Re: [Sursound] [off-topic] Spirals

[Sampo Syreeni]

On 2023-02-22, Fons Adriaensen wrote:

Is flying in a spiral not something you would do in some intentional 
way?


Yes and no...


Yes and no. It can be done and has been done as a showsport. As an 
aerobatics exercise. But going into a death spiral is *definitely* not 
safe; anybody doing it has to be well versed in recovering from it 
unless se wants to hit the ground; even sooner than se thought it would 
be possible. Also, due to the somatogravic illusion which often then 
sets in, and the fact that the situation can progress to a nosedive much 
faster than even trained pilots often think, doing such a thing on 
purpose is rather reckless. It just calls of loss of life.


There is no essential difference between a spiral and a normal turn, 
except that a spiral is usually not intentional and in that case it 
can become so extreme that it puts the aircraft in danger. Both spins 
and spirals are done intentionally as part of pilot training.


Not *quite* true, I think. Because in a spiral you lose altitude, by 
definition. In a normal bank you might not, because you can — and should 
— use thrust and rudder in order to maintain it.


True, you sometimes might want to do a hard bank *and* lose altitude. 
It's being done. But going into such a situation places you in a dynamic 
which pilot-loop-considered is highly unstable. Especially in instrument 
flying conditions, where you don't have a stable, intuitionistic 
attitude reference. And since in those conditions you the pilot often 
get kind of counter-intuitive signals from your middle ear and your body 
as to where you are, you might even half-deterministically guide the 
plane the *exact* wrong way.


In fact my favourite Swedish pilot channel, Mentour Pilot, just made a
video about this: https://www.youtube.com/watch?v=keQSpUq6Vis&t=1497s .

All (normal) aircraft have pitch stability, but few have roll 
stability.


In fact almost all have perturbative roll stability as well. However, 
few to none aircraft have absolute stability, in the sense that they'd 
recover themselves from *all* conditions exceeding their design flight 
envelope, by passive means. Actively, sure, most of today's 4th to 5th 
generation fighter jets can do *unbelievable* stunts under computer 
control in order to recover, automatically, as can modern passenger 
jets, but a purely passive recovery from things like an upset, a stall 
in any flight surface, a spiral... They're just not in the design 
manual; the airplane just isn't designed — nor possibly could be 
designed to be — that stable over the whole state space.


This is then why the flight control systems and warning systems try and 
warn the pilot before they approach the passive stability margin. "Bank, 
bank." Because after that you're wont to go into aerobatics, which 
typical commercial pilots haven't trained for. (My favourite examples to 
the contrary again come from that Swedish pilot of 737's, Mentour Pilot. 
He inverted his plane in a simulator, and recovered from the resulting 
dive. He also analyzed to the hilt an upset resulting from wake 
turbulence, leading to a rapid but again recovered inversion.)


That means that if the wings are not level, there is nothing that 
would make them return to level.


There in fact is, to a point. That's why we have upwards sloping wings 
on aircraft with low wings, and downwards sloping on those such as the 
Stratofortress. They lend a *modicum* of roll stability to an airframe, 
but then they do so only within a slim margin. Beyond it, passive 
stability is lost.


Which is also one of the reasons commercial pilots have trouble handling 
a high, unstable bank angle. Sure, they've undergone one or two 
trainings in a simulator for it, but then they almost never actually 
encouter it on air. Then when it happens, panic sets in, and whoops, you 
but forget about your training, you don't even get to look at your 
instrumentation, as you should. Especially in instrument conditions; 
whence again, 178 seconds; how it feels to do a death spiral. 
https://www.youtube.com/watch?v=pc9xI4kpY4w&t=2s )


And in many cases the aircraft may very well be unstable in that axis: 
if left alone, the roll angle will slowly increase.


No, it necessarily doesn't. If you're within the stable flight envelope, 
it will, but you might not be, and you won't necessarily know whether 
you are.


Then you now have 178 seconds to live. And you don't know it. You'll 
only know it at most tens of seconds before your demise.


The "fun" thing here is that I only started minding the aerodynamics of 
aircraft via this very list. About how air *really* behaves in extreme 
conditions, and what it then does, around physical objects. Like 
long-throw bass speakers. How it becomes turbulent and even transsonic 
there.


This talk about spirals might be kind of tangential here, yes, 
off-topic...but actually it might not be *fully* so.



A non-zero roll angle means that part of the lift force generated
by th

Re: [Sursound] [off-topic] Spirals

[Sampo Syreeni]

On 2023-03-08, Steven Boardman wrote:


I would love to make a sound do a death spiral motion .


As would I. So let's make one.

The thing is that it would have to be slowly elevating, stereophonic. 
Very slowly, because you don't really *understand* a graveyard spiral 
before you die. Any music of this ilk would have to reflect...it. This 
spiral.



With an LFO,


Definitely not to be heard.


on each axis,


Yes, but do you even know how it's heard? I obviously do.

bit a load of doppler, distance attenuation and filtering, i think i 
could kill the thread quite quickly


Over SSB demodulation you probably could not hear any of that. Not 
unless you were talking with an orbital module, crashing down. Doppler 
modulation isn't much of a problem unless you do wideband digital 
thingies, at about fighter jet speeds. Transsonic to something like 2 
Mach, changing all the time, fast, and in angle, so that the antenna 
doesn't track well either.

--
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
___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Sampo Syreeni]

On 2023-03-08, Marc Lavallée wrote:

The article is freely available here: 
https://ntrs.nasa.gov/citations/20080042307


Fuck. What the actual fuck, right here. You just returned to audiditory 
stuff, and showed how a blind pilot could return from a graveyard 
spiral, by ear.


I *certainly* didn't know something like this would be possible. Jesu 
Kristu, this is just...wrong.

--
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
___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Panos Kouvelis]

:-D

*Pan Athen*
SoundFellas , *MediaFlake Ltd
*
Digital Media Services, Content, and Tools


On Thu, Mar 9, 2023 at 10:55 PM Steven Boardman 
wrote:

> Hopefully it would mislead any sursounders from talking about aviation
> here, and kill this thread dead 🤣
>
> On Thu, 9 Mar 2023, 15:07 Panos Kouvelis,  wrote:
>
> > Distance, or in general virtual acoustics, is a good idea. Alternating
> > between early/late reflections, air damping, level, and even Doppler for
> > speed of movement could help with this sonification.
> >
> > I'm no expert in aviation, but would this help the brain of the pilots or
> > mislead them as to what is happening?
> >
> > *Pan Athen*
> > SoundFellas , *MediaFlake Ltd
> > *
> > Digital Media Services, Content, and Tools
> >
> >
> > On Wed, Mar 8, 2023 at 9:44 PM Steven Boardman <
> boardroomout...@gmail.com>
> > wrote:
> >
> > > I would love to make a sound do a death spiral motion .
> > > With an LFO, on each axis, bit a load of doppler, distance attenuation
> > and
> > > filtering, i think i could kill the thread quite quickly
> > >
> >
> >
> -- next part --
> An HTML attachment was scrubbed...
> URL: <
> https://mail.music.vt.edu/mailman/private/sursound/attachments/20230309/480e74eb/attachment.htm
> >
> ___
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here,
> edit account or options, view archives and so on.
>
-- next part --
An HTML attachment was scrubbed...
URL: 

