jsmith wrote

Dutch Roll

Maule Driver wrote:
When you do that fast and hold the nose on a point it's called a
??????,
isn't it. Can't remember the name of that damn manuever but my long
ago
glider instructor used to teach it. I think he just did it to sicken
the male pilots so he could spend more time with the coeds in this
college club but it was a challenge anyway.

From this web site: www. douglasdc3.com/sohn/41.htm

(1) One method would be while in straight and level flight to pick a
point on the horizon and enter a turn away

from it for some amount of turn and then, without stopping, reverse the
turn to pass through the original point

in the opposite direction, then again reverse the turn and so on, while
all the time coordinating the flight

controls (especially the rudder and ailerons). (2) Another variation or
method used is to pick a straight road

or a point on the horizon. Then precisely hold that point while
initiating a bank (takes opposite rudder), then

reverse the bank to an equal amount in the opposite direction. This is
repeated over and over while using the

flight controls to precisely maintain that point (especially the rudder
and ailerons). This variation especially

lends itself to getting the student ready for the aggressive use of the
rudder in acrobatic flight.

Evidently – to a certain number of instructors – the above aileron/rudder
coordination exercises (especially

#2, the one that holds the reference point) that we all give our new
students are called “dutch rolls”.

Well, we’ve got some news for you, chum! Those aren’t “dutch rolls”,
they’re simply plain old garden variety

“coordination exercises” or “coordination rolls”. And – undeniably –
they’re extremely useful for teaching

coordination or for quickly evaluating an aircraft’s handling qualities!
I’ve used them from the very first time

I took my first lesson in an Aeronca Champ right up until the present.
When we were aviation cadets in

“Bevo” Howard’s USAF T-6 school, we were taught them from the very first
day of our flight training. BUT

THOSE ARE NOT DUTCH ROLLS! You copy that? “Sorry Charlie” but no cigar,
those are NOT dutch

rolls! No big deal, you say? Well, OK, but you need to realize that
when you use an incorrect term it’s

teaching your student something completely wrong. It’s sort of like the
media using the term “Piper Cub” for every airplane less than a medium
sized jet. And – besides perpetrating a falsehood – it can later kill

him/her! And if you don’t think or realize that a dutch roll can easily
become lethal, look up the

Braniff/Boeing 707 (N-7071) flight training accident involving the
tossing of a couple of pylon mounted

engines off the wings in the fall of 1959.

And....from the Jeppesen Private Pilot Manual:

Dutch roll is a combination of rolling/yawing oscillations caused either
by your control input or by wind gusts.

Dutch roll will normally occur when the dihedral effects of an aircraft
are more powerful than the directional

stability. After a disturbance resulting in a yawing motion and sideslip,
the dihedral effect will tend to roll the

aircraft away from the direction of the initial yaw. However, due to weak
directional stability, the rolling

movement may overshoot the level position and reverse the sideslip. This
motion continues to repeat, creating

an oscillation that can be felt by the pilot as side-to-side wagging of
the aircraft's tail. If Dutch roll tendency is

not effectively dampened, it is considered objectionable.

The alternative to an airplane that exhibits Dutch roll tendencies is a
design that has better directional

stability than lateral stability. If directional stability is increased
and lateral stability is decreased, the Dutch

roll motion is adequately suppressed. However, this design arrangement
tends to cause spiral instability.