Myth: 1 G barrel rolls are impossible.

In article ,
says...
Dave Doe wrote:

To put it another way, if you closed your eyes, you wouldn't know you've
done a roll (given you go for the 'non-standard' 1G roll), other than
the initial sensation of beginning the turn, and then the sensation of
the turn stopping.


Not sure exactly where you are with this, but as what you are saying
pertains to barrel rolls begun from level flight or from a position with
the nose below the horizon, don't forget that the entire gist of the
misunderstanding that has been running rampant on this thread about
barrel rolls and doing them at 1 positive g can be centered and
completely focused on the fact that it's the ENTRY and the EXIT of the
roll, and how these two factors interplay into the roll itself that is
causing all the confusion.
The one factor that can't be taken out of the barrel roll scenario is
that no matter how you cut it, if PITCH is a factor in a barrel roll,
there will be an indication on a g meter above 1 g as that pitch change
is being made. In a normal barrel roll you have pitch change as the nose
transverses the roll in it's helical path.
If a barrel roll requires the nose of the aircraft to be above the
horizon during the entry and then again brought back to the horizon
during the recovery (as it does) you will absolutely be showing more
than 1 positive g on the g meter during the roll, and if it's a
retaining double needle g meter, after the roll when you bring the
airplane home........period! This is a fact of life. As soon as the
aircraft's nose shows a positive nose rate in PITCH as it's raised
during the roll entry and then again during the recovery as it's raised
again to level flight, that g meter will leave 1 and show more than 1
positive g.

Now here is the part that is causing all the confusion. ONCE the nose
has been raised above the horizon (and that over 1 g has been registered
on the g meter) as you feed in aileron you can PLAY WITH THE BACK
PRESSURE being applied and EASE OFF the positive g to a LOWER LEVEL if
desired over the top of the roll, but that level can't be unloaded below
1 g or the arc of the roll will be destroyed. It's the COMBINATION of
roll and pitch that is producing the roll arc and those TWO pressures
MUST be maintained to produce the roll.
So the bottom line is simply that to do a barrel roll where the nose
must be both above and below the horizon line starting from level flight
you need over 1 g during the entry and exit, but you can reduce the g to
1 through the top of the roll if desired.

I agree with your standard barrel roll exactly - but make the point:
* if you don't do it standard...
* ie don't pitch up
* don't pitch to recover level
* etc

ie do *not* do the standard barrel roll - and do not adjust pitch, other
than to counter any G (+ or -) that will occur in such a roll due to
airspeed changing, ie maintain 1G throughout the roll.

--
Duncan

On 2007-06-18 08:52:34 -0400, Dave Doe said:

In article ,
says...
Dave Doe wrote:

To put it another way, if you closed your eyes, you wouldn't know you've
done a roll (given you go for the 'non-standard' 1G roll), other than
the initial sensation of beginning the turn, and then the sensation of
the turn stopping.


Not sure exactly where you are with this, but as what you are saying
pertains to barrel rolls begun from level flight or from a position with
the nose below the horizon, don't forget that the entire gist of the
misunderstanding that has been running rampant on this thread about
barrel rolls and doing them at 1 positive g can be centered and
completely focused on the fact that it's the ENTRY and the EXIT of the
roll, and how these two factors interplay into the roll itself that is
causing all the confusion.
The one factor that can't be taken out of the barrel roll scenario is
that no matter how you cut it, if PITCH is a factor in a barrel roll,
there will be an indication on a g meter above 1 g as that pitch change
is being made. In a normal barrel roll you have pitch change as the nose
transverses the roll in it's helical path.
If a barrel roll requires the nose of the aircraft to be above the
horizon during the entry and then again brought back to the horizon
during the recovery (as it does) you will absolutely be showing more
than 1 positive g on the g meter during the roll, and if it's a
retaining double needle g meter, after the roll when you bring the
airplane home........period! This is a fact of life. As soon as the
aircraft's nose shows a positive nose rate in PITCH as it's raised
during the roll entry and then again during the recovery as it's raised
again to level flight, that g meter will leave 1 and show more than 1
positive g.

