The Case of the plane and the conveyor belt

The case of the plane and the conveyor belt

A mystery to be solved
I was given a theoretial problem today, lets see if we can solve it. http://www.nonrev.net/infopop/emoticons/icon_wink.gif

A plane is standing on a moving ( some sort of a band conveyer) runway.
The plane moves in one direction, while the conveyor belt moves in the opposite direction. The conveyer belt has a control system that tracks the plane's speed and tunes the speed of the belt to the plane (so you have the plane and the belt at the same speed but moving in opposite directions)
Can the plane take off?

Discussion---

I'm thinking no, but not sure, anybody?

Keep'em flying

Not without a rocket strapped to the tailplane !!! http://www.nonrev.net/infopop/emotic...on_biggrin.gif

The lift for flight is derived from the airflow over the wings creating a pressure differential and causing lift. In the case you mention there is no airflow over the wings as the plane remains static relative to the air around it .. hence no lift .. and no take off ... http://www.nonrev.net/infopop/emotic...n_rolleyes.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BRITSKI99:
Not without a rocket strapped to the tailplane !!! http://www.nonrev.net/infopop/emotic...on_biggrin.gif </div></BLOCKQUOTE>

That's pretty much how I see it.
However there is another school of thought that says, while the moving belt will cause the wheels to spin spin spin, http://www.nonrev.net/infopop/emotic...on_biggrin.gif this friction is not enough to counter the forward thrust of the jet engines. Hmmm does anyone have a model plane and a treadmill? http://www.nonrev.net/infopop/emoticons/icon_wink.gif

Keep'em flying

well, friction aside, the conveyor doesn't matter. The engines move the plane, they don't turn the wheels. It's not like in a car. So while the wheel speed may get to like 400mph, the airspeed would be independent of the wheel speed. The wheels are free spinning, the wheels don't move the aircraft. Thus, the aircraft would take off absolutely normally, it just may feel bumpy with the wheels spinning that fast.

It doesn't matter what the wheel speed is. If it's going 1000 MPH or 2000 MPH, but as the poster implied, the conveyor is moving in conjuction with the speed of the wheels in the other direction. That means, there is NO AIRFLOW. The plane is stationary. No airflow, no takeoff. The plane has to move down the runway to get airflow for lift. Needs about 75 MPH for lift I believe somewhere around there.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ColoAvs19:
well, friction aside, the conveyor doesn't matter. The engines move the plane, they don't turn the wheels. It's not like in a car. So while the wheel speed may get to like 400mph, the airspeed would be independent of the wheel speed. The wheels are free spinning, the wheels don't move the aircraft. Thus, the aircraft would take off absolutely normally, it just may feel bumpy with the wheels spinning that fast. </div></BLOCKQUOTE>

The engines push the aircraft through the air. It wouldn't matter how fast the conveyor goes, as long as the wheels are free spinning enough. No matter the speed of the conveyor, the thrust of the engines in the air should overpower the conveyor. The air would remain static to the conveyor. The engines would simply overpower the conveyor if the wheels would spin free enough with no friction. The engines move the plane through the air, they don't move the plane along the ground. The ground condition should have no effect on the engine moving air.

Lift is not created by the thrust of the engines as you say. Lift is created by the airflow over an AIRFOIL which is the wing. You are thinking the jet engine as some kind of a space ship rocket engine. It doesn't work that way. No airflow underneath the wings, NO LIFT. Cut and dry.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ColoAvs19:
The engines push the aircraft through the air. It wouldn't matter how fast the conveyor goes, as long as the wheels are free spinning enough. No matter the speed of the conveyor, the thrust of the engines in the air should overpower the conveyor. The air would remain static to the conveyor. The engines would simply overpower the conveyor if the wheels would spin free enough with no friction. The engines move the plane through the air, they don't move the plane along the ground. The ground condition should have no effect on the engine moving air. </div></BLOCKQUOTE>

I'm saying that the aircraft would accelerate forward regardless of the conveyor. The aircraft would accelerate just as normal, creating airflow over the airfoils, creating lift. In your car, the engine moves the wheels, they spin along the ground, displacing the ground. Car on a treadmill is going nowhere. However, an aircraft engine doesn't displace ground, it displaces air. Since the air is still, the engines would still displace that air and accelerate the plane forward through the air, creating airflow over the wings

Even if it did have a rocket engine, that wouldn't make a difference from a jet engine.

