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Monday, 7 September 2009

Yank That Stick Back

Posted on 10:32 by Unknown
A quote from the .org:
I actually did try the demo before I bought it, and I found it sorta arcadish as I took off with a King Air 200 and performed barrel rolls on t/o lol! That kind of tuned me out!
I don't mean to pick on that particular poster - we hear that a lot, particularly from people who use MSFS. Andy Goldstein points to Bob Hoover as a counterpoint.

More generally, the criticism is that since X-Plane will allow you to do things in commercial airliners that you've never seen in real life, X-Plane must not be realistic. And phrased like that, you can see the possible flaws in the reasoning:
  1. How do you know your control inputs match real life?
  2. How do you know the real plane is physically incapable of doing such a thing?
The first is the age-old problem of consumer joysticks - to really maneuver an airliner hard you have to put a lot of pressure on the controls - they put up a lot more resistance than a $20 SideWinder.

The second is an issue of falsifiability again - the absence of evidence is not evidence of absence.

Now in truth there are things that X-Plane models and X-Plane does not model. If you load up the airframe too much with fail-on-over-G on and the G limits are set correctly, X-Plane will start removing parts as you try to fly a 747 like an F-16. But we don't necessarily simulate some of the internal things that might go wrong. For example, accelerations on the fuel system might potentially cause flow to the engines to fail, stalling an engine. I don't know how much of this Austin simulates, but we certainly don't simulate the geometry of the fuel lines and the fuel as a fluid flow. So there may be cases where a maneuver is impossible for logistic but not aerodynamic reasons (e.g. you could do it but you'd lose your engines).

With that in mind, here are a few youtube links:
  • Bob Hoover flies a Commander like an aerobatic glider - thanks Andy!
  • Roll an airliner? It's safe, really!
  • The 757 has a lot of power - thanks Andrew.
  • I have no idea what happened here...I thought the Airbus computer prevents you from doing this kind of thing.
On that last video: the first time I flew with Austin in his Cirrus (this is before he traded it for a Columbia) he pulled the same maneuver: take-off, very slow rate of climb to pick up speed, and then: yank. Our climb rate was well over 2000 fpm in a single-engine prop for a while.

(Logistic note: please don't interpret this post as an invitation to contact me regarding any aspect of the flight model - when it comes to the physics engine I am just another user, with no special insight. Physics is Austin's domain, definitely not mine!)
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