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spins from coordinated flight



 
 
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  #41  
Old December 27th 07, 07:35 PM posted to rec.aviation.piloting,rec.aviation.aerobatics
Jim Macklin
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Posts: 2,070
Default spins from coordinated flight

Flight is an art based on a science.



"Stefan" wrote in message
...
| Jim Macklin schrieb:
|
| I don't know of any autopilot that could be programmed to fly an
aerobatic
| maneuver based on predicted actions. Yet an autopilot can be designed
to
| observe and respond to the observed dynamic actions of the airplane.
|
| I don't know of any autopilot that could be programmed to perform
| rolling circles, either. But where's the relevance?


Ads
  #42  
Old December 27th 07, 07:49 PM posted to rec.aviation.piloting,rec.aviation.aerobatics
Dudley Henriques[_2_]
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Posts: 2,546
Default spins from coordinated flight

Stefan wrote:

Different approach. You, as a military pilot (as I think to have
understood), believe in the behavioristic approach. Me, as a scientist
(and amateur pilot) follow the cognitive approach. Your approach yields
pilots who exactly know what to do in this or that situation, but
probably without really understanding the deeper reasons.


Well...I could say that your comment above is a deep personal insult
(which it is BTW :-) but in this case I will respect the fact that you
simply don't know anything at all about me since you have assumed I am a
military pilot which as half the world knows couldn't be further from
the truth.
I am in fact simply a civilian pilot who has flown military airplanes.
It's as simple as that really....oh yes...there is one more
thing....I've spent about 50 odd years directly involved with the flight
training community as both a CFI and an adviser and consultant at levels
ranging from primary training to teaching people to fly the highest
performance airplanes in the world.

If you surmise that the people I have taught to spin airplanes "probably
don't understand the deeper reasons" involved that YOU as a scientist
can provide, or that the pilots I have trained don't know thoroughly the
complete aerodynamics involved with spins, I fear you are in for a deep
disappointment :-))

We just present these things when it is correct to present them and not
when another explanation is the right explanation :-)

--
Dudley Henriques
  #43  
Old December 27th 07, 08:33 PM posted to rec.aviation.piloting,rec.aviation.aerobatics
Dudley Henriques[_2_]
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Posts: 2,546
Default spins from coordinated flight

Stefan wrote:
Dudley Henriques schrieb:

Yaw should only be present in the turn dynamic during the entry into
the turn and exit from the turn. Once stabilized in the turn, there
should be no yaw present.


I don't agree. A coordinated turn is *always* a turn around all three
axes. (The only exception is a turn with a 90 degrees bank.) You can
easily demonstrate this by "hand-flying" a toy airplane.



Axis isn't really used in this way. You will notice if you move your toy
airplane that the axis system remains in place and moves with the
aircraft centered on the aircraft's cg.

To define turn using axis reference is not the best way to explain turn
since once established in a stable turn there should be no movement on
the airplane's axis system. The axis system references the lines
crossing through the aircraft's Cg and are used to define movement and
moment on each axis. The axis system moves in place with the aircraft
and never deviates from it's center point through the cg.
There is movement on the longitudinal axis in roll as the airplane is
rolled into and out of the turn, and movement as well on the lateral
axis in pitch as angle of attack is increased to compensate for the
split in the lift vector. There is movement on the Vertical axis as
rudder is used to compensate for adverse yaw both during and exiting the
turn, but once established in a coordinated turn, (I'm using medium
banked turn here for easy reference as under bank and over bank in
shallow and steep turns cause in turn axis changes complicating the
situation a bit) all movement on the aircraft's axis should be stable.

The proper way to define turn as relates to change in direction is to
define the change in the velocity vector as relates to heading change
not as a change on or around the axis of the aircraft.


--
Dudley Henriques
  #44  
Old December 27th 07, 08:37 PM posted to rec.aviation.piloting,rec.aviation.aerobatics
Neil Gould
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Default spins from coordinated flight

Recently, Todd W. Deckard posted:

That is to say "stall reocover while turning and climbing is not
mandatory"

Any item in the PTS is "required", and can be part of the test. Perhaps
you should re-read item #5 under both power-on and power-off stalls so as
not to be surprised during your check ride.

Neil


  #45  
Old December 27th 07, 11:52 PM posted to rec.aviation.piloting,rec.aviation.aerobatics
Jose
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Posts: 897
Default spins from coordinated flight

To define turn using axis reference is not the best way to explain turn since once established in a stable turn there should be no movement on the airplane's axis system.

I am not sure I'm getting this.

We'll ignore translation (straight line motion).

The axis system is (as I have been using it) fixed to the aircraft, and the axis system moves whenever the aircraft rotates (around any point). It has nothing to do with the actual earth's horizon.

