[lobrobster]

Most treadmills are only capable of certain set speeds... does this version free-wheel?

I'm still getting to know you guys, so I'm not sure how to calibrate my sarcasm meter yet.

The treadmill will match any speed of the plane's wheels.

[Flying Blue Eagle]

ROB :: I need to be in this also ,:: #1- when a plane starts moveing forward from the (THRUST OF THE JET ENGINE) THE wind going past the wings, causes a low pressure on top side and a high pressure on bottom side, as the plane goes faster and LIFT EQUALS WEIGHT THE plane reaches lift (KNOWN BY PILOTS AS ROTATION POINT)IF it's a prop it's the same except it pulls by the props. pulling air through the props. Now the engines ARE what pushes or pulls the air craft forward, they always take off into the wind, on a aircraft carrier, they turn the ship, HEADING INTO THE WIND ONCE THE AIRCRAFT REACHES THE POINT OF ( LIFT EQUALLS WEIGHT < WHEN YOU PULL BACK ON THE STICK {OR YOUK} IT IS GOING TO LEAVE THE GROUND WITH FULL POWER ON::::::" WITH engines running ,that plane is going to move forward. Back ,I BElieve it was late 80's or 90's they redesigned the race car to work on the same princeable as a plane , except in reverse, LOW ON BOTTOM <HIGH PRESSURE ON TOP , this was done so they could hold to the road better ,go faster and not lose control as they used to . I KNOW because iv'e been a pilot since back in50's I've flpwn jet and prop ,I still hold pilots license ,WITH AIRCRAFT SINGLE <MULTI ENG> INSTRUMENT> I was AIR FORCE ,for 12years F.B.E.

[CaptainRich]

I'm still getting to know you guys, so I'm not sure how to calibrate my sarcasm meter yet.

The treadmill will match any speed of the plane's wheels.

Well, then if the treadmill matches the wheel's speed (like a dyno), the Veyron would sound damn good... sitting still!

And let the sarcasm flow freely! With me anyway!

[ebaines]

Would everyone agree that a car on the same treadmill/tarmac would never get above zero mph?

No. Read the question more carefully.

Imagine a car moving at 40 MPH relative to the speed of the treadmill (i.e. the car's speedometer would read 40 MPH). But imagine also that the treadmill is only going at 20 MPH relative to the ground in the opposite direction. This means the car will move at 20 MPH relative to the ground, correct? Under these conditions the car is satisfying the condition of the question as originally posed, that is: "for every mile an hour the [car's] wheels move forward, the treadmill moves a mile an hour in the opposite direction." If we assume that these speeds are measured in a consistent way relative to the ground, then the car does indeed move forward.

[CaptainRich]

Hehe, this keeps me thinking. I hate that!

The vehicle's speedometer may indicate a mechanical interpretation, but the key here is MPH, miles per hour, and if it's sitting still on the treadmill/dyno, it isn't covering any miles.

Going back to thte aircraft analogy... speed over ground (SOG) would be zero. Substitute the speedometer with GPS. I think your car is not moving.

lobroster, next time we want all of the variable, as much of the given info, upfront. OK, buddy?

[ebaines]

The treadmill will match any speed of the plane's wheels.

The problem here is that this phrase is open to different interpretations, and the answer depends on how you think of "the speed of the plane's wheels." If this phrase means that the treadmill matches the forward horizontal velocity of the axle of the wheel, (i.e, the point of its average velocity relative to the ground) then the plane does move forward as I've shown before, and could take off. However, if the phrase means that the treadmill matches the speed of the contact point of the tire relative to the axle (i.e. its spinning velocity relative to the axle), then the plane stands still and it can't take off. By the way, the only way for this to physically work is for the frictional forces between tire and treadmill to exactly counter-balance the thrust of the engine, and if you ignore this rolling friction then it's easy to show that the treadmill must move infinitely fast. But that's another discussion.

[shempAM]

There are too many variables to say whether the plane would take off or not. However, if you say there was NO wind at all and the platform on which the treadmill moves is stationary then the plane would defiantly NOT take off. As people have said, a plane takes off due to the lift under it's wings, it generates this lift by traveling at high velocity. The plane on the treadmill would have high speed, but no velocity. Velocity is movement in a direction. The plane would still be stationary.

If you imagine yourself running on an exercise treadmill, you can run very fast, but you will not feel a strong wind in your face. The same applies to the plane.

