Can a Plane on a Treadmill Take Off?

"Doug" wrote:

What is keeping the airplane's speed up with the conveyor belt? The
propeller. Said propeller moves air. Air causes lift. The problem is
more complicated than it seems to be at first read.

Not at all complicated. The propulsion system is irrelevant. The given
fact is that the airplane's speed (not it's speed relative to the
conveyor) is equal to the conveyor's speed, but in the opposite
direction. When that speed is sufficient for flight, it will fly.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

The propulsion system is irrelevant as long as it is independant of the
treadmill.

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Travis
"alexy" wrote in message
...
"Doug" wrote:

What is keeping the airplane's speed up with the conveyor belt? The
propeller. Said propeller moves air. Air causes lift. The problem is
more complicated than it seems to be at first read.

Not at all complicated. The propulsion system is irrelevant. The given
fact is that the airplane's speed (not it's speed relative to the
conveyor) is equal to the conveyor's speed, but in the opposite
direction. When that speed is sufficient for flight, it will fly.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked
infrequently.

Travis Marlatte wrote:
The propulsion system is irrelevant as long as it is independant of the
treadmill.

No, it doesn't even have to be "independant of the treadmill." Even
if the wheels of the plane were providing the thrust, all that would
happen is that the wheels would be spinning twice as fast by the time
the plane lifted off.

The key is in the wording of the question. The people here who have
gotten it wrong have misinterpreted the riddle to imply that it means
the aircraft is being held stationary. But that's not true. That's
not what it said. It simply said the belt is moving backwards at the
same speed the plane is moving forward. If the belt were moving
backwards fast enough to keep the plane motionless, then you've just
violated the fundamental rule of the riddle. Vbelt != -(Vplane) in
that case.

Picture it this way:


--- Plane @ 100 mph
Treadmill @ 100 mph ---

Now, what is the TAS of that aircraft? 100 mph. I assure you, it
will fly.

The only braintwister is that one must realize that the WHEELS are
turning at 200 mph, rather than 100 mph.

Kevin.

We are in agreement but you took my reply out of context. I was rephrasing
someone else's post who simply claimed that the propulsion system was
irrelevant (and therefore the plane wouldn't fly). In fact, the propulsion
system would be very relevent to this puzzle if it were relative to the
ground as in a wheel driven plane. As you have pointed out, it would then
need to spin the wheels at twice the speed necessary on a staionary runway.

I am beginning to see why some people struggle and even give up getting
their pilot's certificate. I can also begin to see why experienced pilots
crash when something very minor goes wrong in the air. The realities of
physics finally catches up with them.

--
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Travis
"Kevin" wrote in message
...
Travis Marlatte wrote:
The propulsion system is irrelevant as long as it is independant of the
treadmill.

No, it doesn't even have to be "independant of the treadmill." Even
if the wheels of the plane were providing the thrust, all that would
happen is that the wheels would be spinning twice as fast by the time
the plane lifted off.

The key is in the wording of the question. The people here who have
gotten it wrong have misinterpreted the riddle to imply that it means
the aircraft is being held stationary. But that's not true. That's
not what it said. It simply said the belt is moving backwards at the
same speed the plane is moving forward. If the belt were moving
backwards fast enough to keep the plane motionless, then you've just
violated the fundamental rule of the riddle. Vbelt != -(Vplane) in
that case.

Picture it this way:


--- Plane @ 100 mph
Treadmill @ 100 mph ---

Now, what is the TAS of that aircraft? 100 mph. I assure you, it
will fly.

The only braintwister is that one must realize that the WHEELS are
turning at 200 mph, rather than 100 mph.

Kevin.