___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Steven Boardman]

Hopefully it would mislead any sursounders from talking about aviation
here, and kill this thread dead 🤣

On Thu, 9 Mar 2023, 15:07 Panos Kouvelis,  wrote:

> Distance, or in general virtual acoustics, is a good idea. Alternating
> between early/late reflections, air damping, level, and even Doppler for
> speed of movement could help with this sonification.
>
> I'm no expert in aviation, but would this help the brain of the pilots or
> mislead them as to what is happening?
>
> *Pan Athen*
> SoundFellas , *MediaFlake Ltd
> *
> Digital Media Services, Content, and Tools
>
>
> On Wed, Mar 8, 2023 at 9:44 PM Steven Boardman 
> wrote:
>
> > I would love to make a sound do a death spiral motion .
> > With an LFO, on each axis, bit a load of doppler, distance attenuation
> and
> > filtering, i think i could kill the thread quite quickly
> >
>
>
-- next part --
An HTML attachment was scrubbed...
URL: 

___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Panos Kouvelis]

Distance, or in general virtual acoustics, is a good idea. Alternating
between early/late reflections, air damping, level, and even Doppler for
speed of movement could help with this sonification.

I'm no expert in aviation, but would this help the brain of the pilots or
mislead them as to what is happening?

*Pan Athen*
SoundFellas <https://soundfellas.com/>, *MediaFlake Ltd
<http://mediaflake.com/>*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 9:44 PM Steven Boardman 
wrote:

> I would love to make a sound do a death spiral motion .
> With an LFO, on each axis, bit a load of doppler, distance attenuation and
> filtering, i think i could kill the thread quite quickly
>
> On Wed, 8 Mar 2023, 17:00 Chris Woolf,  wrote:
>
> > Ta - looks interesting - there's always someone who's been there before;}
> >
> > Chris Woolf
> >
> >
> > On 08/03/2023 16:21, Marc Lavallée wrote:
> > > The article is freely available here:
> > > https://ntrs.nasa.gov/citations/20080042307
> > >
> > > Marc
> > >
> > > Le 2023-03-08 à 11 h 15, Picinali, Lorenzo a écrit :
> > >> Hello Chris,
> > >>
> > >> this might be interesting for you!
> > >>
> > >>
> >
> https://journals.sagepub.com/doi/pdf/10.1177/154193120805200103?casa_token=CptzIp9vOaQA:fG10j5X-vgVL92L3YHFjBTRAyYUCHfVpsuYDrU3DcGX4wPgzym4ZZoLHSh2I2AfvIZrEyKpIQ54
> > >>
> > >>
> > >> I remember they also presented this work at ICAD in Paris in 2008,
> > >> and if I remember well they won the best paper award!
> > >>
> > >> Best
> > >> Lorenzo
> > >>
> > >>
> > >>
> > >> --
> > >> Lorenzo Picinali
> > >> Reader in Audio Experience Design<https://www.axdesign.co.uk/>
> > >> Dyson School of Design Engineering
> > >> Imperial College London
> > >> Dyson Building
> > >> Imperial College Road
> > >> South Kensington, SW7 2DB, London
> > >> E: l.picin...@imperial.ac.uk
> > >>
> > >> http://www.imperial.ac.uk/people/l.picinali
> > >> https://www.axdesign.co.uk/
> > >> https://www.sonicom.eu/
> > >> 
> > >> From: Sursound  on behalf of Chris
> > >> Woolf 
> > >> Sent: 08 March 2023 16:03
> > >> To: sursound@music.vt.edu 
> > >> Subject: Re: [Sursound] [off-topic] Spirals
> > >>
> > >>
> > >> ***
> > >> This email originates from outside Imperial. Do not click on links
> > >> and attachments unless you recognise the sender.
> > >> If you trust the sender, add them to your safe senders list
> > >> https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email
> > >> stamping for this address.
> > >> ***
> > >> Bringing things round in a circle (rather than a spiral)
> > >>
> > >> Anyone any ideas how one could provide an audio horizon that could be
> a
> > >> mimic of the gyro artificial horizon? That could presumably add an
> > >> additional warning of unintentional spiralling, and one that would
> > >> signal a discrepancy between gravitational/centrifugal pull and
> absolute
> > >> vertical.
> > >>
> > >> I can see the problems of providing a height dimension with
> headphones,
> > >> and also a question of what audio signals would have sufficient rate
> to
> > >> provide the frequency of stimulus needed. ATC and TCAS would be some
> > >> help but I think you would need rather more than just that.
> > >>
> > >> This is just coffee-time thoughts - I'm not planning to go flying any
> > >> time soon;}
> > >>
> > >> Chris Woolf
> > >>
> > >>
> > >> On 08/03/2023 13:23, t.mich...@posteo.de wrote:
> > >>> Hi Panos!
> > >>>
> > >>> First of all: Welcome!
> > >>> Second: YES you are definitely in the right place.
> > >>> Third: If you have any question, feel invite to ask. :-)
> > >>>
> > >>>
> > >>> Take care and stay healthy
> > >>> Cheers
> > >>>
> > >>> Thorsten
> > >>>
> > >>>
> > >>> Am 08.03.2023 00:08 schrieb Panos Kouvelis:
> > >>>> I recently subs

Re: [Sursound] [off-topic] Spirals

[Steven Boardman]

I would love to make a sound do a death spiral motion .
With an LFO, on each axis, bit a load of doppler, distance attenuation and
filtering, i think i could kill the thread quite quickly

On Wed, 8 Mar 2023, 17:00 Chris Woolf,  wrote:

