Quote:
Originally Posted by Sternjaeger II
wow, I'm surprised the thing gets airborne in the first stance! Does X-Plane model propeller cavitation too?
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You can't get cavitation in air; cavitation is a phase-change phenomenon.
You can certainly stall the propeller in X-Plane, and it will suffer shock losses. Actually the propeller model is one of its nicer features.
However, in general the underlying assumptions are undocumented and subject to change without notice. So you build a nice model, and then find that Austin has decided to tweak
something in the next version and suddenly the predicted performance changes dramatically.
For this reason, it can't be used for serious work where fidelity is important.
Austin is a law unto himself and his system does not necessarily follow the conventions one would expect (eg although the underlying model seems to use SI, airframe dimensions are input in decimals of feet. Meanwhile, propeller root and tip chords are input in decimals of inches...). The engine model is a bit crazy, kinetic heating data is very questionable for M>>2, transonic behaviour is obviously lacking in fidelity, etc etc.
It's very good at replicating Austin's personal flying experience, but that's basically limited to GA piston singles. So although the simulator will allow you to build a rocketship and fly into LEO, the results have problems.
Of course, the average user doesn't understand the limitations of the code, not least because the underlying assumptions are undocumented, and therefore tends to believe that because the computer told them that their design would do this then it must be true.
So I fear that it's probably only a matter of time before some fool conducts virtual spin testing of their homebuilt masterpiece in X-Plane and then wins a Darwin award by assuming that X-Plane has validity in this regime simply because it produces output...