an exercise for sim pilots -- a 1 G roll

On Jan 5, 4:58 am, Mxsmanic wrote:
Tony writes:
There is a flight path, taking into account roll, pitch, yah, and
thrust, that will result in a complete roll with an g meter indicating
1 G into the seat.


No, there is not. You cannot change altitude without a change in G.
Indeed, any acceleration of the aircraft, in any direction, will
change the G force. You can keep it normal to the pilot's seat in
many cases, but you cannot hold its magnitude constant.

In fact you are wrong. You may wish to look in the archives of this
newsgroup for the proof.

You can demostrate at least the early part of such a roll by starting a
coordinated turn and adding sufficient forward pressure on the yoke to
remove the additional G's a level turn would induce. One suce flight
path requires you to accelerate downward at 1 G.

This is actually a fairly simple classical physics problem -- at least
one poster solved it using a spread sheet.

You are quite correct, however, in stating most airplanes can be flown
in a loop or a roll safely with positive G forces, but nealy all
general aviation aircraft certified in the United States are not
certified for such flight paths.

I do think you didn't quite say what you meant when you stated you
cannot change altitude without changing G. What g force would you
expect it you were climbing at 500 feet a minute?





My real life airplane, an M20, may not be flown at more than 30 degrees
pitch or 60 degrees bank, but those kinds of limitations do not apply
to someone who games on a flight simulator, or who has a suitably
certified airplane.In theory, any aircraft can do a barrel roll, as long as the net
acceleration vector is kept downward.

My OP request was to have someone who is skilled in
simulated flight see if their simulated airplane had the control
authority to fly that flight path.I was able to do it in the default Cessna on MSFS, not very neatly but
with the G force always positive. It's supposedly an extremely safe
maneuver as long as that number stays positive.

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

Tony writes:

In fact you are wrong. You may wish to look in the archives of this
newsgroup for the proof.

The archives of this newsgroup are proof of nothing.

You cannot change altitude without acceleration, and that changes G
force. You cannot execute any type of roll that involves any change
in altitude without a change in G force. This is basic physics.

If you roll the aircraft without a change in altitude, the magnitude
of the G force can be held constant. However, in that case, you
cannot keep the vector pointed in the same direction.

If you want positive G through the normal vector when moving through
the inverted portion of a roll, you _must_ accelerate downward at at
least one G at some point, otherwise gravity will reduce G to zero and
make it negative. When the aircraft is inverted, gravity produces
-1.0 G of acceleration on the pilot. The only way to counter this is
to accelerate downward at at least 1 G.

I do think you didn't quite say what you meant when you stated you
cannot change altitude without changing G. What g force would you
expect it you were climbing at 500 feet a minute?

None, but you would experience greater than 1 G as you started the
climb, and less than 1 G as you ended it. You have to accelerate
upward to start a climb and downward to stop it. You cannot
accelerate without inducing G forces. The same is true in turns.

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

On Jan 5, 6:51 am, Mxsmanic wrote:
Tony writes:
In fact you are wrong. You may wish to look in the archives of this
newsgroup for the proof.The archives of this newsgroup are proof of nothing.


Ah, but if you are capable of the task, you can apply some classical
physics to the information provided in the archive and do the analysis
yourself.

If you are not capable of the analytical physics you might have to do
experimental physics. In your case if you have the skills those can be
gamed.

Or, remain ignorant, and wrong.

Again.





You cannot change altitude without acceleration, and that changes G
force. You cannot execute any type of roll that involves any change
in altitude without a change in G force. This is basic physics.

If you roll the aircraft without a change in altitude, the magnitude
of the G force can be held constant. However, in that case, you
cannot keep the vector pointed in the same direction.

If you want positive G through the normal vector when moving through
the inverted portion of a roll, you _must_ accelerate downward at at
least one G at some point, otherwise gravity will reduce G to zero and
make it negative. When the aircraft is inverted, gravity produces
-1.0 G of acceleration on the pilot. The only way to counter this is
to accelerate downward at at least 1 G.

I do think you didn't quite say what you meant when you stated you
cannot change altitude without changing G. What g force would you
expect it you were climbing at 500 feet a minute?None, but you would experience greater than 1 G as you started the
climb, and less than 1 G as you ended it. You have to accelerate
upward to start a climb and downward to stop it. You cannot
accelerate without inducing G forces. The same is true in turns.

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

The physics of this 1 g roll are nicely demonstrated at

http://www.stanford.edu/~siegman/one_g_roll.html


The question I had asked in the first posting seems to have been
answered by Kyle.


This was almost as much fun as the airplane on a treadmill thread --
thanks everyone.


Now there's an idea. Let's design a treadmill that follows the 1 g roll
path and sell it to Disney! It wouldn't be much fun for the kids riding
it, would it? ( I have one year from first public disclosure to file a
patent application, right?)

On Jan 5, 9:05 am, "Tony" wrote:
On Jan 5, 6:51 am, Mxsmanic wrote:

Tony writes:
In fact you are wrong. You may wish to look in the archives of this
newsgroup for the proof.The archives of this newsgroup are proof of nothing.Ah, but if you are capable of the task, you can apply some classical
physics to the information provided in the archive and do the analysis
yourself.