I'm in agreement with ColoAvs19. When I run at the gym I like to do the indoor track rather than the treadmill so I can feel the wind in my face. When I'm on the treadmill I remain stationary because the action of my feet and legs normally move me forward. However, an aircraft is different. It is moved forward by displacing air. The wheels are free spinning and therefore would not keep the aircraft from moving forward. It would eventually move forward with enough speed to create lift as it normally does. The spinning wheels underneath would spin faster than normal but would not prevent the planes forward momentum.

A previously stated the engines produce a forward thrust as said by moving the air from infront of the engine to behind it however this air motion itself will not create any lift over the aerodynamic lifting surfaces .. only the movement of the aerodynamic lifting surfaces through the air creates this lift. The crucial element is in the part of the question which states "you have the plane and the belt at the same speed but moving in opposite directions" so even though the aircraft and the belt may have wheel speeds corresponding to 500 mph there is still no resultant movement of the air over the aerodynamic lifting surfaces hence no lift and no take-off.

If it was possible don't you think someone would have developed this for use on an aircraft carrier before now??

What I'm saying is, friction aside, no matter how fast you got the conveyor going, the aircraft would do a normal takeoff roll.

It would still require the same amount of runway. It would still move through the air.

I'm not saying that the engines would create lift. I'm saying the aircraft would roll forward as normal, creating lift by attaining airspeed.

This is sort of on the same page with the high school CO2 cars. They have large back wheels, which makes no sense, because the thrust comes from the CO2 canister, just like a jet or rocket. So you want the smallest surface area possible touching the ground.

I don't know why your stuck on this. Or maybe we don't get your conveyor belt. I see a conveyor belt moving backwards and a jet trying to move foward. They are BOTH PUTTING OUT the same energy to their respective distance. The plane is going 85 MPH one way, the conveyor is going -85 the other way. That means that this airplane isn't moving. It doesn't matter that it travels beyond the plane of the conveyor belt, but as long as the plane is still on the conveyor belt, it aint gonna grab lift. If airflow don't make it up and over the airfoil of the wing, it aint gonna go up. Do the math. +85 THRUST - 85 CONVEYOR (or negative progress)= 0 AIRSPEED. 0 AIRSPEED = NO LIFT.
Or you can say WORK=FORCE+ENERGY. WORK is the "LIFT" and FORCE is the SPEED and ENERGY is the NEGATIVE SPEED. End result is WORK=ZERO meaning all this work placing a plane on a conveyor with fancy gadgets got you alot of oohs and ahhhs but in the end, NO RESULTS!



QUOTE]Originally posted by ColoAvs19:
What I'm saying is, friction aside, no matter how fast you got the conveyor going, the aircraft would do a normal takeoff roll.

It would still require the same amount of runway. It would still move through the air.

I'm not saying that the engines would create lift. I'm saying the aircraft would roll forward as normal, creating lift by attaining airspeed.

