Big Red 67 Posted March 8, 2007 Share Posted March 8, 2007 A plane is standing on a runway that is made of a large conveyor belt. The plane fires up its engines, but as it moves forward, the conveyor belt senses the speed of the plane's wheels and moves at exactly the same speed in the opposite direction. Can the plane take off? Big Red's Ride Blog Link to comment Share on other sites More sharing options...
Fumblyfingers Posted March 8, 2007 Share Posted March 8, 2007 Yes! Link to comment Share on other sites More sharing options...
Strategery Posted March 8, 2007 Share Posted March 8, 2007 Uhmmmm.....Uhmmm-Hmmmm. What were the question agin? :grin: http://sabatos.net/images/slingblade.jpg "Just play!" Link to comment Share on other sites More sharing options...
Guitar Geezer Posted March 8, 2007 Share Posted March 8, 2007 Isn't it the amount of air passing under the wings (lift) that actually gets it airborn? If the plane is physically stationary it doesn't seem like it would work. Unless that huge Mama Conveyor blet is whipping up some air movement .......... Lynn G Link to comment Share on other sites More sharing options...
Kramer Ferrington III. Posted March 8, 2007 Share Posted March 8, 2007 If it's a Hawker Harrier it can! Band MySpace My snazzy t-shirt empire Link to comment Share on other sites More sharing options...
Big Red 67 Posted March 8, 2007 Author Share Posted March 8, 2007 Think about what Kramer said. Big Red's Ride Blog Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 Pretty basic kinetics tells us that YES it will take off. http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
Big Red 67 Posted March 8, 2007 Author Share Posted March 8, 2007 Yes it can,... the thing I found interesting is why it can. Big Red's Ride Blog Link to comment Share on other sites More sharing options...
S. Yeti Bigfoot, Esq. Posted March 8, 2007 Share Posted March 8, 2007 Yes, the engine's thrust is not pushing against the conveyor belt, it is pushing against the air. The engines would still move the plane forward, creating an airflow over the wing, thus a vacuum above the airfoil (lift), and when sufficient forward speed is achieved and the elevators rotate the aircraft on the chord, there you go.... The wheels may be turning at double the normal speed, but the aircraft would still move forward. "And so I definitely, when I have a daughter, I have a lot of good advice for her." ~Paris Hilton BWAAAHAAAHAAHAAA!!! Link to comment Share on other sites More sharing options...
The Geoff Posted March 8, 2007 Share Posted March 8, 2007 No - it will never gain air speed if the conveyor belt moves it backward as fast as it tries to move forward - it will, effectively, stay in the same place. G. "When the power of love overcomes the love of power the World will know Peace": Jimi Hendrix http://www.soundclick.com/bands/default.cfm?bandID=738517&content=music The Geoff - blame Caevan!!! Link to comment Share on other sites More sharing options...
Big Red 67 Posted March 8, 2007 Author Share Posted March 8, 2007 Yeah BigFoot! It is funny how the mind works. I leapt to the no awnser to begin with. Then I realished that the wheels of a plane don't create forward motion. Big Red's Ride Blog Link to comment Share on other sites More sharing options...
S. Yeti Bigfoot, Esq. Posted March 8, 2007 Share Posted March 8, 2007 No - it will never gain air speed if the conveyor belt moves it backward as fast as it tries to move forward - it will, effectively, stay in the same place. G. It wouldn't gain airspeed until it gets airborne, anyway. It gains groundspeed on the ground (they aren't the same)..... The conveyor really has nothing much to do with whether the plane can gain forward momentum. "And so I definitely, when I have a daughter, I have a lot of good advice for her." ~Paris Hilton BWAAAHAAAHAAHAAA!!! Link to comment Share on other sites More sharing options...
