Bodies are used in Plane Maker for all "non-functional" parts of the aircraft (though in a real aircraft they do of course have functions). Bodies include:
- Fuselage (max. 1)
- Misc Bodies (max. 20)
- Engine Nacelles (max. 1 per engine)
- Wheel Fairings (max. 1 per landing gear element)
Weapons also include a body definition.
The only functions Bodies have in the XPlane Sim is to provide an optical representation of parts of the aircraft, to provide drag, and to provide buoyancy so that they can be used for flying boat hulls and seaplane floats.
A numerical drag coefficient for the total body drag is required input. Suggested values are shown in the data entry field's hover text ("bubble help"). To arrive at a realistic figure, an initial 'estimate' should be entered, then the plane should be tested for top speed, and based on the test results the drag coefficient should be decreased or increased to make the plane slower respectively faster as needed to hit the target value. X-Plane 8.xx does not seem to take wetted area into account.
In X-Plane, bodies produce more drag, the further from the horizontal they are with regards to airflow. (Lack of precsion. Discusion/Comments please. . . Bodies with yaw are OK? No increased drag? X-P Plane-Maker 8 and 9 provide heading, pitch, and roll specification for Misc Bodies. For this discussion only heading and pitch are pertinent.) X-Plane calculates extra drag for all bodies at higer than nominal angles of attack. (No incr drag for bodies with pos or neg heading entries in Misc Bodies/BODY LOCATION? Perhaps also "BODY LOCATION' should be re-titled to BODY LOCATION/ORIENTATION)
Note: To avoid excessive drag on some bodies, it's a good idea to design all bodies so that their longitudinal design axis is parallel to the airflow in normal conditions. (Requiring editing of the Pitch setting in Misc Bodies/BODY LOCATION. Which will require knowing what the angle ofattck of the ac is under 'normal' conditons.) Bodies rotated by 90 degrees have been known to cause inordinate amounts of drag.
Fuselage Body[]
Q- Is there anthing special about the fuselage body, or is it just another body except for its name?
A- It is just the main body on the plane.
Engine Nacelles[]
Engine nacelles are bodies that are located automatically so that their coordinate origin (center of bulkhead frame at longitudinal position 0) coincedes with the position of the corresponding engine.
Note: Jet engine nacelles should be designed so that the exit nozzle is centered on the coordinate origin. Otherwise, the jet thrust will not act in the proper position, and flight characteristics will not be realistic if the nozzle is positioned in the visually correct location!
Q- Isn't it true that the paint textures are applied differently to Engine Nacelles, and only Nacelles, in the interest of being able to, for example, depict the inlet fans on large turbofan engines on airliners?
Q- On jet engines with inlet cones (SR-71 Blackbird) how is this occlusion of the inlet area handeled?
All Bodies[]
Q- Isn't there an issue with drag on bodies that are left either open in the front or open ended at the tail?
A- No. Xplane doesn't care. The body drag is calculated based on the product of body drag coefficient and body frontal area.
Body lift?[]
I believe also that a (symetrical arifoil) wing section inside the fusealage (not visible) can be added give calculations for knife edge flight. It may be that some such can be arranged also to assist in modelling (i.e. calc'd values) for spin. This need comment. . . Also would be a neat flight test program in XP to check results of various elements in this context.