Plane on a conveyor belt

[Newc]

Four pages of Mythbusters talk, and not one mention of that hot redhead Kari. Am in still in the JCF, or did I wander into the J.R.R. Tolkien forums?!?

Agreed. She's hawt.


The question is open to interpretation, since it consists only of "Can an airplane on a conveyor belt achieve lift?".

That's it. That's the question.

It does not state JET-powered or PROPELLER powered, nor does it state any physical characteristics of the conveyor.


From the video, I'm seeing a one-sided problem with the giant tarp as opposed to a motorized conveyor. But I would be interested in seeing more of the model plane on the motorized conveyor. They'll have to get a better plane than the one in the video - looks like it had coat-hanger wire for legs, and the tires were too thin.


There are non-motorized treadmills that rotate simply by walking on them. Yes, you have to hold yourself in place with the siderails to get it spinning - if you take off in a full sprint you'll exit the treadmill before it completes one revolution.

However, going from dead stop to take-off speed instantly was not part of the question. This is where individual interpretation comes in on either side.

The wheels on the plane are not motorized - that has been adequately stated and is not what's being debated, so do not bother to mention it again.

The wheels DO TURN as the plane travels along the ground, but not due to a drive shaft or other direct-drive assembly. This also is undisputable fact.

The thrust must be great enough to push the plane forward against its own weight resting on the wheels on the ground. The wheels must rotate for the plane to move forward. That's why you have to unchock the wheels and why you cannot take off until you remove your foot from the brakes. THIS IS NOT SAYING THE WHEELS ARE MOTORIZED OR THAT THE WHEELS PUSH OR PULL THE PLANE ALONG THE GROUND LIKE A CAR.

Before the plane can achieve lift, it must reach a given ground speed.

You can drive a plane on the ground 300+ MPH and never leave the ground. If you never leave the ground, you never have a recordable Air speed. Air speed is the speed something travels through the air, with no part of the object touching the ground. A plane going 60 MPH on the ground has 0 air speed.

Scenario 1:
The plane starts at a dead stop on a standard runway. The engine (jet or prop) is NOT running. The wheels are not chocked.

The engine is then started and the initial thrust pushing air out the back of the engine pushes against the air behind it, which causes the plane to begin moving forward, and according to the laws of physics means the wheels rotate. The plane begins to amble forward down the runway. The pilot applies the brakes to keep the plane from traveling along the ground until the motor has achieved sufficient speed. This is the minimum speed that is required to travel down the runway for a takeoff, not the actual takeoff speed. The motor's RPMs are increased and the plane travels down the runway until it gains enough speed so that airflow over the wings is great enough to generate lift, and it flies away.

Scenario 2:
The plane starts at a dead stop on the level treadmill. The engine (jet or prop) is NOT running. The wheels are not chocked.

The engine is then started and the initial thrust pushing air out the back of the engine pushes against the air behind it, which causes the plane to move forward, which according to the laws of physics means the wheels rotate. The treadmill immediately and equally reacts to the forward rotation of the wheels by rotating in the direction which the friction of the wheels' rotation is pushing it - backwards.
As the motor's RPMs are increased, it pushes more air out the back, but does not achieve ground speed due to the treadmill's immediate response to increased friction: faster rotation.

Scenario 3:
The plane starts at a dead stop on the level treadmill which is as long as the runway. The engine (jet or prop) is NOT running. The wheels are not chocked.

The engine is then started and the initial thrust pushing air out the back of the engine pushes against the air behind it, which causes the plane to move forward, which according to the laws of physics means the wheels rotate. Because the treadmill's design does not allow for immediate and equal reaction to any frictional force applied to it, it slowly reacts to the forward rotation of the wheels by rotating in the direction which the friction of the wheels' rotation is pushing it - backwards.
As the motor's RPMs are increased, it pushes more air out the back, and because of the inability of the treadmill to match the frictional force of the plane's forward thrust against its own wheels, the plane travels along the treadmill at about 3/4 or more the speed it would reach on a traditional runway, where it gains barely enough airflow over the wings to achieve lift.

[Cygnus X1]

Let me repeat:

Won't fly.
Period.

[Endrik]

screw you guys I'm going home

[SeventhSon]

Let me repeat:

Won't fly.
Period.

then put your money where your mouth is! let's do an internet handshake for $20. loser paypals $20 to the winner.

[Snoogans]

does the Hawker Harier ring a bell? if my time line is right it was developed at the end of WWII but scraped due to expense in non war time. But then redisenged with jet engines later and became the Corsair II. during Vietnam. But like i said my time line may be a bit off. It may not be 70 years ago but. It is at least 40 years.

Here's where I flex my aircraft-nerd muscles.

The Harrier, or Hawker Siddeley P1127 was first designed in '57, and first VTO flight was in '60.
The Ling-Tempo-Vought A-7 Corsair II did indeed fly in Vietnam, but had no connection to the Harrier program, being a conventional fixed-wing design.

I don't think either were flown from conveyer belts, but if they try, my money's on the Harrier...

[zeegler]

OK Zeegs, If the plane isn't tethered, how are they going to keep it on the treadmill???
OK, here's my 10 bucks. Matter of fact, make that 20.

That's the point. They would need an awful long treadmill to pull it off.

[mm2002]

That's the point. They would need an awful long treadmill to pull it off.

Exactly! Then of course, what's the purpose of the treadmill?
The only thing I can see the treadmill affecting is the rotation of the wheels, nothing else. It's not going to provide lift via the wings, which is required for the plane to actually fly. Now, if they are going to pull the treadmill behind a vehicle going at least the minimum takeoff speed of the plane, and the engine is at takeoff power, then yes it will fly. But what would that prove? All that will prove is they can use two vehicles, and two supplies of fuel to do the same job one of the vehicles could have done alone.

[Ralph E.]

Straight from my brother-in-law who is a leer jet pilot and flight instructor, the answer is no.

[z1n]

OK I think I see now. For a person, when you walk you push foward off the ground which is why you stay still on a treadmill but for a plane, it pulls itself foward via the air/prop so no matter if it's on a treadmill or not, it should pull itself foward. I think oh but what if... lol

[pjg]

Straight from my brother-in-law who is a leer jet pilot and flight instructor, the answer is no.

The airline I work for has a message board frequented by a bunch of the pilots. Even they can't agree. Half say yes, half say no. These are all part 121 guys.

[Bengal]

$10 says the show doesn't provide a difinitive answer. We will still be debating this issue tomorrow I bet...

[Firebird V]

ok. who is betting on this one. I want in. It will not fly.

[Ralph E.]

No airflow = No lift.

[StukaJU87]

I think the plane will move forward at its normal speed and take off. The wheels will spin twice as fast, but the plane will still move forward because the prop or jet motor will still be pushing against the air behind it. Just my opinion.

[joshulator]

What happens when they turn the treadmill off? I assume at that point the plane moves forward, but is unlikely to have enough momentum to have lift?