spins from coordinated flight

Dudley Henriques schrieb:

There is only one thing you have to know about spins. To enter one you
need 2 things to be present; stall and a yaw rate. All the rest is
simply stating different ways to make these two things happen.

While I agree that this is a correct and simple recipe and therefore
quite useful in practice, I don't agree that it helps to *understand*
the situation, because *reason* for the spin is not the yaw rate. The
reason for the spin is an asymmetric angle of attack, i.e. one wing is
more stalled than the other. Of course this situation can only occur if
there is some yaw, which leads us to the recipe given above.

Recipe: As there is always some yaw in a coordinated turn (otherwise it
wouldn't be coordinated), you can perfectly enter a spin from a
coordinated turn. Aerodynamic reason: The inner wing has a higher angle
of attack than the outer, so it stalls first or, if both wings stall, it
is more stalled. Asymmetric stall condition - spin.

Stefan wrote:
Dudley Henriques schrieb:

There is only one thing you have to know about spins. To enter one you
need 2 things to be present; stall and a yaw rate. All the rest is
simply stating different ways to make these two things happen.

While I agree that this is a correct and simple recipe and therefore
quite useful in practice, I don't agree that it helps to *understand*
the situation, because *reason* for the spin is not the yaw rate. The
reason for the spin is an asymmetric angle of attack, i.e. one wing is
more stalled than the other. Of course this situation can only occur if
there is some yaw, which leads us to the recipe given above.

Recipe: As there is always some yaw in a coordinated turn (otherwise it
wouldn't be coordinated), you can perfectly enter a spin from a
coordinated turn. Aerodynamic reason: The inner wing has a higher angle
of attack than the outer, so it stalls first or, if both wings stall, it
is more stalled. Asymmetric stall condition - spin.


You can argue this until the cows come home but the answer is always the
same. To spin an airplane you need stall and a yaw rate...period! All
the rest of it, the difference in aoa, the dynamics of autorotation, the
whole magilla, is nothing but explaining in aerodynamic terms what
happens AFTER the stall and yaw rate are introduced.

As you say, understanding these things is essential, but they are the
EFFECT of what causes spin.
Look at it this way. Without stall and without a yaw rate being
introduced, you will have none of the things happening that you have
mentioned. None will be present until stall occurs and a yaw rate
introduced.

They are relevant of course, but not the single answer a pilot needs to
know when addressing the subject of spins.

When I ask a student what causes a spin, I don't want that student to
tell me what happens to each wing of the airplane as the spin is
developing. If I get that answer I'm immediately going to ask that
student how the airplane was placed in a position to cause these effects
to happen.

When someone asks what causes a spin, or whether or not an airplane can
be spun from this flight position or that one, the correct answer is
that stall and yaw rate must be present to produce a spin; and that spin
can be entered from ANY flight condition.
If you then ask a student to explain the aerodynamics in play as a spin
develops, it's THEN you want the auto rotational aerodynamics.

--
Dudley Henriques

Dudley Henriques schrieb:

When someone asks what causes a spin, ... the correct answer is
that stall and yaw rate must be present to produce a spin
....
If you then ask a student to explain the aerodynamics in play as a spin
develops, it's THEN you want the auto rotational aerodynamics.

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. My approach
tries to understand the underlying physics and to deduct the needed
pilot action from there. Not nessecairy for a pilot, but it's my style,
I think it's interesting and it's the prerequisite if you want to go on
your own feet beyond the tought stuff.

Now if only that fog around here would go away so I could go and rent
that Cap 10 and do some spins...

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.



"Stefan" wrote in message
...
| Dudley Henriques schrieb:
|
| When someone asks what causes a spin, ... the correct answer is
| that stall and yaw rate must be present to produce a spin
| ...
| If you then ask a student to explain the aerodynamics in play as a spin
| develops, it's THEN you want the auto rotational aerodynamics.
|
| 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. My approach
| tries to understand the underlying physics and to deduct the needed
| pilot action from there. Not nessecairy for a pilot, but it's my style,
| I think it's interesting and it's the prerequisite if you want to go on
| your own feet beyond the tought stuff.
|
| Now if only that fog around here would go away so I could go and rent
| that Cap 10 and do some spins...

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?

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?

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

Stefan,

I am currently chanting the "ball centered = no spin" mantra. However
I am very sympathetic to your explaination that its a difference in AoA.
In the end, that may be the purest way to explain the spin.

If this thread sustains I'll listen in and see what I can sift out.

Todd

"Stefan" wrote in message news:4bb62$4773ba89

While I agree that this is a correct and simple recipe and therefore quite
useful in practice, I don't agree that it helps to *understand* the
situation, because *reason* for the spin is not the yaw rate. The reason
for the spin is an asymmetric angle of attack, i.e. one wing is more
stalled than the other. Of course this situation can only occur if there
is some yaw, which leads us to the recipe given above.

Recipe: As there is always some yaw in a coordinated turn (otherwise it
wouldn't be coordinated), you can perfectly enter a spin from a
coordinated turn. Aerodynamic reason: The inner wing has a higher angle of
attack than the outer, so it stalls first or, if both wings stall, it is
more stalled. Asymmetric stall condition - spin.