Simple string used as artificial horizon?

"Morgans" wrote:
"GARY BOGGS" wrote in message
.
..

I am amazed that anyone with a pilots certificate would actually
think anything hanging in the cockpit would tell you anything about
the horizon!!!! Please tell me these aren't certified pilots!

Amen. It is completely possible to have the string pointed at the
floor in a 90 degree bank, or even upside-down.

I believe it is impossible for a force vector of weight (always at 0
degrees; indicating down) added to a centrifugal force (at 90 degrees in
your example) to yield a resultant that is also at 90 degrees. Unless maybe
you're pulling infinite gees in those turns!

Since there is a structural limit to how much one can bank a plane or
glider and keep the resultant force vector directly through the floor,
there is a moderately large range of bank angles around 90 degrees where
you shouldn't be able to get the string pointed through the floor.

If you hadn't chosen a 90 degree bank as one of your examples I wouldn't
have been able to contest your post. Your statement appears to be true for
all other bank angles. :-)

Bob Whelan wrote:
Youthful ignorance aside, everybody raise their hands who'd rather
have been VFR-on-top in the above-mentioned conditions withOUT the two
pieces of information that worked in this instance...let's talk
afterwards!

Bob - forces matter - W.
Can I do without that information as long as I promise to power up the
T&B when I'm VFR on top?

Regardless of what technique or device you want to use in that
situation, please practice with it at least a few times a year.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

Jim Logajan wrote:
"Morgans" wrote:
Amen. It is completely possible to have the string pointed at the
floor in a 90 degree bank, or even upside-down.

I believe it is impossible for a force vector of weight (always at 0
degrees; indicating down) added to a centrifugal force (at 90 degrees
in your example) to yield a resultant that is also at 90 degrees.
Unless maybe you're pulling infinite gees in those turns!

Correcting myself - I was assuming that level flight was being maintained
or attempted during the turn. Take away that assumption and it is no
problem having the string point through the floor in a 90 degree bank.

So never mind!

On Dec 29, 4:28*pm, brian whatcott wrote:
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

That has zero practical relevance. I'll leave the school master stuff
to Andy (and here I was thinking he's a management consultant with a
masters in aeronautical engineering), anyhow I managed to waste part
of my life working on precision sensors for general relativity physics
experiments. MEMS rate based devices like tuning fork designs etc.
vibrate many orders of magnitude above the signal frequency. Hanging a
weight on an about a foot long string will give a resonant period of
about one second. For movement of the aircraft that happen of order
~seconds the mass on a string is essentially a plumb-bob and the
"pendulum" will be perturbed. Again a focualt pendulum is oscillating
in it's inertial frame with a resonant frequency orders of magnitude
above above any signal frequency (the earth's rotation).

---

The pendulum in the cockpit is one of the most goofball things I've
heard in a while. On the other hand the cat idea has promise. The cat
also has the benefit of being an amusing companion in the event of a
landout, or a nutritious food source in the event of a more serious
survival situation. But unfortunately until I I can overcome my cat
allergy it's a plain old (non-edible) T&B backup for me.

---

As others have pointed out, the important thing is to go try this and
practice, with an instructor if needed. The advice from some others
about the benign spiral, always needs a caveat - whether your ship
will benign spiral or not is glider design and possibly W&B dependent.
My ASH-26E at my normal W&B will not benign spiral. So I carry a
pictorial T&B for backup just in case, and I've spent enough time
under a hood to remind me I really don't want to go there.

Darryl

On 30 Dec, 05:59, Darryl Ramm wrote:

As others have pointed out, the important thing is to go try this and
practice, with an instructor if needed. The advice from some others
about the benign spiral, always needs a caveat - whether your ship
will benign spiral or not is glider design and possibly W&B dependent.
My ASH-26E at my normal W&B will not benign spiral. So I carry a
pictorial T&B for backup just in case, and I've spent enough time
under a hood to remind me I really don't want to go there.

Darryl

At last...my Discus would do a benign spiral without going VNE with
wheel down, brakes out, and hands off. My ASW27 won't and will fall to
bits. I suggest everyone try hanging everything out and taking hands
off to see what happens. If speed goes through rough air, pull out.
You will then know whether you can safely use this technique or not.

