Will the plane take off v.2?

[IronWing]

Originally posted by: preslove
Why wouldn't the plane just turn around and go with the current? I assume that this would be SOP.

The rapids! The rapids! Oh, God! The plane is being dragged toward the rapids!

 

[miniMUNCH]

At some point the pontoons will start to hydroplane and be mostly out of the water and the water current won't really matter as the drag will be significantly reduced by the 'hydroplaning' action.

This all for some reasonable current (say even a 20mph current)... for some crazy current of 100 or 200 mph I would suppose that, most likely, all bets are off.

 

[IEC]

Originally posted by: preslove
Why wouldn't the plane just turn around and go with the current? I assume that this would be SOP.

Winnar!

 

[Chaotic42]

Originally posted by: smack Down
Don't know what kind of a plane you fly on but everyone i have the wheels are directly connected to the plane.

Great, you're back.

 

[jagec]

Originally posted by: KillerCharlie

You're wrong.

In the water case, you're dragging the pontoons against the water. The faster the current, the more skin friction against the pontoons, requiring more force to take off.

In the treadmill case, the friction force on the airplane from the wheels is NOT dependent on the speed of the wheels.

In this case, though, the question is "how fast is the current" because whether or not it will take off depends on this. In the treadmill case, the speed is not relevant.

<--- Professional aerodynamicist for major airplane manufacturer

Then you, of all people, should know that float planes go "on step" when the water speed under the pontoons passes a certain point...leading to a dramatic decrease in friction as the plane goes faster and faster. The difference is that the relative water speed to air speed is lower if there's a countercurrent, meaning that the plane has to have a higher final water speed to achieve takeoff air speed. But it's well on-step at this point, and so frictional forces aren't all that high.

 

[Suspicious-Teach8788]

The plane does not take off. This is your relative motion question because the plane is stuck to the water. Skis are not free "spinning"

 

[jagec]

Originally posted by: DLeRium
The plane does not take off. This is your relative motion question because the plane is stuck to the water. Skis are not free "spinning"

Yes, which also explains why speedboats are unable to move.

 

[StageLeft]

Wheels and pontoons are diff. I would say no if we're doing something like plane's takeoff speed is 30 mph and current is 30 mph and the prop only otherwise has enough speed for 45 mph flight, for a net wash against the wings of 15.

 

[skyking]

Kidding aside, the only time I landed on a river, I landed into the current and took off with it. I suppose the current had some part in making that decision, but the big ass bridge probably had a factor in it as well.
Snohomish River at the highway 522 bridge, between Woodinville and Monroe.

 

[sao123]

Originally posted by: Number1

Originally posted by: Chaotic42

Originally posted by: KillerCharlie

Originally posted by: ScottMac
OP: DIAF for bringing this up again.

The mechanics and physics haven't changed, water or treadmill. Same / Same.

The plane take off.

You're wrong.

In the water case, you're dragging the pontoons against the water. The faster the current, the more skin friction against the pontoons, requiring more force to take off.

In the treadmill case, the friction force on the airplane from the wheels is NOT dependent on the speed of the wheels.

In this case, though, the question is "how fast is the current" because whether or not it will take off depends on this. In the treadmill case, the speed is not relevant.

<--- Professional aerodynamicist for major airplane manufacturer

No, he's right. The pontoons are directly connected to the airplane, and any force that affects them will affect the entire aircraft.

<--- Cartographer

On second tought, he might be right. A current strong enough might generate enough friction to stop the plane.

<---Radio Technician

The plane on wheels will take off. The plane on water may not.

<---Stayed at a fvcking holiday inn express last night.

 

[Chaotic42]

Originally posted by: jagec
Then you, of all people, should know that float planes go "on step" when the water speed under the pontoons passes a certain point...leading to a dramatic decrease in friction as the plane goes faster and faster. The difference is that the relative water speed to air speed is lower if there's a countercurrent, meaning that the plane has to have a higher final water speed to achieve takeoff air speed. But it's well on-step at this point, and so frictional forces aren't all that high.

Have you seen the original plane thread? The question is an idealized question. Yes, we all know that planes can really take off in currents.

 

[jagec]

Originally posted by: Chaotic42

Originally posted by: jagec
Then you, of all people, should know that float planes go "on step" when the water speed under the pontoons passes a certain point...leading to a dramatic decrease in friction as the plane goes faster and faster. The difference is that the relative water speed to air speed is lower if there's a countercurrent, meaning that the plane has to have a higher final water speed to achieve takeoff air speed. But it's well on-step at this point, and so frictional forces aren't all that high.

Have you seen the original plane thread? The question is an idealized question. Yes, we all know that planes can really take off in currents.

Yes, I saw the original. And participated in it, foolishly enough. But the only way that the original plane could be prevented from takeoff was through some VERY questionable assumptions and interpretations of the OP. With most ideal or realistic physics, it would take off.