[Stratmando]

Since the wheels spin free. Jet would move forward. As thrust increases, it will push jet forward, wheels would spin. Jet would jump off treadmill and at rotation speed, it would lift off.

[excon]

Hello lob:

The plane would take off. Unlike a car which pushes against the road, a plane pushes against the air.

Let's say the entire runway was a treadmill geared to the parameters discussed. The plane begins pushing the air and it moves against the ground at 1 mph. The treadmill goes at 1 mph but the plane is pushing against the air at 1 mph and IS moving over the ground. The thrust of the engines against the air isn't going to stop moving the airplane because of its wheels.

Ergo. If the plane is moving against the air at 1 mph, and the treadmill is moving at 1 mph, the treadmill is STILL 1 mph slower than the plane is moving over the ground, so the plane would begin its take off run normally.

As the speed of the plane against the air reaches say, 120 mph, the wheels would ordinarily be going 120 also, but because the treadmill is moving to match the wheels, the treadmill is still 120 mph slower than the air that is pushing the airplane - and the airplane would take off.

What do I win?

excon

[shempAM]

excon:

There is NO AIR PUSHING AGAINST THE PLANE.
Unless I've interpreted the question wrongly, the plane would not take off. If the plane was going 1000000mph on a completely flat, and infinitely long, surface in a vacuum the plan would still not take off. It would just keep going straight. SPEED makes no difference in this conundrum, it's the VELOCITY of the aircraft. Of course, like I said in my previous answer, there are too many variables which would change the output of this question, however we must say (for arguments sake) that 100% of the thrust generated by the engines is converted into kinetic energy in the wheels, and the forces active on the wheels and treadmill are balanced. If this is so then for each 1mph the planes wheels move forward, the treadmill reverses the effect my matching the speed in the reverse direction. Therefore, even when the plane is at max speed it is still standing stationary and there are no forces allowing the plane to take off.

[Flying Blue Eagle]

TO ALL- EXCON & Stratmando , Both of you are getting close to what really makes &causes it to take off and fly. > The wheels on a aircraftARE free spining, it has nothing to do wiyh making the aircraft. The Thrust of the jet engines is all that makes the aircraft,Move forward, ( UNLESS IT HAS JATO ON THE TAIL END BEHIND THE AFT WHEEL, 32bottles, 1000 lbs thrust per bottle,the rack held 32bottles, on the b-47 jet bomber) I'm not giving out any secret stuff::: Each of the 6 engines gave 6700lbs thrust (DRY) WET is over 7000 per eng. . The hot air comeing out the tail cone ,is the thrust, Which CAUSES THE AIRCRAFT TO MOVE FORWARD ::: NOW , FROM THE AIRCRAFT moveing forward, the air moveing under and over the wings starts things in motion for the completion of flight. As the aircraft, picks up speed, IT WILL MEET THE POINT OF LIFT<WHICH WE CALLED THE (ROTATION POINT) - takeoff, The hot air gasses comeing out the tail cone contuious the push that moves it through the air,witch in turn keeps the needed air flow over and under the wings to give the a/c the needed lift to fly .( AS TO AIR FLOWTO THE WINGS< AIR GOING OVER THE TOP<HAS Further TO TRAVEL <WHICH IN TURN CAUSES THE (LOW PRESSURE ON TOP OF WINGS), (THE AIR PASSING UNDER THE WINGS <TRAVELS FASTER < WHICH IN TURN CAUSES THE HIGH PRESSURE NEEDED TO GIVE LIFT TO THE A/C::: For the A/C ,or any a/c to fly (the LAW KNOWNAS - when lift = Weight It WILL FLY) The only difference of a prop POWERED A/c is, ( IT PULLES THE AIR Through THE BLADES AND Expels IT AT MUCH Higher SPEED AND POWER) Durning flight the prope OR props. Keep the a/c FLYING forward giving the needed lift to stay flying, allso the prop,OR props pulls the a/c forward. I could really blow some if I tried to explane the reversing the engines on prop or jets durning landings. Will that's another issiue to discuse later YOU-All have a good day, nice flying F.B.E.

[shempAM]

The more I think about this question the more my answer changes...
I was thinking about how a normal jet plane on a normal tarmac runway would move, and I believe that, relative to the plane, the ground is moving in the reverse direction to the direction of force anyway.

So, I thought, when a plane on a normal runway is moving at 50mph, the ground is moving 50mph in the reverse direction relative to the plane. So, this would be similar the treadmill in question. However on a normal runway the push of the jet engines against the air behind it pushes the plane forward and therefore air flows around it allowing the plane to get the amount of lift needed for a take off.

