Conveyer Belt Takeoff- Mythbusters jumps in!!!

[dmaher 0]

Put my money on Yes it will!

[delta november 0]

Larry;Retry your experiment with a piece of plastic or similar mounted justabove the belt to block the "Wind" that might be generated by the movement of the belt.Also I've seen recent Utube vids of guys launching and recovering MODELaircraft from vertical status.....something that to my knowledge hasnot been done with real aircraft.Probably something to do with not being able to duplicate the horsepowerto weight ratio. Also prop size would figure in.In other words if everything is to SCALE....IT WON'T FLY..

[Guest PARADISE]

What happens after your airplane "takes off" and you move it left or right from your treadmill and the airplane is now over stationary ground. A "successfull" flight is one where you can takeoff and sustain an altitude for some kind of distance.I can make any reasonably sized object "fly" by simply throwing it in the air, yet I can't say it's sustained flight.

[Guest airbus2]

The converyor belt pulls back on the wheels only, which spin freely.Plane takes off.Does anyone know when the episode of Mythbusters will be aired in the UK, or will it be the same as in the US?Dave

[michal 44]

>The whole question as laid out is>a paradox and thats what makes it fun. It is a paradox or it is not - depending on interpretation. If you think it is 'fun' to debate ambiguous statements it is your choice but I think the problem is actually far more interesting when it is stated clearly in which case it becomes a real physics problem.How it can be stated unambiguously? For example: the belt moves in the opposite direction to the airplane with a speed (in relation to the fixed ground) equal to the takeoff speed of the airplane.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

[Guest 247]

It wont take off. It will only spin the wheels.

[Guest Shalomar]

I couldn't pin down the time any more than that the show will air in December. Here is a link to an article.http://www.mercurynews.com/food/ci_7320206?nclick_check=1Best Regards, Donald T. :-waveFLYing? It's cool. Trillions of birds and insects can't be wrong.

[Guest jboweruk]

It won't,here's why I think not:The forward speed of the aircraft is equal to the opposite speed of the belt, therefore the aircraft is not carrying any actual forward speed. No forward speed in real terms means no airflow around the wings, erego no lift, so no take off.I assume we are talking about the belt running against the aircraft anyway?I tried a small experiment in FS, whereby I set the wind speed equal to the takeoff speed of a light aircraft, the result was that with no ground speed, the plane still got lift, so take off was achieved. You don't need ground speed and I think this is the common misconception with flight, you need airspeed alone to lift, so it doesn't matter what ground speed you show, if you have zero airspeed you won't lift. simple as that.

[RobertVA 0]

:-rollThe thing people keep forgetting concerning this issue is that aircraft don't in ANY fashion propel themselves by pushing backwards against the ground, runway or giant treadmill they are supported on prior to takeoff. Note that they don't immediately lose speed, and thus lift, immediately after takeoff. This is because the forward propulsion is produced by exerting force rearward on some combination of air (propeller driven aircraft), engine exhaust (turbojet and the occasional rocket propelled aircraft) or a combination of air and exhaust (the fan jets used by many modern "jet" airliners). Every action (forcing air and/or exhaust rearward) absolutely MUST result in an equal and opposite reaction (forward force against engine and the attached aircraft). The modest amount of bearing friction in the wheel hubs would accomplish little to counter the forces generated by the engine(s).:-jumpyAs long as the wheel brakes are released the treadmill would have negligible effect on the ability of the aircraft to move forward compared to the air and the rest of the world. The ONLY thing the treadmill could accomplish would be making the wheels spin at double the usual RPM.

[bob.bernstein 0]

lol...if the engine is at takeoff setting, and the wheels spin as you say....what stops the forward velocity (and therefore takeoff lift)? Certainly not an interface between the conveyor and the wheels...you've already agreed they spin.So if not that, then what pray tell degrades this planes motion? The answer, of course, is nothing...there is nothing that changes the planes forward motion.Therefore, it takes off.And since its engine is on, the takeoff is no different from a normal takeoff. The only impact from the conveyor would be felt if the conveyor speed was so fast that the wheel bearings failed and the wheel was no longer able to spin freely.Bob

[bob.bernstein 0]

you are incorrect. The rearward speed of the conveyor is not an opposite vector to the forward speed of the aircraft. In fact, the aircraft, and the air around it is the complete forward velocity system. Notice, I left the conveyor out of the picture. It is not part of the system that creates forward velocity.The conveyor is just part of a system that spins the a/c wheels faster than they would ordinarily spin for a given forward velocity. Aircaft wheels are not part of an aircraft propulsion system. They just spin.Until the wheel bearings fail, there is no consequence to spinning the wheels twice as fast, and therefore the plane will never know that the conveyor is even there.

[bob.bernstein 0]

LOL, sorry Tom....couldn't resist...Nice meeting you last week, btw.Best,Bob Bernstein

[michal 44]

>is the common misconception with flight, you need airspeed>alone to lift, so it doesn't matter what ground speed you>show, if you have zero airspeed you won't lift. simple as>that.Yes, and you are surprisingly correct in those statements but wrong with what was above it. In this case the airspeed will be exactly the same as usual, the conveyer belt doesn't affect the airspeed because airplane doesn't need the ground/belt to 'push' from. An airplane is not a car.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

[Guest jboweruk]

Good point, but you still have the friction to overcome, if you spool the conveyer up to the point that it is always going at the aircraft IAS, then friction will keep the plane from obtaining any forward velocity, erego you will eventually blow the tires long before takeoff, as they can only take so much punishment.So if the plane does obtain forward speed, and if they continue to speed up the conveyer, the tires will give out first. If the brakes are held on the plane then it will go backwards with the conveyer, till it falls off and incurs a hefty repair bill.So I still don't think it can take off. Friction is a heluva force to reckon with y'know.

[michal 44]

>Friction is a heluva>force to reckon with y'know.Nope, you are wrong again. Friction is not an issue in this experiment. Friction is overcome by only a small percentage of the full takeoff power and we can assume that friction is constant with speed unless we move into some exotic speeds (basic physics says so). In fact faster spinning wheels will slightly increase friction for the aircraft but again it will still be negligible amount compared to takeoff power. The only thing that may fail in such real-life experiment are tires and wheel bearings. They will be spinning much, much faster and they must withstand the extra heat. So tires/wheel bearing is the only weak link but as long as they can take it - the plane will take off and will hardly tell the difference. By the way - the experiment doesn't have to match IAS with conveyor belt speed - you can set conveyor belt speed constant (say 60-100 mph) for the purpose of this illustration, no need to change belt's speed in time unless one really wants it.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg