Dutch rolls

Cub Driver wrote:

Gilmore, alone, also entered the fray but was quickly latched onto by a Zero
he
shook off with a series of Dutch rolls

What is a Dutch roll in this context? It's usually applied to
oscillations that can't be damped out, as in the Northrop YB-49 Flying
Wing bomber. I can't visualize it as a deliberate maneuver in combat.

From Civil Aeronautics Bulletin No.23, September, 1941:

"Constant-heading slips are sometimes mistakenly called Dutch rolls, but they
are not the same as the natural aerodynamic Dutch roll oscillations discussed
in section 10.6.1. Both involve slipping to one side and then the other, like a
Dutch kid on skates, making a series of slips (left, right, left, right)
without much change in ``direction'', depending on what you mean by
``direction''. But note the differences:

Natural aerodynamic Dutch roll oscillations change the heading, with
more-or-less unchanging direction of motion.
Constant-heading slips change the direction of motion, with unchanging
heading."





Chris Mark

seems an awful long way to go to get something for breakfast ! lol
"Chris Mark" wrote in message
...
Cub Driver wrote:

Gilmore, alone, also entered the fray but was quickly latched onto by a
Zero
he
shook off with a series of Dutch rolls

What is a Dutch roll in this context? It's usually applied to
oscillations that can't be damped out, as in the Northrop YB-49 Flying
Wing bomber. I can't visualize it as a deliberate maneuver in combat.

From Civil Aeronautics Bulletin No.23, September, 1941:

"Constant-heading slips are sometimes mistakenly called Dutch rolls, but
they
are not the same as the natural aerodynamic Dutch roll oscillations
discussed
in section 10.6.1. Both involve slipping to one side and then the other,
like a
Dutch kid on skates, making a series of slips (left, right, left, right)
without much change in ``direction'', depending on what you mean by
``direction''. But note the differences:

Natural aerodynamic Dutch roll oscillations change the heading, with
more-or-less unchanging direction of motion.
Constant-heading slips change the direction of motion, with unchanging
heading."





Chris Mark

Constant-heading slips change the direction of motion, with unchanging
heading."

What makes this a combat maneuver? Is the apparent change of heading
meant to confuse the attacking aircraft? (The attacker thinks he's
jinking right & left?)

Thanks!



all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! blog www.vivabush.org

"Cub Driver" wrote in message
...

Constant-heading slips change the direction of motion, with unchanging
heading."

What makes this a combat maneuver? Is the apparent change of heading
meant to confuse the attacking aircraft? (The attacker thinks he's
jinking right & left?)

Thanks!

I think the surface Navy calls it 'sinuating.'
Confuses the guy aiming the torpedoes.

JK

"Cub Driver" wrote in message
...

Constant-heading slips change the direction of motion, with unchanging
heading."

What makes this a combat maneuver? Is the apparent change of heading
meant to confuse the attacking aircraft? (The attacker thinks he's
jinking right & left?)

Thanks!


I've been thinking about this, and although I'm far from being an authority
on air combat, I can't see dutch rolls being a beneficial combat manoeuvre
in the slightest. Even though the aircraft is oscillating in yaw and pitch
the track heading remains the same, so surely it's straight forward to get
shots on target?



all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! blog www.vivabush.org

"Jim Knoyle" wrote in message ...
"Cub Driver" wrote in message
...

Constant-heading slips change the direction of motion, with unchanging
heading."
What makes this a combat maneuver? Is the apparent change of heading
meant to confuse the attacking aircraft? (The attacker thinks he's
jinking right & left?)
Thanks!
I think the surface Navy calls it 'sinuating.'
Confuses the guy aiming the torpedoes.
JK

Dutch Roll, on purpose - use ailerons to roll the airplane from side
to side while using coarse rudder to yaw the nose in the direction of
roll. (Sort of a reverse to a falling leaf maneuver.) The aircraft
tail describes a horizontal figure eight, size depending on pilot's
energy. Accidentally - some aircraft will do this by themselves if
given the right conditions. (707/KC135 on final following gross use
of aileron to correct heading; F102 with a failed yaw damper at
transsonic speeds.) This maneuver can give problems to a fighter not
right on one's tail. The lead required to hit a crossing target is
generally quite underestimated by inexperienced gunners. Also, IMHO
the Zero pilots generally used the MGs to determine proper lead by
hitting the target - then brought in the 20 mms. No doubt the pilot in
question jinked wildly and irregularly and his pursuer didn't close in
for a kill so obviously the maneuver worked.
Walt BJ

