Dutch roll coordination technique

There is a co-ordination exercise called Dutch Roll. The idea is to rapidly
roll the plane from zero to +nn degress to -nn degrees without stoping at
zero then back to zero while keeping the nose fixed at a point on the
horizon. When doing this correctly are the rudder and ailerons co-ordinated
or opposite? Why?

On Thu, 01 Jan 2004 14:58:41 GMT, "Matthew Jurotich"
wrote:

There is a co-ordination exercise called Dutch Roll. The idea is to rapidly
roll the plane from zero to +nn degress to -nn degrees without stoping at
zero then back to zero while keeping the nose fixed at a point on the
horizon. When doing this correctly are the rudder and ailerons co-ordinated
or opposite? Why?

Coordinated. The wing isn't banked enough to actually start a turn,
and your rudder is mostly correcting adverse yaw when doing things
that quickly.

I've tried it. The maneuver (which I'm told is misnamed, there's
another aerobatic maneuver which is apparantly properly called a Dutch
Roll) is coordinated. I thought it was cross-controlled until I
actually tried it.

Rob

"Matthew Jurotich" wrote

There is a co-ordination exercise called Dutch Roll. The idea is to
rapidly roll the plane from zero to +nn degress to -nn degrees without
stoping at zero then back to zero while keeping the nose fixed at a
point on the horizon. When doing this correctly are the rudder and
ailerons co-ordinated or opposite? Why?

From William Kershner's "The Flight Instructor's Manual"

"Have the student line up with a good reference on the horizon
and roll the airplane from bank to bank, keeping the nose pinned
on the reference. For instance, have the student start (with the
nose lined up with the reference) by using left aileron and left
rudder, as in starting a turn. Before the nose has a chance to
move he should use right rudder so that the point is held. Then
he applies right aileron and more right rudder to roll the airplane
to the right, stopping any turn tendency with opposite (left)
rudder, and so on.
Elevators are part of the exercise and the altitude should stay
within 100 ft of the starting value.
You can also use the coordination exercise at lower airspeeds
(you set the power and trim the airplane) so that the student
can see the effects of adverse yaw, particularly in slow flight.
Again, don't have long sessions of this exercise and be prepared
for some wild swingings of the nose when he first does the
maneuver (and maybe later, too).
And, for Pete's sake, don't call this maneuver a "Dutch roll."
Dutch roll, a stability and control term, is a condition of a
coupling of lateral-directional oscillations with the nose yawing
as the airplane rolls from bank to bank; the object here is to
keep the nose on the point."

Bob Moore
ATP CFI

Read, Stick And Rudder... Wolfgang Langewiesche

Denny

Matthew Jurotich" wrote in

When doing this correctly are the rudder and ailerons co-ordinated
or opposite? Why?

The proper use of the term "Dutch Roll" applies to a characteristic of
the lateral stability of an aircraft, inherent in all aircraft but
thoroughly investigated during the test flight and certification stage.
The manoeuvre can be seen by simply letting go of the stick in trimmed
level flight and yawing the aircraft. Ideally one would provide one yaw
impulse and then let the aircraft return itself to steady flight while
observing the dynamics of the recovery (how many oscillations, damping
etc.) but it is possible to keep the manoeuvre going by alternating the
impulse on the rudder pedals with each change in yaw direction.

Note that I have only mentioned the rudder above. This manoeuvre does
not involve aileron input. In fact a pilot could get himself into
trouble by trying to correct with aileron input and could produce
amplified pilot induced oscillations.

The dynamics are as follows:
With the first rudder input comes a yaw impulse. This causes the
opposite wing (starboard wing if port rudder input) to swing forward -
gaining a few knots (and lift) - and the other wing to swing back -
losing a few knots. This is why the aircraft seems to roll during the
yaw. If the pilot keeps alternating the rudder inputs this will cause an
oscillating yaw condition. Looking at the wing tip you would see it
describing an ellipse on the horizon. The way to stop this motion is not
to fight it. Simply ceasing control input will rapidly stabilise the
aircraft, remember that aircraft are designed to be laterally stable (in
most cases), loosing part of the tailplane or rudder could make this a
problem. Trying to fight the motion with control inputs will only
prolong the motion at best, and amplify it at worst. Your natural
instinct to correct in a particular direction with aileron is working
against you because at the point that you feel you should correct is the
point where the factors influencing the motion are changing direction
and you are now only adding to them. If a pilot got caught out he could
stall one wing tip while overcorrecting and end up in a spiral or even
spin. Unlikely but possible.

