an exercise for sim pilots -- a 1 G roll

About a year ago there was a spirited discussion about maintaining a 1
G 'straight into the seat' force while doing a roll (let's define a
roll as rotating the airplane, somehow, 360 degrees around its axis
with respect to the horizon). As I rmember the analysis, if you have
enough control authority if you accelerate downward at 1 G and pull
hard enough while doing a coordinated roll you can do just that. A
blindfolded passenger would know the roll happened.

Are there any skilled sim players out there who can do this? I'm
especially interested in what airplanes have enough (simulated) control
authority to pull it off.

"Tony" wrote in message
ups.com...
About a year ago there was a spirited discussion about maintaining a 1
G 'straight into the seat' force while doing a roll (let's define a
roll as rotating the airplane, somehow, 360 degrees around its axis
with respect to the horizon). As I rmember the analysis, if you have
enough control authority if you accelerate downward at 1 G and pull
hard enough while doing a coordinated roll you can do just that. A
blindfolded passenger would know the roll happened.

Are there any skilled sim players out there who can do this? I'm
especially interested in what airplanes have enough (simulated) control
authority to pull it off.

Old time pilot (retired by age) and simulator dabbler.

I take it you are talking about a barrel roll. With the real thing, you feel
the roll in the seat of your pants. With the sim, I guess you'd have to do
it with instruments - i.e., coordinate with the ball, and a g-meter. Since
you can't feel it, I don't see how else you would know if you did it right.
Doesn't sound like much fun.

from the http://alexisparkinn.com/general_aviation_videos.htm

http://alexisparkinn.com/photogaller...h-Cocktail.wmv

would this be sort-of what we're talking about?

T o d d P a t t i s t wrote:
"Tony" wrote:

About a year ago there was a spirited discussion about maintaining a 1
G 'straight into the seat' force while doing a roll (let's define a
roll as rotating the airplane, somehow, 360 degrees around its axis
with respect to the horizon).

There was such a discussion - IIRC, it was mostly about
barrel rolls and loops, not pure aileron rolls.

As I rmember the analysis, if you have
enough control authority if you accelerate downward at 1 G and pull
hard enough while doing a coordinated roll you can do just that. A
blindfolded passenger would know the roll happened.

Did you mean to say the passenger would or would not know
the roll happened?

Regardless, if you let the aircraft accelerate at 1G
downward (0 G), you can (theoretically) superimpose a
constant 1G loop or a barrel roll with a 1G inward component
and approximate what you are thinking of, but it's a long
ways from a blindfolded passenger not noticing. For one
thing, you are going to pick up a hefty sink rate during the
falling 0 G loop that you can't get rid of if you keep to
the 1G limit. You hit the ground shortly after this
exercise. Another point is that your speed is increasing
rapidly. Think of the center of the loop "falling" the
entire time this maneuver is being conducted.

Yet another point is that an aircraft must keep its fuselage
roughly lined up with the relative wind, so the angle of
this 1 G relative to the floor is changing as you end up in
a high speed dive at the end. Finally, you can't get the
roll started or ended without imposing forces on the
passenger that he will notice.



--
Do not spin this aircraft. If the aircraft does enter a spin it will return to earth without further attention on the part of the aeronaut.

(first handbook issued with the Curtis-Wright flyer)

"mad8" wrote in message oups.com...
: from the http://alexisparkinn.com/general_aviation_videos.htm
:
: http://alexisparkinn.com/photogaller...h-Cocktail.wmv
:
: would this be sort-of what we're talking about?
:

Hoover wanna b's

It's possible to execute a roll with the acceleration vector
continuously pointing in the proper direction and with continuous
positive G forces, but it is not possible to do it with a constant
level of acceleration. That is, you can keep the acceleration
positive, but you cannot hold it at 1.0 Gs. As long as it is positive
and the vector is stationary (both of which are possible), passengers
will have only the sensation of slightly rising or falling in a
straight line during the roll.

I've seen Bob Hoover demonstrate this by pouring fruit juice into a
cup during a barrel roll. Others have probably done the same thing.

--
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birdog writes:

I take it you are talking about a barrel roll. With the real thing, you feel
the roll in the seat of your pants. With the sim, I guess you'd have to do
it with instruments - i.e., coordinate with the ball, and a g-meter. Since
you can't feel it, I don't see how else you would know if you did it right.
Doesn't sound like much fun.

