Angarak Posted December 10, 2016 Share Posted December 10, 2016 Discuss... (no googling!) [emoji3] Quote Link to comment Share on other sites More sharing options...
kitch79 Posted December 10, 2016 Share Posted December 10, 2016 No. the plane wouldn't move therefore no lift from the air around the wings. Quote Link to comment Share on other sites More sharing options...
Frank Bullitt Posted December 10, 2016 Share Posted December 10, 2016 Yes. Quote Link to comment Share on other sites More sharing options...
Style Posted December 10, 2016 Share Posted December 10, 2016 This did the rounds on Facebook a while back and generated a lot of discussion Plane won't take off Quote Link to comment Share on other sites More sharing options...
ibby Posted December 10, 2016 Share Posted December 10, 2016 Use that red button knightrider has. Quote Link to comment Share on other sites More sharing options...
Alex_GT Posted December 10, 2016 Share Posted December 10, 2016 This did the rounds on Facebook a while back and generated a lot of discussion What? I'm finding it hard to type response that isn't filled with certain four letter words. Quote Link to comment Share on other sites More sharing options...
scott.wild Posted December 10, 2016 Share Posted December 10, 2016 Yes it will take off, a plane doesnt use its wheels to move, its using the thrust of the engine.... Quote Link to comment Share on other sites More sharing options...
Annabella Posted December 10, 2016 Share Posted December 10, 2016 It does use its wheels to taxi before takeoff, with the thrust pushing through the air, which pushes the plane forwards, making the wheels rotate, i'm saying conveyor belt negates the wheels rotating, so there is no air flow, so cannot take off if its technically 'stationary'. Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted December 10, 2016 Share Posted December 10, 2016 If the conveyor belt is long enough, 2,500-3,000m, to allow the 747 to achieve the required take-off "air" speed then yes. If it's only the length shown in the picture then no, you crash and burn. Edit: I missed the part about the conveyor being as long as a runway, which is still a bit vague of a description, but should suffice for the question at hand. Yes, the plane will take off. No problem. Provided the wheel bearings are capable of running at greatly increased RPMs. Quote Link to comment Share on other sites More sharing options...
chainy Posted December 10, 2016 Share Posted December 10, 2016 The size of the conveyor belt doesn't matter the size is just added to add more confusion. the treadmill matches the speed of the wheels so the plane will stay on the same spot. The plane wont take off as there wont be any air flow over the wings to generate lift. Wont matter how much thrust the engine is pushing. The plane could be at full thrust on this tread mill and you could walk past it if you are not on the treadmill Quote Link to comment Share on other sites More sharing options...
Alex_GT Posted December 10, 2016 Share Posted December 10, 2016 Why is this even being discussed? Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted December 10, 2016 Share Posted December 10, 2016 Why is this even being discussed? Because it's fun to mock the poor people who can't get their heads around the basics! Quote Link to comment Share on other sites More sharing options...
jim Posted December 10, 2016 Share Posted December 10, 2016 This was a very very long running argument on here many years ago Quote Link to comment Share on other sites More sharing options...
samdale Posted December 10, 2016 Share Posted December 10, 2016 More info required before the question can be answered. If the conveyor belt moves at the normal take off speed of the plane then yes. The engines will overcome the friction of the wheels rotating and start to move forward. I.e. assume normal take off speed is 200mph. Conveyor moves backwards at 200, wheels spin at 200 (engine thrust matching wheel friction, plane is stationary). Engines rev up, overcoming friction of wheels and eventually plane moves forward. Assuming enough thrust then eventually plane reaches 200mph (wheels spinning at 400mph) and the plane takes off. If however the question is "as the plane revs up the conveyor does too. To a point where the plane is at full chat and stationary due to the friction in the wheels holding it back". In this case, no, it won't take off. For the "it'll stay put" crowd, imagine this. You a walking on a treadmill with wings on your arms. Increase treadmill speed until you are at full sprint. Nothing happens. Do the same, get sprinting then imagine you have a paramotor on your back. Would it blow you forwards? Of course. It's the fact that the thrust it not being applied to the belt that makes the difference. I bet the friction created would very easily be overcome by the jet engines and thus have very little effect. Unless like I say, you have a VERY fast conveyor to increase friction dramatically Quote Link to comment Share on other sites More sharing options...
mc92 Posted December 10, 2016 Share Posted December 10, 2016 The plane can't take off because health and safety regulations mandate the use of stationary runways. Quote Link to comment Share on other sites More sharing options...
