This old chestnut

[redlig]

Swop the obsolete 747 for a glider at London gliding club - I think they use winched launches? Sit it on the same conveyor belt and start winching . . . glider moves forward, wheel rotates, conveyor rotates, so wheel is actually rotating twice as fast as ground speed . . . glider takes off as wings move through the air at usual speed and generate lift.

Winch is providing forward motion - much as the jets do on a 747.

If you are convinced it relies on wheel speed . . how does a float plane, or ski equipped plane, even a flying boat get in the air?

Pilot has to paddle pretty furiously.

 

[MattF]

Someone wants a good slap for starting this thread.

 

[tigdlo]

Swop the obsolete 747 for a glider at London gliding club - I think they use winched launches? Sit it on the same conveyor belt and start winching . . . glider moves forward, wheel rotates, conveyor rotates, so wheel is actually rotating twice as fast as ground speed . . . glider takes off as wings move through the air at usual speed and generate lift.

So for the conveyor and wheels to rotate at the same speed, the plane has to be stationary, so it wont take off.

 

[Seadog]

Same if you run on a belt, need to run faster to move forward.

So it all comes down to if the belt speed is fixed or will adapt to compensate for thrust.

The rotating wheels do not drive the aircraft. Thrust does. It's independent of the wheels.

 

[redlig]

the atmosphere rotates with the earth, we don't have 1000mph winds.

Have you been to Scapa Flow. I often wondered where the came from ,always thought it was from the rotation of the earth, now I know. You will be telling me next that gravity is holding the plane down.

 

[eLuSiVeMiTe]

Someone wants a good slap for starting this thread.

Perfect forum thread Matt.
Umpteen pages of procrastination so business as usual.

 

[redlig]

Someone wants a good slap for starting this thread.

Difficult to tell who is winding who up. Good fun on a dank day.

 

[mtt.tr]

Surely to remain stationary the aircraft needs enough thrust to stay stationary but this might mean the conveyor belt is moving 10mph

The other way round the jet would be moving forward and take off

So it's depends what's driving what

 

[Domdom]

The conveyor bit is a distraction and irrelevant. The 747 produces thrust from the engines which are sufficient for it to take off, pretty much regardless of what's under the wheels. Unless the conveyor was endless the 747 would simply more forwards off the belt.

 

[redlig]

Makes you wonder why aircraft use AIR speed indicators and not wheel driver Speedometers. Just lucky I guess. I suppose the very early aviators using wheel driven speedo's wondered why they could still fly when the speedo registered zero when the wheels left the ground.

 

[bricol]

Can you imagine how over-budget and timescale the supply of that conveyor will be?

Especially given the global shortage of DC bus drivers and invertors at the moment . . .

 

[redlig]

Of more immediate importance is what happens to the light inside the fridge when you close the door?

 

[bricol]

Of more immediate importance is what happens to the light inside the fridge when you close the door?

Bug ger all because the replacement bulb glass bottomed out on the holder before the contacts did . . . so it didn't even work when the door was open . . .

I had to pull the switch out, then the entire thermostat housing and then bulb holder form that to discover that the other day . . .

 

[bricol]

Actually - going back to tyre failure, over-speeding bearings - have we read it wrong?

If the conveyor is rotating in the opposite direction, the wheels are stationary . . . if it rotates the same direction as the wheels, that's when the wheels go a bit quick.

Still takes off though

Now if you could accelerate the entire earth and the air at the same rate as the thrust from the engines accelerate the plane, then you've be asking "are there yet?" for a long time . . .

 

[The_Yellow_Ardvark]

Mythbuster did just this.

It will take off.

 

[Pete.]

The problem is that the only thing you gain from the question is that the conveyor is moving and the plane is on it. Without further info, or extrapolation of likely events, you can't tell if the plane has airspeed or not.

 

[MysterG]

Of course! A big conveyor belt. Thats how they did the final plane chase sequence in Fast and Furious 6

 

[Seadog]

The problem is that the only thing you gain from the question is that the conveyor is moving and the plane is on it. Without further info, or extrapolation of likely events, you can't tell if the plane has airspeed or not.

You know that the conveyor matches the wheel speed. Therefore the wheels must be turning. Therefore there must be thrust from the engines to advance the plane thereby causing rotation of said wheels.

 

[RWD3M]

Makes you wonder why aircraft use AIR speed indicators and not wheel driver Speedometers.

They do, the anti-skid depends on it

 

[fizzy]

Mythbuster covered this years ago

Awful quality sadly.

Yes it will takeoff normally