I have practised using string for slip, ears for speed, and gps for
turn. I reckon that I could descend without my horizon through cloud
most times without spinning or over speeding. Failing that I guess it
is, pull the wings off then pull the chute!

Jim

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

Jim Logajan wrote:

I believe it is impossible for a force vector of weight (always at 0
degrees; indicating down) added to a centrifugal force (at 90 degrees in
your example) to yield a resultant that is also at 90 degrees. Unless maybe
you're pulling infinite gees in those turns!

Actually, in this hypothetical, the bank angle was 90 degrees.
To place a bob towards the floor, it is necessary to induce some slip
too....

Brian W (The impossible takes a little longer)

Darryl Ramm wrote:
/snip/
If you are going to take on the school master role, you had better be
right. /snip/
Brian W

That has zero practical relevance. I'll leave the school master stuff
to Andy (and here I was thinking he's a management consultant with a
masters in aeronautical engineering), anyhow I managed to waste part
of my life working on precision sensors for general relativity physics
experiments. /snip/
Darryl


For a person who appreciates practical relevance, can I suggest you
actually DO the experiment?
Swing a bob on a foot long string in your right hand.
Turn at a reasonable rate in place.
Notice what happens to the pendulum's plane of rotation?

Regards
Brian W
p.s. I can usually detect someone with physics background: no matter how
much they have forgotten, they always retain that 'physics' attitude :-)

jimboffin wrote:
On 30 Dec, 05:59, Darryl Ramm wrote:

As others have pointed out, the important thing is to go try this and
practice, with an instructor if needed. The advice from some others
about the benign spiral, always needs a caveat - whether your ship
will benign spiral or not is glider design and possibly W&B dependent.
My ASH-26E at my normal W&B will not benign spiral. So I carry a
pictorial T&B for backup just in case, and I've spent enough time
under a hood to remind me I really don't want to go there.

Darryl

At last...my Discus would do a benign spiral without going VNE with
wheel down, brakes out, and hands off. My ASW27 won't and will fall to
bits. I suggest everyone try hanging everything out and taking hands
off to see what happens. If speed goes through rough air, pull out.
You will then know whether you can safely use this technique or not.

I have practised using string for slip, ears for speed, and gps for
turn. I reckon that I could descend without my horizon through cloud
most times without spinning or over speeding. Failing that I guess it
is, pull the wings off then pull the chute!

Jim


Now THERE'S a post worth repeating: students are not taught about
'the fatal spiral' for nothing....

Brian W

The cat theory may have merit.
http://www.youtube.com/watch?v=wvRzWYCZ2e0


"Darryl Ramm" wrote in message
...
On Dec 29, 4:28 pm, brian whatcott wrote:
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

That has zero practical relevance. I'll leave the school master stuff
to Andy (and here I was thinking he's a management consultant with a
masters in aeronautical engineering), anyhow I managed to waste part
of my life working on precision sensors for general relativity physics
experiments. MEMS rate based devices like tuning fork designs etc.
vibrate many orders of magnitude above the signal frequency. Hanging a
weight on an about a foot long string will give a resonant period of
about one second. For movement of the aircraft that happen of order
~seconds the mass on a string is essentially a plumb-bob and the
"pendulum" will be perturbed. Again a focualt pendulum is oscillating
in it's inertial frame with a resonant frequency orders of magnitude
above above any signal frequency (the earth's rotation).

---

The pendulum in the cockpit is one of the most goofball things I've
heard in a while. On the other hand the cat idea has promise. The cat
also has the benefit of being an amusing companion in the event of a
landout, or a nutritious food source in the event of a more serious
survival situation. But unfortunately until I I can overcome my cat
allergy it's a plain old (non-edible) T&B backup for me.

---

As others have pointed out, the important thing is to go try this and
practice, with an instructor if needed. The advice from some others
about the benign spiral, always needs a caveat - whether your ship
will benign spiral or not is glider design and possibly W&B dependent.
My ASH-26E at my normal W&B will not benign spiral. So I carry a
pictorial T&B for backup just in case, and I've spent enough time
under a hood to remind me I really don't want to go there.

Darryl