Simple string used as artificial horizon?

It is snowing here in Utah, soaring weather is a ways off and I was
thinking about an episode of Mythbusters: "airplane on a treadmill"
that created lots of interesting conversation over the internet. It
was amazing how many pilots got it wrong.

Obviously in a turn the centrifugal forces should pull a string to the
point that it would not be usable to help keeping things upright.
Just trying to start a fun discussion but now I am realizing that if
someone doesn't read far enough down the threads that they might not
see it doesn't work and might actually rely on it. Don't worry Gary.
Didn't think it would work.

Bruno


On Dec 29, 10:56*am, Andy wrote:
On Dec 29, 8:02*am, karen wrote:



The other reassuring thing was that stupid little string hanging there
told me what was straight up and down, when my senses said we were
banked and slipping or skidding. At higher speeds it was all over the
place. A breath above a stall, it was quite telling.

This is important as one's life potentially is a stake (unless you are
joking, in which case it's a dangerous joke to post).

Anything hanging in the cockpit like a pendulum (or any instruments
working on the same principle) DOES NOT tell you which way is up. *At
best it tells you something about whether you are coordinated. *All
aircraft fly in an accelerated reference frame - that is, the apparent
gravity vector is the sum of the earth's gravity vector and all the
other accelerations the glider is experiencing. The pendulum will
confirm all the incorrect senses you body is telling you - very
dangerous. To demonstrate this for yourself try a couple of
experiments:

- Hang a pendulum in the cockpit and do a straight-ahead negative-G
pushover. *The pendulum will point straight up, apparently telling you
you are inverted when you are not.

- Look at the pendulum when you are in a 45-degree coordinated turn -
it will be pointing 45-degrees off vertical, right through the belly
of the glider, not straight down to the ground.

In the case you describe the real danger is getting into an
accelerated spiral dive where the speed and Gs build up until
something breaks. Through that entire process your little string will
point happily straight through the belly of the glider until the wings
come off. That's why the hands-free benign spiral is preferred - the
natural stability of the aircraft will keep you out of trouble far
better than your internal senses of up and down.

Stay safe out there.

9B

Andy wrote:

Anything hanging in the cockpit like a pendulum (or any instruments
working on the same principle) DOES NOT tell you which way is up./snip/

9B

If you are going to take on the school master role, you had better be
right. Current solid state angular rate sensors act like a mini pendulum
or tuning fork - when turned, the pendulum retains spatial inertia.
Foucault, an' all that. Remember?

Brian W

karen wrote:
/snip/
The other reassuring thing was that stupid little string hanging there
told me what was straight up and down, when my senses said we were
banked and slipping or skidding./snip/
Michael

....but now you realise that it would have stayed straight up and down
even in a steep balanced turn, of course....

Brian W

T8 wrote:

He then mentioned that way back in the early days of flying they would
simply tape a string hanging from the ceiling to act as an artificial
horizon.

It's not April 1 already is it?

Just put a mark on your canopy and spit at it. If spit flies left of
target, you are turning right and vice versa.

-T8

NOW you're talking.
There was a D-I_Y autopilot design which used a blower tube streaming
air onto four thermistors arranged pairwise-differentially. This gave
pitch rate and yaw rate, or if mounted skew, inputs on all three axes.
These days, a three axis acceleraometer goes for $25 and rate sensors
for a little more... One well known Arduino project ["ArduPilot"]
offers the guts of an autopilot suitable for driving R/C servoes, which
will easily fit in a medium size model plane. I expect this could easliy
fit in a homebuilt...

Brian W

On Dec 29, 5:19*pm, brian whatcott wrote:
T8 wrote:

He then mentioned that way back in the early days of flying they would
simply tape a string hanging from the ceiling to act as an artificial
horizon.
It's not April 1 already is it?

Just put a mark on your canopy and spit at it. *If spit flies left of
target, you are turning right and vice versa.

-T8

NOW you're talking.
There was a D-I_Y autopilot design which used a blower tube streaming
air onto four thermistors arranged pairwise-differentially. This gave
pitch rate and yaw rate, or if mounted skew, inputs on all three axes.
These days, a three axis acceleraometer goes for $25 and rate sensors
for a little more... * One well known Arduino project ["ArduPilot"]
offers the guts of an autopilot suitable for driving R/C servoes, which
will easily fit in a medium size model plane. I expect this could easliy
fit in a homebuilt...

Brian W

One thing I think would work is pitot tubes on each wing tip connected
to a Winter type variometer with the vario rotated so the needle
pointed up. Air would flow from the faster wing tip to the slower one
through the vario which would show rate of turn. It's the only "non-
gyro" rate of turn instrument I can think of.

bildan wrote:


One thing I think would work is pitot tubes on each wing tip connected
to a Winter type variometer with the vario rotated so the needle
pointed up. Air would flow from the faster wing tip to the slower one
through the vario which would show rate of turn. It's the only "non-
gyro" rate of turn instrument I can think of.

Yes, I see that. Reminds me that some folk have played with a GPS on
each wingtip and some decode software - not very fast on its feet
though, I don't think - even at 5 frames a second...

Brian W

On Dec 29, 6:48*am, T8 wrote:
On Dec 29, 9:24*am, Andy wrote:





On Dec 29, 6:55*am, Bruno wrote:

I had a very interesting conversation yesterday with *a very
experienced pilot (older) who has spent a lot of time in some amazing
aircraft starting with the P51 Mustang and going up to jets including
the SR-71 blackbird and as we were looking over my glider we started
talking about the yaw string on the canopy.

He then mentioned that way back in the early days of flying they would
simply tape a string hanging from the ceiling to act as an artificial
horizon. *I've never heard this one before! *Next person who reads
this who goes up tape a string hanging from the inside of the canopy
and tell us how it works. *Now you have another reason to take off
work and go soaring.

Bruno -B4http://www.youtube.com/user/bviv

It's not April 1 already is it?

Just put a mark on your canopy and spit at it. *If spit flies left of
target, you are turning right and vice versa.

-T8- Hide quoted text -

- Show quoted text -

That'd work, except for one thing: If I'm in a situation requiring
that trick, my mouth is probably going to be too dry to spit!

On Dec 29, 5:55*am, Bruno wrote:
I had a very interesting conversation yesterday with *a very
experienced pilot (older) who has spent a lot of time in some amazing
aircraft starting with the P51 Mustang and going up to jets including
the SR-71 blackbird and as we were looking over my glider we started
talking about the yaw string on the canopy.

He then mentioned that way back in the early days of flying they would
simply tape a string hanging from the ceiling to act as an artificial
horizon. *I've never heard this one before! *Next person who reads
this who goes up tape a string hanging from the inside of the canopy
and tell us how it works. *Now you have another reason to take off
work and go soaring.

Bruno -B4http://www.youtube.com/user/bviv

Bruno,


I personally use the cat. Just throw it in the air every now and
then. A cat always lands on his feet and the purring can calm your
nerves.


Richard
www.craggyaero.com

I personally use the cat. *Just throw it in the air every now and
then. *A cat always lands on his feet and the purring can calm your
nerves.

Richardwww.craggyaero.com

I hope he's de-clawed! Are you coming to the convention?

Charlie

On Dec 29, 12:31*pm, cfinn wrote:
I personally use the cat. *Just throw it in the air every now and
then. *A cat always lands on his feet and the purring can calm your
nerves.

Richardwww.craggyaero.com

I hope he's de-clawed! Are you coming to the convention?

Charlie

Charlie,

The claws keep you on top of your game.
I will be at the convention Booth 18 & 19

Richard
www.craggyaero.com