Shaping the Body of an Aircraft
From X-Plane Wiki
In this chapter, we’ll look at all the things that go into shaping the body of an aircraft, including the fuselage, wings, airfoils, the tail, and the landing gear. These represent the basics of almost every airplane design.
A few ideas will come up over and over again throughout the creation of an aircraft body. The first is the idea of the reference point, and the second is the idea of how positions in Plane Maker are set relative to the reference point. Understanding these two things ahead of time will make learning the specifics of creating the fuselage, wings, and other objects much faster.
The Reference Point
All objects (the fuselage, wings, etc.) in Plane Maker are placed relative to some arbitrary fixed point, called “the reference point.” This point is created simply by practice. For instance, you might tell Plane Maker that your plane’s fuselage (and, in particular, the front tip of your plane’s fuselage) is located at the reference point—it is zero feet away from it, angled zero degrees away. Likewise, your wings might be located ten feet behind the reference point, angled a few degrees back.
On its own, this point doesn’t mean anything—it’s just some place on the aircraft that everything else gets its location in relation to. While the point could be anything, you should choose a point that makes sense to you. Some aircraft designers prefer to make their reference point the center of the fuselage; many others prefer to make it the tip of the fuselage.
How Positions Are Set in Plane Maker
As we have said, all locations in Plane Maker are defined relative to a fixed, arbitrary point. We said, too, that many designers choose the tip of the fuselage as their reference point. However, there is more to defining the position of, for instance, a wing, than to say that it is five feet behind the tip of the fuselage. How high above this reference point is it? How far left or right?
That’s where Plane Maker’s position settings come in. Figure 3.1 shows the three standard controls for an object’s position.
The standard position controls are the longitudinal arm, the lateral arm, and the vertical arm, as illustrated in Figure 3.2. Each measurement is in relation to the reference point.
Table 3.1 gives a reference for interpreting what the values in these positional controls mean. For instance, a positive number in the “vert arm” parameter indicates the object will move above the reference point by that many feet.
|Parameter||Positive number means...||Negative number means...|
|Long. arm||Behind ref. pt.||Forward of ref. pt.|
|Lat. arm||Right of ref. pt.||Left of ref. pt.|
|Vert. arm||Above ref. pt.||Below ref. pt.|
Note that in cases where an object has lateral symmetry (that is, it is duplicated on both sides of the aircraft, as a wing section is), the guidelines in Table 3.1 apply to the object on the right (starboard) side of the aircraft. Likewise, they are reversed for the object on the left (port) side. Thus, a positive lateral arm value for a certain wing section means the right wing section will move right of the reference point, while the left wing section will move left of the reference point.
Shaping the Fuselage
To begin work on a fuselage, open the Standard menu and click Fuselage, as seen in Figure 3.3.
There are three tabs across the top of the Fuselage window, seen in Figure 3.4. In order, these are Section, Top/Bottom, and Front/Back.
Each tab serves a different purpose. The Section tab displays a cross-section view of the fuselage, sliced into a number of pieces. The Top/Bottom tab shows three different perspectives of the points defined in the cross-section view, allowing you to see their relation in three-dimensional space. Finally, the Front/Back tab shows the same points from the cross section view from a head-on on perspective; this is like looking down the nose and tail of a wireframe model of the aircraft.
In creating a fuselage, it makes sense to take the following approach (note that the parameters mentioned below are discussed in the following sections, which dive into each tab in depth):
- Begin in the Section tab and set the number of stations (usually 20), the number of radii per side (usually 9), and the body radius.
- Referencing whatever specifications you have for your fuselage (this may just be an image of it), set a rough outline of its shape in the cross-sections.
- Move those rough cross-section shapes to the appropriate distances from the reference point.
#Go to the Top/Bottom tab and drag the points around in three dimensions, possibly with reference to a background image.
- Alternate between the three tabs to fine-tune the shape.
The Section Tab
In the top center of the Section tab’s window is a checkbox labeled “aircraft has fuselage.” By default, this box is checked; if the aircraft is a flying wing or another such oddity, it may need to be unchecked.
Use the two buttons in the upper right of the window, labeled Import Weapon Body and Import Aircraft Body, to pull the shape data from either a weapon or another aircraft.
You can save a description of the fuselage (or some other note about it) in the text box in the bottom right corner of the window, labeled “part description.”
Aside from these miscellaneous controls, the Section tab has four parts to the window. These are the Body Data box, the Body Location box, the Body Texture box, and the Cross Sections box, described in the following sections.
The Body Data Box
The Body Data portion of the window, seen in Figure 3.5, controls the basic features of the fuselage. It is, effectively, your first stop when designing a new fuselage. The “number stations” field sets how many individual cross-sections Plane Maker will link together to form your aircraft’s body. In most cases, setting this at the maximum of 20 is not a bad idea, as each additional station will allow you greater control over the body’s shape. In any case, you will probably want to add 2 to the number of sections you had in mind to account for the two closed ends. For instance, if, when looking at the body, you saw 13 “real” divisions, you would input 15 stations here: 13 “real” sections, which meet at a point at each end, for a total of 15.
The “number of radii/side” sets the number of points used in each half of the cross section. Unless your aircraft has a very simple shape to its body, you'll probably want to use the maximum of 9. This number will allow the smoothest curves possible on the body.
The “body radius” setting controls the width of the cross-section views in the bottom half of the window. For the greatest accuracy when placing the points that make up the body, this should be set to the actual maximum radius of the fuselage. You should, however, err on the side of setting this too high so that all your points are visible. The final setting in the Body Data section of the window is the body’s coefficient of drag based on its frontal area. This determines the amount of drag generated by the fuselage. An average fuselage will have a coefficient of drag of 0.1, while a very sleek one will have a coefficient of 0.05.
The Body Location Box
The Body Location portion of the Fuselage window controls the fuselage’s location. The three standard location controls (“long arm,” “lat arm,” and “vert arm”) specify the point in space of the front tip of the fuselage. See the section “Fundamental Concepts” above for an explanation of these three controls.
Since all measurements of location in Plane Maker are relative to the reference point, the fuselage position could be anything—the rest of the aircraft just has to be positioned accordingly. Many aircraft designers, though, prefer the reference point to be the front tip of the aircraft. In this case, the fuselage’s location will be zero feet offset from the reference point.
|Parameter||Positive number means...||Negative number means...|
|Heading offset||Pivots to point right (starboard)||Pivots to point left (port)|
|Pitch offset||Pivots to point up||Pivots to point down|
|Roll offset||Rolls right (to starboard side)||Rolls left (to port side)|
In addition to the standard location controls, the Body Location box also contains directional controls. These are in the form of the heading, pitch, and roll offset parameters. Table 3.2 lists the interpretations of these values. For instance, setting a negative value in the heading offset will cause the fuselage to pivot to point left; when seen from above, the fuselage will pivot counterclockwise however many degrees are input here.
