Visual coordination of turns revisited

Mxsmanic wrote:
Tony writes:


Your model is wrong.


What is wrong with the model?


It's wrong.

Tony writes:

Look up the meaning of coordinated flight and the errors in your model
should be obvious.

In other words, there aren't any errors. Why did you claim otherwise?

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Newps writes:

It's wrong.

That doesn't answer my question.

Do you really believe that a blanket assertion that it is "wrong," followed by
a refusal to explain why, would be credible to anyone seriously interested in
an answer? I suppose that technique might work on the school playground, but
it's not very useful in productive discussions.

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This might be a productive discussion in a sim group.



On Feb 8, 1:57 am, Mxsmanic wrote:
Newps writes:
It's wrong.

That doesn't answer my question.

Do you really believe that a blanket assertion that it is "wrong," followed by
a refusal to explain why, would be credible to anyone seriously interested in
an answer? I suppose that technique might work on the school playground, but
it's not very useful in productive discussions.

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"Mxsmanic" wrote in message
...
I'm still in a bit of a quandry as to how to learn to make coordinated
turns
in a PC simulator that does not include a motion platform.

I've turned on the visual alignment indicator that MSFS provides, which is
a
red "V" that sits squarely ahead in the visual field, effectively bolted
to
the airframe. I've been trying to turn such that this V always moves
along
the horizon at a constant speed for a given bank angle. Logically, a
specific
bank angle in a coordinated turn will always produce a heading change at
the
same speed. If the speed at which the horizon is moving varies, the turn
is
not coordinated.

Also, it seems that in a coordinated, level turn, this V should stay at
the
same distance above the horizon throughout the turn.

As I roll into a turn, the speed of movement of the V along the horizon
should
increase in precise relationship to the bank angle. The opposite should
occur
as I roll out of the turn, with the speed along the horizon slowing as I
return to level flight.

Any problems with this? The only remaining problem is to figure out _how_
fast the V should be moving for a given bank angle. Maybe that can come
with
practice.

Does this help?
For a given bank angle ( theta) the time taken for the heading to change 360
degrees in a coordinated turn will be given by

t = 2 Pi v / g tan( theta)

t = time in secs
Pi = 3.14159
g =gravitational accleration 9.8 m/s2
v = speed ( m/s)

Terry
PPL downunder.

d&tm writes:

Does this help?
For a given bank angle ( theta) the time taken for the heading to change 360
degrees in a coordinated turn will be given by

t = 2 Pi v / g tan( theta)

t = time in secs
Pi = 3.14159
g =gravitational accleration 9.8 m/s2
v = speed ( m/s)

Thanks!

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Mxsmanic wrote:
Gig 601XL Builder writes:

In the real world we don't have that little V superimposed on the
wind sheild. What we do have is that little dodad ball in most cases
in the turn coordinator. Keep that little ball so it looks like this

|O| and you will be in a coordinated turn.

I know, but under VFR I'm supposed to be looking out the window, not
staring at the ball.

It isn't a binary set solution. One of the things you learn in basic flight
training is to use the instruments you have without fixating on them.

On Feb 7, 2:47 pm, Mxsmanic wrote:
I'm still in a bit of a quandry as to how to learn to make coordinated turns
in a PC simulator that does not include a motion platform.

I've turned on the visual alignment indicator that MSFS provides, which is a
red "V" that sits squarely ahead in the visual field, effectively bolted to
the airframe. I've been trying to turn such that this V always moves along
the horizon at a constant speed for a given bank angle. Logically, a specific
bank angle in a coordinated turn will always produce a heading change at the
same speed. If the speed at which the horizon is moving varies, the turn is
not coordinated.

Nope, that's not true. It may be true on a windless day in absolutely
level
flight with no changes in pitch, altitude, or airspeed, but it's not
true
in a real plane.

In coordinated flight, the tangent of the bank angle is the ratio
of the horizontal component of lift to the vertical component of
lift.
The horizontal component of lift is what produces centripetal
acceleration, and thus turning.

But if you change total lift, you change both components of lift
simultaneously without changing bank angle.

Try this. Set up a 30 degree bank angle, keeping things coordinated,
and then pull back on the stick sharply. Your turn rate will
increase as your lift increases. Push forward on the stick and your
turn rate will decrease as your lift decreases.

I know, you're going to say "but I just have to maintain level
flight during the turn!" True enough, but now your head
has to be down in the cockpit watching the altimeter and VSI,
which is a very indirect way of getting the information that you
would have gotten from looking at the ball (or still more
directly by feeling the seat of your pants in a real plane).

Furthermore, as already pointed out, the centripetal acceleration
is related to the turn rate by an equation that includes airspeed.
If your airspeed changes during the turn, your turn rate will
change. And your airspeed WILL change.

When you set up the bank, you must increase total
lift in order to maintain the vertical component of lift, and
thus maintain altitude. You increase total lift by increasing
angle of attack. This increased angle of attack increases
drag. Absent a corresponding change in power setting,
this causes a drop in airspeed. The drop in airspeed
causes a further requirement to increase pitch in
order to maintain altitude, causing more drag,
etc. Most small planes don't have enough power to
maintain cruise airspeed if the pilot attempts to
maintain altitude while steeply banked. Even in a
plane with plenty of power in reserve, it's not easy
to precisely judge exactly how much additional
power must be applied to keep airspeed exactly
constant through the turn -- typically, the
pilot doesn't worry about such things for small
turns, and keeps the throttle at its cruise setting.

Also, it seems that in a coordinated, level turn, this V should stay at the
same distance above the horizon throughout the turn.

No. As stated before, you've got to increase angle of attack to
maintain lift. And as your airspeed drops, you keep having
to further pitch up.

This is an interesting question. My first guess is you would have to have a
massively uncoordinated turn to detect it by looking out the window. If you
have rudders in your sim, try a turn with the rudder almost full left. Then
try it with the rudder full right. The only thing I can think of showing up
in the visuals would be a turn rate either more or less than it should be
based on the bank angle.

Give it a try and tell us if you can tell on your sim.

Danny Deger

MX always experiences 1 g straight down. That's as coordinated as you
can get.


Feb 9, 10:43 am, "Danny Deger" wrote:
This is an interesting question. My first guess is you would have to have a
massively uncoordinated turn to detect it by looking out the window. If you
have rudders in your sim, try a turn with the rudder almost full left. Then
try it with the rudder full right. The only thing I can think of showing up
in the visuals would be a turn rate either more or less than it should be
based on the bank angle.

Give it a try and tell us if you can tell on your sim.

Danny Deger