Whee, here we go again. :)
David Megginson wrote:
> Andy -- can you actually manage the DC-3 in a ground roll and takeoff?
> I have not been able to do so for a long time -- it always ends up
> spinning like a top. If you can do it, perhaps it would help if you
> posted a step-by-step.
First off, you need fine control over differential braking. I do this
with a mapping from /controls/rudder to the mainwheel brakes. I know
you hate this idea, but if you're not doing it, I simply don't see how
you can ever get off the ground.
The DC-3 (the real world plane -- forget YASim for a moment) simply
cannot be controlled on the ground without the use of the toe brakes.
Period. If the simulator pilot cannot use them, the simulated plane
cannot be controlled. Really, this is the truth. I promise.
What happens (again, in the real plane) is that the mainwheels are
forward of the CG. This means that any side force due to not quite
moving straight causes the nose to yaw *away* from the direction of
travel. This is not the way that tricycle gear planes work, and it
requires constant, small and immediate (!) adjustments to prevent
divergence. At low speeds, this is simply impossible without braking
control.
BTW, the most recent aircraft descriptions that were posted contains
the brake mapping (I forgot to remove it), if anyone wants to try
that.
> > (3) YASim doesn't model prop wash, so rudder authority is lower at
> > slow speeds than it should be.
>
> On the contrary, the slightest rudder input at slow speed starts the
> plane spinning right now.
This is simply not so, it just "looks" that way. Here's the proof:
(1) Hard-wire the rudder control to zero. Either take the
<control-input> section out of the YASim file, or the joystick
mapping out of your preferences. Just make sure that there is no
rudder input to YASim at all.
(2) Try to take off. You will still be spinning like a top.
What you are seeing is not rudder force. It is *gear* force, acting
on a point forward of the CG. It only looks like rudder force because
you're not used to dealing with an aircraft that is directionally
unstable on the ground -- your immediate assumption when something
weird happens with yaw is that the yaw control is to blame. Therein
lies the essence of the problem: RUDDER IS NOT THE YAW CONTROL AT LOW
SPEEDS IN A TAIL DRAGGER. :)
Andy
--
Andrew J. Ross NextBus Information Systems
Senior Software Engineer Emeryville, CA
[EMAIL PROTECTED] http://www.nextbus.com
"Men go crazy in conflagrations. They only get better one by one."
- Sting (misquoted)
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