Myth: 1 G barrel rolls are impossible.

Jim Logajan wrote in
:

Mxsmanic wrote:
Jim Logajan writes:

Myth:

It is impossible to perform a barrel roll such that the pilot feels
exactly 1 gee of force perpendicular to the floor of the cockpit.

No maneuver that involves a change in altitude can maintain exactly 1
G along the net acceleration vector (including perpendicular to the
cockpit floor). This is not a myth, it's a fact.

Do you see the word "acceleration" anywhere in my "myth" statement? I
have no idea what it is you think you are trying to say,

Neither does he

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

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot feels exactly
1 gee of force perpendicular to the floor of the cockpit.

No maneuver that involves a change in altitude can maintain exactly 1 G along
the net acceleration vector (including perpendicular to the cockpit floor).
This is not a myth, it's a fact.

The only roll you can perform that does not involve more than 1 G of net
acceleration is one that involves no change in altitude, such as a roll
precisely about the longitudinal axis. But no roll that maintains the net
acceleration vector perpendicular to the cockpit floor is in this category.

A barrel roll is not about the longitudinal axis of the plane, that is
an aileron roll. The barrel roll is about a point about 1/8 mile off
your wing.

-Robert

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

"Robert M. Gary" wrote in
oups.com:

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot feels
exactly 1 gee of force perpendicular to the floor of the cockpit.

No maneuver that involves a change in altitude can maintain exactly 1
G along the net acceleration vector (including perpendicular to the
cockpit floor). This is not a myth, it's a fact.

The only roll you can perform that does not involve more than 1 G of
net acceleration is one that involves no change in altitude, such as
a roll precisely about the longitudinal axis. But no roll that
maintains the net acceleration vector perpendicular to the cockpit
floor is in this category.

A barrel roll is not about the longitudinal axis of the plane, that is
an aileron roll.


Nope, a roll about the longitudinal axis of the airplane is a slow roll.
actaully that's not entirely correct either since a perfect slow roll
follows a perfectly staight line, which means the axis of the aircraft
must change in realation to the line of flight throughout.
A slow roll is, hower, a one G roll. The 1 G should always point
earthward, though.


An aileron roll is actualy not dissimilar to a Barrel roll in flight
path.


Bertie

On 2007-06-11 21:42:18 -0400, Bertie the Bunyip said:

"Robert M. Gary" wrote in
oups.com:

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot feels
exactly 1 gee of force perpendicular to the floor of the cockpit.

No maneuver that involves a change in altitude can maintain exactly 1
G along the net acceleration vector (including perpendicular to the
cockpit floor). This is not a myth, it's a fact.

The only roll you can perform that does not involve more than 1 G of
net acceleration is one that involves no change in altitude, such as
a roll precisely about the longitudinal axis. But no roll that
maintains the net acceleration vector perpendicular to the cockpit
floor is in this category.

A barrel roll is not about the longitudinal axis of the plane, that is
an aileron roll.


Nope, a roll about the longitudinal axis of the airplane is a slow roll.
actaully that's not entirely correct either since a perfect slow roll
follows a perfectly staight line, which means the axis of the aircraft
must change in realation to the line of flight throughout.
A slow roll is, hower, a one G roll. The 1 G should always point
earthward, though.


An aileron roll is actualy not dissimilar to a Barrel roll in flight
path.


Bertie

Actually Bertie, think about it for just a moment. In a slow roll, you
do indeed roll the airplane on it's longitudinal axis but the roll line
isn't exactly straight.
The reason for this is that you have to pull the nose up to it's
inverted level flight attitude before commencing the roll. If you're
flying something fast like a T38 for example or with a symmetrical wing
like a round wing Pitts it isn't as pronounced as slow rolling
something with a cambered wing but it's there just the same.
The actual shape of a slow roll done correctly will look like a capital
letter D or a reverse capital letter D depending on the roll direction,
but take a slow roll to the right and it's easy to see. The bottom of
the vertical line on the left side of the D represents your initial
nose position beginning the roll. You have to fly up the line to the
top of the D which represents the inverted level flight nose attitude
of the aircraft. The roll initiates there and looks from the ground as
a straight line on the longitudinal axis. You roll the aircraft and
hold it while rolling it through the first knife edge and inverted at
the top of the vertical line on the D. This puts the airplane through
inverted exactly at it's inverted level flight nose attitude. Then, as
you pass through inverted and begin the back side of the roll, you have
to fly the airplane down the right side arc of the D to put the nose
back at it's erect level flight attitude again completing the roll.
The effect as seen from the ground is indeed a roll done in a straight
line, but for the pilot doing the roll, there is that slight vertical
pitch input to the roll set position and the easing off back down that
vertical line through the second knife edge back to level flight.
I should add that the higher the performance of the rolling aircraft,
the shorter that vertical line on the D will be.
For example, that line is much more pronounced in something like a
Citabria than it is in the Decathlon, but there is a pull to the roll
set even in the T38 if you want it to look good from the ground.
When I flew an aerobatic eval flight with the Snowbirds Tutor in 71,
one of the first things I noticed about the jet was the need to get the
nose a lot higher in the roll set for a slow roll than in the Talon.
You don't even want to know how high you have to get the nose to get a
slow roll out of a Cessna Aerobat :-))))

Dudley Henriques

Dudley Henriques wrote in
news:2007061122074775249-dhenriques@rcncom:

On 2007-06-11 21:42:18 -0400, Bertie the Bunyip
said:

"Robert M. Gary" wrote in
oups.com:

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot
feels exactly 1 gee of force perpendicular to the floor of the
cockpit.

