About Modeling
This section briefly touches on some broad topics concerning mathematical modeling concepts and may prove helpful in understanding PlaneMaker and creating the best aircraft simulation you can, but this information is supplementary only and not necessary to create an aircraft for X-Plane and you may skip over this section if you like.
Aircraft in X-Plane are nothing more than a collection of mathematical models running in parallel. The ACF file produced by Plane-Maker is a pre-processed (processed previously by PlaneMaker) input file, whereupon X-Plane takes that input file and applies numerous mathematical models to simulate / emulate a variety of engineering phenomena: aerodynamic forces, dynamic responses, systems behaviors, atmospheric effects, etc.
Simulation vs. Emulation
The distinction between simulation versus emulation can be quite narrow, indeed can overlap; however, the distinction as it applies to X-Plane is worthy of some discussion. Simulation, in general, seeks to predict the behavior of something and produce predictive results beyond actual measured values, whereas emulation seeks to imitate real behaviors that have previously been measured or observed. Simulation algorithms are usually based on first principle governing equations, whereas generic emulation algorithms are more commonly curve_fits that need to be 'configurable' so they can be tuned to match existing behavior. X-Plane uses both methods.
Real behaviors are complex and influenced by an infinite number of input factors. For example, every molecule of air moving against a body has an effect on that body. There is no way a computer can account for that level of detail and variability. What we can do instead is characterize behaviors on a simpler level which gets us close enough to the real behaviors to satisfy our goals. The task at hand for PlaneMaker and X-Plane then is to choose HOW to best characterize a given behavior.
There are hundreds of behaviors that have to be characterized within X-Plane to form the final aircraft simulation that you experience in sim. X-Plane uses a variety of numerical and mathematical models to characterize behaviors, including first principle physics equations, PID algorithms, Curve-Fits and Linear and Non-Linear interpolations of various kinds (power curves, logarithmic, 1/x, etc). The method employed for each behavior is dependent upon the characteristics of the behavior and the inputs to those math models are those inputs that you enter in PlaneMaker.
Static Stability
- Talk about how "static stability" needs to make sense mathematically, or your aircraft will be wonky and you might blame X-Plane, but you need to have a modicum of engineering knowledge.
XPlane is not CFD
Many folks mistakenly think that X-Plane is (or should be) real time CFD (Computational Fluid Dynamics), but this is not the case. While X-Plane does calculate atmospheric and aerodynamic forces in real time, the force model is a streamlined, yet quite accurate idealization that is better suited for real-time calculations. X-Plane's algorithms rely on an existing definition of an airfoil's 2D characteristics, rather than calculating its characteristics from its shape alone, such as would be done with XFOIL or XFLR5. In addition, X-Plane approximates drag in several macro regimes using statistical heuristics, but again, is not CFD. PlaneMaker / Airfoil Maker do have parameters though, for making fine-tuned tweaks to the lift and drag model.
Collision Physics
- Talk about landing gear, Hard objects, etc.
PM Feature Creep
PlaneMaker and X-Plane is subject to Feature Creep. Feature Creep refers to "new feature behaviors" that "creep their way into X-Plane". This can be an entirely new behavior or the refinement or expansion of an existing behavior. Feature Creep is generally manifested in PlaneMaker in the form of new widgets as newer versions of X-Plane and PlaneMaker become available.
Feature Creep is more common for transport class airliner simulations as they have more options and are more complex and for airliner models in X-Plane, this is a good thing. A lot of widgets in PlaneMaker are the result of feature creep and are simply not relevant for many simpler aircraft simulations. You will have to examine the widget and its tooltips to determine if its relevant for your aircraft model. Those widgets and their functionalities may be explored here in this manual using the UI Reference Pages