Myth: 1 G barrel rolls are impossible.

Jim Logajan wrote:
Mxsmanic wrote:
Jim Logajan writes:

Most everyone agrees that keeping the coffee in the cup is possible.
What some people don't seem to believe is possible is that the force
felt by the pilot (or tea/coffee) can be 1 gee during the entire
roll. They believe it has to vary during the roll. I'm hesitant to
name names. ;-)
It has to vary during the roll, because the constant 1 G acceleration
due to gravity does not change. The net acceleration of the aircraft
must always be at least one G in consequence, and if the aircraft
begins a climb or ends a descent, it _must_ be greater than +1.0 G.

Sigh. Yes, the force that is felt is greater then one g-force at the
beginning and end of the maneuver. But that is not the case "during the
roll" itself. Again, as in the other post of yours I responded to, you
appear to be confusing force and acceleration.

Well, if you can't begin and end the roll, then you can't do a roll.
Arguing that you can omit these phases of the roll is simply silly.
That is like saying that you can do a spin without stalling since
stalling is just the entrance to the spin, not the spin itself.

Matt

On Mon, 11 Jun 2007 22:24:02 -0000, Jim Logajan
wrote:

Mxsmanic wrote:
Jim Logajan writes:

Most everyone agrees that keeping the coffee in the cup is possible.
What some people don't seem to believe is possible is that the force
felt by the pilot (or tea/coffee) can be 1 gee during the entire
roll. They believe it has to vary during the roll. I'm hesitant to
name names. ;-)

It has to vary during the roll, because the constant 1 G acceleration
due to gravity does not change. The net acceleration of the aircraft
must always be at least one G in consequence, and if the aircraft
begins a climb or ends a descent, it _must_ be greater than +1.0 G.

Sigh. Yes, the force that is felt is greater then one g-force at the
beginning and end of the maneuver. But that is not the case "during the
roll" itself. Again, as in the other post of yours I responded to, you
appear to be confusing force and acceleration.

Not a serious confusion, as force and acceleration are stricly
proportional (F=mA) as long as the mass of the object (plane) is not
changing. Over the time intervals involved, not enough fuel is burned
to significantly change the mass. Now, if the pilot scares the s--t
out of himself during the manouver, then the proportionality might not
hold up. :-)
---
Jay (remove dashes for legal email address)

Mxsmanic wrote in
:

Jim Logajan writes:

Most everyone agrees that keeping the coffee in the cup is possible.
What some people don't seem to believe is possible is that the force
felt by the pilot (or tea/coffee) can be 1 gee during the entire
roll. They believe it has to vary during the roll. I'm hesitant to
name names. ;-)

It has to vary during the roll, because the constant 1 G acceleration
due to gravity does not change. The net acceleration of the aircraft
must always be at least one G in consequence, and if the aircraft
begins a climb or ends a descent, it _must_ be greater than +1.0 G.

You're an idiot and you will never ever do a barrel roll.

Bertie

On Jun 11, 12:54 pm, Mxsmanic wrote:
Jim Logajan writes:
Most everyone agrees that keeping the coffee in the cup is possible. What
some people don't seem to believe is possible is that the force felt by the
pilot (or tea/coffee) can be 1 gee during the entire roll. They believe it
has to vary during the roll. I'm hesitant to name names. ;-)

It has to vary during the roll, because the constant 1 G acceleration due to
gravity does not change. The net acceleration of the aircraft must always be
at least one G in consequence, and if the aircraft begins a climb or ends a
descent, it _must_ be greater than +1.0 G.

You are assuming that the center of the roll makes a straight line,
that is not the case.

-Robert

Robert M. Gary writes:

You are assuming that the center of the roll makes a straight line,
that is not the case.

I'm making no such assumption.

The reality is that there will always be an acceleration of 1 G imposed on the
aircraft, in the direction of the ground. There is nothing that you can do in
an aircraft that will eliminate this acceleration, and there is nothing you
can do in an aircraft that changes its height above the ground or its path
over the ground that will not introduce additional acceleration. This is all
basic physics.

Jim Logajan wrote
Most everyone agrees that keeping the coffee in the cup is possible.
What some people don't seem to believe is possible is that the force
felt by the pilot (or tea/coffee) can be 1 gee during the entire roll.
They believe it has to vary during the roll. I'm hesitant to name
names. ;-)

My name is Bob Moore :-)

Just what is a barrel roll has been debated between "Big John", Dudley,
and myself at least twice in the past. It IS difficult to describe
without having a model airplane in one's hand and flying it through the
maneuver.