From: (WaltBJ)

Dutch Roll, on purpose - use ailerons to roll the airplane from side
to side while using coarse rudder to yaw the nose in the direction of
roll. (Sort of a reverse to a falling leaf maneuver.) The aircraft
tail describes a horizontal figure eight, size depending on pilot's
energy. Accidentally - some aircraft will do this by themselves if
given the right conditions. (707/KC135 on final following gross use
of aileron to correct heading; F102 with a failed yaw damper at
transsonic speeds.) This maneuver can give problems to a fighter not
right on one's tail. The lead required to hit a crossing target is
generally quite underestimated by inexperienced gunners. Also, IMHO
the Zero pilots generally used the MGs to determine proper lead by
hitting the target - then brought in the 20 mms. No doubt the pilot in
question jinked wildly and irregularly and his pursuer didn't close in
for a kill so obviously the maneuver worked.
Walt BJ

That probably nails it.
The pilot in question, Edwin Gilmore, earned his wings in 1940, flew P-26As
before transitioning to P-35As. He had been flying P-40Bs for several months
when the combat in question happened. His flight leader was Joe Moore, in
later years CO of the 4th Tactical Fighter Wing. Moore, Gilmore and Randall
Keator scrambled from Clark, intercepted 9 Zeros of the Tainan Kokutai, led by
Sachio Maki. Moore attacked Maki and Maki's wingman, Yoshio Hirose, came after
Moore. Keator shot down Hirose, killing him, as confirmed after the war, and
then the whole Zero formation, according to Gilmore, "exploded like a covey of
quail" and the P-40Bs became definitely on the defensive, but none were shot
down or even hit (although Gilmore thought that he had been during the fight).
Gilmore on a later date shot down a Zero directly over Del Carmen Field. He
went with a group of other pilots to Australia at the end of the month to
collect more P-40s to bring back to the Philippines, but they were diverted to
Java. After being driven out of there, he helped out in Australia for a while,
briefing incoming crews on what to expect from the Japanese, returned to the
States to a training command, then did a second tour in the MTO.


Chris Mark

On Fri, 14 May 2004 17:21:39 +0100, "Jim Doyle"
wrote:

I've been thinking about this, and although I'm far from being an authority
on air combat, I can't see dutch rolls being a beneficial combat manoeuvre
in the slightest. Even though the aircraft is oscillating in yaw and pitch
the track heading remains the same, so surely it's straight forward to get
shots on target?

Dutch roll is an unavoidable dynamic response, not a desirable
maneuver. It's no more useful than the phugoid. And no more
intentional.

Mary

--
Mary Shafer Retired aerospace research engineer

Dutch roll is an unavoidable dynamic response, not a desirable
maneuver. It's no more useful than the phugoid. And no more
intentional.

I think what we have here is two different terms with the same name.
Flight instructors call for a "Dutch roll" when they want to see how
the (unfamiliar) student handles the controls. When asked, I just
cross-control at fixed intervals. It seemed and seems pointless to me,
which is why I asked the question about its use in combat.

I once edited Glen Edwards's diaries for a book, which is where I
first heard the term. His successor as head of the YB-49 project at
Muroc (later Edwards) told me how the bombardier would get seasick on
the Flying Wing because of Dutch roll, which is the sense you are
using it.

Over on rec.aviation.piloting they recently argued about this, and
everyone attributed the term to nautical use (wave abaft the beam,
very sick-making). But no sailor I've talked to is familiar with it.

Thanks for all the responses, everybody!

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! blog www.vivabush.org

Dutch roll is an unavoidable dynamic response, not a desirable
maneuver. It's no more useful than the phugoid. And no more
intentional.

You've never seen Dutch roll til you've seen it at high Mach. Quite
disconcerting @ 1.75 (at this speed, we're supposed to be going straight,
eh?).

On the subject of instability, what was the aerodynamic cause of the X-2's
departure and crash? Adverse yaw + minimal directional stability?

R / John