In the vast majority of aircraft designs, it makes sense to think of the fuselage as the center of the aircraft, so these parameters will not be used in most aircraft models.
The Body Texture Box
The Body Texture box is used for fine-tuning the painted texture on the aircraft (alternately known as a skin or a livery). For information on working with paint textures on the aircraft, see Chapter 8, Modifying the Appearance of an Aircraft. For information on the parameters found in this box in particular, see the section of that chapter titled “Fine-Tuning a Paint Job.”
The Cross Sections Box
The Cross-Sections box shows slices of the aircraft’s fuselage. There is one slice of the fuselage for each gridded, white box, as seen in Figure 3.7. Each of these slices is composed of the number of points you specified in the “number radii/side” parameter in the Body Data box (see the section “The Body Data Box” above for more information on this). Since most designs warrant the maximum of nine radii per side, each of your slices will probably be composed of nine points.
When building your model, Plane Maker will stitch these slices together, so the cross sections together will form a complete aircraft body.
We’ve been referring to each of the gridded white boxes as containing a “slice” of the fuselage. In reality, they each contain a half-slice. The nine (or however many) points visible here compose the right side of a slice; they will me mirrored by another nine points on the left side, for a total of eighteen (or so) points to compose a “full” slice.
Up to twelve of these half-slices are shown at any one time; if you have set more than twelve “stations” (as described in the section “The Body Data Box” above), you can use the left and right arrows to cycle through the slices not seen. These arrows are highlighted in red boxes in Figure 3.8.
Let’s dissect each cross section view (each “station”) in detail.
At the top of each cross section view is an input field controlling how far behind the reference point this particular slice will be. For instance, in the example cross section of Figure 3.9, the slice is located 15.15 feet behind the reference point (indicated by the box labeled 1 in the image). Thus, in an aircraft whose reference point is the tip of the nose, this section would be about 15 feet from the nose. Of course, a cross section could have a negative value here and be moved in front of the reference point.
Note that Plane Maker will stitch your cross sections together in the (left-to-right) order that they appear in this box—even if the distances behind the reference point that you set in this box do not always increase from left to right. In this way, you could have a fuselage that overhangs itself, or curves inward in some way.
The gridded white box, labeled 2 in Figure 3.9, is the cross section box itself. Click any point and drag it to reposition it and thus to reshape this slice of the fuselage. Double click on a point to lock its position, protecting it from being smoothed. (Note that smoothing operations are described in the section “Smoothing the Fuselage” below.)
The left and right arrows beneath the cross section box (labeled 3 in Figure 3.9) are used to copy a cross section as a whole into the station to the left or right, respectively. This might be useful if you added a new station after working on the stations you already had. In this case, you would start with the farthest right of the stations you had previously worked on and press the right arrow. Then, you would move left and keep pressing the “copy to the right” button, stopping when you got to the place in the station order that you needed a new one.
Beneath those copy-left and copy-right buttons are general copy and paste buttons, labeled 4 in Figure 3.9. Press the Copy button beneath the cross section you want to copy from, and press the Paste button beneath the cross section you want to copy to.
Beneath the general copy and paste buttons are two fields for setting the left/right and up/down location of a point in relation to the reference point. The box labeled 5 in Figure 3.9 sets the distance to the side, with positive values indicating a point is on the right side of the reference point. The box labeled 6 in Figure 3.9 sets distance above or below, with positive values indicating a point is above the reference point.
Note that these two fields act on the radius points of the cross section, not the cross section as a whole. Click any point to see its distance both to the side and above or below the reference point, and modify these fields to modify its position accordingly.
Finally, at the bottom of each station is the Ellipse button, labeled 7 in Figure 3.9. Clicking this button will round the cross section above into the closest fitting, smoothly curving ellipse.
Note also the Reset editing offsets button beneath the “Cross Sections” box itself. Sometimes in the course of editing the cross sectional slices themselves may be moved away from the left side of their gridded white boxes. This does not affect the model itself so much as it just makes it more difficult to edit. To correct this, aligning the left side of the cross sections with the left side of the boxes, click the Reset editing offsets button.
The Top/Bottom Tab
The Top/Bottom tab of the Fuselage window displays the fuselage’s cross sectional “slices” stitched together in three different views; that is, it shows the top, side, and bottom views of the complete fuselage formed from the cross sections. (Recall that these cross sections may initially be laid out in the Section tab, described above.)
To shape a station, simply click the radius points that make it up and drag them around. Just like in the Section tab, you can double click a point to lock it, preventing future smoothing operations from moving it on it.
The standard movement controls (the up, down, left, and right arrows, as well as the – and = keys for zooming) all operate as you would expect in this window, allowing you to zoom in or out and shift your view around.
Now, how do these three views (top, side, and bottom) fit together? It all starts with the side view—the left side view, in particular. The points that make up the left side are mirrored on the right, similar to the way the half-slices of the Section tab’s cross section view are mirrored to form a complete slice. The centermost line in the side view corresponds to the top- and bottommost lines in the top and bottom views.
The top and bottom views are mirrored in their upper and lower halves; dragging a point in the upper half of the top view will drag its corresponding point in the lower half of that view (in addition to dragging the same point in the side view). They are mirrored like this because the left side view itself is mirrored on the right; thus, the top view, for instance, shows the top half of both the left and right sides.
At the top of the window are two buttons, Reset this section to vertical and Reset all sections to vertical. Often in the course of editing the points of a fuselage, the points of a given section will get out of alignment purely by accident, due simply to the inaccuracy of using a mouse. That’s where these buttons come in. For instance, in the example fuselage in Figure 3.10, you might want to click the Reset all sections to vertical button, thus lining up each cross section.
However, in some cases, it is desirable to not have all your sections vertically aligned. In this case, if you still wanted to align the out-of-whack section seen in Figure 3.10, you would need to first click one of the points in the section to be reset. Then, after you have effectively told Plane Maker which section you want to modify, you would click the Reset this section to vertical button.
At the bottom of this window are buttons to load an image or clear it. This can be quite useful for laying out your points properly. For instance, you could take two scale drawings of your aircraft (one to be used in both the top and bottom views and one to be used in the side view) and drag the radius points to match up with this image.
For instance, in Figure 3.11, we cut up two scale images to be the same size, with the center of the image corresponding to the center of the fuselage, and loaded the images into Plane Maker. From there, we simply dragged the outermost points (or uppermost points, as the case may be) to match the edges of the fuselage in the image, then dragged the inner points to match.
