RVM
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Joined: 3/12/2006
From: Sacramento,
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Out of curiousity, how do the mathematics for describing the aerodynamics of a spin differ from that in "normal" flight? What makes it so difficult? Why hasn't more research been done into this single, and very important, aspect of flight?
quote:
ORIGINAL: MSelig
Yes, that's me. Good to hear that you've enjoyed the airfoil work.
It's a product of a lot of people - myself, students, other
collaborators, and many volunteers.
The FS One project is a bit like that - lots of people behind it and
hopefully a lot of people will enjoy it! I've focused on doing the
aerodynamics for all the airplanes in the sim.
You asked me a question - how "real" is it? I think that's the first
time I've been asked that question in these forums.
I can answer it best by example (new videos). The toughest thing to
simulate are the aerodynamics/flight dynamics of spin. Spin
aerodynamics is rarely covered in the textbooks, and often if it is
covered it's near the end of the book (e.g. McCormick's aero book
starts spins on page 577 and the main text of the book ends on page
601). Research on spins is also pretty sparse, but I think by far
Bihrle Applied Research has looked at spins the most (various NASA CR
reports on particular configurations measured in spin tunnels).
More info: To some degree our lack of understanding of spins and
stalls - stall/spin - accounts for ~25% of general aviation accidents
each yr (biggest category). The second on the list at ~15% is loss of
control in adverse weather, and I'd guess much of that involves
stall/spin - usually icing related. US Private Pilots reading this
will know that spin training is not required by the FAA, and it's a
big debate whether or not there should be spin training. For some
period of time long ago when there was spin training, 48% of all fatal
stall/spin accidents occurred during spin training! That's the argument for
why we don't have required spin training today.
So spins are the biggest challenge (in my book). Leading up to spins
are stalls, and related to that is all the wild "3D"/aerobatic flying
that we're witnessing today with RC models. In general a lot of this
is called post-stall aero. The videos that are posted on the FSOne
site show a lot of the "3D" aero, and to all involved (on our side) it
looks right and hence I'll say "real" - very real. "You be the
judge."
In another thread I made the argument that if the videos look right,
then the physics are right. I'll stand by that claim. I guess the
counter claim would be if the videos look wrong ... then the physics
are right??? That does not make sense to me.
Back to spins - the hardest thing to do (in low speed configuration
aerodynamics): We have taken real video of the planes in the sim and
we often capture spins. Here's a short video showing REAL model
airplanes in spins:
http://www.inertiasoft.com/videos/fs1_RealSpins.wmv (21 Mb)
The video includes the ParkZone J-3 Cub, H9 Edge 540 33%, Cessna 182
Skylane, Twist, Ultra Stick Lite and EFL Tribute.
I used FS One to fly the same airplanes in the sim (all stock
airplanes) and made a video of them in the same sequence here:
http://www.inertiasoft.com/videos/fs1_SimulatedSpins.wmv (24 Mb)
Basically, the agreement between the real video and simulator video is
very good I think. Hence I'll say that the sim is very close to real
and in particular especially good at doing one of the toughest things
- spins. After getting spins "right", a lot of other stuff "comes for
free" to some degree.
I need to say that in addition to the aero side, the graphics of the
models, the skies, the panos, engine/motor sounds, ground reactions,
etc all help to create the overall illusion of things being "real".
Michael
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There is no substitution for human competition.
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RE: FS one by Horizon Hobbies - 
