physics question

Fill the aircraft with dozens of helium balloons on a high density altitude day....

Problem solved!!!;)

Helium balloons are your friend...everyone should fly with them.:D
 
Silvaire said:
Helium floats because it's lighter than an equivalent volume of air. If there's no air then what is it lighter than? Of course a Mylar or rubber ballon isn't going to be able to hold it's cookies in a vacuum anyway so the point is moot.
Click to expand...

There are two forces involved, buoyancy and gravity. Buoyancy lifts the helium against gravity, remove the the fluid that provides the buoyancy and gravity takes over and the helium atoms would sink to the bottom.
 
Next time I fly, I'm bringing a spirit level.
I think it work be an interesting visual to see it at an angle but showing level
 
Henning said:
There are two forces involved, buoyancy and gravity. Buoyancy lifts the helium against gravity, remove the the fluid that provides the buoyancy and gravity takes over and the helium atoms would sink to the bottom.
Click to expand...
or just fill the cockpit with helium....problem solved. :goofy:
 
Why not a string like glider pilots use? Or does that just look at yaw?
 
SixPapaCharlie said:
You are flying along in IMC and have a total instrument failure.
Vacuum pump, electric, and a bird hit the pitot tube. Part of it went into both static ports.

Fortunately you are flying to a child's birthday party and have a mylar helium filled balloon with you.

Keeping the balloon centered on the cabin ceiling you should be able to maintain level flight and also determine if your attitude changes correct?

Ascend, it moves forward. Pitch down, it moves back etc...

Would it work like that?
Click to expand...

The friction of the ballon on the cabin ceiling would prevent the movement of the ballon during very small pitch changes, i.e. 1 degree, and the pilot would not be able to maintain an altitude.

If the balloon did move, the pilot would have no information as to how much the pitch had changed or how much to correct. Control of the aircraft on the lateral axis would be lost chasing a large occilation.
 
It was really meant to be a (too subtle) tongue-in-cheek implication that you'd be just as dead in a vacuum as you would be trying to fly a plane by reference to a balloon.

But it's been fun watching you guys turn it into a plane-on-a-treadmill discussion...
 
Sac Arrow said:
Same way an AI would tell you. Balloon would be sideways in a dive.
Click to expand...
Why?
It would only give you attitude information reliably, to the extent that it isn't upset by contacting the cabin.
Click to expand...
The gyro in the AI is trying to maintain a stable orientation in space. The balloon has no such constraint and very little inertia. If this would work, we could just replace our gyros with heavy damped pendulums. The problem is, you're only measuring acceleration.
 
Lindberg said:
Why?
The gyro in the AI is trying to maintain a stable orientation in space. The balloon has no such constraint and very little inertia. If this would work, we could just replace our gyros with heavy damped pendulums. The problem is, you're only measuring acceleration.
Click to expand...

Would it work if we integrated the pendulums?
 
Lindberg said:
Why?
The gyro in the AI is trying to maintain a stable orientation in space. The balloon has no such constraint and very little inertia. If this would work, we could just replace our gyros with heavy damped pendulums. The problem is, you're only measuring acceleration.
Click to expand...

The balloon is not equivalent to a pendulum. As long as it is ballasted but not physically connected to the plane, it should maintain a constant upright position relative to the earth regardless of the plane's attitude, should it not? At least discounting the effects of acceleration.

As a practical matter, I don't think you could get it to hover freely in one spot for it to work effectively.
 
SixPapaCharlie said:
Next time I fly, I'm bringing a spirit level.
I think it work be an interesting visual to see it at an angle but showing level
Click to expand...

Your iPhone already has a built in bubble level and inclinometer app.

Sac Arrow said:
As long as it is ballasted but not physically connected to the plane, it should maintain a constant upright position relative to the earth regardless of the plane's attitude, should it not?
Click to expand...

Not really, it isn't antigravity. It just floats in the surrounding air trying to find an area of equlibrium, and that air could be sloshing around inside the cabin.
 
Sac Arrow said:
The balloon is not equivalent to a pendulum. As long as it is ballasted but not physically connected to the plane, it should maintain a constant upright position relative to the earth regardless of the plane's attitude, should it not? At least discounting the effects of acceleration.
Click to expand...
Yes, if one spot is heavier, that spot will tend to be on the "bottom." But that doesn't necessarily mean it will point towards the earth. And you can't ignore the effects of acceleration. Instead of a balloon, imagine a gimbaled weight (not a gyro).

Isn't a tethered balloon just an upside-down plumb bob? And what is the difference between a free-floating balloon on the ceiling, and bowling ball on the floor?
 
Lindberg said:
Yes, if one spot is heavier, that spot will tend to be on the "bottom." But that doesn't necessarily mean it will point towards the earth. And you can't ignore the effects of acceleration. Instead of a balloon, imagine a gimbaled weight (not a gyro).

Isn't a tethered balloon just an upside-down plumb bob? And what is the difference between a free-floating balloon on the ceiling, and bowling ball on the floor?
Click to expand...

Let's see now, are we talking about the angle of the dangle, the mass of the a**, or the torque of the pork???
 
Henning said:
There are two forces involved, buoyancy and gravity. Buoyancy lifts the helium against gravity, remove the the fluid that provides the buoyancy and gravity takes over and the helium atoms would sink to the bottom.
Click to expand...

Two problems: unless the helium atoms where contained in a separate vessel it would be impossible to remove only the air molecules and any vessel strong enough to contain the helium in a vacuum would be too heavy for the helium to carry even when surrounded by air.