Then, as I understand it, rotation of the aircraft involves a rotation around one or more of the axes. Yaw involves rotation (=of= the longitudinal axis, and thus the airplane) =about= the (airplane) vertical axis, =in= the plane (roughly described by the wing tips and tail) of the (airplane) horizontal axes.

In a turn, slipping, skidding, or coordinated, the nose of the airplane (dragging the longitudinal axis with it) is changing its direction. The airplane is changing heading. If this happens at a constant rate (say, 3 degrees per second), I would say the aircraft is yawing at a steady angular velocity, and undergoing no acceleration in yaw. To =enter= or =leave= this state would require an =acceleration= of yaw in one direction or another.

Where do our understandings and vocabulary diverge?

Jose
--
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for Email, make the obvious change in the address.
  #46  
Old December 28th 07, 12:08 AM posted to rec.aviation.piloting,rec.aviation.aerobatics
Dudley Henriques[_2_]
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Posts: 2,546
Default spins from coordinated flight

Jose wrote:
To define turn using axis reference is not the best way to explain
turn since once established in a stable turn there should be no
movement on the airplane's axis system.


I am not sure I'm getting this.

We'll ignore translation (straight line motion).

The axis system is (as I have been using it) fixed to the aircraft, and
the axis system moves whenever the aircraft rotates (around any point).
It has nothing to do with the actual earth's horizon.
Then, as I understand it, rotation of the aircraft involves a rotation
around one or more of the axes. Yaw involves rotation (=of= the
longitudinal axis, and thus the airplane) =about= the (airplane)
vertical axis, =in= the plane (roughly described by the wing tips and
tail) of the (airplane) horizontal axes.

In a turn, slipping, skidding, or coordinated, the nose of the airplane
(dragging the longitudinal axis with it) is changing its direction. The
airplane is changing heading. If this happens at a constant rate (say,
3 degrees per second), I would say the aircraft is yawing at a steady
angular velocity, and undergoing no acceleration in yaw. To =enter= or
=leave= this state would require an =acceleration= of yaw in one
direction or another.

Where do our understandings and vocabulary diverge?

Jose

Jose;
Do some research on the aircraft axis system and what each axis
represents, then research forces in turns. It should become clearer then.
Thank you


--
Dudley Henriques
  #47  
Old December 28th 07, 01:18 AM posted to rec.aviation.piloting,rec.aviation.aerobatics
Dave S
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Posts: 406
Default spins from coordinated flight

Todd W. Deckard wrote:
Can you depart and spin from coordinated flight? Specifically a coordinated
climbing turn?


During training and several BFR's I have done stalling turns with a CFI
present. I have never spun.

Your Mileage May Vary.
  #48  
Old December 28th 07, 06:29 AM posted to rec.aviation.piloting, rec.aviation.aerobatics
[email protected]
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Posts: 1,130
Default spins from coordinated flight

On Dec 27, 10:07 am, Dudley Henriques wrote:
Todd W. Deckard wrote:
But the links that Dan_Thomas sent me indicated that the airplane would not
stall "straight ahead" if you were in a climbing turn. The outside wing
has a higher AoA
which diverges even further as it initially drops.


Dan isn't wrong.
Climbing turn stalls are a bit complicated to nail down to a strict
behavioral pattern as each airplane and indeed each stall entered in a
specific airplane will probably be exhibiting slightly different stall
behavior due to varying control inputs by the pilot. The result of this
is that climbing turn stalls can produce different results depending on
what the pilot is doing with the airplane up to and at the instant of
the stall break.
Basically, if you are (as we say) coordinated, the top wing will stall
first and the airplane will roll off in that direction. The reason for
this is that as the stall is approached both wings start losing lift
causing the airplane to mush into a slip. The highest wing gets
interference from the fuselage and usually quits first. If you watch the
ball as this happens, as you get near to stall, you'll probably notice
that if you can't hold it centered, and a slip develops, that high wing
will usually be the one to go first.
This doesn't always happen however :-)) and if you skid the airplane,
the bottom wing can break first.
The bottom line is that in most climbing turn stalls, you will get a
roll off as the stall breaks, but remember, this is a ROLL OFF, not a
yaw rate!! Just reduce the angle of attack and use aileron to raise the
lowering wing and no pro spin forces are present.

--
Dudley Henriques


But we've had full-blown spins develop from the climbing-turn
stall. If the pilot isn't expecting it, it will roll off the high side
and start yawing in that direction, and if full power is still on it
can get violent. It'll spin readily, as this re-quoted excerpt states:

"Full power stalls in a balanced climbing turn tend to result in the
outer
wing stalling first, because of the higher aoa of the outer wing, with
a
fairly fast wing and nose drop (particularly so if the propeller
torque
effect is such that it reinforces the roll away from the original
direction
of turn and the aircraft is a high wing configuration) and likely to
result
in a stall/spin situation that any pilot lacking spin recovery
experience
may find difficult to deal with."

