Sampo, to still answer this "personal posting" below (and then taking
the discussion offline...):
The (also) Swedish pilot I know has been both a military pilot and
some (civilian) pilot. I know that he has worked in a very
professional sense on air traffic safety. (Means: He has been on
security "boards"/committees.)
So I don't care if I am an aviation layman or not, but compared to him
we are probably all laymen.
Regarding avoid death spirals, you might "learn" about how to avoid
these, via YT channels and other means. ;-)
Do you really think that any modern passenger airplane should come
even close to any such a state? (I mean, there are potent autopilots
nowadays.)
This is why you have sensors, automatic plane stabilization, etc.
In this sense I also don't quite know why we are discussing these
issues here. It seems to be a special air safety "issue", and of
course this should not happen. Regarding military airplanes, these are
aerodynamically relatively unstable - which actually is a feature.
Even in this case the main safety issue is certainly not some death
spiral. (Rather: to crush into a tree or mountain, because you were
flying just "a few meters" too low? But this is more for the military
aviation case, I guess...)
We can happilty discuss ALL these issues between us, and I will
happikly add Anders to the discussion. (Who might know the "young
Swedish pilot discussing security stuff on YT for laymen", probably.)
""But whoever cares, really?"
"We should. Because none of us wants to drive an aircraft into the
ground, or a mountain."
Frankly, I trust in Airbus and "my pilot". (Because I am not better
than them...)
Best,
Stefan
----- Mensagem de Sampo Syreeni <de...@iki.fi> ---------
Data: Wed, 1 Mar 2023 05:04:53 +0200 (EET)
De: Sampo Syreeni <de...@iki.fi>
Assunto: [Sursound] about aviation [ot]
Para: Surround Sound discussion group <sursound@music.vt.edu>
On 2023-02-22, Stefan Schreiber wrote:
Maybe it is me who now really would need some crash course in aviation,
Yes.
Is flying in a spiral not something you would do in some intentional way?
Sometimes you might do it purposely, yes, but no, you typically
would not do that sort of thing willingly. Because it's *highly*
dangerous. Most likely if you go there, you will dive, and then die,
with no means of recovery. You'd crash yourself and all of your
passengers.
https://en.wikipedia.org/wiki/Graveyard_spiral
Stefan, lately I've been minding the Mentour Pilot channel on
Youtube. The guy doing that is a Swedish pilot, used to piloting the
Boeing 737, and not so much anything AirBus. He then also takes down
*all* of the disasters which have happened in the recent decades,
talking down and analysing what happened in talk and instrumentation.
I'd thoroughly recommend that Swedish Chef. He's stupendously good,
physically minded, all of it. He knows what he does. In fact, just
now, within weeks, he took upon himself to spin a 737 in a
simulator, upside down, going into an upset and something which
could go into a lateral spin. "Yes, you can do it, but..."
https://www.youtube.com/watch?v=JhzaogGQNFU
Then on the other hand... https://www.youtube.com/watch?v=AaA7kPfC5Hk
Everybody thinks this sort manoeuvre is hazardous. Whereas it
isn't: a barrel roll is just a 1G monoeuvre with pretty much no risk
at all. An aileron roll carries much more risk, and is much more
difficult to execute properly. Flipping a helicopter is harder, but
not *much* harder; these aerodynamics go to superavionics and high
control, of the kind leading to such movements as the infamous
Pugachev Cobra ( https://www.youtube.com/watch?v=kcLavSl58yQ ).
Of course, there will be more. One of the things here is active
parametric arrays. To order twenty or more, in military radars, such
as there are in the F-36. Those AESA's work interferometrically just
as would a high order coherent ambisonic rig. They only do so at
VHF/UHF/Ka-band fŕequencies, in radio, at about 2000-6000 closely
spaced "speakers"/transmitters, all of them spaced about a quarter
of a wavelength apart. Each of them doing gigabits per second, and
maybe a 50W max. In toto, some continuous 100kW in software defined
radio, in intermittent, fully superfast transmittance and
receivership.
