Conveyor belt controversy put to rest :-)

[Manny 1,293]

>I have trouble believing that the test holds sway over the>debate. Why was the aircraft in the test moving forward (the>camera had to pan) if the conveyor belt was "matching" the>plane's speed? If it was matching the plane's speed, then the>plane should not have moved, no matter how much it>accelerated. Zero movement would have meant zero airflow over>the wings, resulting in no takeoff. I agree!Either the conveyor belt was moving at less than the aircrafts speed and the net effect reached greater than stall speed and hence it lifted off.orThis is not a conveyor belt at all. Since the aircraft wheel was touching the ground. If it was a conveyor belt, there should have been a gap between the conveyor and the ground underneath. Because the aircraft wheel was moving forward due to the friction between the wheel and the ground. The cloth simply slid underneath. Manny

[Comanche 417]

Using this logic, if the plane landed on the conveyor rather than took off, the plane would come to a complete stop on the ground once the wheels would hit the conveyor. I think not.The wheels being on a conveyor have nothing to do with forward motion for a powered plane since the plane is not powered by the wheels but rather the propellers effect of pulling it through the air. The conveyor only makes the wheels spin faster.Rob

[slashed2 53]

I was back and forth on this one, probably overanalyzing it to death in my head but similar to the rubber band test, the simplest experiment solves this. They put a model car on a belt and had it at the same speed forward as the belt was going backwards, net speed was zero.Put the wheels in neutral the car moved backwards, but apply an external force unrelated to the treadmill such as a hand and they were able to push the car forward with very little resistance. Slap a plane on there and apply propeller force which has nothing to do with the treadmill but forces acting on external forces like air and the plane moves forward as long as the thrust from said propeller can overcome whatever resistance is created by the wheels, skis, undercarriage etc. influenced by the friction of the treadmill moving in the opposite direction.On wheels, the aircraft easily overcomes the resistance and takes off without a problem. Ski's present more resistance but with a powerful enough engine the aircraft will still manage to move forward and most likely take off.

[Guest Jimbofly]

There is no point in over-analyzing.If you have a conveyor belt moving at 100kts, and a cessna facing the opposite direction powered up as it was placed on the conveyor belt, the friction of the wheels would be negligible and the cessna would accelerate as normal in the opposite direction and take off at around 55kts. The speed of the wheels on takeoff would be 155kts but that would be inconsequential to the end result.It really is that simple :)James

[Manny 1,293]

>Using this logic, if the plane landed on the conveyor rather>than took off, the plane would come to a complete stop on the>ground once the wheels would hit the conveyor. I think not.>The wheels being on a conveyor have nothing to do with forward>motion for a powered plane since the plane is not powered by>the wheels but rather the propellers effect of pulling it>through the air. The conveyor only makes the wheels spin>faster.>>RobYes..the propeller effect moves the plane forward and the conveyor belt (if its a true conveyor belt) moves it backward. Net effect = 0

[Manny 1,293]

>There is no point in over-analyzing.>>If you have a conveyor belt moving at 100kts, and a cessna>facing the opposite direction powered up as it was placed on>the conveyor belt, the friction of the wheels would be>negligible and the cessna would accelerate as normal in the>opposite direction and take off at around 55kts. The speed of>the wheels on takeoff would be 155kts but that would be>inconsequential to the end result.>>It really is that simple :)>>Jamesthats why you need to pay attention. The assumption was..They are at the same speed. Not asymmetric.

[Guest ronht]

>There is no point in over-analyzing.>>If you have a conveyor belt moving at 100kts, and a cessna>facing the opposite direction powered up as it was placed on>the conveyor belt, the friction of the wheels would be>negligible and the cessna would accelerate as normal in the>opposite direction and take off at around 55kts. The speed of>the wheels on takeoff would be 155kts but that would be>inconsequential to the end result.>>It really is that simple :)>>JamesHere's something even simpler - The Cessna will take off at 55kts regardless. The ONLY thing the conveyor belt is doing is making the wheels spin faster. As I watched that video I felt sorry for the pilot that doesn't understand what creates lift and makes his airplane fly. Airflow over the wings is the only thing that will produce lift. Now, if you want something to think about consider this. If you are taking off with a 55kt direct tailwind at which speed with the Cessna fly?55kt ground speed? or 55kt indicated speed?Have fun.ron

