We are in complete agreement -except where I live bud is the worst and I could show you some local brew and wines that would make you happy-I found many in Italia which met the criteria this summer-changing the subject to beer/wine models which ultimately might be more important than fm's!

On www.x-plane.org there are 2 RL pilots of Rutan aircrafts, one has a VariEze and the other a Cozy. They both say that the roll effect due to torque is very exaggerated in X-Plane, while in RL it is much less, if practically non-existent.

 

http://forums.x-plan...?showtopic=7777

 

Hehe, I was already fighting torque in XPlane around 2004 :-) Thx for reminding me Marco... Recently, when I bought XP10, I went there again, just to check about it and the problems with ground handling under x-wind... unfortunatley brett and others promptly confirmed the problems are still there awaiting some retouch by Austin :-)

 

Now here's the riddle for you: as you probably know, both the VariEze and the Cozy have a canard, push-propeller configuration. So, there is absolutely _nothing_ in the slipstream of the propeller. What is then compensating the varying torque of the propeller in flight?

 

Hmmm, interesting question... and one that raises another question... On some books / articles about aerodynamics, including the well known "See How It Flies" by John Denker, the authors point out that torque effects shouldm only be present during power increase / decrease! Power / Weight ratios are also important as well as the fact that on most GA aircraft the dynamic pressure and lift generation by the wings will easily overcome any torque-induced forces once you get flying straight, while when climbing it is more the p-factor (not that much though...) and the spiraling slipstream that will cause the left yaw tendency requiring right foot...

 

Back to John Denker's excellent "See How it Flies", read across Section 9 and particularly the comments at 9.5 and 9.6 as well as the final considerations at 9.8 where he states:

 

"If the speed and direction of rotational motion is unchanging, engine torque will have no noticeable effects. (Engine torques will of course exist, but they will be part of “closed circuits” of torque within the fuselage, so they will not affect the handling of the airplane.)"

 

I still think the Rutan's should exhibit torque though, probably faint but it should be there, while the slipstream effects and associated compensation are absent in their case...

 

I know I haven't answered your question :-/ but I will have to think more about it ;-)

Can somebody please call Austin to watch this thread? He can learn a thing or two here! B)

I'll chime in... For a lot of people, especially real pilots, what it counts is the final result, not how one gets there: it doesn't matter if one uses all the possible "tricks" to get realistic handling and feeling, the final result is the only thing that matters. in LAdamson words, there are no real air molecules inside the simulated flight model, it's all a "trick" after all, and that is true.

That is not only absolutely legitimate, but also absolutely understandable.

 

On the other hand, I'll try to explain why those who look at it from a different point of view, an "engineering" point of view (like me, jcomm, tkyler, GoranM) are more wary and sometimes use words like "cheat" and the alikes.

 

I actually do have a "experimental" aviation point of view, when it comes to performance of airplanes. Well, at least with the smaller stuff. Since we're involved in building these things, I often seen flight tests, which can include stall testing with wing "tuffs" (yarn taped to the wing), testing of different sizes of horizontal/vertical stabs which can effect spin characteristics...................

 

then on to vortex generators, root cuffs, wing cuffs, small triangular plates above the boundary layer of a high wing, metal plates running horizontally between two cowl halves, 90 degree wing/fuselage intersections versus flared intersections, so on & so on. Perhaps some of these items in this second paragraph could be considered "cheats", and I'm quite positive that X-Plane doesn't have the power to accurately predict the difference, with & without.

 

Since I've seen so many flight tests with tuffs attached to real live flying airplanes, I'm not all that impressed with those X-Plane arrows sprouting out in different directions, that are suppose to imply flight characteristics. The tuffs will show the exact airflow, when the flow separates from the wing, and the corresponding turbulence. And when these "cheat" devices I've described above, are applied, the tuffs once again, immediately show the new paths of airflow. Can X-Plane predict or show this? I'll assume not. Therefor, even if the exact wing dimensions, fuselage intersections, incidence & dihedral are put into the X-Plane model.................it may still require the addition of cheats/programming changes, or what ever you want to call them............to subsitute for those cuffs, vortex generators, flat metal & trianuglar plates, etc. that dramatically change the flight characteristics from the base dimensions of an airplane.

 

Edit: and I can go on & on. Shape of trailing edges.....sharp or cut off. The inlet & outlet sizing of cowls for cooling, drag, and additional speed performance. To seal or not seal ailerons, flap, & hinge gaps. The shape of wing tips & props for speed, drag, & tip vortices. Effects & shapes of wheel pants, leg fairings, exhaust fairings. Cooling drag through radiators versus air cooled. Flush rivets versus exposed universal rivets, etc. etc. ----- Not exactly an engineer's point of view, but more of a practical hands on view.

 

L.Adamson

then on to vortex generators, root cuffs, wing cuffs, small triangular plates above the boundary layer of a high wing, metal plates running horizontally between two cowl halves, 90 degree wing/fuselage intersections versus flared intersections, so on & so on. Perhaps some of these items in this second paragraph could be considered "cheats", and I'm quite positive that X-Plane doesn't have the power to accurately predict the difference, with & without.

 

Sorry, you did not understand the point of my post.

 

1st example: modeling the missing effects of a vortex generator, root cuff, etc. as a change in the airfoil characeristics and coefficients, would _not_ be considered a "cheat" to me (and, AFAIK, to MortenM, GoranM, Tkyler, etc.).

 

2nd example: modeling the possible lack of "carryover" lift of the fuselage between the wings as an hidden wing, again, would _not_ be considered a "cheat" as well.

 

On the other hand, some designers would consider a "cheat" e.g. adding artificial stability, for the various reasons I explained in the long post above.

 

Marco

The thing is, you may not chop the throttle as you know what it can cause in an expensive engine and that smoothly advancing and decreasing the throttle will allow you to feel and eliminate yaw introduced from p-factor, torque and gyroscopic procession. These things should be present in the flight model to teach people who are not pilots why it is so important to straighten up and fly right. Not doing so can have adverse impacts on flight efficiency and performance.

The roll I experience comes with no change in power settings in level flight.

I know what you're talking about Geof. No arguments. Just saying about how it has been said that some aspects aren't important such as misuse of controls and the results they cause. I believe that if you make a control input, the reactions that actually happen should happen, no matter how trivial they appear. Some of us have to substitute our sims for the reality that we miss and I'd like to know that if I do things improperly in the sim, I will suffer the same or nearly the same consequences as in the real thing. Keeps me frosty for those rare instances I get back in the cockpit, that I don't develop bad habits by simming.

On this issue of "cheating" I have a small story to tell...

I really do not like to find that a given aircraft is made to exhibit some flight characteristics because Art Stab had to be used for it, and I thought that from a designer perspective, probably a 3pd making commercial products for XP, it would be nice to be able to hide certain parts of the flight model file that we can open with Plane Maker, or simply encrypt them.

 

I suggested Austin the inclusion af an option to hide certain sections of the "airfile" on an email I sent him some months ago. Austin, being an honest guy in the very 1st place, promptly replied: " I do not cheat!!! No way!"

 

:-)