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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