> Ta - looks interesting - there's always someone who's been there before;}
>
> Chris Woolf
>
>
> On 08/03/2023 16:21, Marc Lavallée wrote:
> > The article is freely available here:
> > https://ntrs.nasa.gov/citations/20080042307
> >
> > Marc
> >
> > Le 2023-03-08 à 11 h 15, Picinali, Lorenzo a écrit :
> >> Hello Chris,
> >>
> >> this might be interesting for you!
> >>
> >>
> https://journals.sagepub.com/doi/pdf/10.1177/154193120805200103?casa_token=CptzIp9vOaQA:fG10j5X-vgVL92L3YHFjBTRAyYUCHfVpsuYDrU3DcGX4wPgzym4ZZoLHSh2I2AfvIZrEyKpIQ54
> >>
> >>
> >> I remember they also presented this work at ICAD in Paris in 2008,
> >> and if I remember well they won the best paper award!
> >>
> >> Best
> >> Lorenzo
> >>
> >>
> >>
> >> --
> >> Lorenzo Picinali
> >> Reader in Audio Experience Design<https://www.axdesign.co.uk/>
> >> Dyson School of Design Engineering
> >> Imperial College London
> >> Dyson Building
> >> Imperial College Road
> >> South Kensington, SW7 2DB, London
> >> E: l.picin...@imperial.ac.uk
> >>
> >> http://www.imperial.ac.uk/people/l.picinali
> >> https://www.axdesign.co.uk/
> >> https://www.sonicom.eu/
> >> 
> >> From: Sursound  on behalf of Chris
> >> Woolf 
> >> Sent: 08 March 2023 16:03
> >> To: sursound@music.vt.edu 
> >> Subject: Re: [Sursound] [off-topic] Spirals
> >>
> >>
> >> ***
> >> This email originates from outside Imperial. Do not click on links
> >> and attachments unless you recognise the sender.
> >> If you trust the sender, add them to your safe senders list
> >> https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email
> >> stamping for this address.
> >> ***
> >> Bringing things round in a circle (rather than a spiral)
> >>
> >> Anyone any ideas how one could provide an audio horizon that could be a
> >> mimic of the gyro artificial horizon? That could presumably add an
> >> additional warning of unintentional spiralling, and one that would
> >> signal a discrepancy between gravitational/centrifugal pull and absolute
> >> vertical.
> >>
> >> I can see the problems of providing a height dimension with headphones,
> >> and also a question of what audio signals would have sufficient rate to
> >> provide the frequency of stimulus needed. ATC and TCAS would be some
> >> help but I think you would need rather more than just that.
> >>
> >> This is just coffee-time thoughts - I'm not planning to go flying any
> >> time soon;}
> >>
> >> Chris Woolf
> >>
> >>
> >> On 08/03/2023 13:23, t.mich...@posteo.de wrote:
> >>> Hi Panos!
> >>>
> >>> First of all: Welcome!
> >>> Second: YES you are definitely in the right place.
> >>> Third: If you have any question, feel invite to ask. :-)
> >>>
> >>>
> >>> Take care and stay healthy
> >>> Cheers
> >>>
> >>> Thorsten
> >>>
> >>>
> >>> Am 08.03.2023 00:08 schrieb Panos Kouvelis:
> >>>> I recently subscribed to this mailing list for insightful
> >>>> discussions on
> >>>> surround sound.
> >>>>
> >>>> Up 'till now, the material I have received is about aviation.
> >>>>
> >>>> Am I in the wrong place?
> >>>>
> >>>> :-)
> >>>>
> >>>> *Pan Athen*
> >>>> SoundFellas <https://soundfellas.com/>, *MediaFlake Ltd
> >>>> <http://mediaflake.com/>*
> >>>> Digital Media Services, Content, and Tools
> >>>>
> >>>>
> >>>> On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:
> >>>>
> >>>>> On 2023-02-22, Fons Adriaensen wrote:
> >>>>>
> >>>>>> And in many cases the aircraft may very well be unstable in that
> >>>>> axis:
> >>>>>> if left alone, the roll angle will slowly

Re: [Sursound] [off-topic] Spirals

[Chris Woolf]

Ta - looks interesting - there's always someone who's been there before;}

Chris Woolf


On 08/03/2023 16:21, Marc Lavallée wrote:
The article is freely available here: 
https://ntrs.nasa.gov/citations/20080042307


Marc

Le 2023-03-08 à 11 h 15, Picinali, Lorenzo a écrit :

Hello Chris,

this might be interesting for you!

https://journals.sagepub.com/doi/pdf/10.1177/154193120805200103?casa_token=CptzIp9vOaQA:fG10j5X-vgVL92L3YHFjBTRAyYUCHfVpsuYDrU3DcGX4wPgzym4ZZoLHSh2I2AfvIZrEyKpIQ54 



I remember they also presented this work at ICAD in Paris in 2008, 
and if I remember well they won the best paper award!


Best
Lorenzo



--
Lorenzo Picinali
Reader in Audio Experience Design<https://www.axdesign.co.uk/>
Dyson School of Design Engineering
Imperial College London
Dyson Building
Imperial College Road
South Kensington, SW7 2DB, London
E: l.picin...@imperial.ac.uk

http://www.imperial.ac.uk/people/l.picinali
https://www.axdesign.co.uk/
https://www.sonicom.eu/

From: Sursound  on behalf of Chris 
Woolf 

Sent: 08 March 2023 16:03
To: sursound@music.vt.edu 
Subject: Re: [Sursound] [off-topic] Spirals


***
This email originates from outside Imperial. Do not click on links 
and attachments unless you recognise the sender.
If you trust the sender, add them to your safe senders list 
https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email 
stamping for this address.

***
Bringing things round in a circle (rather than a spiral)

Anyone any ideas how one could provide an audio horizon that could be a
mimic of the gyro artificial horizon? That could presumably add an
additional warning of unintentional spiralling, and one that would
signal a discrepancy between gravitational/centrifugal pull and absolute
vertical.

I can see the problems of providing a height dimension with headphones,
and also a question of what audio signals would have sufficient rate to
provide the frequency of stimulus needed. ATC and TCAS would be some
help but I think you would need rather more than just that.

This is just coffee-time thoughts - I'm not planning to go flying any
time soon;}

Chris Woolf


On 08/03/2023 13:23, t.mich...@posteo.de wrote:

Hi Panos!

First of all: Welcome!
Second: YES you are definitely in the right place.
Third: If you have any question, feel invite to ask. :-)


Take care and stay healthy
Cheers

Thorsten


Am 08.03.2023 00:08 schrieb Panos Kouvelis:
I recently subscribed to this mailing list for insightful 
discussions on

surround sound.

Up 'till now, the material I have received is about aviation.

Am I in the wrong place?

:-)

*Pan Athen*
SoundFellas <https://soundfellas.com/>, *MediaFlake Ltd
<http://mediaflake.com/>*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:


On 2023-02-22, Fons Adriaensen wrote:


And in many cases the aircraft may very well be unstable in that

axis:

if left alone, the roll angle will slowly increase.

Actually, most modern aircraft are stable in the bank axis as well.
Part
of why they have swept wings, bent wings and wingtips and the 
like, is
to this regard. (Part of: most of it has to with approaching 
transonic

flight. But not all.)