The Front/Back Tab
The Front/Back tab of the fuselage window contains two views of the cross section, front and back. The front view shows the first twelve stations (if there are twelve stations to show) as though you were looking down the nose of a wireframe fuselage model. The back view, on the other hand, shows the last ten stations (again, if there are ten stations to show) as though you were standing at the tail looking down the wireframe model.
The standard movement controls (the up, down, left, and right arrows, as well as the – and = keys for zooming) all operate as you would expect in this window. Using the arrow keys, you can move the wire model over to view the whole fuselage, too, instead of just a half.
The radius points displayed in both these views operate just like the ones in the other two tabs. Simply click a point and drag it to change the fuselage shape there. You can also double click a point to prevent it from being changed in a future smoothing operation (described in the section “Smoothing the Fuselage” below).
The buttons Reset this section to vertical and Reset all sections to vertical are available in this tab as they are in the Top/Bottom tab. However, it may be wise to confine your use of them to the Top/Bottom tab, as you will not be able to see its effect in this view—the view is essentially without perspective, so a point that is far away looks the same as a much closer point with its same up/down and left/right position.
Smoothing the Fuselage
[tk] Don’t know quite how this all works
Adding Other Bodies to the Fuselage
Some aircraft have odd protrusions (such as a large fuel tank poking out from under the fuselage) or even special physical objects attached to them. In this case, it may be best to model the fuselage as not having these things. Instead, you might model these things as separate “bodies” (physical objects) which intersect the fuselage. X-Plane doesn’t care whether the large protrusion from the underside of the aircraft is actually part of the fuselage or just another object touching the fuselage; it will model the aerodynamics the same way.
In this case, you would model the other things using the Miscellaneous Bodies window, found in the Standard menu.
Each body created in this window is modeled just like the fuselage; there is a Section, Top/Bottom, and Front/Back tab for each body. To add a new body, simply click a new tab from the top of the window and check the box labeled “aircraft has this external fuel tank, float, or other external body,” as seen in Figure 3.13. You can add up to twenty miscellaneous bodies in this window.
[tk] talk about the INSERT and copy geo from part # buttons
Shaping the Wings
All wings in Plane Maker are composed of individual wing sections. A very simple wing might be made up of a single wing section, while a very complex wing might be made up of four or more wing sections.
To create and modify wing sections, open the Wings window from the Standard menu.
The Wings window houses a number of tabs which all look identical. The only difference between them is that, whereas the tabs labeled “wing” and “horizontal stabilizer” control two identical wing sections mirrored on either side of the fuselage, the tabs labeled “vertical stabilizer” control only a single wing section.
When you click on any of the tabs, you will see three boxes in the window: the Foil Specs box, the texture fine-tuning box, and the Element Specs box.
The Foil Specs box controls all the basic properties of a wing section. All wing sections have the following properties:
- a semi-length, the length of the wing section from its root to its tip when measured 25% of the way back from the wing’s leading edge,
- a root chord length, the width of the wing section where it is closest to the fuselage,
- a tip chord length, the width of the wing section where it is farthest from the fuselage,
- a sweep angle, the angle backward or forward that the wing is pointing (when viewed from above),
- a dihedral angle, the upward or downward angle of the wing section relative to horizontal, and
- a location.
Figure 3.15 shows the foil specifications not including the location controls; for information on using the standard location controls, see the section “How Positions Are Set in Plane Maker” above.
In most cases, a wing is composed of more than one wing section. In this case, you could specify the location of the outer wing sections manually so that they meet up with the next sections closest to the fuselage. However, in the upper right corner of the fuselage window is a drop-down menu labeled “snap to,” as seen in Figure 3.16. To snap a wing section to another one—that is, to have Plane Maker automatically align the root of the section you’re applying the snap to with the tip of the section you choose—simply click the drop down button and click on the wing section to snap to.
You can import a wing by… [tk]
To the right of the Foil Specs box is the texture box, used for fine-tuning the painted texture on the aircraft (alternately known as a skin or a livery). For information on working with paint textures on the aircraft, see Chapter 8, Modifying the Appearance of an Aircraft. For information on the parameters found in this box in particular, see the section of that chapter titled “Fine-Tuning a Paint Job.”
Finally, the Element Specs box in the bottom half of the window determines where ailerons, elevators, flaps, or other control surfaces go on the wing surface.
Adding Ailerons, Flaps, and Other Control Surfaces
To add control surfaces like elevators, rudders, ailerons, or flaps to a given wing section, you must tell Plane Maker where you want each control surface on the wing and you must define the control surfaces themselves. The first part is done using the Element Specs box found in the Wings window, while the second part is done in the Control Geometry window, launched from the Standard menu. The order in which you do these does not matter; do them in whatever order makes the most sense to you.
For our purposes, we will start off in the Control Geometry window. The only thing to be concerned with in this window, at least until after the first test flight, is the Controls tab. (Information on fine-tuning the controls following a test flight can be found in Chapter 10, in the section “Tuning the Controls.”)
In the Controls tab, a number of possible control surfaces can be created, from ailerons to elevators to rudders to speedbrakes to flaps. Each of these works in a similar way. The right half of the window, in the box labeled Control Sizes, sets up ailerons, elevators, rudders, roll spoilers, drag rudders, and speedbrakes. The right half of the window, labeled Flap Specs, sets up flaps and slats only.
Specifying Ailerons, Elevators, and Other Surfaces
The right half of the Control Geometry’s Controls tab is labeled Control Sizes, and it is used for all control surfaces except the flaps and slats.
Figure 3.17 shows the parameters to specify a single control surface (namely, an aileron). There are four input fields here. On the far left is the control surface’s root-side width, as a decimal part of whatever wing section it is placed on. Thus, if this root width were set at 0.50 and it were used in a wing whose root was 5 feet wide, the control surface would have a width of 2.5 feet on the side closest to the fuselage.
To the right of the root width is the tip width, also specified as a decimal part of the wing it is placed on. So, if the tip width were set at 0.1 and it were used on a wing whose tip was 10 feet wide, the control surface would have a width of 1 foot on the side farthest from the fuselage.
These two parameters, root and tip width, function identically on all the control surfaces available.
To the right of the two size parameters are the fields controlling how far the surface can move, measured in degrees. For instance, in the aileron of Figure 3.17 these are, from left to right, how far up the aileron can deflect and how far down it can deflect.
Specifications for ailerons, elevators, and rudders all follow this same pattern: parameters for the root and tip width, followed by parameters for the maximum deflections. The roll spoilers and drag rudder are exceptions to this pattern. They move one at a time, and they only move upward. For this reason, they have only one parameter for maximum deflection. [tk] roll input to engage
Additionally, the speedbrake may have two maximum deflections: one for normal, in-flight operation, and one for ground use. Unlike the other control surface types, speedbrakes don’t have to be mounted to a wing—they can also be mounted directly on the fuselage (or anywhere else, for that matter). For information on doing this, see the section “Adding Body-Mounted Speedbrakes” below.
