Plane on a treadmill ?

duplicate2 · Post by **duplicate2** » Wed Feb 08, 2006 2:03 am

FlyYukon

I'm answering your posts mostly because you are putting in a lot of effort to explain your theories and doing it in a very friendly manner which I appreciate.

The biggest problem with your formulas, examples and theories is that you are mixing velocity (speed) and force as if they are the same thing. You cannot add velocity to force to come up with a vector sum.

If you haven't already, I suggest you read this link (previously posted by TJ)
http://www.avweb.com/news/columns/191034-1.html

Out of all your examples, I'll choose your one with the model plane on wheels sitting on a treadmill. With the treadmill moving in a constant backwards direction and the model plane not attached to anything, you are right, the model will move backwards. This is only because of the small amount of friction in the wheel axles. If they were frictionless, the model would not move because there would be no force to accelerate it backwards.

If you now attach the model to a fixed point ahead of it with string, again you are right that the model will stay put relative to the ground. This is because the forces are balanced, i.e. the force of the string is balancing the very small force of friction in the wheel axles.

If you pull on the string now, the model will move forward because the force you are applying is much greater than the small wheel axle friction force. This is the situation that most closely represents a real aircraft on a giant treadmill. Obviously the thrust capabilities of the aircraft must be greater than the wheel axle friction, otherwise it would not be able to move the aircraft forward even on the regular (non-treadmill) pavement.

Hope this helps
duplicate2

FlyYukon · Post by **FlyYukon** » Wed Feb 08, 2006 7:24 am

Force and velocity. Your right! And as I said in my last post, I could very well be wrong. I've just been having fun typing all this up and prepping my mind for an overload of Multi-IFR information in the coming weeks

. I'll give that link a read, thanks! E=MC^2

l_reason · Post by **l_reason** » Thu Feb 09, 2006 6:43 pm

One more take on your magical aircraft vs. treadmill conundrum. Lets say you take the plane as mentioned before rotate it 180 degrees. Start up the treadmill while holding the aircraft in position with reverse thrust. The treadmill will be in effect working in reverse from back to front…. Wined the treadmill up to just above take off speed. the aircraft still holding its self with a groundspeed of 0000kts. Turn off reverse thrust and nail the brakes. If everything can hold together the aircraft should go along with the treadmill and take off. Not needing any of its own forward trust at all.

w squared · Post by **w squared** » Thu Feb 09, 2006 7:56 pm

What a great idea! Treadmill runways and thrust reversers when combined would alleviate the need for STOL aircraft!

Now back to my Turbo Mallard on skis with eight turbocharged rotax reindeer.

Who can I buy my turbo mallard/skis/reindeer PPC from?

CID · Post by **CID** » Thu Feb 09, 2006 8:49 pm

Is this thing still going? Why don't we just stop this thread and start a new one on perpetual motion machines?

hazatude · Post by **hazatude** » Thu Feb 09, 2006 9:16 pm

CID wrote:Is this thing still going? Why don't we just stop this thread and start a new one on perpetual motion machines?

@#$! off

CID · Post by **CID** » Fri Feb 10, 2006 10:59 am

@#$! off

I guess "BP" stands for "Big Prick".

Kilo-Kilo · Post by **Kilo-Kilo** » Fri Feb 10, 2006 11:33 am

Simply put, the long lab example is not using free rotating wheels if the A/C moves in the direction of the treadmill. Imagine the plane is a dinner plate or vase and the treadmill is a tablecloth. It doesn't take David Copperfield to tell you that when the tablecloth/treadmill accelerates the plane/plate remains motionless.

Now how about if the Rotax Reigndeer powered, ski-equipt, turbo Mallard is carrying 2500 lbs. of canaries overgross. If we put a cat on board that scares the canaries to fly while we approach take off, will we be under gross?

w squared · Post by **w squared** » Fri Feb 10, 2006 11:49 am

How is cat driver going to threaten the canaries into flight? Even a retarded canary would realize that Cat Driver wouldn't be able to eat more than 15 or 20 canaries at one sitting, so they're relatively safe.

Let's try it. What are you doing next Tuesday, Cat?

niss · Post by **niss** » Fri Feb 10, 2006 12:49 pm

I like the idea of the Turbo Mallard on skis with eight turbocharged rotax reindeer and I think I will get one, but first what is the TBO of the reindeer? Do I really need the Multi to fly a malard with 8 reindeer? Also is the compression of the reindeer up to snuff?

About the plane on tredmill thing. If the engine is positioned in front of the wings then it will take off, it will not work if the engine is pushing the wings.

Niss

w squared · Post by **w squared** » Fri Feb 10, 2006 7:53 pm

You absolutely need your multi to fly it. I mean we're talking about two turbines, and eight rotaxes...that's ten powerplants. Let's not even get into what your procedures would be like for shutting down a turbine and two reindeer at the same time.

As far as I know, the TBO on the reindeer is determined by their antlers. Since you have to take them into the AME (Animal Medical Examiner) to get the weight and balance corrections for each year's worth of antlers, it's seen as a commonly accepted practice to get an overhaul each year.

I still wanna know who's offering PPC's on this unit...

niss · Post by **niss** » Fri Feb 10, 2006 8:03 pm

Whats the glid ratio on that beast, what happens if we loose our reindeer? God forbid on takeoff? What if we loose 4 reindeer will wee still have enough power to deliver all the toys to the good girls and boys?

niss · Post by **niss** » Mon Feb 13, 2006 7:38 am

Bumpity bump bump