Guitar Geezer Posted March 8, 2007 Share Posted March 8, 2007 I am SUCH a Sucker for these things Lynn G Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 I am SUCH a Sucker for these things Well see, if your not already a engineer, you should have been, we get to have that fun everyday!! Come over to the dark side! http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
Griffinator Posted March 8, 2007 Share Posted March 8, 2007 No - it will never gain air speed if the conveyor belt moves it backward as fast as it tries to move forward - it will, effectively, stay in the same place. G. Remember these are jet propulsion systems. The plane gains forward motion by moving air. No escalator could push it back fast enough to prevent it from accelerating, since it's accelerating by displacing air, not spinning its wheels... A bunch of loud, obnoxious music I USED to make with friends. Link to comment Share on other sites More sharing options...
mdrs Posted March 8, 2007 Share Posted March 8, 2007 Don't you hate trick questions?? :grin: And, as for you engineers, STOP GLOATING! Don "There once was a note, Pure and Easy. Playing so free, like a breath rippling by." http://www.soundclick.com/bands/pagemusic.cfm?bandID=574296 http://www.myspace.com/imdrs Link to comment Share on other sites More sharing options...
Big Red 67 Posted March 8, 2007 Author Share Posted March 8, 2007 Don't you hate trick questions?? :grin: And, as for you engineers, STOP GLOATING! I love that I can be wrong so I like them! It is even better when I can figure out that I am wrong by my self! Big Red's Ride Blog Link to comment Share on other sites More sharing options...
Hardtail Posted March 8, 2007 Share Posted March 8, 2007 I'm going to say no. Here's why. I was in aviation in the Marines. I'm kind of still in it now. When I was in Japan, the power plants guys used to run the F4 Phantoms in test cells. That basically means blocking the wheels so that they don't move the plane forward and gunning the engines. The plane NEVER moved. This is certainly a similar case of running a plane on a conveyor belt in the opposite direction. In both cases, you have a net speed of 0 on the ground. Also, if being able to create lift at a standstill was possible, catapult systems on Navy aircraft carriers would be vastly different than what they are now. Nope... I'm saying you gotta have sufficient net groundspeed to create the thrust against the air(creating a fast enough air current) then the lift under its wings. That's what I think and I'm sticking to it... well, not if I'm wrong. LOL! Link to comment Share on other sites More sharing options...
Griffinator Posted March 8, 2007 Share Posted March 8, 2007 I'm going to say no. Here's why. I was in aviation in the Marines. I'm kind of still in it now. When I was in Japan, the power plants guys used to run the F4 Phantoms in test cells. That basically means blocking the wheels so that they don't move the plane forward and gunning the engines. The plane NEVER moved. This is certainly a similar case of running a plane on a conveyor belt in the opposite direction. In both cases, you have a net speed of 0 on the ground. Nope. Completely different situation. Your setup actually prevented the plane from moving forward. In that case, the air displacement energy from the jet systems becomes really, really high winds in the back. The plane becomes a glorified fan. The conveyor belt just attempts to move the plane backward - but the air displacement involved overcomes this opposite force, since the plane is still free to generate forward motion. A bunch of loud, obnoxious music I USED to make with friends. Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 Yeah but HT, the rollers you where using where the same as the dynomometers we use for stationary vehicle powertrain runup and road simulation, the tires are sunk down IN between the rollers and the force of the tires against those creat a wall of resistance that is more than enough to counter any forward thrust you could create off the engines. The steam catapult systems on the carriers are only necessary because of the reduced length of rollout required to lift the aircraft off the carrier deck, not required under normal ground based operations. Am I wrong here? Yes you have or can simulate a overall net 0 condition but that is only revelant to wheel fricdtional conditions, thrust and lift are a different set of parameters, thrust is is not independent of lift when you have an airfoil. http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
Hardtail Posted March 8, 2007 Share Posted March 8, 2007 You're a pilot ellwood. I've never piloted a plane. I was just a wrench monkey on the ground. LOL! Can you actually create lift in a Cessna standing still? You gotta HIT that air. Standing still isn't going to do it. I just think that dismissing the groundspeed factor is wrong. If ground speed were insignificant for the lift of a "fixed wing" aircraft (not counting Harriers and Ospreys), there would be no need for runways. Ok... where's Warthog? LOL! Link to comment Share on other sites More sharing options...
