Aerodynamics tab discussed above. You select a parameter and make your changes, which are saved after you click Apply. The first parameter highlighted below is a multiplier on the engine power. For instance, if you want 10% more power, then use a value of 1.1 for the power User Factor value.

You can click on each item to read the descriptions. In particular, note that the Motor Type parameter lists the type of motor and it should not be changed. For that parameter, “Gas” indicates glow/gas (I.C. engine) and “Electric” is as it sounds - electric motor.

27.5.5. Propeller

The propeller tab lets you adjust the propeller diameter (ft) and additional propeller properties. Again, if you have used the scaling method to resize your airplane (Parts 1 and 2 above), then the propeller size will be automatically scaled off of the value used here, i.e., 1 ft in this case.

27.5.6. Sounds

The screen shot below shows the Sounds tab with the dropdown expanded to show a sample of the engine sounds that can be used.

If you want to make a new selection, then scroll through the list and click to make a new selection.

If you do not want to change the sound, then do not click on an item in the list. There is no “OK” button. If you click on item in the list, you have a new sound.

Tip: You may want to make a note of any new selection (i.e., the name) because this screen will not show you the actual current motor sound.

The entries in the list indicate the RPM range for the sound. Make a selection that brackets (as best possible) the propeller RPM that you experience when you fly the airplane in the sim, then click on a different tab item to have your selection take effect. The requested sound files are copied when moving away from this tab item.

Tip

Make a note of the sound file name because the sim One does not indicate later what sound you selected previously.

To add the sound of air rush (swoosh and whistle sounds), also click on one of the AirRush items in the list, then click on a different tab item to have your selection take effect. The requested sound files are copied when moving away from this tab item.

To test any air-rush sound selection, start a Flight Session and climb to a high altitude. If there is a gas/glow engine, then throttle back and press K to kill the engine. Now dive past your position and listen for the air rush sound (noise) or use an airborne/airframe camera, like, F8 to “put your ears” on the airplane.

27.5.7. Servos

The Servos tab lets you make servo adjustments. In most all cases, you will not need to make changes to the servos. In fact, making no changes is recommended.

Clicking on the Servos menu item takes you to the servo side of the Edit Transmitter window as shown below. If you move the transmitter sticks you can see the servo arms move in response, and you can monitor the amount of deflections (in degrees). Also, you can click Show A/C to see your airplane and watch the control surfaces move.

Note that the left side (transmitter data) is grayed out (yet visible and expandable) and the right side (servo data) is active and editable. The reason is that the servos are part of the airplane and you are in the airplane editor menu. (To separately edit the transmitter requires making a transmitter selection and then making a copy for editing in the Edit Transmitter window.)

Clicking on one of the animated servo icons opens up the Servo Settings screen as shown below. The servo can be changed by clicking on the Servo Type dropdown. All servos in the list are rotary servos like shown. The settings displayed are the recommended settings. Per mention before, the maximum control surface deflection can be changed by increasing the servo arm on this screen, but the standard value of 1.41 should be used and the maximum surface deflection should be input using the Surface Deflections group in the Aerodynamics tab.

The inputs that you can change are shown below. The typical values provided are for a control surface like an elevator that deflects both up and down.

• Servo horn angle to the control surface (+90 or -90 deg is typical, i.e., directly off center to one side or the other).

• Servo arm length (as discussed above the value of 1.41 should be left alone).

• Angle that the control rod makes to servo body (0 or 180 deg is typical, i.e., perfectly lined up with the servo).

  If you check the box for Manual Zero Rod Displacement, then below that you can specify at what horn angle the control rod has zero displacement, i.e., at what horn angle the servo is centered. This lets you make asymmetric linkages for differential ailerons, etc. Nowadays, differential is usually managed through the transmitter settings for most airplanes (unless some mechanical advantage is important, e.g., with flaps).

Typical servo values for a flap that only deflects down are shown below.

The servo edit screen also includes a Gyros section. For most all airplanes, this section is not hooked up to any servos, i.e., has no effect. For one airplane (the Sbach 342 with “SCAS” in the name), the Gyros section is expanded as shown below. It shows that each of the servos are being driven not directly by the receiver but by a gyro that “sits” between the receiver and servos. The name “SCAS” used in the sim stands for “Stability and Control Augmentation System” which in SeligSIM was a precursor to general category of the popular RC model stabilization systems, e.g., AS3X. SCAS in SeligSIM (in FS One) was developed in the year 2007 by one of the early developers/engineers working on the project. With SCAS turned on (via the gear 2-pos switch for the Sbach 342), the airplane is more stable flying in turbulence and cruising around. It has characteristics similar to the AS3X and Aura® RC stabilization systems.

Clicking on a gyro controller driving any given servo shows the Edit Gyro Settings screen containing the parameters that drive the behavior of the gyro for that axis/servo(s).