At the bottom of the Control Sizes box is the “control surface type” setting, which modifies how effective the surfaces are in X-Plane. Surfaces which are “corrugated with gaps” are least effective. [tk] arranged in order of…?
For more on speedbrakes, see [tk] check out the speedbrakes tab…
Specifying Flaps and Slats
The right half of the Control Geometry’s Controls tab is labeled Flap Specs, and it is used to set up the aircraft’s flaps and slats.
Let’s walk through the settings here.
Slats change the lift characteristics of a wing. They allow a higher angle of attack for the wing, resulting in a lower stall speed. Two slats can be set up for each aircraft. Using the parameters seen in Figure 3.18, you can set the type of slat—either true slats or Krueger flaps. (Note that Krueger flaps are not technically slats. They deploy by hinging forward from the wing instead of sliding from the top of the wing’s leading edge like slats do.)
Next to the “slat type” control is the “increase in stall angle from leading edge device deployment” parameter, seen in Figure 3.18. Slats work by allowing the wing to go to a higher angle of attack without stalling—that is, without losing lift. Slats in the real world allow the wing to gain up to eight degrees without stalling.
Like slats, flaps alter a wing’s lift characteristics. They allow the wing to generate a given amount of lift at a lower speed, resulting in the aircraft stalling at a lower speed. Two flaps can be set up for each aircraft. Using the parameters shown in Figure 3.19, you can set the type of flap, chosen from a large number of options. Each type of flap has unique lift, drag, and moment characteristics, as described in the dark gray box below the flap type setting. Four types of flaps available in X-Plane are illustrated in Figure 3.20.
To the right of the flap type setting are the two parameters controlling the size of the flaps. Just like setting up ailerons, rudders, and elevators, you must specify the flap size on both the root side and the tip side. These are set as a decimal part of whatever wing section the flap is placed on.
Beneath the flap type and size settings are the parameters that control the aerodynamic coefficients for each flap, as seen in Figure 3.21. Plane Maker will automatically calculate the coefficients of lift (Cl), drag (Cd), and moment (Cm) based on the size of the flap, but these may be modified manually as well.
Beneath the flaps’ coefficients, you can set the deflection time as well as the detent (or stop-point) characteristics for both the flaps and slats, as seen in Figure 3.22.
Checking the box labeled “flaps are infinitely adjustable between detents” allows a pilot in X-Plane to hold the “flaps up” or “flaps down” button to select any flap setting, not just the ones at the detents. Even for aircraft with infinitely adjustable flaps, though, it is still useful to set the detents below, as they will be used in the maximum allowable flap deployment speeds. (Note that the max allowable speeds are set in the Viewpoint menu, as described in Chapter 4, in the section “Setting the Instrument Limits.”)
Beneath the “flaps are infinitely adjustable” checkbox is the flap deflection time parameter, as seen in Figure 3.22. This sets the amount of time in seconds that it takes the flaps to go from fully retracted to fully extended.
Beneath the flap deflection time is the number of flap detents (as seen in Figure 3.22). A detent is a stopping place for the flaps, a middle-of-the-road between being totally retracted and totally extended. General aviation aircraft might have only one or two stopping points, while airliners might have many more.
Finally, beneath the number of detents are the detent parameters themselves—one set of detent boxes for each flap and slat. Each box sets the flap/slat deflection in degrees at that detent. Note that there is one more box here than the number of detents you set above. This is to account for the “zeroth” detent, which in most aircraft will be a flap deflection of zero degrees.
For instance, in in Figure 3.22, three flap detents were set. Thus, there are four boxes for “flap 1,” four boxes for “slat 1,” and so on.
Adding Control Surfaces to the Wings
With the control surfaces (elevators, ailerons, rudders, flaps, etc.) all set up in the Control Geometry window, as described -in the sections above, it’s time to actually add those control surfaces to the wings. You will need to set the control surfaces individually for each wing section.
To do this, open the Wings window from the Standard menu. In the bottom half of each wing’s tab is a box labeled Element Specs, as shown in Figure 3.23.
Highlighted in red in Figure 3.23 is the box controlling the number of pieces that the wing section will be broken into. The wing section will be divided into this many pieces of equal size.
These pieces serve a couple of purposes. First, they represent the divisions of the wing on which X-Plane will calculate forces for its flight simulation. The simulation works by breaking the wing into a number of pieces, calculating the forces on the pieces, and adding the forces on all the pieces in order to move the aircraft as a whole.
These pieces also serve as divisions across which control surfaces are stretched. For instance, in Figure 3.23, the first four pieces (and thus the first four-ninths of the wing section as a whole) will have the “flap 1” on them. Likewise, the last five pieces (and thus the final five-ninths of the wing section, moving from root to tip) will have the “aileron 1” on them.
This brings us to the next feature of the Element Specs box. Highlighted in orange is a single control surface (the “flap 1”), with the boxes checked corresponding to the wing section pieces that it is present on.
We have said that the wing section is broken into a number of equal-sized pieces. These pieces are represented here, from left to right, from the root to the tip of the wing section. Thus, when the checkbox on the far left is checked, it means the piece of this wing section that is closest to the fuselage has that control surface. This means that, in Figure 3.23, the four pieces closest to the fuselage have flap 1.
Check each of the boxes for the control surfaces that a wing section has. (Note once again that these boxes will only actually do something to the wing if the control surfaces have been set up as described in the sections “Specifying Ailerons, Elevators, and Other Surfaces” and “Specifying Flaps and Slats” above.)
It may be useful when deciding how many pieces of the wing section a given control surface takes up to use the “Show with still/moving controls” option from the Special menu, as shown in Figure 3.24. This will cause Plane Maker to move all the aircraft model’s control surfaces, so you can see immediately where the surface extends to.
Adding Body-Mounted Speedbrakes
Speedbrakes may be added to an aircraft in one of two ways. The first, and most common, is to specify them in the Controls tab of the Control Geometry window, as described in the section “Specifying Ailerons, Elevators, and Other Surfaces” above. However, you can also add them directly to an aircraft’s body (its fuselage, wings, etc.), placing them using the standard Plane Maker position controls.
Body-mounted speedbrakes like these are created in the Speedbrakes tab of the Control Geometry window. Once again, the Control Geometry window is launched from the Standard menu.
Up to four body-mounted speedbrakes can be added to an aircraft using this tab; there is one box per speedbrake, as seen in Figure 3.25.
Since each speedbrake is created in the same way, we will look at the parameters for creating a single speedbrake.
In the upper left of the speedbrake’s box is the “copy from” drop-down menu, labeled 1 in Figure 3.26. To copy the geometry, location, and texture from another body-mounted speedbrake to this one, just click the drop-down button here and click the number of the surface you want to copy from. (Note that for the purpose of copying, the speedbrakes are numbered beginning with 1 in the upper left box. Figure 3.25 shows the numbering for each of the boxes.)
