Coordinated turns without rudder, and autopilots

"Dan" wrote in message
ups.com...
On May 28, 10:26 am, Andrew Sarangan wrote:
On May 28, 11:59 am, Luke Skywalker wrote:





On May 28, 8:11 am, Ron Natalie wrote:

Dan wrote:
On May 27, 5:44 pm, Mxsmanic wrote:
How do autopilots make coordinated turns even when they cannot
control the
rudder?

If they don't control the rudder, they do not make coordinated
turns!

--Dan

Boy we have the blind leading the blind here.

The whole point of that big vertical slab of metal sticking out of
the
ass-end of your airplane is to provide a natural tendency for the
aircraft to fly coordinated. The pedals are just there for the
outlying conditions (low speed, high AOA for example) and fine
adjustment.

Ron...

oh my goodness...get some time with a good book on the subject and
then a CFI.

Robert- Hide quoted text -

Ron is correct. The vertical fin makes the airplane weather-vane into
the wind, and that's what co-ordination is all about. The rudder is
there only to help the vertical stab do this job.

A perfect airplane will not need rudder.- Hide quoted text -

- Show quoted text -

So where is this perfect airplane? I don't know about you, but I need
the rudder pedals to fly the aircraft.

--Dan

Basically the vertical stabilizer is there for directional stability and to
control yaw; the rudder is there to change yaw. This is VERY basic, but you
can say that the rudder is there to keep the tail alligned with the nose
:-))
Rudder use to acheive the objective of keeping the tail lined up with the
nose can accurately be said to be relative to aircraft type and airspeed.
You need a fair amount of rudder to handle yawfor example in a typical light
general aviation type airplane to execute a coordinated turn entry and exit.
On the other hand however, in a T38, you can fly a complete aerobatic
sequence including point rolls with both feet planted firmly on the floor of
the rudder tunnels.
Dudley Henriques

Mxsmanic wrote
How do autopilots make coordinated turns even when they cannot control
the rudder?

From Wikipedia, the free encyclopedia

An unwanted side-effect of aileron operation is adverse yaw — a yawing
moment in the opposite direction to the turn generated by the ailerons. In
other words, using the ailerons to roll an aircraft to the right would
produce a yawing motion to the left. It is caused by an increase in induced
drag due to the greater effective camber of the wing with a downward-
deflected aileron, and the opposite effect on the other wing. Modern
aileron systems have minimal adverse yaw, such that it is barely noticeable
in most turns. This may be accomplished by the use of differential
ailerons, which have been rigged such that the downgoing aileron deflects
less than the upward-moving one. Frise ailerons achieve the same effect by
protruding beneath the wing of an upward deflected aileron, increasing drag
on that side. Ailerons may also use a combination of these methods.

Bob Moore

Andrew Sarangan wrote:
On May 28, 11:59 am, Luke Skywalker wrote:
On May 28, 8:11 am, Ron Natalie wrote:





Dan wrote:
On May 27, 5:44 pm, Mxsmanic wrote:
How do autopilots make coordinated turns even when they cannot control the
rudder?
If they don't control the rudder, they do not make coordinated turns!
--Dan
Boy we have the blind leading the blind here.
The whole point of that big vertical slab of metal sticking out of the
ass-end of your airplane is to provide a natural tendency for the
aircraft to fly coordinated. The pedals are just there for the
outlying conditions (low speed, high AOA for example) and fine
adjustment.
Ron...

oh my goodness...get some time with a good book on the subject and
then a CFI.

Robert- Hide quoted text -



Ron is correct. The vertical fin makes the airplane weather-vane into
the wind, and that's what co-ordination is all about. The rudder is
there only to help the vertical stab do this job.

A perfect airplane will not need rudder.

Not true. The vertical fin can only provide a weather-vane affect when
a slip or skid has been induced. In coordinated flight there is no slip
or skid and hence the fin provides no lateral force. When you begin a
turn, most airplanes will induce adverse yaw and the rudder can counter
than before a skid occurs. The fixed fin can only act once an
uncoordinated condition has been induced. Sure, it does mitigate the
skid or slip, but it absolutely can't prevent it as it can't provide a
force until uncoordinated flight is already established. The rudder can
do this and is why it is included.