No maneuver that involves a change in altitude can maintain exactly
1 G along the net acceleration vector (including perpendicular to
the cockpit floor). This is not a myth, it's a fact.

The only roll you can perform that does not involve more than 1 G
of net acceleration is one that involves no change in altitude,
such as a roll precisely about the longitudinal axis. But no roll
that maintains the net acceleration vector perpendicular to the
cockpit floor is in this category.

A barrel roll is not about the longitudinal axis of the plane, that
is an aileron roll.


Nope, a roll about the longitudinal axis of the airplane is a slow
roll. actaully that's not entirely correct either since a perfect
slow roll follows a perfectly staight line, which means the axis of
the aircraft must change in realation to the line of flight
throughout. A slow roll is, hower, a one G roll. The 1 G should
always point earthward, though.


An aileron roll is actualy not dissimilar to a Barrel roll in flight
path.


Bertie

Actually Bertie, think about it for just a moment. In a slow roll, you
do indeed roll the airplane on it's longitudinal axis but the roll
line isn't exactly straight.


Not for competition. You're judged by the line you fly. Mind you, if you
can make it look like you're not pushing the nose all over the place,
all the better.


Bertie

On 2007-06-11 22:26:31 -0400, Bertie the Bunyip said:

Dudley Henriques wrote in
news:2007061122074775249-dhenriques@rcncom:

On 2007-06-11 21:42:18 -0400, Bertie the Bunyip
said:

"Robert M. Gary" wrote in
oups.com:

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot
feels exactly 1 gee of force perpendicular to the floor of the
cockpit.

No maneuver that involves a change in altitude can maintain exactly
1 G along the net acceleration vector (including perpendicular to
the cockpit floor). This is not a myth, it's a fact.

The only roll you can perform that does not involve more than 1 G
of net acceleration is one that involves no change in altitude,
such as a roll precisely about the longitudinal axis. But no roll
that maintains the net acceleration vector perpendicular to the
cockpit floor is in this category.

A barrel roll is not about the longitudinal axis of the plane, that
is an aileron roll.


Nope, a roll about the longitudinal axis of the airplane is a slow
roll. actaully that's not entirely correct either since a perfect
slow roll follows a perfectly staight line, which means the axis of
the aircraft must change in realation to the line of flight
throughout. A slow roll is, hower, a one G roll. The 1 G should
always point earthward, though.


An aileron roll is actualy not dissimilar to a Barrel roll in flight
path.


Bertie

Actually Bertie, think about it for just a moment. In a slow roll, you
do indeed roll the airplane on it's longitudinal axis but the roll
line isn't exactly straight.


Not for competition. You're judged by the line you fly. Mind you, if you
can make it look like you're not pushing the nose all over the place,
all the better.


Bertie

Therin lies the "art form" :-) Kirk Brimmer, solo for the 71
Thunderbirds told me the hardest thing to do for him in the entire show
was to make his super slow roll look flat from the ground.
Never flew competition, but I agree totally that making the line look
good is the whole 9 yards.
Funny thing about competition judging is inverted spins. The pilot does
the spin to the left and all the "new" judges put it down with a nice
Aresti figure and a notation to the right :-))
As the man says, it's all in the perspective :-))
Dudley Henriques

Dudley Henriques wrote in
news:2007061122543716807-dhenriques@rcncom:

On 2007-06-11 22:26:31 -0400, Bertie the Bunyip
said:

Dudley Henriques wrote in
news:2007061122074775249-dhenriques@rcncom:

On 2007-06-11 21:42:18 -0400, Bertie the Bunyip
said:

"Robert M. Gary" wrote in
oups.com:

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot
feels exactly 1 gee of force perpendicular to the floor of the
cockpit.

No maneuver that involves a change in altitude can maintain
exactly 1 G along the net acceleration vector (including
perpendicular to the cockpit floor). This is not a myth, it's a
fact.

The only roll you can perform that does not involve more than 1 G
of net acceleration is one that involves no change in altitude,
such as a roll precisely about the longitudinal axis. But no
roll that maintains the net acceleration vector perpendicular to
the cockpit floor is in this category.

A barrel roll is not about the longitudinal axis of the plane,
that is an aileron roll.


Nope, a roll about the longitudinal axis of the airplane is a slow
roll. actaully that's not entirely correct either since a perfect
slow roll follows a perfectly staight line, which means the axis of
the aircraft must change in realation to the line of flight
throughout. A slow roll is, hower, a one G roll. The 1 G should
always point earthward, though.