If you are not copying the gear door’s geometry, you must start by selecting the door’s type. The drop down box labeled 2 in Figure 3.26 selects a type of either “none” or “body mounted.” Any speedbrake box that you are not using should have a type of “none” set for it. Likewise, if you do intend to use a body-mounted speedbrake, set its type to “body mounted.”
After turning on any body-mounted speedbrakes you want to use, it makes sense to jump down to the door geometry box, labeled 6 in Figure 3.26. Speedbrakes in X-Plane are 2-dimensional, composed of up to four points. Click away from any existing points to create a new one, and click a point and drag it to change the speedbrake’s geometry.
Note that the maximum width of the speedbrake geometry box here is controlled by the maximum gear door size parameter, located in the Gear Data tab of the Landing Gear menu. For information on setting this, see the section “Finishing Retractable Gears” below.
After creating at least a rough model of the speedbrake’s shape, you can position it on the aircraft and set its extended and retracted angles.
To begin positioning a speedbrake, you can set its roll attitude. This is done using the axis of rotation parameter, located beneath the speedbrake type control and labeled 3 in Figure 3.26. A roll of 90 degrees makes the speedbrake point straight up, while a roll of 0 degrees makes it completely horizontal.
Next are the standard location controls, labeled 4 in Figure 3.37. These are presented here in longitudinal-lateral-vertical order, from left to right. For information on using these controls, see the section “#How Positions Are Set in Plane Maker|How Positions Are Set in Plane Maker]]” at the beginning of this chapter.
Beneath the location controls are the speedbrake’s open and closed angles, labeled 5 in Figure 3.37. The parameter on the left is the angle of the speedbrake when it is retracted; the one on the right is its angle when extended. Positive values here will cause the speedbrake to hinge upward, while negative values cause it to hinge downward.
The final settings in each speedbrake’s box (labeled 7 in Figure 3.26) are related to its paint textures. Information on working with the paint is found in Chapter 8, in the section “Creating a Basic Paint Job.”
Customizing a Wing’s Pieces (for Incidence, Size and Position)
In the Element Specs box—the same box used for applying control surfaces to wing pieces—is the piece incidence setting, highlighted in blue in Figure 3.23. This sets the upward angling (or incidence) of each piece, in degrees. This allows you to warp a wing section to point up or down.
Using the checkbox labeled “customize chords,” you can change the width of the wing section from its leading edge to its trailing edge (that is, its chord length) for each piece. Pieces are modified just like when adding a control surface to a piece; the boxes on the far left correspond to the piece of the wing section that is closest to the fuselage, while the boxes on the far right correspond to the pieces farthest from the fuselage.
Normally, Plane Maker calculates the chord length of each piece (again, the distance from its leading to its trailing edge) by interpolating between the root chord and the tip chord, which you set in this tab’s Foil Specs box. Using the “chord ratio” setting, though, you can modify the width of each piece. The Plane Maker-calculate value for the chord length is multiplied by the ratio you set here to get the actual width of this piece.
For instance, if Plane Maker saw that the chord length should be 5 feet at the center of a given piece, and you used a chord ratio of 2, the center would end up with a 10 foot chord length. Likewise, if you had chosen a ratio of 0.5, it would end up with a chord length of 2.5 feet.
Finally, the “chord offset” setting, seen in Figure 3.27, determines how far forward or back a given piece gets shifted. Positive values will push the wing section behind the reference point, while negative values will push it forward of the reference point. This is specified as a ratio of the Plane Maker-calculated chord length. Thus, with a calculated chord length of 5 feet, and a chord offset of 0.5, a given piece will be pushed farther behind the reference point by 2.5 feet.
Use the above settings to customize the fine details of a wing section’s size and shape.
Setting a Wing’s Airfoils
Creating a wing in the standard Wings window specifies only the wing’s size, location, and the direction it’s pointing. It does not specify what shape the wing has. Is it thin along the trailing edge and fat along the trailing edge? Maybe it is fat along both edges, or maybe it is fat in the middle and thin at the edges. To tell Plane Maker just what shape the wing has, we need the Airfoil window, which is launched from the Expert menu.
Each wing section can have four different airfoils set for it. These four airfoils come in two sets, one for high Reynolds numbers and one for low Reynolds numbers. Each set has one airfoil for the root and one for the tip. These airfoil shapes are then blended together linearly in the portion between the root and tip, and the two sets (the low and high Reynolds number sets) are blended together between the Reynolds numbers. [tk]
The airfoil shapes themselves must be created using the separate Airfoil Maker application, which, like Plane Maker, is included in the X-Plane installation folder. X-Plane does not look at the shape of the wing and then decide how much lift, drag, etc. the foil will put out—X-Plane is not a computational fluid dynamics program. Instead, X-Plane uses pre-defined airfoils that list the performance of any airfoil (lift, drag, moment) to predict how the plane will fly with that foil. For information on using Airfoil Maker to create these airfoils with predefined performance, see the supplement to the X-Plane Desktop manual.
To apply an airfoil shape to a wing after the wing has been created, open the Expert menu and click Airfoils. In the Airfoils window, go to the Wings tab. Here, you can set two versions of both the root and the tip airfoil for each wing section. The foils on the left are for the root side of the section, and the ones on the right are for the tip side, as seen in Figure 3.28. Plane Maker will interpolate between the root and tip airfoil to create the shape of the middle of the wing section.
The top root-and-tip pair of foils in each wing's box specifies the low Reynolds number version of the foil; the bottom pair specifies the high Reynolds number version. Once again, X-Plane will interpolate between these two… [tk]
The following two pages may be useful in determining what airfoils to use in your wing (assuming you’re modeling an aircraft that is already in production): The Incomplete Guide to Airfoil Usage StrategyWiki: Airfoils
To set an airfoil to be used on a particular wing, in a particular place (root or tip), and for a particular Reynolds number (high or low), click the gray box to the left of that position on that wing. A dialog box will appear for you to navigate to the airfoil file’s location. X-Plane's default airfoils are found in the X-Plane 9\Airfoils directory.
Making a Wing Movable
Just like in the real world, wings in X-Plane do not have to be static. They can be swept forward or back, they can be angled up or down, they can even be retracted.
In the Airfoils window (launched from the Expert menu), each wing has a group of four checkboxes, as seen in Figure 3.29.
Setting Variable Wing Sweep
Checking the first box in Figure 3.29, labeled “variable sweep,” will allow you to set the maximum wing sweep in degrees. Positive values here will allow the wing to angle further behind the reference point, while negative values will allow it to angle forward of the reference point. This variable sweep is illustrated in Figure 3.30.
