Change the name to trainers.

On Sat, 22 Nov 2003 23:23:07 -0000, "Simon Robbins"
wrote:

Flight Simulator implies replicating the
dynamics of the science behind the process, which is plainly modelled only
very simply in a "game."

Please define for me what is specifically modeled "very simply" in Aces High
or MSFS.

Do you think it's flight modeling?

My regards,

Widewing
Widewing (C.C. Jordan)
http://www.worldwar2aviation.com
http://www.cradleofaviation.org

On Sun, 23 Nov 2003 00:26:55 GMT,
(Corey C. Jordan) wrote:

On Sat, 22 Nov 2003 23:23:07 -0000, "Simon Robbins"
wrote:

Flight Simulator implies replicating the
dynamics of the science behind the process, which is plainly modelled only
very simply in a "game."

Please define for me what is specifically modeled "very simply" in Aces High
or MSFS.

The dynamics of the airframe. Frequency, damping, poles, zeros,
transfer functions, the stability and control coefficients of the six
equations of motion, the atmosphere, the actuators, controller
dynamics, mass characteristics, that kind of stuff. As well as the
flight control system.

The mathematical model of the vehicle, in other words. That which
makes each airplane fly like that kind of airplane.

I spent a lot of my career determining this stuff so it could be put
into engineering simulations. Read Iliff & Shafer on the estimation
of S&C derivatives for the Space Shuttle to see how we determine such
numbers and put them into the mathematical model used in the
simulation. You'll find it on www.dfrc.nasa.gov, in the technical
reports section.

Mary

--
Mary Shafer Retired aerospace research engineer

Wow

On Sat, 22 Nov 2003 19:10:26 -0800, Mary Shafer
wrote:

On Sun, 23 Nov 2003 00:26:55 GMT,
(Corey C. Jordan) wrote:

On Sat, 22 Nov 2003 23:23:07 -0000, "Simon Robbins"
wrote:

Flight Simulator implies replicating the
dynamics of the science behind the process, which is plainly modelled only
very simply in a "game."

Please define for me what is specifically modeled "very simply" in Aces High
or MSFS.

The dynamics of the airframe. Frequency, damping, poles, zeros,
transfer functions, the stability and control coefficients of the six
equations of motion, the atmosphere, the actuators, controller
dynamics, mass characteristics, that kind of stuff. As well as the
flight control system.

The mathematical model of the vehicle, in other words. That which
makes each airplane fly like that kind of airplane.

I spent a lot of my career determining this stuff so it could be put
into engineering simulations. Read Iliff & Shafer on the estimation
of S&C derivatives for the Space Shuttle to see how we determine such
numbers and put them into the mathematical model used in the
simulation. You'll find it on www.dfrc.nasa.gov, in the technical
reports section.

Mary

On Sat, 22 Nov 2003 19:10:26 -0800, Mary Shafer wrote:

On Sun, 23 Nov 2003 00:26:55 GMT,
(Corey C. Jordan) wrote:

On Sat, 22 Nov 2003 23:23:07 -0000, "Simon Robbins"
wrote:

Flight Simulator implies replicating the
dynamics of the science behind the process, which is plainly modelled only
very simply in a "game."

Please define for me what is specifically modeled "very simply" in Aces High
or MSFS.

The dynamics of the airframe. Frequency, damping, poles, zeros,
transfer functions, the stability and control coefficients of the six
equations of motion, the atmosphere, the actuators, controller
dynamics, mass characteristics, that kind of stuff. As well as the
flight control system.

The mathematical model of the vehicle, in other words. That which
makes each airplane fly like that kind of airplane.

I spent a lot of my career determining this stuff so it could be put
into engineering simulations. Read Iliff & Shafer on the estimation
of S&C derivatives for the Space Shuttle to see how we determine such
numbers and put them into the mathematical model used in the
simulation. You'll find it on www.dfrc.nasa.gov, in the technical
reports section.

That's very interesting and extremely impressive work.

However, can anyone tell me what data is used to generate the mathmatical
model coded for the previously mentioned simulators?

My regards,

Widewing (C.C. Jordan)
http://www.worldwar2aviation.com
http://www.cradleofaviation.org

"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.

Obviously there's varying different methods and levels of fidelity. I'm not
trying to denegrate PC sims, I love 'em and it's the main reason why I spend
a fortune at regular intervals upgrading my PC. But I'm not under the
illusion that they compare in method or fidelity to the "real" thing.
(Favourites being Falcon 4 SP3, EAW and FS2002.)

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.

Si

Subject: Change the name to trainers.
From: "Simon Robbins"
Date: 11/23/03 4:35 AM Pacific Standard Time
Message-id:

"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.

Obviously there's varying different methods and levels of fidelity. I'm not
trying to denegrate PC sims, I love 'em and it's the main reason why I spend
a fortune at regular intervals upgrading my PC. But I'm not under the
illusion that they compare in method or fidelity to the "real" thing.
(Favourites being Falcon 4 SP3, EAW and FS2002.)

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.

Si



And of course no one has ever said that MSFS or any other home PC simulator
program was a military simulator. But hope springs eternal. (:-))

Regards,



Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

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

"Mary Shafer" wrote in message
...
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.

Ok, I take your correction. But my point was essentially that pc sims
generally concentrate on the back end of the simulation process, i.e. what
is represented to the operator, rather than the front end, the inputs to the
process. i.e. accurate descriptions of the airframe qualities and
environmental modelling.

Si

ubject: Change the name to trainers.
From: Mary Shafer
Date: 11/23/03 9:02 AM Pacific

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

TADAAAAH !!!


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

"Mary Shafer" wrote in message
...
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.

Only a select few simulators actually produce a correct mathematical
modeling of the aircraft's characteristics, but in many cases a simulator
has a different purpose than modeling. In the case of the F-18, there was
no mathematically correct simulator until HARV was built in '86.

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.

During the development of flight controls the simulator is where flight
dynamics are modeled. The YF-22 deviated from this formula and it's fate is
directly tied to skipping a step. Much the same as skipping full scale
development does not necessarily eliminate the work.

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.

The need for predictor correctors has been addressed with faster machines
these days. I did see an instance with TCAS III flight test where I thought
a rate based stabilization algorythem might have made the system work, but
it is a lot of processor overhead.