How come you don't seem to belive the following from Wikipedia?

Barrel roll
From Wikipedia, the free encyclopedia

This article is about the aerial sport. For the military operation, see
Operation Barrel Roll.
A barrel roll occurs when an object (usually an airplane or roller coaster)
makes a complete rotation on its longitudinal axis while following a
helical path, approximately maintaining its original direction. The G load
is kept positive (but not constant) on the aircraft throughout the
maneuver, commonly not more than 2-3 G.

In aviation, the maneuver includes a constant variation of attitude in all
three axes, and at the midpoint (top) of the roll, the aircraft is flying
inverted, with the nose pointing at a 90-degree angle ("sideways") to the
general path of flight. The term "barrel roll" is frequently used,
incorrectly, to refer to any roll by an airplane (see aileron roll), or to
a helical roll in which the nose remains pointed generally along the flight
path. In fact, the barrel roll is a specific and difficult maneuver; a
combination of a roll and a loop. It is not used in aerobatic competition.

From:
http://acro.harvard.edu

The Barrel Roll is a not competition maneuver. The barrel roll is a
combination between
a loop and a roll. You complete one loop while completing one roll at the
same time.
The flight path during a barrel roll has the shape of a horizontal cork
screw. Imagine a big
barrel, with the airplanes wheels rolling along the inside of the barrel in
a cork screw path.
During a barrel roll, the pilot experiences always positive G's. The
maximum is about 2.5 to
3 G, the minimum about 0.5 G.

"Bob Moore" wrote in message
46.128...
My name is Bob Moore :-)

Just what is a barrel roll has been debated between "Big John", Dudley,
and myself at least twice in the past. It IS difficult to describe
without having a model airplane in one's hand and flying it through the
maneuver.

How come you don't seem to belive the following from Wikipedia?

Barrel roll
From Wikipedia, the free encyclopedia

This article is about the aerial sport. For the military operation, see
Operation Barrel Roll.
A barrel roll occurs when an object (usually an airplane or roller
coaster)
makes a complete rotation on its longitudinal axis while following a
helical path, approximately maintaining its original direction. The G load
is kept positive (but not constant) on the aircraft throughout the
maneuver, commonly not more than 2-3 G.

In aviation, the maneuver includes a constant variation of attitude in all
three axes, and at the midpoint (top) of the roll, the aircraft is flying
inverted, with the nose pointing at a 90-degree angle ("sideways") to the
general path of flight. The term "barrel roll" is frequently used,
incorrectly, to refer to any roll by an airplane (see aileron roll), or to
a helical roll in which the nose remains pointed generally along the
flight
path. In fact, the barrel roll is a specific and difficult maneuver; a
combination of a roll and a loop. It is not used in aerobatic competition.

From:
http://acro.harvard.edu

The Barrel Roll is a not competition maneuver. The barrel roll is a
combination between
a loop and a roll. You complete one loop while completing one roll at the
same time.
The flight path during a barrel roll has the shape of a horizontal cork
screw. Imagine a big
barrel, with the airplanes wheels rolling along the inside of the barrel
in
a cork screw path.
During a barrel roll, the pilot experiences always positive G's. The
maximum is about 2.5 to
3 G, the minimum about 0.5 G.


Then would you label the roll that Jim has described here as a form of
aileron roll, instead of a barrel roll? Or do you think it is possible to
do a 1g aileron roll?

"Maxwell" wrote in
:


"Bob Moore" wrote in message
46.128...
My name is Bob Moore :-)

Just what is a barrel roll has been debated between "Big John",
Dudley, and myself at least twice in the past. It IS difficult to
describe without having a model airplane in one's hand and flying it
through the maneuver.

How come you don't seem to belive the following from Wikipedia?

Barrel roll
From Wikipedia, the free encyclopedia

This article is about the aerial sport. For the military operation,
see Operation Barrel Roll.
A barrel roll occurs when an object (usually an airplane or roller
coaster)
makes a complete rotation on its longitudinal axis while following a
helical path, approximately maintaining its original direction. The G
load is kept positive (but not constant) on the aircraft throughout
the maneuver, commonly not more than 2-3 G.