Wing sweep is measured in degrees of sweep along the 25% chord (that is, along the line 25% of the way behind the leading edge of the wing). Note that you set the maximum sweep here; the minimum sweep is set as the default wing sweep, found in the Wings window (opened from the Standard menu).
Variable wing sweep is useful in aircraft that approach or exceed the speed of sound, but which must also perform well at low speeds. As your speed increases toward Mach 1, a wing that meets the air head-on generates more and more drag. Variable sweep wings are most popular in military aircraft (like the B-1 Lancer and the F-14 Tomcat).
To use a variable sweep in X-Plane, you can add a sweep control to the instrument panel. Alternatively, you could assign a button or key to the “vector sweep aft” and “vector sweep forward” controls in the Joystick and Equipment window.
Setting Variable Wing Dihedral
Checking the box labeled “variable dihedral” in the Airfoils window (seen in Figure 3.29) will allow you to change the angle of the wing above or below the horizontal plane in flight. This is illustrated in Figure 3.31.
Entering a positive value here corresponds to an angle upward from horizontal (like the wings in Figure 3.31). Likewise, entering a negative value will correspond to a downward angle. A relatively high dihedral angle will increase the “dihedral effect” on the wings—that is, the wings’ tendency to stabilize and level the aircraft in a roll.
You can use this variable dihedral in flight like this … [tk]
Setting Variable Wing Incidence
Checking the box labeled “variable incidence” in the Airfoils window (seen in Figure 3.29) will allow you to change the wing’s angle of attack in flight. This angle, known as the angle of incidence, is illustrated in Figure 3.32.
Enter the maximum incidence here, in degrees. Positive values correspond to an upward angle of the wing when viewing the aircraft from the side, while negative values correspond to a downward angle.
A small positive angle of incidence is used in most aircraft in order to keep the fuselage horizontal when the aircraft is cruising. Thus, changing the angle of incidence in flight will also change the angle of the fuselage as the aircraft flies.
To use the variable incidence in X-Plane, do this… [tk]
Making a Wing Retractable
The final dynamic wing checkbox in the Airfoils menu is labeled “retractable” (as seen in Figure 3.29). Check this box, then set the maximum retraction as a ratio of the wing section’s semi length. For instance, if the wing section was 10 feet long and you set the max retraction ratio at 0.5, the section would retract up to 5 feet into the fuselage.
To use the wing retraction in X-Plane, do this… [tk]
Adding More Wing Sections
In some cases, the four “regular” wing sections, two vertical stabilizer sections, and single horizontal stabilizer section found in the Wings window are not enough to accurately model an aircraft’s wings. In this case, you can add more wing sections by launching the Misc Wings window from the Standard menu.
Wing sections here are added and modified just like in the regular Wings window, with one exception: wing sections are not mirrored across the body. Instead, when you need a section duplicated on each side of the craft, you’ll need to duplicate the wing section and check the box labeled “this wing is on the left side,” as shown in Figure 3.33.
Shaping the Tail
A typical aircraft tail is made up of a horizontal stabilizer and a vertical stabilizer. With this in mind, there are two vertical stabilizer sections and a single horizontal stabilizer wing section available in the Wings window (launched from the Standard menu). These wing sections are shaped just like a standard wing, as described in the previous section, “Shaping the Wings.”
If you need more wing sections than are present in the Wings window, you can add more sections using the Misc Wings window, as described in the section “Adding More Wing Sections” above.
Shaping the Landing Gear
The landing gear is created using the Landing Gear window, which is launched from the Standard menu.
Setting the Gear’s Type, Size, and Position
Landing gears come in a variety of configurations, ranging from simple metal skids, to a single wheel, to groups of many wheels. Additionally, any landing gear needs to have its position on the aircraft specified. If the gear is retractable, it must have a retracted position that is different from its extended position. The gear also must have a size—both its tire size and its strut length.
These properties of the gear are defined using the first tab of the Landing Gear window, labeled Gear Loc (that is, gear location). In this tab, you can create up to ten different gears. Each gear has a column dedicated to setting its properties; Figure 3.34 highlights a single gear’s column.
Let’s walk through the settings for each gear.
Note: If you are using a retractable gear, you will want to do two things before trying to specify the gear’s properties. First, move to the Gear Data tab of the Landing Gear window and check the box labeled “gear is retractable.” Then, close the Landing Gear window and click “Show with still/moving controls,” found in the Special menu. This will animate the gear as you work on it, so you can see just how far it extends and retracts.
At the top of the Landing Gear window’s Gear Loc tab is the gear type parameter. Click the drop-down button and select from a wide array of wheel (or skid) configurations. A lateral wheel configuration arranges the wheels side-by-side, while a truck configuration arranges them in rows. A “long” wheel configuration arranges them one in front of another. Finally, note that any gears you will not be using should have a type of “none” selected.
Next, beneath the gear type parameter, are the three standard positional controls. These are, in order, the longitudinal arm, the lateral arm, and the vertical arm. For information on using these position controls, see the “Fundamental Concepts” section at the beginning of this chapter, which discusses the reference point and its use in determining locations on the aircraft.
Following the standard position controls are the parameters determining the gear’s angle when extended and retracted. There is a “gear extended” pair of parameters, and there is a “gear retracted” pair. Each of the angles measures the gear strut’s deviation in degrees from being perfectly vertical, lined up with the reference point.
In the case of the longitudinal angles, the parameters measure how far the gear is angled to the fore of the reference point. Thus, if the gear needed to angle toward the aft of the reference point, you would use a negative number here. Positive 90 degrees will angle the gear forward and perfectly horizontal, while negative 90 degrees will angle it backward and horizontal.
In the case of the lateral angles, the parameters measure how far the gear’s strut is angled to the right of the reference point. Thus, if the gear needed to angle to the left, you would use a negative number. Positive 90 degrees will angle the gear to the right to be horizontal.
Following the gear’s extended and retracted angles is the leg length parameter. This sets the length of the strut, or the “leg” of the gear, when it is extended. (For many aircraft, the extended and retracted length will be the same; some, though, may compress the gear when retracting it.)
Next are the two parameters controlling the tire size. Each of the tires on a given gear must be the same size. The tire radius is the length from the outer edge to the center of the tire, when viewing the aircraft from the side. Don’t confuse this with the diameter, which is the length from one side to the other when crossing through the tire’s center. The tire semi-width is half the width of the tire, when viewing the aircraft from head-on. In Figure 3.35, the tire radius is shown in red, while its semi width is shown in blue.
Beneath the tire size settings are the “retract axis” and “strut compress” controls (in left to right order, respectively). The first parameter sets the amount, in degrees, that the wheel rotates around its own axis when it is retracted. Note that its axis is effectively the gear’s strut. Positive numbers here correspond to a clockwise rotation when viewed from the aircraft’s underside.