Now here is the part that is causing all the confusion. ONCE the nose
has been raised above the horizon (and that over 1 g has been registered
on the g meter) as you feed in aileron you can PLAY WITH THE BACK
PRESSURE being applied and EASE OFF the positive g to a LOWER LEVEL if
desired over the top of the roll, but that level can't be unloaded below
1 g or the arc of the roll will be destroyed. It's the COMBINATION of
roll and pitch that is producing the roll arc and those TWO pressures
MUST be maintained to produce the roll.
So the bottom line is simply that to do a barrel roll where the nose
must be both above and below the horizon line starting from level flight
you need over 1 g during the entry and exit, but you can reduce the g to
1 through the top of the roll if desired.

I agree with your standard barrel roll exactly - but make the point:
* if you don't do it standard...
* ie don't pitch up
* don't pitch to recover level
* etc

ie do *not* do the standard barrel roll - and do not adjust pitch, other
than to counter any G (+ or -) that will occur in such a roll due to
airspeed changing, ie maintain 1G throughout the roll.

Again I'm totally lost as to what you are trying to say with this, but
in the interest of clarification, it's the pitch input that is creating
the helical arc for a barrel roll. No positive pitch; no helical arc.
No helical arc, no barrel roll.

The heading change realized at any point in the roll by this helical
arc will be a direct result of the combination of pitch input and the
roll rate applied.
You can perform a barrel roll at any time and at any beginning nose
attitude by rolling the aircraft and applying a diagonal pitch input at
the same time. The one common denominator in all this is thatany barrel
roll requires offset positive pitch input.
In military training, you initially learn barrel rolls as a precision
maneuver requiring specific heading changes at various points in the
roll. If you go into fighter lead in training, you re-address the
barrel roll scenario once more in the BFM/ACM stage of your training as
a maneuver classified as ANY roll performed in 3 dimensions through 3
dimensional space.
This completely opens the Pandora's box on the issue of barrel roll,
which is then dealt with as moving the aircraft through all 3
dimensions as tightly or as loosely as the envelope will allow.
Dudley Henriques

Dudley Henriques wrote
This completely opens the Pandora's box on the issue of barrel roll,
which is then dealt with as moving the aircraft through all 3
dimensions as tightly or as loosely as the envelope will allow.

Dudley...just point us to a reference that states the above. :-)

I have posted several of my references in the past, waiting on you.

Bob Moore

On 2007-06-18 12:51:04 -0400, Bob Moore said:

Dudley Henriques wrote
This completely opens the Pandora's box on the issue of barrel roll,
which is then dealt with as moving the aircraft through all 3
dimensions as tightly or as loosely as the envelope will allow.

Dudley...just point us to a reference that states the above. :-)

I have posted several of my references in the past, waiting on you.

Bob Moore

Quite frankly Morre, I don't believe you really want references at all,
but rather references YOU agree with. :-)
You seem to enjoy quoting Bill Kershner, who is a source I highly
respect and have used for many years.
Considering this, I have gone to the DL (dusty library) room up here
and dug out a Kershner source on this for you.
If you go to page 289 in Bill's "Flight Instructor Manual" third
edition, you will find a section on Barrel Rolls.
If you read that section through, you will notice that Kershner first
treats the issue of Barrel Roll in the Classic manner that asks for the
90 degree heading change at the inverted point half way through the
roll.
Now read on a bit further to where Bill summerizes the issue of Barrel
Rolls. On page 290, down at the bottom of the page, start reading where
Bill writes;
"ANOTHER METHOD OF DOING A BARREL ROLL"
This section completely explains in plain English what I have been
telling you since God knows when about barrel rolls; that what YOU are
describing as a barrel roll, is simply the way barrel rolls are taught
as a precision maneuver by many training programs (including the Navy
BTW).
All I have been trying to explain to you from the gitgo is that this is
NOT the only way a barrel roll can be performed AERODYNAMICALLY. What
you have been describing as a barrel roll is nothing more or less than
ONE PROCEDURE by which a Barrel roll can be performed.
If you like, I will be most happy to fly with you in a Decathlon at any
time you desire and SHOW you a barrel roll with a 90 degree change of
heading at the inverted point........an 80 degree change of heading at
the inverted point......a 70 degree change of heading at the inverted
point....and so on, right down to the maximum helical arc the Decathlon
is capable of managing. YOU of course can pay for the flight :-)
I of course will buy the drinks :-)))
Dudley Henriques