Plane on a conveyor belt

[zeegler]

So, it doesn't take too much lift to actually lift the airplane off the ground at this point, I take it....I'll have to see the vid to see how much speed they were able to get, but it doesn't sound like much..

Someone said 35 mph in this case. It doesn't really matter how much speed it requires. If it needed 90mph it would still take off.

[SeventhSon]

^^^
Thrust is in horizontal direction, is it not? If it is partially vertical, I could maybe see some effect on lift.

Better yet, someone get a diagram and post it for us n00bs who didn't get this right.

thrust is based on newton's laws of motion. for every action there is always an equal and opposite reaction. e.g., ejecting something in one direction in order to move in the opposite direction. this is how a rocket launches into orbit. the principal is independent of whether it's up/down or forwards/backwards.

so a jet plane throws exhaust backwards which propels it forward fast enough to generate lift on its wings. these particular forces are simply not affected by the presence of a conveyor belt.

imagine if it were a sea plane on pontoons sitting on a long block of ice. do you think moving the block of ice moving backwards is going to affect the plane's ability to thrust forward and take off?

[pjg]

So, it doesn't take too much lift to actually lift the airplane off the ground at this point, I take it....I'll have to see the vid to see how much speed they were able to get, but it doesn't sound like much..

It takes the same amount of lift on a treadmill to make the plane fly as it would take on a normal runway. Lift opposes gravity (weight). That value is the same in either case.

[SEEGERMANY]

BIG RED!

[fuel0707]

^^^
Thrust is in horizontal direction, is it not? If it is partially vertical, I could maybe see some effect on lift.

Better yet, someone get a diagram and post it for us n00bs who didn't get this right.

Thrust can be in any direction, depending on the motion of the aircraft. For instance, if the aircraft is pitched up relative to its flight path, some of the effect of the thrust force will be in the vertical direction while a good portion of the thrust will act in the "forward" direction.

Here's a pretty good and not too technical (at times) explanation of the four forces that affect powered aircraft. Note the discussion of what happens with thrust when an aircraft climbs. Here's the link: aircraft info

An extreme that would also illustrate that thrust does not necessarily always act in a horizontal direction would be the Harrier, which has nozzles that can direct all of the engine's exhaust gases at the ground and allow the Harrier to either take off straight up or to remain motionless over a spot on the ground.

[SEEGERMANY]

I fell asleep before the final outcome because frankly, they drag shit out too far. Being a Platinum Member has really sapped the energy from me!

[mm2002]

I didn't get to see the show, but I take it it flew! I'll have to see the vid, and see exactly what they did. Did they just pull the treadmill?

[Bengal]

I didn't get to see the show, but I take it it flew! I'll have to see the vid, and see exactly what they did. Did they just pull the treadmill?

Yep, pulled a 2000 tarp behind a pickup truck. The plane was on the tarp...

[mattsmusiccenter]

The plane only needed to go 25mph to take off.

[mm2002]

Ahhhh I see. In the original video they said nothing about moving the conveyor belt. The way they explained it, it appeared that the belt would be stationary, and running opposite the direction of the plane. So, (and excuse the details I obviously didn't catch)
exactly what did their experiment prove? That pulling a plane behind a tow vehicle can achieve lift? I guess I won't get it until I see the vid.

[zeegler]

Ahhhh I see. In the original video they said nothing about moving the conveyor belt. The way they explained it, it appeared that the belt would be stationary, and running opposite the direction of the plane. So, (and excuse the details I obviously didn't catch)
exactly what did their experiment prove? That pulling a plane behind a tow vehicle can achieve lift? I guess I won't get it until I see the vid.

No, they didn't pull the plane. I didn't see it, but I assume they pulled the tarp the opposite direction of the plane to achieve the same effect as a treadmill. The plane moved forward under it's own power.

[z1n]

No, they didn't pull the plane. I didn't see it, but I assume they pulled the tarp the opposite direction of the plane to achieve the same effect as a treadmill. The plane moved forward under it's own power.

Yes this is what happened.

[fuel0707]

So, (and excuse the details I obviously didn't catch)
exactly what did their experiment prove? That pulling a plane behind a tow vehicle can achieve lift? I guess I won't get it until I see the vid.

What they effectively demonstrated is that once the forward force (or thrust) of the airplane's engine is greater than the sum of the frictional force produced by the aircraft on the tarp/treadmill and a little bit of aerodynamic drag, the aircraft will accelerate to a sufficient speed to produce lift and fly away.

They didn't tow the plane behind a truck to get the plane's wings to produce lift. However, that is one way to launch gliders.