The strut compression parameter sets the amount, in feet, that the strut collapses on itself when the gear is retracted. In some aircraft, like the F-4 Phantom II, the gear compresses on itself like this to save space.
Next, beneath the retract axis and strut compression parameters is the “cycle time.” This is the time, in seconds, that it takes for the gear to go from fully extended to fully retracted, and vice versa.
Finally, at the bottom of the window are two checkboxes. The first, labeled “this gear steers,” should be checked for all gears that are used to steer the aircraft. The final checkbox, labeled “gear has fairing,” should be checked if the wheels have a streamlined fairing (also known as a wheel pant or spat). These structures are used to reduce the drag the gear generates by presenting a streamlined surface for the air to interact with. For information on creating the fairings themselves, see the section later in this chapter titled “Designing Wheel Fairings and Skids.”
Using the parameters above, you can create a basic gear with wheels and a simple strut. If the gear is retractable, you will still need to set a few more of its properties, as described in the following section, “Finishing Retractable Gears.” To fine-tune a gear’s steering properties, see the section “Customizing Wheels and Steering” below, as well as the section “Tuning the Landing Gear” in Chapter 10.
Finishing Retractable Gears
When creating a retractable gear, you will need to specify a few properties in addition to the size, position, and type. Many of these are located in the Landing Gear window’s Gear Data tab.
The most important property here is the “gear is retractable” checkbox, located in the upper quarter of the window, as seen in Figure 3.36. This must be checked for the gear to be retractable.
Directly beneath the “gear is retractable” checkbox is the “gear can retract on ground” checkbox. With this unchecked, the aircraft will sense that the gear is bearing the weight of the craft when it is on the ground and will thus not allow you to retract the gear. This is useful for preventing damage to the aircraft.
If you’re using an emergency gear pump in the instrument panel (used for extending the gear manually in the event of a power failure), you can use the “manual gear pumps” field to set the number of times you must “pump” the button in X-Plane for the gear to actually extend. This field is located just to the right of the “gear is retractable” checkbox, as seen in Figure 3.36.
To the right of the “gear is retractable” checkbox is the “max gear door size” parameter. This sets the maximum width of the gear doors in feet. The gear doors are created in the five Doors tabs up at the top of the window, which we will discuss momentarily.
Beneath the max gear door size is the “additional gear flatplate area.” X-Plane will automatically consider the area of the struts, the wheels, and the doors in its flight model. However, any time a gear door opens up to let a wheel out, it also opens the gear wells. These wells disrupt the airflow over the craft, so you should enter the frontal area of the inside of this well here so that X-Plane can calculate the drag generated by it.
What’s left to create on the retractable gears? The gear doors, of course! Move to one of the Doors tabs at the top of the Landing Gear window to begin creating these. (It doesn’t matter which Doors tab, though Doors 1 is a logical place to start.)
Each Doors tab contains four boxes, each box able to create one gear door. Each of the doors is created in the same way.
At the top of the gear’s box is the “copy from” drop-down menu, labeled 1 in Figure 3.37. To copy the geometry, location, and texture from another gear door to this one, just click the drop-down button here and click the number of the gear door you want to copy from. (Note that, for the purpose of copying, the doors are numbered beginning with 1 in the upper left of the Door 1 tab. Figure 3.38 shows the numbering pattern; the upper left box in the Doors 2 tab is gear door number 5, and the lower right box in the Doors 3 tab is door number 12.)
If you are not copying the gear door’s geometry, you must start by selecting the door’s type. The drop down box labeled 2 in Figure 3.37 selects between four different door types.
Any gear door box that you are not using should have a type of “none” set for it.
The “open while extended” door type creates a door that opens around the extending landing gear, as seen in the left half of Figure 3.39.
The “attached to strut” type creates a door that is stuck to the leg of the gear, as seen in the right half of Figure 3.39.
Finally, the “closed while extended” door type creates a gear door that closes when the gear is extended. This is useful for minimizing the drag associated with the gear well, which would otherwise be open to the air and disrupting the airflow over the craft.
After setting the door type, it makes sense to jump down to the door geometry box, labeled 6 in Figure 3.37. Gear doors in X-Plane are 2-dimensional, composed of up to four points. Click away from any existing points to create a new one, and click a point and drag it to change the door’s geometry.
After creating at least a rough model of the door’s shape, you can position the door on the aircraft and set its opening and closing angles.
To begin positioning the door, you can set its heading (that is, the direction the door is pointing). This is done using the axis of rotation parameter, located beneath the gear door type and labeled 3 in Figure 3.37. A heading of 90 degrees makes the door point straight ahead, presenting the least surface area possible in flight.
Next are the standard location controls, labeled 4 in Figure 3.37. These are presented here in longitudinal-lateral-vertical order, from left to right. For information on using these controls, see the section “How Positions Are Set in Plane Maker” at the beginning of this chapter.
Beneath the location controls are the door’s open and closed angles, labeled 5 in Figure 3.37. The parameter on the left is the door’s angle when the gear is retracted; the one on the right is its angle when the gear is extended. Positive values here will cause the door to hinge to the right of the reference point, while negative values will cause it to hinge to the left.
The final settings in each gear door’s box (labeled 7 in Figure 3.37) are related to its paint textures. Information on working with the paint is found in Chapter 8, in the section “Creating a Basic Paint Job.”
Gear Retraction Warnings
If a landing gear is retractable, there will often have a speed above which it is not safe to have the gear extended (the maximum landing gear extended speed, Vle) and a speed above which it is not safe to extend or retract the gear (the maximum landing gear operating speed, Vlo).
X-Plane will play a gear warning noise [tk] under what conditions?
Customizing Wheels and Steering
Using the preceding sections, you can build a landing gear with the right wheel configuration, the right position, the right retraction characteristics, even the right gear doors. What we haven’t touched on yet is the steering characteristics of the gear, as well as the properties of the wheels themselves. These settings are all found in the Gear Data tab of the Landing Gear window.
There are two “nosewheel steering” parameters here (the top two input boxes in Figure 3.40). These control how far, in degrees, the wheels responsible for steering can deflect. The one on the left sets the maximum deflection at speeds below the transition speed, and the one on the right sets the maximum deflection above the transition speed.
If the aircraft does not use the typical nosewheel steering configuration and instead uses free caster wheels which are controlled using differential braking, set this parameter to zero. (Note that nosewheel steering is a general term for steering by moving the wheels—it applies to taildraggers that steer with the tail wheel also.)
Beneath the low-speed nosewheel steering parameter is the transition speed. This is the speed in knots at which you can no longer steer using the brakes, tiller, or nosewheel steering, whichever the case may be, and must instead steer using the rudder. Above this speed, it would be unsafe to significantly deflect the steering controls.
