The Impossibility of Flying Heavy Aircraft Without Training

Jose wrote:
Suppose we have a 1500 lb airplane in level flight at 120 mph.
What are its horizontal and vertical components of momentum?

Suppose we have a 1500 lb rocketship hovering over the moon on its
rocket exhaust. What are its horizontal and vertical componnts of momentum?


I asked first.

--

FF

On Fri, 03 Mar 2006 08:00:45 -0800, fredfighter wrote:


Jose wrote:
Suppose we have a 1500 lb airplane in level flight at 120 mph.
What are its horizontal and vertical components of momentum?

Zero at equalibrium.


Suppose we have a 1500 lb rocketship hovering over the moon on its
rocket exhaust. What are its horizontal and vertical componnts of momentum?

Again, zero.



I asked first.

Same answer, different criteria. Net energy for a given mass will be
the same whether the craft is flying, rocketing, or in orbit.

F=MA

But, only in the instance of 'flying' does Bernuolli apply.

In article ,
"00:00:00Hg" wrote:

On Fri, 03 Mar 2006 08:00:45 -0800, fredfighter wrote:


Jose wrote:
Suppose we have a 1500 lb airplane in level flight at 120 mph.
What are its horizontal and vertical components of momentum?

Zero at equalibrium.

Incorrect. It has considerable horizontal momentum and no vertical
momentum.



Suppose we have a 1500 lb rocketship hovering over the moon on its
rocket exhaust. What are its horizontal and vertical componnts of
momentum?

Again, zero.

Correct, but how can you possibly get zero for this answer and think
that an aircraft moving horizontally at 120 mph has no horizontal
momentum...

snip

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

On Fri, 03 Mar 2006 17:56:39 +0000, Alan Baker wrote:

Suppose we have a 1500 lb airplane in level flight at 120 mph.
What are its horizontal and vertical components of momentum?

Zero at equalibrium.

Incorrect. It has considerable horizontal momentum and no vertical
momentum.

I thought the focus was forces.

The 'aircraft' with respect to the media, air.

If the ground is at play with respect to horizontal 'componet'
is it in the form of 'gravity' (a force) or geologial energy
of some sort expressed as the force of location?

This is hightly interesting. Never thought of it before.

00:00:00Hg wrote:
On Fri, 03 Mar 2006 17:56:39 +0000, Alan Baker wrote:

Suppose we have a 1500 lb airplane in level flight at 120 mph.
What are its horizontal and vertical components of momentum?

Zero at equalibrium.

Incorrect. It has considerable horizontal momentum and no vertical
momentum.

Whereas for the hovering spacecraft both components are zero.


I thought the focus was forces.

It should be.

The hovering spacecraft has zero horizontal and vertical momentum.
It has weight, directed downwards. The engine accelerates
mass downward producing an upward force equal in magnitude
and opposite in direction to the weight of the spacecraft. This
imparts an acceleration to the spacecraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

Now of course weight is a convenient fiction. There is really no such
thing as gravitational force, what we model as a force acting at a
distance is in reality the distortion of spacetime in the presence of
mass. Perhaps other forces are similarly ficticious.

But how sure can we be that mass and velocity are any less ficticious
than force?

--

FF

On Fri, 03 Mar 2006 10:55:59 -0800, fredfighter wrote:

Now of course weight is a convenient fiction.

Can I allocate excess fat that same definition?

There is really no such
thing as gravitational force, what we model as a force acting at a
distance is in reality the distortion of spacetime in the presence of
mass. Perhaps other forces are similarly ficticious.

I hope not the Air Force.

So you want to bring general and special relativity into
the frey `eh? Newton ain't good enough for you, huh? Ok.

Gimme your Lorentz transformations for -Mach 1 to +Mach 1
at the transition point. I wanna see how time and gravity
are related to mass transactions. The speed of sound must
be a nodal harmonic of the speed of light. I wanna see it
too. Gimme gimme...


But how sure can we be that mass and velocity are any less ficticious
than force?

Gravity seems to work to it's own advantage so it's the
ultimate taxing authority in the universe. That really sucks.

The hovering spacecraft has zero horizontal and vertical momentum.
It has weight, directed downwards. The engine accelerates
mass downward producing an upward force equal in magnitude
and opposite in direction to the weight of the spacecraft. This
imparts an acceleration to the spacecraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

The flying wing has some horizontal momentum which is secondary here,
and zero vertical momentum.
It also has weight, directed downwards. The wing accelerates
mass downward (mass it finds in the air molecules) producing
an upward force equal in magnitude and opposite in direction to
the weight of the wing (and its presumably attached aircraft. It does
so by finding air in front of it, flinging it downwards and forwards
(which causes the air in front to try to get out of the way by rising).
In the steady state, one can measure high pressure below and low
pressure above, but this is just the macroscopic manifestation of the
greater number of molecular collisions below, and the lesser number of
collisions above. That's what pressure is - we have both agreed on this.

The greater number of collisions below
imparts an acceleration to the aircraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

Unlike the spacecraft (at least to first order), the wing is actually
supported by the earth, as the pressure below the wing is higher than it
would have been absent the wing's passage, and this higher pressure
(spread out over many square miles) pushes down on the earth with a
force equal to the weight of the aircraft.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

Jose wrote:
The hovering spacecraft has zero horizontal and vertical momentum.
It has weight, directed downwards. The engine accelerates
mass downward producing an upward force equal in magnitude
and opposite in direction to the weight of the spacecraft. This
imparts an acceleration to the spacecraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

The flying wing has some horizontal momentum which is secondary here,

How much?

and zero vertical momentum.
It also has weight, directed downwards. The wing accelerates
mass downward (mass it finds in the air molecules) producing
an upward force equal in magnitude and opposite in direction to
the weight of the wing (and its presumably attached aircraft. It does
so by finding air in front of it, flinging it downwards and forwards
(which causes the air in front to try to get out of the way by rising).
In the steady state, one can measure high pressure below and low
pressure above, but this is just the macroscopic manifestation of the
greater number of molecular collisions below, and the lesser number of
collisions above. That's what pressure is - we have both agreed on this.

The greater number of collisions below
imparts an acceleration to the aircraft equal in magnitude and
opposite in direction from the local acceleration due to gravity.

I agree that lift is a force, exerted on the aircraft by the air,
which in steady level flight is equal in magnitude and opposite
in direction to the weight of the aircraft. Energy is 'pumped'
into the air by the plane. There is no need for a net momentum
exchange between the airplane and the air in order for
energy to be exchanged or for forces to be applied.
Indeed, in those last two paragraphs above, you make
no mention of momentum.

BTW, I was wrong to invoke conservation of momentum.
Momentum is conserved in elastic collisions, like the
collision between a cue ball and the eight ball. Momentum
is not conserved in inelastic collisions, like the collision
between a cue ball and a nerf ball.

Roll the airplane into a 90 degree bank. The weight is
now orthogonal to the lift. As teh airplane falls, it
banks even though there is no Earth 'under' the
belly. Why?

--

FF

I asked first.

Ok, vertical momentum of a wing in level flight is zero.

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.