In aviation, the maneuver includes a constant variation of attitude
in all three axes, and at the midpoint (top) of the roll, the
aircraft is flying inverted, with the nose pointing at a 90-degree
angle ("sideways") to the general path of flight. The term "barrel
roll" is frequently used, incorrectly, to refer to any roll by an
airplane (see aileron roll), or to a helical roll in which the nose
remains pointed generally along the flight
path. In fact, the barrel roll is a specific and difficult maneuver;
a combination of a roll and a loop. It is not used in aerobatic
competition.

From:
http://acro.harvard.edu

The Barrel Roll is a not competition maneuver. The barrel roll is a
combination between
a loop and a roll. You complete one loop while completing one roll at
the same time.
The flight path during a barrel roll has the shape of a horizontal
cork screw. Imagine a big
barrel, with the airplanes wheels rolling along the inside of the
barrel in
a cork screw path.
During a barrel roll, the pilot experiences always positive G's. The
maximum is about 2.5 to
3 G, the minimum about 0.5 G.


Then would you label the roll that Jim has described here as a form of
aileron roll, instead of a barrel roll? Or do you think it is
possible to do a 1g aileron roll?

It's less of a roll than it is a loop.


In fact, that's how I used to teach it. Get a hula hoop, cut it and pull
the ends apart. you are now looking at the path of a barrel roll. A
skewed loop


Bertie

Bob Moore wrote:
Jim Logajan wrote
Most everyone agrees that keeping the coffee in the cup is possible.
What some people don't seem to believe is possible is that the force
felt by the pilot (or tea/coffee) can be 1 gee during the entire
roll. They believe it has to vary during the roll. I'm hesitant to
name names. ;-)

My name is Bob Moore :-)

Hi Bob. Glad you could make it to B.R.A. (Barrel Rollers Anonymous.) :-)

Just what is a barrel roll has been debated between "Big John",
Dudley, and myself at least twice in the past. It IS difficult to
describe without having a model airplane in one's hand and flying it
through the maneuver.

How come you don't seem to belive the following from Wikipedia?

You know what is odd? The flight path of the maneuver I wrote about
appears to violate the Harvard definition you quote (it can't be done in
a straight horizontal path - my corkscrew/helical path must follow a
parabolic arc) but oddly the Wikipedia definition leaves me a big "out."
Straight down. ;-)

Drop the nose straight down so as to make the plane & pilot weightless.
Then start doing horizontal loops so the centrifugal force yields the
equivalent of one gravity of weight. At least the longitudinal axis of
the helical path will maintain a constant direction - but the pilot will
quickly be screwed. :-)

Barrel roll
From Wikipedia, the free encyclopedia

This article is about the aerial sport. For the military operation,
see Operation Barrel Roll.
A barrel roll occurs when an object (usually an airplane or roller
coaster) makes a complete rotation on its longitudinal axis while
following a helical path, approximately maintaining its original
direction. The G load is kept positive (but not constant) on the
aircraft throughout the maneuver, commonly not more than 2-3 G.

In aviation, the maneuver includes a constant variation of attitude in
all three axes, and at the midpoint (top) of the roll, the aircraft is
flying inverted, with the nose pointing at a 90-degree angle
("sideways") to the general path of flight. The term "barrel roll" is
frequently used, incorrectly, to refer to any roll by an airplane (see
aileron roll), or to a helical roll in which the nose remains pointed
generally along the flight path. In fact, the barrel roll is a
specific and difficult maneuver; a combination of a roll and a loop.
It is not used in aerobatic competition.

From:
http://acro.harvard.edu

The Barrel Roll is a not competition maneuver. The barrel roll is a
combination between
a loop and a roll. You complete one loop while completing one roll at
the same time.
The flight path during a barrel roll has the shape of a horizontal
cork screw. Imagine a big
barrel, with the airplanes wheels rolling along the inside of the
barrel in a cork screw path.
During a barrel roll, the pilot experiences always positive G's. The
maximum is about 2.5 to
3 G, the minimum about 0.5 G.

Jim Logajan writes:

Drop the nose straight down so as to make the plane & pilot weightless.
Then start doing horizontal loops so the centrifugal force yields the
equivalent of one gravity of weight.

The total force on the aircraft will still be above 1 G unless the entire loop
is in free fall.