mdrs Posted March 8, 2007 Share Posted March 8, 2007 In this situation, the wheels are totally insignificant. The jet thrust will create a negative pressure in front of the plane and a high pressure behind the plane. Therefore, since the plane is not fixed to the ground, the plane will move forward, towards the lower pressure. The wheels simply "lubricate" the planes movement, and will do so even if the ground is moving backwards (i.e. the "conveior belt" in this example). Once the plane if moving forward, according to Bernoulli's principle, the plane's wings will create lift, and off she goes. How'd I do, engineers??? :grin: Don "There once was a note, Pure and Easy. Playing so free, like a breath rippling by." http://www.soundclick.com/bands/pagemusic.cfm?bandID=574296 http://www.myspace.com/imdrs Link to comment Share on other sites More sharing options...
S. Yeti Bigfoot, Esq. Posted March 8, 2007 Share Posted March 8, 2007 HT, The point that you're missing is that they conveyor will NOT keep the plane from moving forward. You don't have the wheels chocked....you're just on a conveyor. The thrust from the engines is pushing against the AIR....that's what moves the plane forward. As long as the wheels aren't actually restrained, the plane can move forward. "And so I definitely, when I have a daughter, I have a lot of good advice for her." ~Paris Hilton BWAAAHAAAHAAHAAA!!! Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 No I cannot HT but only because I cannot creat enough thrust off of that fan attached to the nose of the Cessna LOL!! See once you are out of the ground effect, the difference in relative pressure between the air foil and the ground, any kind of ground speed becomes a non issue and the aircraft will lift, if you can create enough thrust you can defeat ground effect and mechanical friction from the landing gear, the aircraft will lift. http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
mdrs Posted March 8, 2007 Share Posted March 8, 2007 Yea, Yeti!! In this illustration, the only thing the conveior belt will do is make the wheels turn twice as fast. It will NOT stop the plane from advancing forward, thus creating lift. Don "There once was a note, Pure and Easy. Playing so free, like a breath rippling by." http://www.soundclick.com/bands/pagemusic.cfm?bandID=574296 http://www.myspace.com/imdrs Link to comment Share on other sites More sharing options...
mdrs Posted March 8, 2007 Share Posted March 8, 2007 Wow, such talented musicians, AND BRILLIANT AEROSPACE ENGINEERS!! Don "There once was a note, Pure and Easy. Playing so free, like a breath rippling by." http://www.soundclick.com/bands/pagemusic.cfm?bandID=574296 http://www.myspace.com/imdrs Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 But just as a side note, I can however hover! and have done so, when the forward speed of wind equals the forward thrust or air speed in opposite directions I can through manipulation of my controls and engine settings ...in fact hover momentarily, in a slightly nose up attitude, when pitch and yaw are equal. http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
Hardtail Posted March 8, 2007 Share Posted March 8, 2007 Wow, such talented musicians, AND BRILLIANT AEROSPACE ENGINEERS!! Well... I'm actually a software engineer. I just work on the radar. LOL! Also in the Marines... I only loaded the bombs and missiles. LOL! Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 LOL!! not aerospace engineers..those and the chemical and electrical guys left us poor mechanical guys in the dust! but allot of this stuff is basic mechanics and dynamics that are common to all engineering, http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
Dr. Ellwood Posted March 8, 2007 Share Posted March 8, 2007 Wow, such talented musicians, AND BRILLIANT AEROSPACE ENGINEERS!! Well... I'm actually a software engineer. I just work on the radar. LOL! Also in the Marines... I only loaded the bombs and missiles. LOL! Ok so... if you where prepairing this aircraft we could just bomb the hell out of that stinkin conveyor and there would be no issue at all LOL!!!!!!!!!!! http://www.thestringnetwork.com Link to comment Share on other sites More sharing options...
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