The thing is though, and as you say below, the pilot won't feel
anything
weird when approaching a spiral. The built in stability of the 
airplane

will keep everybody in their seat at 1g acceleration perpendicular to
the floor, evenas the airplane banks to something approaching 90
degrees, and loses all of its lift. Then it just falls, sideways.

When that happens, you're in what's called a "death spiral", because
it's extremely difficult to recover from the condition, and you
typically don't even know you've entered one. When you do, you as a
pilot are already in a state of spatial disorientation; you 
*literally*

don't know which way is up and which down, and since the plane is by
now
basically half-way inverted, with now absolutely no lift, losing
altitude like a falling rock, you as the pilot have very little
possibility of correcting.

*Technically*, in *theory*, you often *could* recover, if you have
enough altitude, speed and sturdiness of airframe; even I have run it
through in a game. But in practice, recovery from a well developed
death
spiral is mostly beyond human ability. Especially once you lose 
height,

because at low altitudes, already going nose down, you can't even
convert high air speed/energy into a corrective manoeuvre before you
hit
the terrain, and there will only be seconds to lose.

This is then why the pilot flying is supposed to only look at the
instrumentation, and why there are auditory warnings about bank
angle on
the modern jets. The Swedish commercial midsize Boeing pilot, 
Mentour,

on YouTube, is first rate in explaining all of this stuff.

Okay, so, finally, how would you recover from 

Re: [Sursound] [off-topic] Spirals

[Eero Aro]

Chris Woolf wrote:

Anyone any ideas how one could provide an audio horizon that could be a 
mimic of the gyro artificial horizon?


A vague thought, that applies only to a small amount of surround sound 
recordings.


I do mostly nature recordings and record also in urban areas, where the 
distant
traffic hum is always present. The hum can be heard as a horizontal 
noise somewhere
in the distance. Here in the north the distant traffic noise is also 
different in the
winter and in the summer. We use studded tyres in the cars and they 
cause more
high frequencies in the noise than unstudded tyres. Another thing that 
changes the
sound scene in the winter is snow, it makes the general acoustics more 
dry and then

it is easier to detect the direction of single sound sources.

The problem is that a constant wide spectrum noise (the traffic hum) is 
more difficult

to localize than signals that have transient content.

Having said that, we _do_ localize an above flying jetplane, although it 
produces a noise
type sound. We know from experience, that an aeroplane almost always is 
flying above us.
But are we actively aware of the fact, that distant traffic hum appears 
as a zone above

the horizon?

Also, it would be somewhat strange to put artificially some kind of 
signal "beacons"
at the horizon level around the listener, because they aren't part of 
the actual recording.


Eero
___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Marc Lavallée]

The article is freely available here: 
https://ntrs.nasa.gov/citations/20080042307


Marc

Le 2023-03-08 à 11 h 15, Picinali, Lorenzo a écrit :

Hello Chris,

this might be interesting for you!

https://journals.sagepub.com/doi/pdf/10.1177/154193120805200103?casa_token=CptzIp9vOaQA:fG10j5X-vgVL92L3YHFjBTRAyYUCHfVpsuYDrU3DcGX4wPgzym4ZZoLHSh2I2AfvIZrEyKpIQ54

I remember they also presented this work at ICAD in Paris in 2008, and if I 
remember well they won the best paper award!

Best
Lorenzo



--
Lorenzo Picinali
Reader in Audio Experience Design<https://www.axdesign.co.uk/>
Dyson School of Design Engineering
Imperial College London
Dyson Building
Imperial College Road
South Kensington, SW7 2DB, London
E: l.picin...@imperial.ac.uk

http://www.imperial.ac.uk/people/l.picinali
https://www.axdesign.co.uk/
https://www.sonicom.eu/

From: Sursound  on behalf of Chris Woolf 

Sent: 08 March 2023 16:03
To: sursound@music.vt.edu 
Subject: Re: [Sursound] [off-topic] Spirals


***
This email originates from outside Imperial. Do not click on links and 
attachments unless you recognise the sender.
If you trust the sender, add them to your safe senders list 
https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for 
this address.
***
Bringing things round in a circle (rather than a spiral)

Anyone any ideas how one could provide an audio horizon that could be a
mimic of the gyro artificial horizon? That could presumably add an
additional warning of unintentional spiralling, and one that would
signal a discrepancy between gravitational/centrifugal pull and absolute
vertical.

I can see the problems of providing a height dimension with headphones,
and also a question of what audio signals would have sufficient rate to
provide the frequency of stimulus needed. ATC and TCAS would be some
help but I think you would need rather more than just that.

This is just coffee-time thoughts - I'm not planning to go flying any
time soon;}

Chris Woolf


On 08/03/2023 13:23, t.mich...@posteo.de wrote:

Hi Panos!

First of all: Welcome!
Second: YES you are definitely in the right place.
Third: If you have any question, feel invite to ask. :-)


Take care and stay healthy
Cheers

Thorsten


Am 08.03.2023 00:08 schrieb Panos Kouvelis:

I recently subscribed to this mailing list for insightful discussions on
surround sound.

Up 'till now, the material I have received is about aviation.

Am I in the wrong place?

:-)

*Pan Athen*
SoundFellas <https://soundfellas.com/>, *MediaFlake Ltd
<http://mediaflake.com/>*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:


On 2023-02-22, Fons Adriaensen wrote:


And in many cases the aircraft may very well be unstable in that

axis:

if left alone, the roll angle will slowly increase.

Actually, most modern aircraft are stable in the bank axis as well.
Part
of why they have swept wings, bent wings and wingtips and the like, is
to this regard. (Part of: most of it has to with approaching transonic
flight. But not all.)

The thing is though, and as you say below, the pilot won't feel
anything
weird when approaching a spiral. The built in stability of the airplane
will keep everybody in their seat at 1g acceleration perpendicular to
the floor, evenas the airplane banks to something approaching 90
degrees, and loses all of its lift. Then it just falls, sideways.

When that happens, you're in what's called a "death spiral", because
it's extremely difficult to recover from the condition, and you
typically don't even know you've entered one. When you do, you as a
pilot are already in a state of spatial disorientation; you *literally*
don't know which way is up and which down, and since the plane is by
now
basically half-way inverted, with now absolutely no lift, losing
altitude like a falling rock, you as the pilot have very little
possibility of correcting.

*Technically*, in *theory*, you often *could* recover, if you have
enough altitude, speed and sturdiness of airframe; even I have run it
through in a game. But in practice, recovery from a well developed
death
spiral is mostly beyond human ability. Especially once you lose height,
because at low altitudes, already going nose down, you can't even
convert high air speed/energy into a corrective manoeuvre before you
hit
the terrain, and there will only be seconds to lose.

