You are in IMC, when *everything* fails! Now what?

i think you also need to restrict vertical movement of the pendulum's fulcrum
(and therefore vertical translation of the pendulum), which is not practical in
an airplane that can move in 3 dimensions. Regardless, just in keeping the
pendulum swinging, you probably have as much complexity as a gyro.

Michael wrote:

"Gary L. Drescher" wrote
Two differences. First, the ball is not given a shove to keep it
oscillating back and forth even when the plane is going straight (any such
oscillation damps out almost instantly). Second, the ball is constrained to
move in only one plane. The idea of the pendulum is to start it swinging
side to side (say, east-west if you're heading north) but let it move
freely; then, if the plane yaws, the pendulum is still swinging east-west,
so the yaw is detectable. At least in principle.

OK, now I get it. You're using the principle that the plane of
oscillation in a pendulum is rigid in space, just like the plane of
rotation of a gyroscope. Sure, that makes a lot of sense. Should
work just like a gyro. Only issue is how you're going to keep it
swinging. You would need a drive system and an escapement.

Michael

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"Michael" wrote in message
om...
"Gary L. Drescher" wrote
Two differences. First, the ball is not given a shove to keep it
oscillating back and forth even when the plane is going straight (any
such
oscillation damps out almost instantly). Second, the ball is
constrained to
move in only one plane. The idea of the pendulum is to start it
swinging
side to side (say, east-west if you're heading north) but let it move
freely; then, if the plane yaws, the pendulum is still swinging
east-west,
so the yaw is detectable. At least in principle.

OK, now I get it. You're using the principle that the plane of
oscillation in a pendulum is rigid in space, just like the plane of
rotation of a gyroscope. Sure, that makes a lot of sense. Should
work just like a gyro. Only issue is how you're going to keep it
swinging. You would need a drive system and an escapement.

Michael

I think the pendulum's 'rigidity in space' is a qualified
circumstance, and depends upon the accelerations imposed
upon it.

Consider the typical bob-on-a-string pendulum. At the top of
the swing the bob has zero velocity, maximum potential energy,
at the bottom, maximum velocity and minimum potential energy.

Potential energy with respect to what? - with respect to
whatever net forces are involved, which are also the forces
that cause the bob to accellerate to maximum, and back to 0.

What is there about the pendulum bob that will cause it to
swing back in the same plane as it was formerly swinging?
Normally it will be its position relative to the pendulum
anchor and with respect to the external forces upon it.

There are other ways to make pendulums, of course,
but I think you'll find they all share this limitation.

Move the anchor point in some direction perpendicular
to the direction of the forces, or change the direction of
the forces, and you will in general change the plane in
which the pendulum swings. Both of these can be
expected to occur in a moving aircraft, which should
make the pendulum useless.

Julian Scarfe wrote:

In a nose-low attitude the ailerons will be more effective than the
rudders
at recovering to wings level, but rudder may well do the job too.

"Roy Smith" wrote in message
...

Well, just to pick a nit, in a spin, you're very much nose low, but
the ailerons won't work at all.

Ah, er yes thanks for the picking. It feels better without that nit. I've
seen smaller ones... :-)

Julian

Greg Esres wrote:
Use rudder to stop the rotation (wing dropping),

Isn't necessary. No stall, no spin.



Gee, make up your mind. First you complained that we were talking about
stalls, not spins; now you say "No stall, no spin." Well, yeah, no
airplane, no stall...

Seriously though, if you look back you will see that I was responding to
another poster saying: "...Using ailerons to pick up a wing in a stall
and actually cause the wing to drop further (by increasing its angle of
attack)." Which I clearly agree with.

Considering the core topic of the thread, under the conditions of
"everything failed" are you suggesting that if you suspect that you have
the beginnings of a stall and possibly a roll into the more stalled wing
that you should pitch "down" and then roll level? Good luck with that!

Perhaps because I fly mostly aerobatics in the Pitts I automatically
stop any rotation while either wing is stalled before changing pitch or
roll.

I'm not sure I agree.

With what?


I am not sure I agree that a non-pilot (or non-instrument-rated pilot) should
just turn on the autopilot if they end up in IMC (or even if a non-pilot needs
to take over for a disabled pilot). An autopilot can take you quickly to where
you don't want to go, and didn't think you were going to be headed.

One needs to understand how to work the autopilot first, and know what it's set
for (and what needs to be un-set, if anything). Ditto a GPS - the advice often
given to non-pilots acting as pinch hitters is to use the GPS - fine but the
GPS is often a fussy device that takes the head out of the windshield, to the
detriment of the flight.

The interface is hard enough for a pilot, let alone a non-pilot facing an
emergency.

But, once mastered it's handy.

Jose

(for Email, make the obvious changes in my address)