Tyson Posted December 10, 2016 Share Posted December 10, 2016 The size of the conveyor belt doesn't matter the size is just added to add more confusion. the treadmill matches the speed of the wheels so the plane will stay on the same spot. The plane wont take off as there wont be any air flow over the wings to generate lift. Wont matter how much thrust the engine is pushing. The plane could be at full thrust on this tread mill and you could walk past it if you are not on the treadmill Correct the plane will not take off as it's air passing over the wings generating lift that makes the aeroplane take off. For those that think it will imagine the planes engines cut out in flight does the plane immediately drop out of the air ? No it doesn't as the air passing over the wings still generates lift allowing the plane to glide whilst losing altitude. The plane will be stationary on the belt, it's not moving so it can't take off. Quote Link to comment Share on other sites More sharing options...
samdale Posted December 10, 2016 Share Posted December 10, 2016 . The plane will be stationary on the belt, it's not moving so it can't take off. See my previous post. If it's not moving forwards, I agree, no lift. But why wouldn't it move forwards? Quote Link to comment Share on other sites More sharing options...
Al Massey Posted December 10, 2016 Share Posted December 10, 2016 Mythbusters did this episode. The plane took off. The wheels are free rolling, so technically the runway already acts as a conveyor belt as the ground and the wheels move at the same speed. Quote Link to comment Share on other sites More sharing options...
chainy Posted December 10, 2016 Share Posted December 10, 2016 See my previous post. If it's not moving forwards, I agree, no lift. But why wouldn't it move forwards? Because the way the question is worded "the conveyor belt is designed to exactly match the speed of the wheels" This means no forward momentum caused by the thrust. Because the conveyor belt will match the speed increase in the wheels. If the quote wasnt added then your point would be valid... Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted December 10, 2016 Share Posted December 10, 2016 Ah Jaysus lads. The wheels rolling along a conveyor or a runway has nothing to do with the plane getting into the air. The lift is generated by the movement of air over the wings. The movement of air is provided by the engines thrusting the plane forward. Technically the conveyer could be running in the same direction that the plane needs to travel to generate lift, faster than the planes wings are passing through the air, meaning the wheels could actually be rolling in reverse and the plane would still take off as the movement of the air over the wings has no relationship to the conveyor speed or the direction in which the wheels are turning. Regardless of which direction or how fast the conveyor is moving the air above it is static and it is the engine's affect on the air that produces forward movement of the plane, which generates the lift. Quote Link to comment Share on other sites More sharing options...
Digsy Posted December 10, 2016 Share Posted December 10, 2016 More info required before the question can be answered. If the conveyor belt moves at the normal take off speed of the plane then yes. The engines will overcome the friction of the wheels rotating and start to move forward. I.e. assume normal take off speed is 200mph. Conveyor moves backwards at 200, wheels spin at 200 (engine thrust matching wheel friction, plane is stationary). Engines rev up, overcoming friction of wheels and eventually plane moves forward. Assuming enough thrust then eventually plane reaches 200mph (wheels spinning at 400mph) and the plane takes off. If however the question is "as the plane revs up the conveyor does too. To a point where the plane is at full chat and stationary due to the friction in the wheels holding it back". In this case, no, it won't take off. Best answer yet Quote Link to comment Share on other sites More sharing options...
Scooter Posted December 10, 2016 Share Posted December 10, 2016 Another way to think of it is, if the plane were on the stationery conveyor belt and they started it up, it would take very little thrust to counter the wheel friction and get back to a stationery state on the now moving conveyor. Even with the conveyor increased to 200mph still not much thrust would be needed to maintain a stationery position relative to the ground/an observer. So then when full take off thrust is applied the plane will move forwards as normal and obtain the lift it needs to take off. Quote Link to comment Share on other sites More sharing options...
Paul Posted December 10, 2016 Share Posted December 10, 2016 full of immigrants, no hope of it taking off Quote Link to comment Share on other sites More sharing options...
chainy Posted December 10, 2016 Share Posted December 10, 2016 Another way to think of it is, if the plane were on the stationery conveyor belt and they started it up, it would take very little thrust to counter the wheel friction and get back to a stationery state on the now moving conveyor. Even with the conveyor increased to 200mph still not much thrust would be needed to maintain a stationery position relative to the ground/an observer. So then when full take off thrust is applied the plane will move forwards as normal and obtain the lift it needs to take off. Once the thrust that you mention counters the wheel friction then the wheels are going faster than the conveyor. The Question says this imaginary conveyor belt will always match the speed of the wheels so the plane will always be in the 1 spot on this conveyor so no lift for the wings... Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted December 10, 2016 Share Posted December 10, 2016 Can it take off, yes. Will it take off, no. Quote Link to comment Share on other sites More sharing options...
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