Opposite to the spin situation, because this is kind of uncontrolled.
Or you "have to do something".)
I've never flown a plane. Yet I think I could recover a plane from
such a spiral. What you do there is: 1) you push down on the yoke to
recover airspeed, 2) you use ailerons to level off, and 3) if you
then have to go to too much airspeed while descending, you'll spoil
your airfoil, and then apply lift and drag via flaps, while not
approching aerodynamic stall.
So in which sense would you have to "recover" from the spiral?
You need to see which attitude you're at. You will need to put
slight ailerons in the opposite diretion. You'd be falling and you'd
need to follow your airspeed. If too much, you'd have to even spoil.
If not, you'd need to increase thrust in order to gain kinetic
energy. In any case, you'd want to keep yourself at about 160-200
knots of equivalent speed and so kinetic energy, in order to
stabilize the aircraft, and then level off.
I read this before, btw:
"But whoever cares, really?
We should. Because none of us wants to drive an aircraft into the
ground, or a mountain.
We all know what we're talking about.
I know. Do we all?
Especially when you have to use the instrument in order to deliver
yourself and your passengers from a death spiral."
One of these things really is the death spiral. The thing here is
that you don't *feel* at *all* that you're in it. It's kind of like
the barrel roll, at one G. It's just a manoeuvre or a mistake, which
feels like nothing bad is happening. Yet if you don't follow your
instrumentation, you might be going into a death spiral. (This is
why the synthetic horizon in an airplane *is*. You're supposed, as a
pilot, to follow it, precisely *because* when it isn't level while
you feel level, *then* you're off in your feelings. You might be
going into a dive or spiral, and you're supposed to fly by
meters/instrumentation, not by your seat.
So what is this spiral? A situation when the plane is spinning,
even a stall (interruption of air flow), or what else?
The typical death spiral isn't a stall at first at all. Rather it's
a continuously advancing bank to either side of the airplane. As a
pilot, you won't feel it happening, because the airplane is
intrinsically stable by design. Even if you go into that bank,
you'll just feel 1G of acceleration towards the floor.
However, now the floor might be at 15, 30, 45, 60, 90, and
eventually even 180 degrees from upright. Before you even know it.
And when you go even half there, think about the lift your wings
give you: going to 90 degrees, you suddenly have no horizontal lift
at all. You will sink. You might not lose control right yet, but you
will be in a situation which needs fast correction manoeuvres if you
don't want to run into terrain. And you typically don't know that
you have this problem, because you feel like you're in level flight,
even if you're factually falling out of the sky.
I've never flown a plane. But I'm a nerd to try to fly one. In
here, I've taken heed of instrument flying rules, the synthetic
horizon, and all of them accidents which have happened over the
years. I know how airplanes behave, and just, *just*, in theory, I
might even be able to land one or at least control one. Because I
*do* know what these things have, their basic controls, airbrakes,
thrust reversers, autopilots (two of them on Boeings, better yet on
an AirBus), all of the usual stuff.
Then I'd have to still tell you what the death spiral really is.
Because it's a about bank and losing lift by it. You'll never feel
it as a pilot, because se airframe will keep you at 1G downwards.
What happens is that you'll bank, and you'll progressively start to
lose lift, making your way sideways. You'll lose altitude, without
even knowing you drop as fuck, continuously. Your situational
awareness is bunk, and you only have a nigh minute now to recover;
if you go into this, you can crash straight down in a minute,
without knowing you'd done it, especially coming down through a
clowd cover. You might find yourself coming straight down at over
Mach 1, without ever having thought to do so.
( https://en.wikipedia.org/wiki/Spatial_disorientation I think
there is another name for this as well. )
A 'spiral', very different from any spin, was mentioned,
and Sampo seemed to think that recovery from that would
require regaining speed.
Take rapid suceeding accelerations against your XY and then XZ
planes. That will feel much worse than one of either. When done
harsly, it might lead to unconsciousness, or even permanent physical
injury. Because of the "spiral".
--
Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front
+358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2
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