This is sort of on the same page with the high school CO2 cars. They have large back wheels, which makes no sense, because the thrust comes from the CO2 canister, just like a jet or rocket. So you want the smallest surface area possible touching the ground.[/QUOTE]

You're right. The jet engines push the airplane through the air to create airflow, but it has to get off the ground first to capture the airflow. Once its in the air, the engines do the work, but if its on the ground in a tread mill, and this tread mill is going equal to the thrust the opposite direction, there is no airflow so its impossible to fly. If this were the case, the MARINES would not be spending huge bucks on HARRIERS jet fighters and you could be taking B-777's off aircraft carriers equipped with a huge tread mill that could carry alot more personell. Right? That is why they use HELICOPTERS or HARRIERS off AIRCRAFT CARRIERS. The jets that take off ships face off into the wind and utilize the slingshot effect to push them through the carrier flight decks to gain the needed lift. What you're saying, is that any airplane would take off any carrier equipped with a huge tread mill because the engines would eventually lift the plane up right? The design is just not there my friend.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ColoAvs19:
Thanks Chris.

Thanks Palms for coming around a little.

I still say that the engines push it through the air, creating airflow. The ground could go incredibly fast, it wouldn't matter. Plus, a rocket vs. a jet wouldn't make an ounce of difference in this situation. </div></BLOCKQUOTE>

Yep Matt. That's what I think. The conveyor would not prevent the aircraft from moving forward. It would prevent a car or motorcylce or any vehicle whose forward motion was dependent on drive to the wheels but the plane would still move forward and eventually take off as normal.

A conveyor on an aircraft carrier would not help because the aircraft would still need runway length to move forward, create lift, and take off.

So Mig, got an answer for us?

Hmmmmm, forward thrust versus free rolling wheels....will have to do more scientific testing. http://www.nonrev.net/infopop/emoticons/icon_wink.gif
Just got back in town give me some time to set up my equipment. http://www.nonrev.net/infopop/emotic...on_biggrin.gif

Keep'em flying

I have got to admit. This question and your responses had me thinking about this for some time, and the more I think of it, the more I see what you guys that think this plane would still flight despite the conveyor. Being that the engines push against the air instead of the wheel spinning on the belt itself, I can just visualize this and the more I think about it, you guys may be right. But this leads to another possible problem. Tires aren't designed to withstand speeds that fast and my question then would be this. Would the wheel bearings take the heat? Would the tires become too hot also causing a possible explosion? SO, this being the case in theory that this plane overcomes the conveyor for flight, the question is, how fast and for how long would these wheels spin before the plane would gain enough speed for lift? Obviously about double its speed more than it would be normally made for. Not being to nit picky, the tires aren't designed for spinning that fast, with that much weight. If a tire explodes on take off, that's crucial. If a tire explodes from heat after the landing gear is put into the wheel wells, without enough time to cool, that could cause rupture inside the wheel well to alot of hydraulic lines or the resevoir and electrical components itself. Would have to leave the landing gear down for a long time up in the air to give them a chance to cool down. Then upon landing, hope your bearings don't piss off too much the poor mechanic that has to change wheel bearings.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Migflanker:
Hmmmmm, forward thrust versus free rolling wheels....will have to do more scientific testing. http://www.nonrev.net/infopop/emoticons/icon_wink.gif
Just got back in town give me some time to set up my equipment. http://www.nonrev.net/infopop/emotic...on_biggrin.gif

Keep'em flying </div></BLOCKQUOTE>

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">the more I think of it, the more I see what you guys that think this plane would still flight despite the conveyor. </div></BLOCKQUOTE>

Funny, I sent this to a couple of friends, one agreed with my position and the other did not. The one that did not reminded me of the force of gravity pulling the plane downward and pointing out that if the conveyor moved with no force from the engines the plane would move backwards. So he has me doubting my original position. Definitely the conveyor would keep the plane stationary for a while but would it be able to continue? Oh, Mig what have you done to us? More sleepless nights until it's solved! http://www.nonrev.net/infopop/emoticons/icon_frown.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chris:
Oh, Mig what have you done to us? More sleepless nights until it's solved! http://www.nonrev.net/infopop/emoticons/icon_frown.gif </div></BLOCKQUOTE>

Update
Had trouble getting a conveyor belt, but things are rolling now. http://www.nonrev.net/infopop/emoticons/icon_wink.gif

In the meantime, something else to ponder--
True or False? --The Boeing 747 is capable of flying upside down, if it weren't for the fact the wings would shear off when trying to roll over. http://www.nonrev.net/infopop/emotic...on_biggrin.gif http://www.nonrev.net/infopop/emotic...on_biggrin.gif http://www.nonrev.net/infopop/emotic...on_biggrin.gif

Keep'em flying

MythBusters (Discovery Channel) December 12 is taking on the airplane and the conveyor belt conundrum. Check your local listings for time.

