# Will the airplane fly?

flyUnity
Posers and Puzzles 21 Oct '06 06:02
1. 21 Oct '06 06:02
A plane is standing on a runway that can move (some sort of treadmill). The plane moves in one direction, while the conveyer moves at the same speed but in the opposite direction. Can the plane take off?"

(copied and pasted from another source)
2. AThousandYoung
All My Soldiers...
21 Oct '06 06:43
No. The plane needs to move relative to the air to take off, not the ground.
3. 21 Oct '06 09:21
Originally posted by AThousandYoung
No. The plane needs to move relative to the air to take off, not the ground.
If you need 60 knots to lift an airplane from the ground what happens is the wind comes at 60 knots towards you when you are still on the ground with propellers running in full speed?
4. 21 Oct '06 09:54
Originally posted by FabianFnas
If you need 60 knots to lift an airplane from the ground what happens is the wind comes at 60 knots towards you when you are still on the ground with propellers running in full speed?
The plane will take off... then stall (if the pilot isn't controlling the plane properly). This is why planes are tied to the ground when parked (or in a hanger).

On a flight a few years ago, I was practically hover although flying at 80 knots. My ground speed was probably only about 10 knots. It was very frustrating, because there was little I could do about it (although I had predicted this was the case in advance and actually landed on-time and as expected).
5. 21 Oct '06 14:50
yes, it's air speed and not ground speed thats important.
6. 21 Oct '06 15:43
haha, i mean no!
7. sonhouse
Fast and Curious
21 Oct '06 16:161 edit
Originally posted by flyUnity
A plane is standing on a runway that can move (some sort of treadmill). The plane moves in one direction, while the conveyer moves at the same speed but in the opposite direction. Can the plane take off?"

(copied and pasted from another source)
Isn't the plane then standing still? I think you are saying the treadmill is moving the plane say to the left from a POV of someone off the runway and the plane is moving to the right at the same speed, so it looks to me like the plane is treading water, not moving at all in relation to either the air or the ground but at double its speed in relation to the treadmill. That is the case of the plane moving opposite to the treadmill. If its moving the same as the treadmill, then its airspeed is doubled and would therefore take off faster since the air speed is increased, just like the catapult on an aircraft carrier.
BTW, how goes the family band? Still gigging or do you quit for school?
Maybe you are homeschooled?
8. 21 Oct '06 17:11
Originally posted by sonhouse
Isn't the plane then standing still? I think you are saying the treadmill is moving the plane say to the left from a POV of someone off the runway and the plane is moving to the right at the same speed, so it looks to me like the plane is treading water, not moving at all in relation to either the air or the ground but at double its speed in relation to the ...[text shortened]... how goes the family band? Still gigging or do you quit for school?
Maybe you are homeschooled?
Some of my flying buddies were having this discussion, And IMO the plane WILL take off, The plane is moving forward 100 kts, the treadmill is going backwards 100 kts, Tires are spinning at 200 kts which has nothing to do with flight. But some of my friends say Im wrong,

I left the family band for flight school, I have about 1 month until I got all my ratings, then Im going to do a big tour back east with my family, Then maybe move back to AZ and see if I can get a job flying.
9. sonhouse
Fast and Curious
21 Oct '06 20:25
Originally posted by flyUnity
Some of my flying buddies were having this discussion, And IMO the plane WILL take off, The plane is moving forward 100 kts, the treadmill is going backwards 100 kts, Tires are spinning at 200 kts which has nothing to do with flight. But some of my friends say Im wrong,

I left the family band ...[text shortened]... ig tour back east with my family, Then maybe move back to AZ and see if I can get a job flying.
Where are you going back east? Maybe your family and mine can have a get together, scratch out some tunes. We live north of Philly, I guess you know that. We just did a couple of local gigs, first my wife has been able to do, tough being a singer when you are stricken with asthma. We did one of the gigs with just me and Kevin, my son, we did just instrumentals, guitars and mandolin. It was fun but would have been better with Susan.
10. 22 Oct '06 00:39
no
there needs to be air pressure change under and over the wings.
when a plain does a preflight check the engin gets reved up, and the props rpm goes up, and the plain just sits on the tarmac. there needs to be a forward thrust and if the "tredmill" and plain wheels are going at same time then no.
11. narya
pawnic attack
22 Oct '06 01:56
Is it a Harrier? ðŸ™‚
12. abejnood
Independant Thinker
22 Oct '06 02:43
According to the laws of physics:

For every action, there is an equal in magnitude but opposite in direction magnitude.

In this case, the plane is moving in one direction. However, the frictional force, or the force of the treadmill in addition to that force creted by the plane, is acting on the treadmill, not the plane. This is why things move. Therefore, the plane will fly.
13. XanthosNZ
Cancerous Bus Crash
22 Oct '06 02:59
Plane wheels are not driving in any regard. They freely rotate. Therefore the engine running will cause the plane to move forward (wrt the air) no matter what speed the treadmill runs at.

Anyone saying otherwise clearly doesn't know how a plane works.

PS. Wings don't work via the low/high pressure thing. It's the angle of attack that does it.
14. 22 Oct '06 04:16
Originally posted by XanthosNZ
Plane wheels are not driving in any regard. They freely rotate. Therefore the engine running will cause the plane to move forward (wrt the air) no matter what speed the treadmill runs at.

Anyone saying otherwise clearly doesn't know how a plane works.

PS. Wings don't work via the low/high pressure thing. It's the angle of attack that does it.
ok, so say the treadmill is going backwards 50 kts, the plane will need x amount of power to stay stationary plus whatever it needs to take off. It should still be able to take off, right?

PS: On most planes, the majority of lift is created by the low pressure on top, and high pressure on the bottom, When at high air speeds, or in cruising flight, you can have ZERO angle of attack, yet the plane will still fly. Some fighter jets though eliminated the curved wing (to reduce drag so they can go faster) so rely only on Angle of Attack
15. AThousandYoung
All My Soldiers...
22 Oct '06 04:43
Let's look at this from another angle. Suppose an airplane was on a normal, stationary runway and had a tailwind blowing at 100 knots. Could the plane take off if it could go only 100 knots relative to the ground and could not change it's direction?