[JSkorna 137]

What I want to know is how many times you all are going to beat this poor horse to death? The Outer Marker thread went on forever and is now locked and now here we are again in the FSX Forum, beating that same horse.Jimhttp://www.hifisim.com/banners/hifi-community-sigbanner.jpghttp://www.hifisim.com/

[Manny 1,293]

>>There is no point in over-analyzing.>>>>If you have a conveyor belt moving at 100kts, and a cessna>>facing the opposite direction powered up as it was placed on>>the conveyor belt, the friction of the wheels would be>>negligible and the cessna would accelerate as normal in the>>opposite direction and take off at around 55kts. The speed>of>>the wheels on takeoff would be 155kts but that would be>>inconsequential to the end result.>>>>It really is that simple :)>>>>James>>>Here's something even simpler - >>The Cessna will take off at 55kts regardless. The ONLY thing>the conveyor belt is doing is making the wheels spin faster. >>As I watched that video I felt sorry for the pilot that>doesn't understand what creates lift and makes his airplane>fly. Airflow over the wings is the only thing that will>produce lift. >>Now, if you want something to think about consider this. If>you are taking off with a 55kt direct tailwind at which speed>with the Cessna fly?>>55kt ground speed? >or >55kt indicated speed?>>Have fun.>>ron>>>55k IAS. If you thought anything else.. I wouldn't want to fly with youThe tail wind comes into play the moment the wheel leaves the ground!:)

[Mike T 208]

Indicated. The Cessna doesn't care what speed its moving over the ground as long as the IAS shows the proper speed for flight. But in this case the answer is neither as you'd hit the pole at the end of the runway long before you took off :-lolRegards,Mike T.

[Geofa 108]

This has been in the hangar chat for quite a while-moving it there-again!http://www.mediafire.com/imgbnc.php/1b5baf...b9f427f694g.jpgMy blog:http://geofageofa.spaces.live.com/

[slashed2 53]

It's because we all stayed at a Holiday Inn last night. :)

[Avcomware 1]

Hello everyone.It is really surprising that some real

[n4gix 4,947]

>>What I don't understand is that this isn't a terribly>>difficult physics problem! :-lol >>I do have to grin a bit, when I see so many references to a>rather "simple" physics problem, as though much of the public>are physics wizards.. :D Larry, this is simple eighth grade physics... ;)It may be essentially reduced to a case of four forces acting on a single object: the aircraft.Force#1 is that which is imparted by the treadmill and transmitted to the aircraft via the wheels. Since the friction coefficient is negligible, the net force transmitted is effectively ZERO.Force#2 is the force from the propellor. Since that force is several magnitudes greater than the net opposite from Force#1, it may be treated as though Force#1 does not exist.Force#3 is the force of gravity, which is a constant for our purposes.Force#4 is that which is transmitted to the aircraft via the 'lift' from the wings (and let's not get sidetracked on this topic!).Ergo, the presence or absence of Force#1 is reduced to irrelevancy. The aircraft will take off, assuming the pilot isn't too drunk to fly... ;)

[sluggy 3]

The way I look at it, the prop affects AIRSPEED, the conveyer belt affects GROUNDSPEED. The two are (almost) unrelated (I've been in a de Havilland Caribou flying into a headwind that was within 40kts of the plane's cruising speed, resulting in a groundspeed of around 40kts; should've gotten out and walked). The prop pulls the plane through the AIR which (for all intents and purposes in this exercise) isn't moving because it isn't affected by the conveyor belt. Once there is enough thrust to overcome the wheels' friction and aircraft's inertia (same as moving off to taxi) the wheels simply turn faster (higher groundspeed) but the plane's airspeed will be the same as in a normal taxi or takeoff. So the plane will take off in the same distance as normal whilst it's rolling on the conveyor belt. The wheel bearings may get hotter, but that's what maintenance is for. :)I've really tried not to get involved in this debate, but just for once I'd thought I'd treat myself.Cheers, SLuggy