I've done it successfully as an experiment, out of curiosity, but you
are right, it's not much fun. It has the merit of being a very safe
maneuver.

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Here's what I remember thinking about when it was being discussed. We
all know if we skid into a turn using only rudder the ball swings to
the outside, and if we roll into it with ailerons the ball rolls
inside, so with the correct combination (since we are all expert
pilots, it's always like this for us) the ball is nailed to the center.
However, we will, if in level flight, feel increased g's -1.41 times
body weight at 45 degrees in a coordinated turn, you guys all know
that. However, if you while coordinating rudder and aileron you put
forward pressure on the yoke, you can take off those G's -- push hard
enough and you can probably go to negative g's and only have the seat
belt holding you down. So, there is some forward pressure that will
just compensate for the additional g's the coordinated level turn will
cause.

So, I can talk myself into the start of a roll (more barrel than
anything else) thinking I can keep the ball centered and the scale I'm
sitting on registering my actual weight. The engineering analysis can
continue from that point, saying at any incremental distance or roll
angle there's some combination of aileron, rudder, and yoke that will
result in an additional roll with one g postive force into the seat.

I remember someone running the numbers and concluding the diameter of
this descending barrel roll thing would be about 80 feet (not far from
a snap roll, huh?). That's nothing the little rudder and ailerons on
airplanes I know can do. The question is, is there a simulator jock out
there who can call up the parameters of a real life airplane that can
fly the thing? Do simulators allow the inclusion of a three axis G
force meter on the panel?

Tony writes:

However, if you while coordinating rudder and aileron you put
forward pressure on the yoke, you can take off those G's -- push hard
enough and you can probably go to negative g's and only have the seat
belt holding you down. So, there is some forward pressure that will
just compensate for the additional g's the coordinated level turn will
cause.

The additional Gs are unavoidable in a coordinated turn at constant
altitude. They arise from the fact that you are being accelerated not
only downward by gravity but also towards the center of the turn by
the aircraft's bank, which essentially uses part of the lift provided
by the wings to accelerate the aircraft inward. The bank insures that
the resulting acceleration vector remains normal to the wings (and the
aircraft's occupants), but its magnitude must increase.

If you do nothing to maintain altitude, you can stay at one gravity of
acceleration, but you'll descend in the turn.

In a barrel roll, you cannot avoid accelerations greater than 1 G at
some point. At some point, the aircraft must descend, and then level
out. At that point the acceleration will exceed 1 G.

You should be able to make the additional increment of acceleration
arbitrarily small, however, at least in theory.

Do simulators allow the inclusion of a three axis G
force meter on the panel?

Not that I've seen, but there are many simulators in the world.

In MSFS, you can do a barrel roll while monitoring vertical
acceleration. If the acceleration stays positive, you're good. If it
stays close to 1.0, that's better still.

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Mxsmanic wrote:

I've seen Bob Hoover demonstrate this by pouring fruit juice into a
cup during a barrel roll. Others have probably done the same thing.


Water, not fruit juice.

Think.... why would someone deliberately pour a stickey substance onto
their instument panel/engine control cluster if there was risk of
spilling it into said instruments/controls?

There is no requirement to hold a constant level of acceleration or
level flight. The requirement is simply that the weight vector be into
the seat at 1 G. It is possible to take the airplane through a 360 roll
about its axis doing this, so such a flight pattern would NOT be
noticed by a blindfolded with hearing blocked PX. I do appreciate the
airplane will not end the manouver straight and level and will not have
its initial heading. Recovering those values may be physically
impossible -- it will be going down pretty fast, and I can't imagine a
flight path that take the airplane back to S&L without inducing more
than 1 G on the cockpit. The question I have is, does an airplane exist
that has the control authority to fly such a roll?



On Jan 2, 4:13 pm, Mxsmanic wrote:
It's possible to execute a roll with the acceleration vector
continuously pointing in the proper direction and with continuous
positive G forces, but it is not possible to do it with a constant
level of acceleration. That is, you can keep the acceleration
positive, but you cannot hold it at 1.0 Gs. As long as it is positive
and the vector is stationary (both of which are possible), passengers
will have only the sensation of slightly rising or falling in a
straight line during the roll.

I've seen Bob Hoover demonstrate this by pouring fruit juice into a
cup during a barrel roll. Others have probably done the same thing.

--
Transpose mxsmanic and gmail to reach me by e-mail.