You've made it too complicated. All the plane needs to do is float along with the river. If the plane is pointing DOWN river and the river is flowing at 80 kts, then all the plane has to do is lift off, as the airflow over the wings is 80 kts. It would be the same as if the plane were sitting on a trailer being pulled at 80 kts, all the pilot would have to do is lift off, as the airflow over the wings is 80 kts The plane doesn't know if it's on a river or a trailer. Watch this and pretend the plane is floating down the river instead of sitting on the trailer. https://www.youtube.com/watch?v=-JDogTLtels
Hell, you can obviously fool 50% of the guys all the time. FACT : To get airbourne you need airspeed Airspeed at the start of the experiment is ZERO Airspeed will remain at ZERO. Groundspeed will increase.........so what Lift is a result of airflow over the wing. Not how fast the dam wheels are going. Not a difficult question, just needs some common sense. Do the 50% of you who think it will fly, think you will also take off if you run fast enough on a tread mill.
Airplane on a Treadmill Definitive Analysis This guy started this blog just because of this question. Guess what...some are right and some are wrong. I can't believe some are so vehement about defying the laws of physics. this is fun
The people who say "the plane flies" are depending on the engine's thrust to move the plane. They are making the grand assumption that thrust IMPLIES airspeed (at least, eventually it results in airspeed). Yet, we know of situations where a plane with thrust stops flying due to insufficient airspeed - this is the power-on stall. The key to the people saying that "the plane does not fly" is the conveyor belt's ability to keep the plane from moving forward in spite of its thrust. Only the rolling resistance of the plane's wheels (on the conveyor belt) will keep the plane from moving forward as the engine's thrust increases. This rolling resistance must act in a similar fashion as gravity does against the weight of the airplane in a power-on stall situation. That is, in spite of the thrust, the plane has no relative wind to create lift on the wings. Granted, it would take an incredible conveyor belt to keep the plane stationary. However, such a conveyor belt is assumed to exist, and be effective, in the very premise of the question. .
it is obvious the plane is moving forward in relation to the cones! there is air flow over the wings! I love it how people that are most adamant about others being stupid are the ones being most stupid themselves.
People can experience this for themselves using a gym treadmill. Go for a quick jog outside. Take special notice of the slight wind it creates against your face as you run. Now, go to the gym and do the same thing on a treadmill. Take special notice that there is NO WIND sensation on your face, even though you are running the same speed you were running previously outside. That is the same effect that the conveyor belt would have on the airplane. Without that relative wind, there is no lift on the wings. .
This guy simply runs with his bias and discounts those of everyone else, saying "that's not what the problem is about." Well, I suppose it's his blog so he can make the rules on his blog for his question. But he's not any more right than anyone else in the universe of potential answers. I wised up nine years ago and realized that the conclusion isn't whether the plane flys or not, it's analyzing how the person trying to solve the problem goes about solving it. It's a very interesting study for those interested in such things. My observation is that people tend to go to their comfort zones. So the pilots all believe that the plane cannot fly because they have all been there. The engineers all jump to analyzing drag coefficients and the temperature of wheel bearings. Mr. Blogger is essentially correct that the only way to answer the question is to infer limitations that are not presented in the original question as posted here on F-Chat: Imagine a plane is sat on the beginning of a massive conveyor belt/travelator type arrangement, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. There is no wind. Can the plane take off? So immediately everyone imagines what the plane and what the conveyor belt look like. One must imagine, because no blueprints or specifications are presented. Most seem to imagine the conveyor belt to be not much larger than the footprint of the plane. Not sure why, since it's described as being massive "as wide and as long as a runway." Many just say that it's impossible to build such a contraption. No kidding? It could be built, but at great expense. So why build one? But the big issue is what type of plane is it? Note that there isn't anything said about the plane at all, other than it's a plane. This is where all of the trouble starts. Everyone has his own idea of what type of plane it is and demands that everyone else abide by his definition. Most seem to picture in their minds a small, single engine, propeller driven monoplane. But it could be anything with multiple wings wider than the conveyor belt, made of composite materials with extremely powerful engines. My plane was powered by a Saturn V Rocket engine because I was originally in the thrust camp that Mr. Blogger (and many others here) simply dismisses (because it doesn't fit their interpretation of the problem's parameters). They don't allow Harriers or similar VTOL designs, "because the problem is about air foils." Who says the problem is about air foils? That's not what the question asks. It simply asks if the plane (any plane) can take off. In support of my position, I pointed out that in real life an F-15 can accelerate vertically, as its thrust exceeds its weight. I also picture a derivative of a rubber band powered balsa wood plane. Again, there is no rule stated that the plane has to be capable of carrying passengers or even a pilot. But those who do not want the plane to fly, dismiss each and every airplane design that could conceivably take off without a running start saying that it's not conventional and no such plane exists. Well, neither does the conveyor belt, but they seem to accept that parameter on its face. We go round and round because there aren't enough rules established in the original problem to reach a definitive conclusion. The correct poll response is, "Question doesn't allow answer." We aren't arguing the physics, we are arguing the rules to be applied because they haven't been established...except in the minds of those who adamantly adhere to their personal set of rules. If you look at the results of the poll, we are not grouped by fly vs. no fly. We are grouped by inside the box vs. outside the box thinkers, or if you prefer those who want strict rules of conduct and will make them where absent and those who don't much care for artificial rules. It's a study of how we are individually wired and how we each approach the solution to a problem, physics aside. Fascinating.
Ah come on Rob! the wheels have NOTHING to do with the aircraft. If the treadmill was the leanth of a normal runway for a jet (10,000') the aircraft would just accelerate down the treadmill and take off. Think if the aircraft was hovering over the treadmill it would do the same thing it accelerates down the treadmill (past the cones as you saw) giving the wing lift. If you run on a treadmill you are using your feet for speed on the treadmill and airplane doesn't give a **** about the wheels, they can be going backward, forward, the airplane doesn't care.
Very true in the real world. Wax just reposted the original post....and herein lies the problem with the question: "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." Can anyone here say they know precisely what the statement means, and that it is entirely unambiguous? I posit you can't...
If you read the thread you would see that was one of my main points, but your water and mythbusters example along with challenging me indicates you don't understand it takes air movement to fly. 99.99% of us on the thread AT LEAST understand that simple principle, so why don't you join the club.
Yes Rob I like you know how to fly and what the wings need to fly. The "wheel thing" makes you miss the point. Now we have had a few real physicist and pilots including my 19,000 hours flying all over the world say it flys. It is going to accelerate down the treadmill gain airspeed and FLY. the wheels and belt don't matter. BTW 50% of us understand this. To make it simple, the plane will accelerate (ie move) down the treadmill thus gaining airspeed. Now, after the really smart guys on this site (physicists) and others have tried to explain this I hereby give up!
Why is it some people can't see that the two statements above are in direct conflict with one another? By the very premise of the question, it would be IMPOSSIBLE for the plane to move down the treadmill. .
so why don't you take your pompous condescending ******* attitude and look up in this thread what I say about it before challenging me. the ONLY reason you would have challenged me is because you were one of the 0.01% of the idiots that doesn't know what it takes to fly.
+1 When people wonder how it is that we seem to elect such dolts to public office I direct them to this thread and have them read it for a while.
It is not impossible! The wheels have to move same speed as the treadmill, but the plane doesn't have to move at the same speed as wheels! How does a float or ski plane move forward with 0 wheel movement? The answer is skid.
Rob I have no idea how you could think that I was condescending to you, I certainly did not mean it if that's what you interpreted. Now you somehow you think I'm that 0.01% of the idiots that doesn't know what it take to fly.