An aileron roll is actualy not dissimilar to a Barrel roll in
flight path.


Bertie

Actually Bertie, think about it for just a moment. In a slow roll,
you do indeed roll the airplane on it's longitudinal axis but the
roll line isn't exactly straight.


Not for competition. You're judged by the line you fly. Mind you, if
you can make it look like you're not pushing the nose all over the
place, all the better.


Bertie

Therin lies the "art form" :-) Kirk Brimmer, solo for the 71
Thunderbirds told me the hardest thing to do for him in the entire
show was to make his super slow roll look flat from the ground.
Never flew competition, but I agree totally that making the line look
good is the whole 9 yards.

Yes. In fact, going vertical, it's expected you make a drift line to
compensate for wind. So if you're doing a vertical roll, you must do it
off the veritcal to make itlook good for the judges.

Not that I've ever competed in anything that would go vertical long
enough to make a difference!

Funny thing about competition judging is inverted spins. The pilot
does the spin to the left and all the "new" judges put it down with a
nice Aresti figure and a notation to the right :-))

They even confused me from inside.

Never Spin a Stearman (the 75 in case we have any nitpickers here) to
the right (pilot's perspective) cuz you'll get a face ful of fuel..


bertie

On 2007-06-11 23:02:16 -0400, Bertie the Bunyip said:

Dudley Henriques wrote in
news:2007061122543716807-dhenriques@rcncom:

On 2007-06-11 22:26:31 -0400, Bertie the Bunyip
said:

Dudley Henriques wrote in
news:2007061122074775249-dhenriques@rcncom:

On 2007-06-11 21:42:18 -0400, Bertie the Bunyip
said:

"Robert M. Gary" wrote in
oups.com:

On Jun 11, 12:51 pm, Mxsmanic wrote:
Jim Logajan writes:
Myth:

It is impossible to perform a barrel roll such that the pilot
feels exactly 1 gee of force perpendicular to the floor of the
cockpit.

No maneuver that involves a change in altitude can maintain
exactly 1 G along the net acceleration vector (including
perpendicular to the cockpit floor). This is not a myth, it's a
fact.

The only roll you can perform that does not involve more than 1 G
of net acceleration is one that involves no change in altitude,
such as a roll precisely about the longitudinal axis. But no
roll that maintains the net acceleration vector perpendicular to
the cockpit floor is in this category.

A barrel roll is not about the longitudinal axis of the plane,
that is an aileron roll.


Nope, a roll about the longitudinal axis of the airplane is a slow
roll. actaully that's not entirely correct either since a perfect
slow roll follows a perfectly staight line, which means the axis of
the aircraft must change in realation to the line of flight
throughout. A slow roll is, hower, a one G roll. The 1 G should
always point earthward, though.


An aileron roll is actualy not dissimilar to a Barrel roll in
flight path.


Bertie

Actually Bertie, think about it for just a moment. In a slow roll,
you do indeed roll the airplane on it's longitudinal axis but the
roll line isn't exactly straight.


Not for competition. You're judged by the line you fly. Mind you, if
you can make it look like you're not pushing the nose all over the
place, all the better.


Bertie

Therin lies the "art form" :-) Kirk Brimmer, solo for the 71
Thunderbirds told me the hardest thing to do for him in the entire
show was to make his super slow roll look flat from the ground.
Never flew competition, but I agree totally that making the line look
good is the whole 9 yards.

Yes. In fact, going vertical, it's expected you make a drift line to
compensate for wind. So if you're doing a vertical roll, you must do it
off the veritcal to make itlook good for the judges.

This is also a serious problem in demonstration flying. You're nearly
always dealing with a crosswind because the show line is fixed and
crowd positioning is critical to meet waivers. In the Mustang going
vertical, the torque changes are horrendous as you bleed energy on the
up line and require copious amounts of rudder and some opposite aileron
to hold the line. Throw in a crosswind and you can really have your
hands full on occasion
:-)

Not that I've ever competed in anything that would go vertical long
enough to make a difference!

You and Duane Cole! I honestly think it was the constant extension of
the vertical line brought on by the influx of the higher powered Pitts'
and some others that did him in with his clipped wing T Craft.
What that man could do with that little puddle jumper had to be seen to
be believed.

Funny thing about competition judging is inverted spins. The pilot
does the spin to the left and all the "new" judges put it down with a
nice Aresti figure and a notation to the right :-))

They even confused me from inside.
You TOO huh??? Count me in on that one. The first one I got into was a
botched multiple outside snap in the Pitts. Took me several turns to
figure out what the hell was going on. I've always recommended to acro
pilots that they install a T&B in their airplanes. The needle shows
the spin direction either erect or inverted which on occasion can be
"quite useful" :-)


Never Spin a Stearman (the 75 in case we have any nitpickers here) to
the right (pilot's perspective) cuz you'll get a face ful of fuel..

Got a few hours in the 650 way back when. Man, were those pedals wide
apart!! :-))
DH


bertie