This is then why the pilot flying is supposed to only look at the
instrumentation, and why there are auditory warnings about bank
angle on
the modern jets. The Swedish commercial midsize Boeing pilot, Mentour,
on YouTube, is first rate in explaining all of this stuff.

Okay, so, finally, how would you recover from a well developed death
spiral, presuming you realized you were in one? Well, the optimum way
would be to use all of the airfoils at the pilot's control

Re: [Sursound] [off-topic] Spirals

[Picinali, Lorenzo]

Hello Chris,

this might be interesting for you!

https://journals.sagepub.com/doi/pdf/10.1177/154193120805200103?casa_token=CptzIp9vOaQA:fG10j5X-vgVL92L3YHFjBTRAyYUCHfVpsuYDrU3DcGX4wPgzym4ZZoLHSh2I2AfvIZrEyKpIQ54

I remember they also presented this work at ICAD in Paris in 2008, and if I 
remember well they won the best paper award!

Best
Lorenzo



--
Lorenzo Picinali
Reader in Audio Experience Design<https://www.axdesign.co.uk/>
Dyson School of Design Engineering
Imperial College London
Dyson Building
Imperial College Road
South Kensington, SW7 2DB, London
E: l.picin...@imperial.ac.uk

http://www.imperial.ac.uk/people/l.picinali
https://www.axdesign.co.uk/
https://www.sonicom.eu/

From: Sursound  on behalf of Chris Woolf 

Sent: 08 March 2023 16:03
To: sursound@music.vt.edu 
Subject: Re: [Sursound] [off-topic] Spirals


***
This email originates from outside Imperial. Do not click on links and 
attachments unless you recognise the sender.
If you trust the sender, add them to your safe senders list 
https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for 
this address.
***
Bringing things round in a circle (rather than a spiral)

Anyone any ideas how one could provide an audio horizon that could be a
mimic of the gyro artificial horizon? That could presumably add an
additional warning of unintentional spiralling, and one that would
signal a discrepancy between gravitational/centrifugal pull and absolute
vertical.

I can see the problems of providing a height dimension with headphones,
and also a question of what audio signals would have sufficient rate to
provide the frequency of stimulus needed. ATC and TCAS would be some
help but I think you would need rather more than just that.

This is just coffee-time thoughts - I'm not planning to go flying any
time soon;}

Chris Woolf


On 08/03/2023 13:23, t.mich...@posteo.de wrote:
> Hi Panos!
>
> First of all: Welcome!
> Second: YES you are definitely in the right place.
> Third: If you have any question, feel invite to ask. :-)
>
>
> Take care and stay healthy
> Cheers
>
> Thorsten
>
>
> Am 08.03.2023 00:08 schrieb Panos Kouvelis:
>> I recently subscribed to this mailing list for insightful discussions on
>> surround sound.
>>
>> Up 'till now, the material I have received is about aviation.
>>
>> Am I in the wrong place?
>>
>> :-)
>>
>> *Pan Athen*
>> SoundFellas <https://soundfellas.com/>, *MediaFlake Ltd
>> <http://mediaflake.com/>*
>> Digital Media Services, Content, and Tools
>>
>>
>> On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:
>>
>>> On 2023-02-22, Fons Adriaensen wrote:
>>>
>>> > And in many cases the aircraft may very well be unstable in that
>>> axis:
>>> > if left alone, the roll angle will slowly increase.
>>>
>>> Actually, most modern aircraft are stable in the bank axis as well.
>>> Part
>>> of why they have swept wings, bent wings and wingtips and the like, is
>>> to this regard. (Part of: most of it has to with approaching transonic
>>> flight. But not all.)
>>>
>>> The thing is though, and as you say below, the pilot won't feel
>>> anything
>>> weird when approaching a spiral. The built in stability of the airplane
>>> will keep everybody in their seat at 1g acceleration perpendicular to
>>> the floor, evenas the airplane banks to something approaching 90
>>> degrees, and loses all of its lift. Then it just falls, sideways.
>>>
>>> When that happens, you're in what's called a "death spiral", because
>>> it's extremely difficult to recover from the condition, and you
>>> typically don't even know you've entered one. When you do, you as a
>>> pilot are already in a state of spatial disorientation; you *literally*
>>> don't know which way is up and which down, and since the plane is by
>>> now
>>> basically half-way inverted, with now absolutely no lift, losing
>>> altitude like a falling rock, you as the pilot have very little
>>> possibility of correcting.
>>>
>>> *Technically*, in *theory*, you often *could* recover, if you have
>>> enough altitude, speed and sturdiness of airframe; even I have run it
>>> through in a game. But in practice, recovery from a well developed
>>> death
>>> spiral is mostly beyond human ability. Especially once you lose height,
>>> because at low altitudes, already going nose down, you can't even
>>> convert high air speed/energy into a corrective manoeuvre before you
>

Re: [Sursound] [off-topic] Spirals

[Chris Woolf]

Bringing things round in a circle (rather than a spiral)

Anyone any ideas how one could provide an audio horizon that could be a 
mimic of the gyro artificial horizon? That could presumably add an 
additional warning of unintentional spiralling, and one that would 
signal a discrepancy between gravitational/centrifugal pull and absolute 
vertical.


I can see the problems of providing a height dimension with headphones, 
and also a question of what audio signals would have sufficient rate to 
provide the frequency of stimulus needed. ATC and TCAS would be some 
help but I think you would need rather more than just that.


This is just coffee-time thoughts - I'm not planning to go flying any 
time soon;}


Chris Woolf


On 08/03/2023 13:23, t.mich...@posteo.de wrote:

Hi Panos!

First of all: Welcome!
Second: YES you are definitely in the right place.
Third: If you have any question, feel invite to ask. :-)


Take care and stay healthy
Cheers

Thorsten


Am 08.03.2023 00:08 schrieb Panos Kouvelis:

I recently subscribed to this mailing list for insightful discussions on
surround sound.

Up 'till now, the material I have received is about aviation.

Am I in the wrong place?

:-)

*Pan Athen*
SoundFellas , *MediaFlake Ltd
*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:


On 2023-02-22, Fons Adriaensen wrote:

> And in many cases the aircraft may very well be unstable in that 
axis:

> if left alone, the roll angle will slowly increase.

Actually, most modern aircraft are stable in the bank axis as well. 
Part

of why they have swept wings, bent wings and wingtips and the like, is
to this regard. (Part of: most of it has to with approaching transonic
flight. But not all.)

The thing is though, and as you say below, the pilot won't feel 
anything

weird when approaching a spiral. The built in stability of the airplane
will keep everybody in their seat at 1g acceleration perpendicular to
the floor, evenas the airplane banks to something approaching 90
degrees, and loses all of its lift. Then it just falls, sideways.