Place your bets now.
Mig--I&#39;m still going with the plane will not take off. http://www.nonrev.net/forums/style_e...DIR#>/wink.gif

Oh m&#39; gosh! I thought you were teasing us.

Dec 12, 9:00 pm

(60 minutes)
MythBusters
Air Plane Hour
TV-PG

Jamie and Adam take wing to test if a person with no flight training can safely land an airplane and if a plane can take off from a conveyor belt speeding in the opposite direction. Tory, Grant, and Kari jump on some Hollywood-inspired skydiving myths.

I&#39;ll be watching!!!

So Chris, do you still think the plane will take off, or have you finally come to your senses? http://www.nonrev.net/forums/style_e...#>/biggrin.gif

Contrary to published reports, (Discovery Channel website) yesterday&#39;s episode of "Mythbusters" did not have an airplane/conveyor belt segment. What happened......well, rumor is....
madly spinning airplane wheels aren&#39;t all that interesting to watch http://www.nonrev.net/forums/style_e...#>/biggrin.gif http://www.nonrev.net/forums/style_e...#>/biggrin.gif

Keep&#39;em flying

I think my friend convinced me it wouldn&#39;t take off by making me consider the gravity factor.

I was so bummed it wasn&#39;t on there. http://www.nonrev.net/forums/style_e...IR#>/angry.gif

Do you think they might show it on another episode?

This was posted on the MythBusters&#39; website--

"First up, for those concerned that this story has been cancelled, don&#39;t worry, planes on a conveyer belt has been filmed, is spectacular, and will be part of what us Mythbusters refer to as &#39;episode 97&#39;. Currently that is due to air on January 30th....."
Dan Tapster, executive produce of MythBusters

We shall see.

That&#39;s a cool show and quite interesting but that one red headed dude with the glasses is one flamboyant idiot. I saw him on his last show adopting a FRENCH ACCENT explaining his gadget and how it works. Whatajackass! His female assistant puts on a very good "I&#39;M GONNA PUKE" face when dealing with gross things. Even has me running away from the television so I don&#39;t get sprayed.

<div class='quotetop'>QUOTE (29Palms @ Dec 16 2007, 10:26 AM) <{POST_SNAPBACK}></div>

Quote:

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His female assistant puts on a very good "I&#39;M GONNA PUKE" face when dealing with gross things. Even has me running away from the television so I don&#39;t get sprayed.[/b]

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http://www.nonrev.net/forums/style_e...IR#>/laugh.gif

Another mystery---
A Bugatti Veyron versus a Eurofighter Typhoon - a horizontal versus a vertical drag race over two miles. A mile out/up turn and return to start. Who&#39;s the fastest?
*cue Jeopardy theme music*
Thnk about it carefully, the Veyron can go from 0-100 in 5.7 seconds; of course it is racing an airplane.

Place your bets and then watch the video http://www.nonrev.net/forums/style_e...DIR#>/wink.gif
The Race

Dad gum it. I forgot to watch for planes on a conveyor on Jan. 30th. http://www.nonrev.net/forums/style_e...IR#>/angry.gif

Did anyone see it?

So, 6 years after the original question was asked, here I sit with my brother watching the Mythbusters episode and trying to explain to him why the airplane takes off like normal...

You mean to say the airplane actually took off? :cool:

I saw that episode a long time ago, and before I realized its date (Chris posting definitely helped :P ) I was going to mention that it was covered by MythBusters. And yes, it does take off :)