From: raveling@Unify.com (Paul Raveling)
Newsgroups: rec.aviation
Subject: Re: Stay off the rudder!
Date: 8 Oct 92 20:01:57 GMT
Organization: Unify Corporation (Sacramento)

In article <1992Oct6.174556.22431@nntpd2.cxo.dec.com>, peterson@specxn.enet.dec.com (Harlo Peterson) writes:
> 
> In article <BvpE8E.361@access.digex.com>, stephens@access.digex.com
>  (John Stephens) writes...
> >In article <1992Oct5.161019.23694@nntpd2.cxo.dec.com>
> > peterson@specxn.enet.dec.com (Harlo Peterson) writes:
> >>
> >>
> >>Another way to look at what's happening is that turbulance is caused by wind
> >>gusts that may hit the plane from any direction.  The vertical component of
> >>the gust hits the bottom of the plane and will act to move the tail up or
> >>down.  This is countered with elevator control.  The horizontal
> >>component will move the tail sideways.  This is countered with rudder.
> >>A gust will not directly cause a rolling movement. ...
> >>
> >I diagree that "A gust will not directly cause a rolling movement."
> > ...
> >If you have never been tossed up on your ear (30-degree plus) roll, ...
> 
> To get a rolling movement directly requires different wind forces on each
> wing.  You can get this in certain cases such as in rotors or flying on the
> edge of a vertical gust.

	Or flying through the edge of a thermal.  This is more obvious
	in sailplanes, where wingspan is generally between 15 and 25 meters,
	than in light powered planes, which usual have a span of about
	a dozen meters.

	Sticking a wing into the core of a thermal can cause an
	uncontrollable roll.  In the worst examples in my own experience,
	the sailplane went from about a 45-degree bank to a 60-degree
	bank in the opposite direction before full aileron and full rudder
	could stop the roll.

	"Plain" turbulence is often on a much smaller scale, and gusts
	often have a highly local effect on particular flight surfaces.
	It's not unusual in good thermal soaring weather (unstable air)
	to feel as if someone else is wrestling you for the controls.

> In most cases though, the roll seen is the result
> of a gust caused yaw. Correcting the yaw does much more for recovery than
> trying to correct the roll.  In reality you do both.  What people do wrong
> though is trying to correct the effects of turbulance with aileron only.  It
> is better to be agressive with rudder as the primary control and use aileron
> to handle whats left.

	It's definitely worth giving more attention to rudder than
	most non-soaring power pilots do.  Part of the reason is that
	the rudder IS an effective tool for leveling the wings through
	yaw/roll cross-coupling, another part is that a coordinated high-rate
	roll requires a lot of rudder; if you apply A LOT of aileron
	without much rudder, the adverse yaw becomes substantial and it'll
	couple against the roll.  In the token powered acro lessons
	that I took in Citabrias and Aerobats, maximum roll rate came
	with both full aileron and full rudder.

	The ideal solution is to stay notoriously coordinated.  One of
	the reasons flying gliders contributes to power flying skills
	is that it's excellent rudder-consciousness conditioning.


------------------
Paul Raveling
Raveling@Unify.com