When that happens, you're in what's called a "death spiral", because
it's extremely difficult to recover from the condition, and you
typically don't even know you've entered one. When you do, you as a
pilot are already in a state of spatial disorientation; you *literally*
don't know which way is up and which down, and since the plane is by 
now

basically half-way inverted, with now absolutely no lift, losing
altitude like a falling rock, you as the pilot have very little
possibility of correcting.

*Technically*, in *theory*, you often *could* recover, if you have
enough altitude, speed and sturdiness of airframe; even I have run it
through in a game. But in practice, recovery from a well developed 
death

spiral is mostly beyond human ability. Especially once you lose height,
because at low altitudes, already going nose down, you can't even
convert high air speed/energy into a corrective manoeuvre before you 
hit

the terrain, and there will only be seconds to lose.

This is then why the pilot flying is supposed to only look at the
instrumentation, and why there are auditory warnings about bank 
angle on

the modern jets. The Swedish commercial midsize Boeing pilot, Mentour,
on YouTube, is first rate in explaining all of this stuff.

Okay, so, finally, how would you recover from a well developed death
spiral, presuming you realized you were in one? Well, the optimum way
would be to use all of the airfoils at the pilot's control at the same
time to convert kinetic and potential energy of the frame into first 1)
orientation, and then 2) into safe height in level flight.

The optimum control trajectory going there is universally wild, so that
you can't even practice for it in a simulator. It can even be chaotic,
in the true mathematical sense. Many of the attempts at automated
recovery I known of literally crashed on that point; you can't do
optimum control here, because it leads you into an unstable 
calculation.

Instead, you have to have your algoritm flying off the optimum path, in
order to keep a stability margin. (Knowing how much off the optimum 
path

it should be, and what a stability margin even *is*, is to date an
unknown as well. It's difficult to quantify.)

So, how would I fly out of a death spiral, suddenly and against
expectation fully knowing I was in one? Fully knowing which way, how
fast, at which height, I and my aeroplane was going? Well, obviously, I
would have to regain lift, evenas I was falling. I'd use ailerons to
gain "level flight" evenwhile falling. While that was done, I'd yoke 
up,

no matter the orientation of the airframe (assuming I wasn't downright
inverted), in order to gain altitude and *true* level flight. I'd put
the engines in idle and maybe spoil the airfoil, for want of
structurally sound airspeed and the g-forces which necessarily come
after a recovery

Re: [Sursound] [off-topic] Spirals

[t . michels]

Hi Panos!

First of all: Welcome!
Second: YES you are definitely in the right place.
Third: If you have any question, feel invite to ask. :-)


Take care and stay healthy
Cheers

Thorsten


Am 08.03.2023 00:08 schrieb Panos Kouvelis:
I recently subscribed to this mailing list for insightful discussions 
on

surround sound.

Up 'till now, the material I have received is about aviation.

Am I in the wrong place?

:-)

*Pan Athen*
SoundFellas , *MediaFlake Ltd
*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:


On 2023-02-22, Fons Adriaensen wrote:

> And in many cases the aircraft may very well be unstable in that axis:
> if left alone, the roll angle will slowly increase.

Actually, most modern aircraft are stable in the bank axis as well. 
Part

of why they have swept wings, bent wings and wingtips and the like, is
to this regard. (Part of: most of it has to with approaching transonic
flight. But not all.)

The thing is though, and as you say below, the pilot won't feel 
anything
weird when approaching a spiral. The built in stability of the 
airplane

will keep everybody in their seat at 1g acceleration perpendicular to
the floor, evenas the airplane banks to something approaching 90
degrees, and loses all of its lift. Then it just falls, sideways.

When that happens, you're in what's called a "death spiral", because
it's extremely difficult to recover from the condition, and you
typically don't even know you've entered one. When you do, you as a
pilot are already in a state of spatial disorientation; you 
*literally*
don't know which way is up and which down, and since the plane is by 
now

basically half-way inverted, with now absolutely no lift, losing
altitude like a falling rock, you as the pilot have very little
possibility of correcting.

*Technically*, in *theory*, you often *could* recover, if you have
enough altitude, speed and sturdiness of airframe; even I have run it
through in a game. But in practice, recovery from a well developed 
death
spiral is mostly beyond human ability. Especially once you lose 
height,

because at low altitudes, already going nose down, you can't even
convert high air speed/energy into a corrective manoeuvre before you 
hit

the terrain, and there will only be seconds to lose.

This is then why the pilot flying is supposed to only look at the
instrumentation, and why there are auditory warnings about bank angle 
on

the modern jets. The Swedish commercial midsize Boeing pilot, Mentour,
on YouTube, is first rate in explaining all of this stuff.

Okay, so, finally, how would you recover from a well developed death
spiral, presuming you realized you were in one? Well, the optimum way
would be to use all of the airfoils at the pilot's control at the same
time to convert kinetic and potential energy of the frame into first 
1)

orientation, and then 2) into safe height in level flight.

The optimum control trajectory going there is universally wild, so 
that

you can't even practice for it in a simulator. It can even be chaotic,
in the true mathematical sense. Many of the attempts at automated
recovery I known of literally crashed on that point; you can't do
optimum control here, because it leads you into an unstable 
calculation.
Instead, you have to have your algoritm flying off the optimum path, 
in
order to keep a stability margin. (Knowing how much off the optimum 
path

it should be, and what a stability margin even *is*, is to date an
unknown as well. It's difficult to quantify.)

So, how would I fly out of a death spiral, suddenly and against
expectation fully knowing I was in one? Fully knowing which way, how
fast, at which height, I and my aeroplane was going? Well, obviously, 
I

would have to regain lift, evenas I was falling. I'd use ailerons to
gain "level flight" evenwhile falling. While that was done, I'd yoke 
up,

no matter the orientation of the airframe (assuming I wasn't downright
inverted), in order to gain altitude and *true* level flight. I'd put
the engines in idle and maybe spoil the airfoil, for want of
structurally sound airspeed and the g-forces which necessarily come
after a recovery from a spiral. Something like that.

Even if I did all of that *just* right, I'd probably contact terrain.
All on-board would be lost. Because recovering from a death spiral, 
once

it's started and developed well, is pretty much an inhuman feat. It's
almost impossible for a computer to do, as well. The many algorithms
which have been tried out, taking control away from the human pilot,
none of them have been shown to do any good either.

Fons, this is one of the other things I follow. Amateurishly, but I
still do.

https://www.youtube.com/watch?v=b7t4IR-3mSo
https://www.youtube.com/watch?v=JhzaogGQNFU&t=1056s
https://www.youtube.com/watch?v=o7N0pshAC0k

Now the fun thing is, as my pilot friends say, you can actually *even*
do a full, level, aileron roll on all of

Re: [Sursound] [off-topic] Spirals

[Jack Reynolds]

Any chance you could take your aeroplane based discussions offline?

