On Sun, 23 Nov 2003 12:35:11 -0000, "Simon Robbins"
wrote:

"Corey C. Jordan" wrote in message
.. .
However, can anyone tell me what data is used to generate the mathmatical
model coded for the previously mentioned simulators?

No, but the procedure for simulation is approached from a different angle.
For example, a "true" simulation of an aircraft will model the atmosphere
and airframe so that the resultant parameters determine its performance,
i.e. the exit parameters will cause (for example) a Spitfire to roll at say
45 degrees a second, whereas a PC simulator will use a previously defined
input parameter to dictate the aircraft rolls at that rate. It's not a
simulation of the airframe, but of its known performance. Not the same
thing. You're not going to be able to design an aircraft and predict it's
flight envelope using MS-FS because you have to start by knowing the
performance envelope you're wanting to simulate. A militray simulator will
take the design of the aircraft and inform you of its likely real-world
envelope.

No, no, no. Only at the very beginning do we use predictions based on
the design. Those predictions come from the wind tunnel, CFD, and
prior experience. The instant we get such data from flight we update
the simulation with the actual, not the predicted, numbers.

Simulators are not tools used to predict the actual flight dynamics at
all. This is exactly backward. Simulators mimic the real thing. The
flight envelope is usually defined by _design_ limits, like load
factor and qbar.

Read the paper I mentioned. You'll find a very complete explanation
of how the actual data is used.

The PC games use a very generic model, not a detailed model of the
specific vehicle. They're not predicting anything, either.

A good example is at (generally) how badly departed flight is modelled. They
generally model the instability of the aircraft and its predicted behaviour
outside the envelope, rather than the extremely complicated chaotic dynamics
which go into causing that behaviour. Anyone who's performed spins and
stalls in a Cessna and then tried the same thing in MS-FS or any WW2 prop
sim will likely agree.

That's usually because we don't have data for post-stall flight.
Aircraft are not necessary unstable in that region, either. Stall and
spin don't imply instability.

Mary

--
Mary Shafer Retired aerospace research engineer