[tk] nosewheel spring force?? What does this do?
Another important set of parameters impacting the aircraft’s ground steering is the landing gear’s coefficients of friction. These parameters, found in the bottom of the Gear Data tab, are shown in Figure 3.41. The rolling coefficient of friction (the box on the left) controls how much friction is produced by the weight of the airplane on the wheels when rolling on pavement. A value of 0.025 is typical, indicating that the drag of the wheels on the pavement is 0.025 times the weight of the aircraft when rolling. X-Plane will modify this value automatically when rolling on grass strips or off a runway.
The maximum coefficient of friction, the box on the right in Figure 3.41, controls the maximum amount of friction that the tires can generate, both by braking and from side loads.
The final gear parameters we will consider here are those controlling the wheel and tire geometry. Figure 3.42 shows these controls, which are found in the middle of the Gear Data tab. The “wheel lateral separation” specifies the distance between wheels in a side-by-side configuration. This is measured in half-tire widths, from one tire’s middle to the other’s. Thus, a lateral separation ratio of 2 here puts the tires touching each other side by side. [tk] check how lateral separation is measured
The corresponding “wheel longitudinal separation” parameter sets the distance between wheels in an inline configuration. This is measured in tire radii (the distance from the center of the tire to its edge), from one tire’s middle to the other’s. Thus, a ratio of 2 here puts the tires touching along their edges as they rotate.
Designing Wheel Fairings and Skids
For each of your gears created in the Gear Loc tab of the Landing Gear window, you can select to add a streamlined fairing. Sometimes known as a wheel pant or spat, a fairing is designed to reduce the drag generated by a landing gear by presenting a streamlined surface for the air to interact with.
[tk] what does this actually have to do with skids?
Before actually designing your fairings, you must tell Plane Maker which gears have them. This is done using the checkboxes in the bottom of the Gear Loc tab, as described in the section “Setting the Gear’s Type, Size, and Position.”
With at least one fairing specified in the Landing Gear window, open the Wheel Fairings/Skids windows from the Standard menu. Each fairing you specified has its own tab here at the top of the window. With one possible fairing per gear, and ten possible gears, that makes for a total of ten fairing tabs at the top of the window.
Fairings are modeled just like the fuselage and the miscellaneous bodies; there is a Section, Top/Bottom, and Front/Back tab for each fairing. See the “Shaping the Fuselage” for information on using these tabs.
[tk] the copy geo from part # control
Adding Other Surfaces and Bodies
In the previous sections, we’ve talked about creating a fuselage, a tail, wings, and a landing gear. What about everything else?
Some extra bodies have their own special windows for modeling. These include engine pylons, engine nacelles, weapons, and slung loads. All other extra bodies, like external fuel tanks, get no such special windows; instead, they are modeled in the Miscellaneous Bodies window, described in the section “Adding Other Bodies to the Fuselage.”
For information on engine pylons and engine nacelles, read on to the following sections.
Adding Engine Nacelles
An engine in X-Plane is primarily a point from which thrust is generated: propellers are no more than spinning, thrust-producing blades, jet engines are no more than points from which thrust is produced, and so on. To create the body of the engine (like the tip of the propeller or the body of a jet engine), you must add an engine nacelle. Figure 3.43 shows the parts of a propeller and a jet engine which would be modeled as nacelles in Plane Maker. Like every surface in X-Plane, these nacelles will have both visual and aerodynamic consequences. Note that it only really makes sense to create the nacelles after you have created the engines themselves, as described in the section “Working with the Internals of an Aircraft#Creating the Engines|Creating the Engines]]” of Chapter 4.
The Engine Nacelles window is used to model these bodies. Bodies in this window are created just like the fuselage and the miscellaneous bodies; for more information, see the sections “Shaping the Fuselage” and “Adding Other Bodies to the Fuselage” previously in this chapter.
There are eight tabs at the top of this window, corresponding to the maximum of eight engines you can specify in the Engine Specs window. For each engine you want to build a nacelle on, check the box at the top of the tab reading “aircraft has a nacelle over this engine,” as seen in Figure 3.44. This box cannot be checked for engines the aircraft does not have. For instance, if the aircraft has two engines, the third tab at the top of this window cannot have its “aircraft has a nacelle over this engine” box checked.
Note that unlike in the creation of the fuselage and miscellaneous bodies, each station’s distance behind the reference point (found in each nacelle’s Section tab, above the white gridded box used to create the sections) are set relative to the engine itself—not relative to the aircraft’s reference point. This makes sense; the nacelles are attached to a particular engine, not to the aircraft as a whole. [tk] right?
Figure 3.45 shows a wireframe view of a nacelle, side-by-side with its skinned counterpart. Note the large black dot on the left side of the nacelle in the wireframe view. This is the position specified for the engine itself; it is the “center of thrust” for the engine. This point serves as the reference point for this nacelle. [tk] right?
Adding Engine Pylons
Engine pylons—the hardpoints of an aircraft designed to have engines mounted to them—are modeled using the Engine Pylons window, launched from the Standard menu. (Note that it only really makes sense to create the pylons after you have created the engines themselves, as described in the section “Creating the Engines” of Chapter 4.)
Modeling a pylon is very similar to modeling a wing—a pylon just ends up being a short, stubby, oddly shaped wing, which might itself be attached to a real wing. In light of this, the controls found in the Engine Pylons window are identical to those in the Wings window, with a couple exceptions. For information on using the standard wing controls, see the section “Shaping the Wings” above.
The most important thing to note is that unlike in the creation of a wing, each pylon is place with respect to the engine to which it is (assumedly) attached—it is not placed relative to the aircraft’s reference point. Since engines in Plane Maker are just points from which thrust is generated, this works well.
Up to two pylon designs can be created for each aircraft. To apply a pylon design to a certain engine, check the box corresponding to that engine at the top of that pylon’s tab, as seen in Figure 3.47. These engines are numbered as they are in the Engine Specs window; the engine on the far left in the Location tab of that window corresponds to the checkbox on the far left here, and so on.
Setting the Location of the Tow Hook, Winching Hooks, Boarding Door, and Refueling Port
A few miscellaneous features of the aircraft’s body are set up using the Viewpoint window, launched from the Standard menu. In the Viewpoint window’s Default tab, the position of the aircraft’s tow hook, winching hook, refueling port, and boarding door can be specified using standard position controls, as described in the “Fundamental Concepts” section at the beginning of this chapter.
The position of these features of the body will only be visible when using the wireframe view (toggled using the spacebar). There, they will be represented as large black dots, just like the point representing the aircraft’s center of gravity.
Note that both the winching hook and the tow hook must be centered laterally along the aircraft’s body, so they do not have a “lat arm” parameter.