Sent from my iPhone

> On 7 Mar 2023, at 23:26, Fernando Lopez-Lezcano  
> wrote:
> 
> On 3/7/23 3:08 PM, Panos Kouvelis wrote:
>> I recently subscribed to this mailing list for insightful discussions on
>> surround sound.
>> Up 'till now, the material I have received is about aviation.
>> Am I in the wrong place?
> 
> Hi Panos, you are in the right place, please stay, there will be eventually 
> insightful posts about surround sound. I've seen it happen!
> 
> -- Fernando
> 
> 
>>> On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:
 On 2023-02-22, Fons Adriaensen wrote:
>>> 
 And in many cases the aircraft may very well be unstable in that axis:
 if left alone, the roll angle will slowly increase.
>>> 
>>> Actually, most modern aircraft are stable in the bank axis as well. 
> ... [MUNCH]
> 
> ___
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
> account or options, view archives and so on.
___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Panos Kouvelis]

Haha, thanks Fernando!

*Pan Athen*
SoundFellas , *MediaFlake Ltd
*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 1:26 AM Fernando Lopez-Lezcano <
na...@ccrma.stanford.edu> wrote:

> On 3/7/23 3:08 PM, Panos Kouvelis wrote:
> > I recently subscribed to this mailing list for insightful discussions on
> > surround sound.
> >
> > Up 'till now, the material I have received is about aviation.
> >
> > Am I in the wrong place?
>
> Hi Panos, you are in the right place, please stay, there will be
> eventually insightful posts about surround sound. I've seen it happen!
>
> -- Fernando
>
>
> > On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:
> >
> >> On 2023-02-22, Fons Adriaensen wrote:
> >>
> >>> And in many cases the aircraft may very well be unstable in that axis:
> >>> if left alone, the roll angle will slowly increase.
> >>
> >> Actually, most modern aircraft are stable in the bank axis as well.
> ... [MUNCH]
>
>
-- next part --
An HTML attachment was scrubbed...
URL: 

___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Fernando Lopez-Lezcano]

On 3/7/23 3:08 PM, Panos Kouvelis wrote:

I recently subscribed to this mailing list for insightful discussions on
surround sound.

Up 'till now, the material I have received is about aviation.

Am I in the wrong place?


Hi Panos, you are in the right place, please stay, there will be 
eventually insightful posts about surround sound. I've seen it happen!


-- Fernando



On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:


On 2023-02-22, Fons Adriaensen wrote:


And in many cases the aircraft may very well be unstable in that axis:
if left alone, the roll angle will slowly increase.


Actually, most modern aircraft are stable in the bank axis as well. 

... [MUNCH]

___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.

Re: [Sursound] [off-topic] Spirals

[Panos Kouvelis]

I recently subscribed to this mailing list for insightful discussions on
surround sound.

Up 'till now, the material I have received is about aviation.

Am I in the wrong place?

:-)

*Pan Athen*
SoundFellas , *MediaFlake Ltd
*
Digital Media Services, Content, and Tools


On Wed, Mar 8, 2023 at 1:03 AM Sampo Syreeni  wrote:

> On 2023-02-22, Fons Adriaensen wrote:
>
> > And in many cases the aircraft may very well be unstable in that axis:
> > if left alone, the roll angle will slowly increase.
>
> Actually, most modern aircraft are stable in the bank axis as well. Part
> of why they have swept wings, bent wings and wingtips and the like, is
> to this regard. (Part of: most of it has to with approaching transonic
> flight. But not all.)
>
> The thing is though, and as you say below, the pilot won't feel anything
> weird when approaching a spiral. The built in stability of the airplane
> will keep everybody in their seat at 1g acceleration perpendicular to
> the floor, evenas the airplane banks to something approaching 90
> degrees, and loses all of its lift. Then it just falls, sideways.
>
> When that happens, you're in what's called a "death spiral", because
> it's extremely difficult to recover from the condition, and you
> typically don't even know you've entered one. When you do, you as a
> pilot are already in a state of spatial disorientation; you *literally*
> don't know which way is up and which down, and since the plane is by now
> basically half-way inverted, with now absolutely no lift, losing
> altitude like a falling rock, you as the pilot have very little
> possibility of correcting.
>
> *Technically*, in *theory*, you often *could* recover, if you have
> enough altitude, speed and sturdiness of airframe; even I have run it
> through in a game. But in practice, recovery from a well developed death
> spiral is mostly beyond human ability. Especially once you lose height,
> because at low altitudes, already going nose down, you can't even
> convert high air speed/energy into a corrective manoeuvre before you hit
> the terrain, and there will only be seconds to lose.
>
> This is then why the pilot flying is supposed to only look at the
> instrumentation, and why there are auditory warnings about bank angle on
> the modern jets. The Swedish commercial midsize Boeing pilot, Mentour,
> on YouTube, is first rate in explaining all of this stuff.
>
> Okay, so, finally, how would you recover from a well developed death
> spiral, presuming you realized you were in one? Well, the optimum way
> would be to use all of the airfoils at the pilot's control at the same
> time to convert kinetic and potential energy of the frame into first 1)
> orientation, and then 2) into safe height in level flight.
>
> The optimum control trajectory going there is universally wild, so that
> you can't even practice for it in a simulator. It can even be chaotic,
> in the true mathematical sense. Many of the attempts at automated
> recovery I known of literally crashed on that point; you can't do
> optimum control here, because it leads you into an unstable calculation.
> Instead, you have to have your algoritm flying off the optimum path, in
> order to keep a stability margin. (Knowing how much off the optimum path
> it should be, and what a stability margin even *is*, is to date an
> unknown as well. It's difficult to quantify.)
>
> So, how would I fly out of a death spiral, suddenly and against
> expectation fully knowing I was in one? Fully knowing which way, how
> fast, at which height, I and my aeroplane was going? Well, obviously, I
> would have to regain lift, evenas I was falling. I'd use ailerons to
> gain "level flight" evenwhile falling. While that was done, I'd yoke up,
> no matter the orientation of the airframe (assuming I wasn't downright
> inverted), in order to gain altitude and *true* level flight. I'd put
> the engines in idle and maybe spoil the airfoil, for want of
> structurally sound airspeed and the g-forces which necessarily come
> after a recovery from a spiral. Something like that.
>
> Even if I did all of that *just* right, I'd probably contact terrain.
> All on-board would be lost. Because recovering from a death spiral, once
> it's started and developed well, is pretty much an inhuman feat. It's
> almost impossible for a computer to do, as well. The many algorithms
> which have been tried out, taking control away from the human pilot,
> none of them have been shown to do any good either.
>
> Fons, this is one of the other things I follow. Amateurishly, but I
> still do.
>
> https://www.youtube.com/watch?v=b7t4IR-3mSo
> https://www.youtube.com/watch?v=JhzaogGQNFU&t=1056s
> https://www.youtube.com/watch?v=o7N0pshAC0k
>
> Now the fun thing is, as my pilot friends say, you can actually *even*
> do a full, level, aileron roll on all of the AirBus jumbojets.
> Definitely not recommended, might lose your licence, and you'd have to
> disengage a number o

Re: [Sursound] [off-topic] Spirals

[Sampo Syreeni]

On 2023-02-22, Fons Adriaensen wrote:

And in many cases the aircraft may very well be unstable in that axis: 
if left alone, the roll angle will slowly increase.