If you are not capable of the analytical physics you might have to do
experimental physics. In your case if you have the skills those can be
gamed.

Or, remain ignorant, and wrong.

Again.





You cannot change altitude without acceleration, and that changes G
force. You cannot execute any type of roll that involves any change
in altitude without a change in G force. This is basic physics.

If you roll the aircraft without a change in altitude, the magnitude
of the G force can be held constant. However, in that case, you
cannot keep the vector pointed in the same direction.

If you want positive G through the normal vector when moving through
the inverted portion of a roll, you _must_ accelerate downward at at
least one G at some point, otherwise gravity will reduce G to zero and
make it negative. When the aircraft is inverted, gravity produces
-1.0 G of acceleration on the pilot. The only way to counter this is
to accelerate downward at at least 1 G.

I do think you didn't quite say what you meant when you stated you
cannot change altitude without changing G. What g force would you
expect it you were climbing at 500 feet a minute?None, but you would experience greater than 1 G as you started the
climb, and less than 1 G as you ended it. You have to accelerate
upward to start a climb and downward to stop it. You cannot
accelerate without inducing G forces. The same is true in turns.

--
Transpose mxsmanic and gmail to reach me by e-mail.- Hide quoted text -- Show quoted text -

Tony writes:

Ah, but if you are capable of the task, you can apply some classical
physics to the information provided in the archive and do the analysis
yourself.

Acceleration is a change in velocity. Climbing from the ground (or
from any constant altitude) is a change in vertical velocity (since
the initial rate of climb is zero). Therefore climbing involves
acceleration. G forces are nothing more than acceleration. Therefore
climbing changes G forces. QED.

If you are not capable of the analytical physics you might have to do
experimental physics.

Nothing that complicated is required. See above.

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

"Mxsmanic" wrote in message
...
Tony writes:

Ah, but if you are capable of the task, you can apply some classical
physics to the information provided in the archive and do the analysis
yourself.

Acceleration is a change in velocity. Climbing from the ground (or
from any constant altitude) is a change in vertical velocity (since
the initial rate of climb is zero). Therefore climbing involves
acceleration. G forces are nothing more than acceleration. Therefore
climbing changes G forces. QED.

You are correct, but for typical climbing and decending the amount of G away
from 1 is so small that as a pilot it is still "1". Entering a climb or a
decent moves a G meter such a small amount, you can't see the needle move
and you can't feel the small difference in the seat of your pants. There
are small G changes in a barrel roll, but not enough to really feel. As a
pilot, the manuever is called "1 G". Keep in mind this is in comparison
with other aerobatic manuevers that go to routinely 3 to 10 Gs.

Danny Deger

Danny, you are correct when you say the actual deviation from 1 G is
small for climbs, but small isn't good enough. I wanted what we trained
in the sciences would call 1, an integer, not 1.00. The problem I could
not resolve in entering a climb is not getting the airplane to pitch up
30 degrees and maintaining 1 g into the seat -- it just has to
decelerate to do that. I just don't seem to have the degrees of freedom
that are needed.

Some - Mx is an example -- don't quite understand how to do the
analysis, and would rather argue than show where the math I cited is in
error. Too bad, it could have been a learning experience for them.

Do take a look at the neat family of curves in the citation: it's
interesting stuff, and guess what? If the equations of motion are
solved in closed form, G is 1, into the seat.



On Jan 5, 5:53 pm, "Danny Deger" wrote:
"Mxsmanic" wrote in messagenews:bfftp2t07l335t5qr0s08dsdb80vjr1bnt@4ax .com...

Tony writes:

Ah, but if you are capable of the task, you can apply some classical
physics to the information provided in the archive and do the analysis
yourself.

Acceleration is a change in velocity. Climbing from the ground (or
from any constant altitude) is a change in vertical velocity (since
the initial rate of climb is zero). Therefore climbing involves
acceleration. G forces are nothing more than acceleration. Therefore
climbing changes G forces. QED.You are correct, but for typical climbing and decending the amount of G away
from 1 is so small that as a pilot it is still "1". Entering a climb or a
decent moves a G meter such a small amount, you can't see the needle move
and you can't feel the small difference in the seat of your pants. There
are small G changes in a barrel roll, but not enough to really feel. As a
pilot, the manuever is called "1 G". Keep in mind this is in comparison
with other aerobatic manuevers that go to routinely 3 to 10 Gs.

Danny Deger

Tony writes:

Some - Mx is an example -- don't quite understand how to do the
analysis, and would rather argue than show where the math I cited is in
error. Too bad, it could have been a learning experience for them.

I've explained the error. You cannot change your rate of climb
without accelerating. You cannot accelerate without deviating from 1
G. You cannot maintain a constant rate of climb forever, so you must
change the rate of climb from time to time. And any maneuver that
changes the rate of climb (which, in practice, is roughly the same as
saying any maneuver that changes altitude) will change the G forces.
It's very simple, and doesn't require any fancy physics.

Do take a look at the neat family of curves in the citation: it's
interesting stuff, and guess what? If the equations of motion are
solved in closed form, G is 1, into the seat.

You can solve all the equations you want, but you cannot escape from
the reality I've described above.

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