You could say you'd introduce only helium atoms into a vacuum chamber and wonder if they'd float but of course not. It would be the same as oil floating on top of water, take the water out and what is the oil going to float on top of?
 
What is the definition of a gas for $100 Alex.
 
Lindberg said:
Yes, if one spot is heavier, that spot will tend to be on the "bottom." But that doesn't necessarily mean it will point towards the earth. And you can't ignore the effects of acceleration. Instead of a balloon, imagine a gimbaled weight (not a gyro).

Isn't a tethered balloon just an upside-down plumb bob? And what is the difference between a free-floating balloon on the ceiling, and bowling ball on the floor?
Click to expand...

Well if it is either in the ceiling or floor, it isn't free floating and it will be subject to the acceleration of the plane. I agree that in practice you can't ignore the effects of acceleration and fluid movement in the cabin, but this is a thought exercise.

Why wouldn't the heaviest part of the balloon point towards earth, it were not otherwise subject to acceleration imparted from the airplane? I would think for small attitude changes it would probably work okay, and for large ones not so much.
 
So lets ask this:

If I have a round balloon on the top center of the cabin (unteathered) and I am flying straight and level, speed unchanging and I make a left 30 degree bank, perfectly cordinated, the balloon will stay put?

My brain wants it to climb to the highest part of the cabin.


Next question.
I am just trying to fly straight and level. I am in the clouds and scared like a little girl and I am thinking if I can just keep going, eventually I will break out since I have 15 hours of fuel on board. In this scenario, I am not turning so no rudder inputs, just watching the balloon.

The balloon drifts to the front of the cabin. Can I assume I have pitched up?
The balloon drifts to the right side of the cabin. Can I assume I have banked left?



Grumble.... If I pitched up the balloon would go forward but airspeed would decrease and the balloon would go backwards erg....
 
Sell one of your testicles, have it swapped out with a helium filled testicle. When your testicle drops...oh we might be waiting a while.
 
EdFred said:
Sell one of your testicles, have it swapped out with a helium filled testicle. When your testicle drops...oh we might be waiting a while.
Click to expand...

If I sell em, I am replacing them with those benwah balls so it jingles when I walk
 
SixPapaCharlie said:
So lets ask this:

If I have a round balloon on the top center of the cabin (unteathered) and I am flying straight and level, speed unchanging and I make a left 30 degree bank, perfectly cordinated, the balloon will stay put?

My brain wants it to climb to the highest part of the cabin.


Next question.
I am just trying to fly straight and level. I am in the clouds and scared like a little girl and I am thinking if I can just keep going, eventually I will break out since I have 15 hours of fuel on board. In this scenario, I am not turning so no rudder inputs, just watching the balloon.

The balloon drifts to the front of the cabin. Can I assume I have pitched up?
The balloon drifts to the right side of the cabin. Can I assume I have banked left?



Grumble.... If I pitched up the balloon would go forward but airspeed would decrease and the balloon would go backwards erg....
Click to expand...

No. Don't forget about the Coriolis effect.
 
SixPapaCharlie said:
So lets ask this:

If I have a round balloon on the top center of the cabin (unteathered) and I am flying straight and level, speed unchanging and I make a left 30 degree bank, perfectly cordinated, the balloon will stay put?

My brain wants it to climb to the highest part of the cabin.


Next question.
I am just trying to fly straight and level. I am in the clouds and scared like a little girl and I am thinking if I can just keep going, eventually I will break out since I have 15 hours of fuel on board. In this scenario, I am not turning so no rudder inputs, just watching the balloon.

The balloon drifts to the front of the cabin. Can I assume I have pitched up?
The balloon drifts to the right side of the cabin. Can I assume I have banked left?



Grumble.... If I pitched up the balloon would go forward but airspeed would decrease and the balloon would go backwards erg....
Click to expand...

In a level steep turn, the increase in G creates an increase in friction which will hold the balloon in place. If the surfaces were frictionless, the balloon would go to the high side.

Don't worry about balloons, work on real, known, partial panel procedures, they will get you through.
 
Funny how a discussion on balloons can prompt everyone to try to burst each other's bubble.
 
SixPapaCharlie said:
So lets ask this:

If I have a round balloon on the top center of the cabin (unteathered) and I am flying straight and level, speed unchanging and I make a left 30 degree bank, perfectly cordinated, the balloon will stay put?

My brain wants it to climb to the highest part of the cabin.


Next question.
I am just trying to fly straight and level. I am in the clouds and scared like a little girl and I am thinking if I can just keep going, eventually I will break out since I have 15 hours of fuel on board. In this scenario, I am not turning so no rudder inputs, just watching the balloon.

The balloon drifts to the front of the cabin. Can I assume I have pitched up?
The balloon drifts to the right side of the cabin. Can I assume I have banked left?



Grumble.... If I pitched up the balloon would go forward but airspeed would decrease and the balloon would go backwards erg....
Click to expand...

Imagine the balloon is in a curved tube running the width of the airplane. The tube curves up in the middle. Which way does the balloon move when you make a coordinated turn?

Now, imagine the tube is filled with water, and the balloon is just a bubble.

CY40_2_Plastic_Level_Vial.jpg


Same question.

Now, turn the tube upside down and replace the bubble with a metal ball.

10-00700.jpg


The ball can tell you if a turn is coordinated, but it can't tell you whether you're turning. You can be straight and level or turning and the ball/balloon can be centered or not.
 
You must log in or register to reply here.
Back
Top