Actually, most modern aircraft are stable in the bank axis as well. Part 
of why they have swept wings, bent wings and wingtips and the like, is 
to this regard. (Part of: most of it has to with approaching transonic 
flight. But not all.)


The thing is though, and as you say below, the pilot won't feel anything 
weird when approaching a spiral. The built in stability of the airplane 
will keep everybody in their seat at 1g acceleration perpendicular to 
the floor, evenas the airplane banks to something approaching 90 
degrees, and loses all of its lift. Then it just falls, sideways.


When that happens, you're in what's called a "death spiral", because 
it's extremely difficult to recover from the condition, and you 
typically don't even know you've entered one. When you do, you as a 
pilot are already in a state of spatial disorientation; you *literally* 
don't know which way is up and which down, and since the plane is by now 
basically half-way inverted, with now absolutely no lift, losing 
altitude like a falling rock, you as the pilot have very little 
possibility of correcting.


*Technically*, in *theory*, you often *could* recover, if you have 
enough altitude, speed and sturdiness of airframe; even I have run it 
through in a game. But in practice, recovery from a well developed death 
spiral is mostly beyond human ability. Especially once you lose height, 
because at low altitudes, already going nose down, you can't even 
convert high air speed/energy into a corrective manoeuvre before you hit 
the terrain, and there will only be seconds to lose.


This is then why the pilot flying is supposed to only look at the 
instrumentation, and why there are auditory warnings about bank angle on 
the modern jets. The Swedish commercial midsize Boeing pilot, Mentour, 
on YouTube, is first rate in explaining all of this stuff.


Okay, so, finally, how would you recover from a well developed death 
spiral, presuming you realized you were in one? Well, the optimum way 
would be to use all of the airfoils at the pilot's control at the same 
time to convert kinetic and potential energy of the frame into first 1) 
orientation, and then 2) into safe height in level flight.


The optimum control trajectory going there is universally wild, so that 
you can't even practice for it in a simulator. It can even be chaotic, 
in the true mathematical sense. Many of the attempts at automated 
recovery I known of literally crashed on that point; you can't do 
optimum control here, because it leads you into an unstable calculation. 
Instead, you have to have your algoritm flying off the optimum path, in 
order to keep a stability margin. (Knowing how much off the optimum path 
it should be, and what a stability margin even *is*, is to date an 
unknown as well. It's difficult to quantify.)


So, how would I fly out of a death spiral, suddenly and against 
expectation fully knowing I was in one? Fully knowing which way, how 
fast, at which height, I and my aeroplane was going? Well, obviously, I 
would have to regain lift, evenas I was falling. I'd use ailerons to 
gain "level flight" evenwhile falling. While that was done, I'd yoke up, 
no matter the orientation of the airframe (assuming I wasn't downright 
inverted), in order to gain altitude and *true* level flight. I'd put 
the engines in idle and maybe spoil the airfoil, for want of 
structurally sound airspeed and the g-forces which necessarily come 
after a recovery from a spiral. Something like that.


Even if I did all of that *just* right, I'd probably contact terrain. 
All on-board would be lost. Because recovering from a death spiral, once 
it's started and developed well, is pretty much an inhuman feat. It's 
almost impossible for a computer to do, as well. The many algorithms 
which have been tried out, taking control away from the human pilot, 
none of them have been shown to do any good either.


Fons, this is one of the other things I follow. Amateurishly, but I 
still do.


https://www.youtube.com/watch?v=b7t4IR-3mSo
https://www.youtube.com/watch?v=JhzaogGQNFU&t=1056s
https://www.youtube.com/watch?v=o7N0pshAC0k

Now the fun thing is, as my pilot friends say, you can actually *even* 
do a full, level, aileron roll on all of the AirBus jumbojets. 
Definitely not recommended, might lose your licence, and you'd have to 
disengage a number of safety systems, then flying by eye and touch 
alone. But I'm told all of them *can* do showflying manoeuvres if need 
be. My nerd friends even claim to me, if need be, the things might be 
capable of autonomous inverted flight; I'm not too sure if any flight 
manufacturer actually ever went so far, but if one did, it surely would 
be AirBus. Damn, woman, stop it right *here*!


A non-zero roll angle means that part of the lift force generated by 
the wings is no

Re: [Sursound] [off-topic] Spirals

[Fons Adriaensen]

On Wed, Feb 22, 2023 at 12:50:31AM +, Stefan Schreiber wrote:
 
> Is flying in a spiral not something you would do in some intentional way?

Yes and no... There is no essential difference between a spiral
and a normal turn, except that a spiral is usually not intentional
and in that case it can become so extreme that it puts the aircraft
in danger. Both spins and spirals are done intentionally as part
of pilot training.

All (normal) aircraft have pitch stability, but few have roll
stability. That means that if the wings are not level, there is 
nothing that would make them return to level. And in many cases
the aircraft may very well be unstable in that axis: if left
alone, the roll angle will slowly increase.

A non-zero roll angle means that part of the lift force generated
by the wings is now sideways. That - and not the rudder - is what
makes the aircraft make a turn. The vertical component of lift is
reduced, and a pitch-stable aircraft will just by itself increase
its airspeed to restore it. It can do that only by going down at
that same time.

Unless you watch the horizon or the attitude indicator, you will
not be aware that this is happening. As the roll angle increases,
the g-force will apparently remain vertical (relative to the
aircraft) but increase as well. And at some point you will notice
that you are pinned down in your seat and unable to move - you
are effectively in a centrifuge, way too fast, going down, and
the g-forces will be so high that they can break up the aircraft. 

To recover:

1. Reduce power to idle.

2. Bring the wings level. This has to be done gently, to
   avoid even more mechanical stress.

3. As the wings return to level, the excessive speed will
   put the aircraft into a steep climb. Let it happen but
   keep the pitch angle under control. You will regain
   some of the lost altitude, and airspeed will decrease.

4. As you approach normal airspeed, bring back power and
   level off.

   
Ciao,

-- 
FA

___
Sursound mailing list
Sursound@music.vt.edu
https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit 
account or options, view archives and so on.