The rudder isn't there to help the vertical stab do its job, it is there
to do a job that the vertical stab can't do.


Matt

On May 28, 12:26 pm, Andrew Sarangan wrote:
On May 28, 11:59 am, Luke Skywalker wrote:





On May 28, 8:11 am, Ron Natalie wrote:

Dan wrote:
On May 27, 5:44 pm, Mxsmanic wrote:
How do autopilots make coordinated turns even when they cannot control the
rudder?

If they don't control the rudder, they do not make coordinated turns!

--Dan

Boy we have the blind leading the blind here.

The whole point of that big vertical slab of metal sticking out of the
ass-end of your airplane is to provide a natural tendency for the
aircraft to fly coordinated. The pedals are just there for the
outlying conditions (low speed, high AOA for example) and fine
adjustment.

Ron...

oh my goodness...get some time with a good book on the subject and
then a CFI.

Robert- Hide quoted text -

Ron is correct. The vertical fin makes the airplane weather-vane into
the wind, and that's what co-ordination is all about. The rudder is
there only to help the vertical stab do this job.

A perfect airplane will not need rudder.- Hide quoted text -

- Show quoted text -

No he is not. Mark W...said the word.

Robert

On May 27, 7:44 pm, Mxsmanic wrote:
How do autopilots make coordinated turns even when they cannot control the
rudder?

As others have posted, most lightplane autopilots don't adjust the
rudder for adverse yaw when turning, so you do get a few seconds of
slightly uncoordinated flight. However at normal cruise speeds this
creates no hazard or discomfort.

If flying close to stall, the autopilot should be turned off even for
straight and level flight. If the airplane is on the verge of
stalling and starts to turn because of engine p-factor or any other
reason, the autopilot will attempt to correct with aileron. This may
actually induce stall on one wing, producing sudden wing drop and a
potential spin.

Dan writes:

So where is this perfect airplane? I don't know about you, but I need
the rudder pedals to fly the aircraft.

But autopilots apparently do not, and that's what puzzles me.

Dudley Henriques writes:

Rudder use to acheive the objective of keeping the tail lined up with the
nose can accurately be said to be relative to aircraft type and airspeed.
You need a fair amount of rudder to handle yawfor example in a typical light
general aviation type airplane to execute a coordinated turn entry and exit.

So how does the autopilot do it? As far as I understand, autopilots in small
aircraft don't generally have control over the rudder, and yet they can
execute coordinated turns.

John Theune writes:

What makes you think they do not control the rudder?

The absence of rudder movement, and the expense of providing servos for the
rudder as well as the ailerones. It's possible that autopilots on transport
aircraft do control the rudder, but the small ones for small aircraft
apparently do not.

Bob Moore writes:

Swept wing and some straight wing aircraft have independent Yaw Damper(s)
that control the rudder(s). Their primary function is to control (prevent)
dutch roll. They operate with the autopilot on or off.

I'm thinking along the lines of small aircraft such as a C172 or Baron. They
do not have AP control of the rudder, and yet the AP can still execute
coordinated turns.

Bob Moore writes:

An unwanted side-effect of aileron operation is adverse yaw — a yawing
moment in the opposite direction to the turn generated by the ailerons. In
other words, using the ailerons to roll an aircraft to the right would
produce a yawing motion to the left. It is caused by an increase in induced
drag due to the greater effective camber of the wing with a downward-
deflected aileron, and the opposite effect on the other wing. Modern
aileron systems have minimal adverse yaw, such that it is barely noticeable
in most turns. This may be accomplished by the use of differential
ailerons, which have been rigged such that the downgoing aileron deflects
less than the upward-moving one. Frise ailerons achieve the same effect by
protruding beneath the wing of an upward deflected aileron, increasing drag
on that side. Ailerons may also use a combination of these methods.

Except I do see adverse yaw in turns in my (simulated) Baron, so either the
simulation is in error, or the AP knows something about making coordinated
turns without rudder input that I do not.