Incidentally this manoeuvre is best experienced in the tail of the
aircraft. The pilots are usually near the wing junction and as such are
on the centre line of a helix that the the passengers in the rear of the
fuselage are following.


Dennis O'Connor wrote:
Read, Stick And Rudder... Wolfgang Langewiesche

Denny

Matthew Jurotich" wrote in

When doing this correctly are the rudder and ailerons co-ordinated

or opposite? Why?

The proper use of the term "Dutch Roll" applies to a characteristic of
the lateral stability of an aircraft, i

One of the more famous aircraft subject to Dutch Roll was the Northrop
YB-49 turbojet Flying Wing bomber. The military test pilot Robert
Cardenas (who took over the project after Glen Edwards was killed)
recalled that the bombardier used to get seasick from the
oscillations.

(The YB-49 is cited as the predecessor of the B-2 Spirit stealth
bomber, because it was from Northrop and had the identical span. In
fact, the B-2 more closely suggests the German "nurflugel" designed by
the Horten brothers. www.warbirdforum.com/edwards.htm )


all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

Cub Driver wrote:
The proper use of the term "Dutch Roll" applies to a characteristic of
the lateral stability of an aircraft, i


One of the more famous aircraft subject to Dutch Roll was the Northrop
YB-49 turbojet Flying Wing bomber. The military test pilot Robert
Cardenas (who took over the project after Glen Edwards was killed)
recalled that the bombardier used to get seasick from the
oscillations.

(The YB-49 is cited as the predecessor of the B-2 Spirit stealth
bomber, because it was from Northrop and had the identical span. In
fact, the B-2 more closely suggests the German "nurflugel" designed by
the Horten brothers. www.warbirdforum.com/edwards.htm )


all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

Yup I would definately believe that. The lateral stability in those
tail-less designs was achieved through wing sweep rather than the usual
vertical fin. I would imagine that they had interesting spin
characteristics as well, although I don't remember it being mentioned
anywhere. The father of flying wing / tail-less designs was Alexander
Lippish.

I would imagine that they had interesting spin
characteristics as well,

I think it was Eric Brown who wrote about flying the British all-wing
aircraft, and having it almost rotate backward on him.

This is probably exactly what happened to the YB-49 that crashed near
Muric (now Edwards AFB) killing the pilot Danny Forbes, co-pilot Glen
Edwards, and the crew.

There are two files on the Warbird's Forum consisting of interviews
with Robert Cardenas, the military test pilot after Edwards, and a
very different view from Northrop test pilot Charlie Tucker
www.warbirdforum.com/edwards.htm


all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

"Matthew Jurotich" wrote in message .. .
There is a co-ordination exercise called Dutch Roll. The idea is to rapidly
roll the plane from zero to +nn degress to -nn degrees without stoping at
zero then back to zero while keeping the nose fixed at a point on the
horizon. When doing this correctly are the rudder and ailerons co-ordinated
or opposite? Why?

Matthew
I think this one has been debated for as long as I have been flying
(1950's) I was taught a "Dutch Roll" in a Piper J-3 by an instructor
with 6 digits in his license number. Put nose on a point, add aileron
and use rudder to hold the nose on point. When you reach the maximum
of rudder vs aileron and still hold the point, ease out one or other
until you reach level coordinated flight, then repeat to the opposite
side. Altitude hold is of course required.
Anyone who thinks this does not require coordination is not paying
attention. I have taught this to a myriad of pilots over the course of
my aviation career. Nearly any taildragger pilot uses the technique
either conciously or otherwise while making a landing.
Some have labeled it a forward slip and pooh poo its use for cross
wind landings
and prefer the crab type approach with a "kick out" at touchdown.
Damned if I can see how that can be done with consistency regardless
of aircraft. It has never worked for me in spite of thousands of hours
trying it. Note: thousands of hours in a log book do not mean jack
@#*& if its all flying straight and level on autopilot and at
altitude. My experience has been in the lowest reaches of the airspace
system for the most part and at about 3'agl.
I will contend the "Dutch Roll", use of aileron vs rudder to prevent a
turn, is the most valuable coordination exercise ever developed to
train and hone a pilot in the use of each.
Each time I get into a different airplane, I will try the dutch roll
to see how the aircraft is rigged and see what the limits of the
aileron/rudder are for that particular aircraft. When it comes time
for a cross wind landing in that airplane I'm not faced with any
surprises or lack of control on one axis.
Ah what the hell do I know after 12,000 hours crop dusting.....
Ol Shy & Bashful