Two conveyor belt scenarios

wrote in message
ups.com...
[...]
And find out what a troll means before using the word, Grumman.

For the record, while I disagree with his usage of the word in this case, he
has used the word in a perfectly correct way, grammatically speaking.

Not to defend his knee-jerk response, but it might be helpful to know that
the newsgroup has been under siege from another particularly troll-like
individual, putting lots of people on-edge. Grumman is usually already
pretty on-edge as it is, so he didn't have far to go before snapping at you.

Peter Duniho wrote:

Not to defend his knee-jerk response, but it might be helpful to know that
the newsgroup has been under siege from another particularly troll-like
individual, putting lots of people on-edge. Grumman is usually already
pretty on-edge as it is, so he didn't have far to go before snapping at you.



k, sure
And just for the record - I *never* troll anyone. Jest often yes, but
troll never

Ramapriya

"Peter Duniho" wrote in message
...
Grumman is usually already pretty on-edge as it is, so he didn't
have far to go before snapping at you.

Yeah, I'm a grumpy old man... If I knew I was going to live this ****in'
long, I would have taken better care of my body when I was growing up...

wrote in message
ups.com...
An airplane lands on a conveyor belt that's moving at a constant speed
of Vref

(a) in the direction of the airplane's landing
(b) in the opposite direction of the airplane's landing

What do you suppose will happen?

Motion of the ground relative to the air is equivalent to motion of the air
relative to the ground. So:

(a) That's equivalent to landing on stationary ground with the headwind
increased by Vref.
(b) That's equivalent to landing on stationary ground with the headwind
decreased by Vref.

--Gary

There are three speeds here. Speed relative to the air. Speed relative
to the belt. Speed relative to ground.

And actually, this does have a real world analogy. Taking off in a
seaplane on a river that is moving. Now add in wind blowing upstream or
wind blowing downstream and the takeoff and landing upstream vs
downstream comparison gets quite complicated.

"Doug" wrote in message
oups.com...
There are three speeds here. Speed relative to the air. Speed relative
to the belt. Speed relative to ground.

The only velocities that matter are that of the plane relative to the air,
and that of the air relative to the landing surface (in this case, the
constant-speed conveyor belt). The landing surface's velocity relative to
the surrounding ground has no physical effect on the landing (except perhaps
with respect to turbulence, but that's not part of the hypothetical
scenario).

And actually, this does have a real world analogy. Taking off in a
seaplane on a river that is moving. Now add in wind blowing upstream or
wind blowing downstream and the takeoff and landing upstream vs
downstream comparison gets quite complicated.

If the river is arbitrarily long (as we're assuming the conveyor belt to be)
and you don't care where on it you end up, then the landing isn't
complicated at all: you just ignore the land completely, and pay attention
to the wind speed relative to the water. (It helps to have a wind sock
that's riding on the river or on the conveyor belt.)

--Gary

Actually, on a moving river, water speed matters and frequently speed
(well, distance really) relative to the ground matters. The ideal setup
is to have a headwind while pointing downstream. That way you have
slowest waterspeed and shortest run. BUT....local obstructions dictate
you concern yourself with distance of run relative to the land....

Like I said, it can get complicated.

Gary Drescher wrote:
"Doug" wrote in message
oups.com...
There are three speeds here. Speed relative to the air. Speed relative
to the belt. Speed relative to ground.

The only velocities that matter are that of the plane relative to the air,
and that of the air relative to the landing surface (in this case, the
constant-speed conveyor belt). The landing surface's velocity relative to
the surrounding ground has no physical effect on the landing (except perhaps
with respect to turbulence, but that's not part of the hypothetical
scenario).

And actually, this does have a real world analogy. Taking off in a
seaplane on a river that is moving. Now add in wind blowing upstream or
wind blowing downstream and the takeoff and landing upstream vs
downstream comparison gets quite complicated.

If the river is arbitrarily long (as we're assuming the conveyor belt to be)
and you don't care where on it you end up, then the landing isn't
complicated at all: you just ignore the land completely, and pay attention
to the wind speed relative to the water. (It helps to have a wind sock
that's riding on the river or on the conveyor belt.)

--Gary

"Doug" wrote in message
ps.com...
Actually, on a moving river, water speed matters and frequently speed
(well, distance really) relative to the ground matters.
....local obstructions dictate
you concern yourself with distance of run relative to the land....

Sure. That's why I said that *if* the river is arbitrarily long, and if you
don't care where you land, *then* you just ignore the land and care only
about the speed of the air relative to the water. (Those stipulations make
the situation analogous to the hypothetical conveyor belt scenario.)

The ideal setup
is to have a headwind while pointing downstream. That way you have
slowest waterspeed and shortest run.

The plane's speed relative to the water (the plane's waterspeed) depends
only on the plane's airspeed and the speed of the air relative to the water.
It doesn't depend in any way on the speed of the water relative to the land;
hence, it doesn't depend on whether you're going upstream or downstream.
Rather, it just depends on whether you're going upwind (relative to the
water) or downwind.

As for making the shortest run (relative to the land), wouldn't you want to
be going upwind (relative to the water) and upstream, rather than upwind and
downstream?

--Gary