In reality of course the runway is not moving an inch, but the treadmill IS.

Imagine a whole runway replaced by the treadmill, and the plane starts its run at the END of the runway. Now, switch the treadmill on so it's moving backwards at 50mph. The plane would travel along the treadmill backwards at 50mph, and with wind rushing into it from the back. Now slowly accelerate the plane until it is no longer moving backwards, obviously the wheels of the plane would have to have a high enough RPM to keep the plane at 50mph. Now, the speed and velocity of the plane are non-existent, (it's not covering any distance so it is moving at 0mph, and it's not moving in a direction so it has no velocity).
However... the plane is using the thrust of it's engines to push itself forward, not the wheels . So, the wheels would be moving twice as fast, the combined speed of the wheels and treadmill, but the pane would, as long as the thrust is great enough, still be moving forwards and therefore would have the wind speed etc to take off.


I correct my previous answers.

[Flying Blue Eagle]

SHempAM- YOU are getting very close to the answer to all this. Remember that the wheels on any aircraft have nothing to do with the power of the aircraft takeing off. they are (FREE SPINNING). The engines provide all the power to take off and to fly;;; think of this ( A plane takeing off on snow or ice or even water,) t's only way to move is from the engines, and as it moves it has wind passing ,over and under the wings. which in turn starts in motion WHEN LIFT = WEIGHT <ROTATION POINT IS MEANT AND IT TAKES OFF AND FLYS) THE WHEELS BEING FREE SPINNING < WILL NOT KEEP IT FROM MOVEING FORWARD;; IT was mentioned about VACUMN, What about the space shuttle. It fly in the vacumn of space. Don't IT?? F.B.E. I SURE WISH SOME other PILOTS OR AIRCRAFT ENGINEERS WOULD GET INVOLVED IN THIS . HAVE A GOOD DAY & GOD BLESS good flying

[CaptainRich]

Especially my post # 13 on page two.

...the jet's engines are pushing against stationary air, irrespective of the tarmac, thereby producing thrust. The speed of the wheels on the landing gear don't enter into this equation.

The landing gear, as you mentioned, could be ski's on snow or ice, or pontoon's on water, which in the case of landing on a river, the effective surface could be moving with the aircraft or could be moving against the aircraft. The aircraft carrier is a poor analogy here because it represents a "treadmill" moving forward.

[shempAM]

Yeah, I get the gist of this now. But I still think that a small variation in the question, or the interpretation of the question, could change the answer (that's how I got confused). I hadn't read the question properly, I thought it said:

"For every mile an hour the PLANE moves forward, the treadmill moves backward one mile an hour."

Of course now I see that the question said the WHEELS would be moving backward for each mph, not the whole plane.


Satisfaction at last..

[excon]

Hello again:

That's what I was saying. Actually at the time of rotation, the wheels would be going backwards at twice the speed of R. Half the speed would be taken up by the airplane moving down the runway, and the other half of the speed would be the treadmill moving backwards at that same speed.

And, the plane takes off. I didn't splain it good, but I knew what I meant.

excon

[Flying Blue Eagle]

CapyainRich- I kind of figuered that you were ,but I didn't realluy catch it on the first page, sorry . Iv'e been trying hard to explain it in what is called (LAYMANS TERMS ) like I tell MY doctor ,when he snows me in. You know that on landing and take off , no matter what kind of water snow ice a/c carrier ground , the airplane always lands& takes Into the wind as stright as possible, although there are times known as cross wind. I was taught in the USAF instead of slide slipping (nose into cross Wind) to use what is called cross control , I liked it a lot better, that's what I always use. HAVE A GOOD DAY< NICE FLYING F.B.E.

[Stratmando]

I like Cross control, Accelerated Stalls, and Critically Slow Flight(at the edge of stall)
EAA+AOPA

[Flying Blue Eagle]

Hey stratmando- Do you ever let it go to the horn ? Let the right wing stall and go into deliberet stall and following spin? Totsal of 1 1/2 turns for recovery? IT'S FUn HAVE a good DAY Happy Flying. F.B.E.

[Stratmando]

I love Stalls/Spins, Unusual Attitude and Recovery(DUH). I used to smile when flying "Under the Hood", Eyes Closed, Instructor would fly random turns/climbs, and I then recover from where ever he left me. Nose high, rapidly declining airspeed, or in the middle of spins. Those were good times.
Take Care Blue Eagle.