From: ptran@watserv1.uwaterloo.ca (Phat H Tran)
Subject: Flight model in CYAC (Why I don't like it)
Organization: University of Waterloo
Date: Mon, 31 Aug 1992 12:51:57 GMT

It just amazes me that so many people think so much of the flight
model in Chuck Yeager's Air Combat (CYAC).  I, personally, think it's
one of the worst.  I'll try to explain why.  (Hit 'n' now to save
yourself from my rambling.)
 
Basically, I hate the fact that CYAC's flight model, like those of so
many other supposed "sims", is simply based on a set of procedures and
conditions instead of physics. The game really has no concept of
flight dynamics. In it, the behaviour of aircraft is controlled by
if's and then's, eg. if speed<140 and joystick=up then stall, instead
of dynamics formulae.  Many variables are not taken into account, and
no attempt is made at calculating many of the pertinent forces acting
on the aircraft and what their effects would be.
 
For example, CYAC ignores one of the most fundamental of aerodynamic
forces, lift.  In the game, there isn't any, and there isn't any
gravity either.  You merely travel in whatever direction your nose
points. If your nose is pointing above the horizon you'll ascend, if
below, you descend. If you are perfectly level, you will fly perfectly
straight. Even in a propellor plane like the P-51, you will *not* gain
or lose altitude if your pitch is 0 degrees. There is no lift to take
you higher, and, as luck would have it, no gravity to bring you down.
Even when you are banked at close to 90 degrees, where there would be
no vertical lift to talk of, you will not descend unless your nose is
below the horizon.  Only at extremely low speeds will you descend
without having to be pitched downward, and even then, the descent is
based on some very simplistic rules.
 
The angle of attack (AOA), which is unrealistically almost always
zero, has no influence on lift or stalls. I stall at the exact same
speed with a pitch of +45 degrees as I do with pitch -20. Each case
should have had vastly different AOA's at the stall limit, and thus
the stalls should have occurred at different speeds.
 
Aside from altitude, the only other factor that changes the stall
speed limit is whether the stick is pulled back or not.  Merely
yanking back on the stick automatically raises the stall speed by a
fixed amount.  I don't even have to be doing a high-G or high-AOA
manoeuvre.  For instance, say that the stall speed with a centred
joystick is 100, and with a pulled-back joystick, 150. While flying
along perfectly level at 120 MPH, if I happen to pull slightly back on
the stick, the stall speed will immediately jump to 150, and I will
suddenly find myself in danger of stalling, long before the AOA would
reach a critical level (but then again, AOA isn't even calculated nor
considered).
 
The G forces do not vary continuously.  G's are shown with a
resolution of 0.1, but turns are all either 2.0G, 3.0G, 4.0G etc. This
is clear evidence of a flight model that is relying on discrete
conditions and discrete consequences instead of dynamics equations and
continuous variables.
 
The stall routine is preposterous.  When you stall, your plane simply
gains a tendency to nose down and roll.  (In fact, you *always* roll
during a CYAC stall, even when there should be no difference in lift
between your wings, such as when you're flying level, or when you're
pointed straight down.  I also found that using your elevator when
stalling increases the roll rate for some strange reason.)  The flight
model fails to see the significance of a stall as a loss of lift and
loss of manageable airflow over the control surfaces. Thus, even
though your plane wants to roll and nose down when you stall, you will
still have extraordinary control through the ailerons and elevators,
and the plane will not descend unless pointed downward.  Also, during
a stall, the engine mysteriously becomes ineffective.  Even at max
throttle, you will have a hard time accelerating yourself above the
stall speed unless you dive steeply.  I have managed to remain stalled
in CYAC for several minutes, simply by pulling my joystick back to
keep my nose pointed at the horizon, while keeping my throttle at
max.  I can even gain altitude during a stall.
 
Since the flight model ignores even basic physical laws, inertial
effects aren't properly simulated.  The rolling of the plane is simply
dampened to give the impression of angular momentum.  There is no
aileron torque being calculated, no moment of inertia being accounted
for.  The result is unrealistically sluggish handling.
 
In summary, I hate CYAC because it purports to be a flight simulator,
but it isn't. It's a shallow replica of the symptons of flight, but
not the causes. CYAC makes me feel like I'm flying a flowchart. Using
discrete conditions and consequences is no way to model the continuous
nature of flight. I would much rather be flying Falcon 3.0 or Flight
Simulator 4, which are true simulations in that their flight models
are built out of respect for physics, instead of irreverence. As a
result, they handle very much like a plane should in the real world,
and do not betray what common sense and education tell you.
 
Phat.

Xref: sparky comp.sys.ibm.pc.games:11711 rec.arts.int-fiction:682