By "balanced" I presume these Aussies mean "coordinated." And if
the stall is fully developed the aileron won't help and might
aggravate things.
Of course if the pilot gets the nose down quick, and uses rudder
rather than aileron, it will recover OK. But he has to understand
immediately what's happening.

Dan
  #49  
Old December 28th 07, 06:44 AM posted to rec.aviation.piloting,rec.aviation.aerobatics
Dudley Henriques[_2_]
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Posts: 2,546
Default spins from coordinated flight

wrote:
On Dec 27, 10:07 am, Dudley Henriques wrote:
Todd W. Deckard wrote:
But the links that Dan_Thomas sent me indicated that the airplane would not
stall "straight ahead" if you were in a climbing turn. The outside wing
has a higher AoA
which diverges even further as it initially drops.

Dan isn't wrong.
Climbing turn stalls are a bit complicated to nail down to a strict
behavioral pattern as each airplane and indeed each stall entered in a
specific airplane will probably be exhibiting slightly different stall
behavior due to varying control inputs by the pilot. The result of this
is that climbing turn stalls can produce different results depending on
what the pilot is doing with the airplane up to and at the instant of
the stall break.
Basically, if you are (as we say) coordinated, the top wing will stall
first and the airplane will roll off in that direction. The reason for
this is that as the stall is approached both wings start losing lift
causing the airplane to mush into a slip. The highest wing gets
interference from the fuselage and usually quits first. If you watch the
ball as this happens, as you get near to stall, you'll probably notice
that if you can't hold it centered, and a slip develops, that high wing
will usually be the one to go first.
This doesn't always happen however :-)) and if you skid the airplane,
the bottom wing can break first.
The bottom line is that in most climbing turn stalls, you will get a
roll off as the stall breaks, but remember, this is a ROLL OFF, not a
yaw rate!! Just reduce the angle of attack and use aileron to raise the
lowering wing and no pro spin forces are present.

--
Dudley Henriques


But we've had full-blown spins develop from the climbing-turn
stall. If the pilot isn't expecting it, it will roll off the high side
and start yawing in that direction, and if full power is still on it
can get violent. It'll spin readily, as this re-quoted excerpt states:

"Full power stalls in a balanced climbing turn tend to result in the
outer
wing stalling first, because of the higher aoa of the outer wing, with
a
fairly fast wing and nose drop (particularly so if the propeller
torque
effect is such that it reinforces the roll away from the original
direction
of turn and the aircraft is a high wing configuration) and likely to
result
in a stall/spin situation that any pilot lacking spin recovery
experience
may find difficult to deal with."

By "balanced" I presume these Aussies mean "coordinated." And if
the stall is fully developed the aileron won't help and might
aggravate things.
Of course if the pilot gets the nose down quick, and uses rudder
rather than aileron, it will recover OK. But he has to understand
immediately what's happening.

Dan


It's nothing unusual for an airplane to spin out of a climbing turn
stall.....IF yaw isn't corrected as the stall breaks. It depends in a
large part on how ham handed the pilot is as the stall is approached.
The break can be clean nose down, usually high wing first, and can even
be low wing first. In ALL scenarios, yaw must be eliminated from the
equation as the stall breaks to prevent spin. If the angle of attack is
recovered normally as the stall breaks, even if roll off is present, by
coordinated use of flight controls raising the wing and the yaw is
eliminated, a normal recovery will be accomplished.
If the pilot applies incorrect control responses and doesn't eliminate
the yaw, the combination of stall and a yaw rate can easily spin the
airplane.
These power on climbing turn stalls can be done all day long by pilots
using proper recovery technique as the stall breakes with absolutely no
spin issue in the recovery equation.


--
Dudley Henriques
  #50  
Old December 28th 07, 02:58 PM posted to rec.aviation.piloting,rec.aviation.aerobatics
Todd W. Deckard
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Posts: 65
Default spins from coordinated flight

For my conclusion I am fixed in the stall + yaw = spin (where I was to start
with).

I appreciate the references to the Transport Canada material as the tendency
for the airplane to
"go over the top" when snapping over from a climbing turn was a very needed
reminder and
I intend to experiment with it aggressively next year with the appropriate
equipment and circumstances.

At Mr. Henriques suggestion I solicited an explaination from Rich Stowell:

He is the evangelist for the P-A-R-E recovery acronymn.

Power (to idle)
Ailerons (to neutral)
Rudder (against the spin)
Elevator (briskly forward to break the stall).

I must say he drafted a very thoughtful response to me in a direct email.

The only conclusion I can offer to this essay is to point to his web site,
and his book(s):

http://www.richstowell.com/

He articulately explained that the inclinometer is not a precise indication
of coordinated flight and that
some form of yaw is a necessary ingredient to the spin.

With this I'll sign off, thanks for the responses.

Todd Deckard




 




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