Will it fly(don't answer too fast)?

[H]

You're right ........ the conveyor is a distraction  ;D

Totally: it had nothing to do with traction!*

*Except, maybe, in the case where somebody fell off the conveyor/treadmill.

[Gary R.]

"Anyone who doubts that the plane will lift off should ask themselves what happens aboard an aircraft carrier. If a CVN is travelling at 30 KTS does a plane have to reach normal takeoff speed plus that 30 kts? Of course not...all that mattes is the planes airspeed, not it's groundspeed."

Take it from a 6 year navy boy here.  A plane leaves a carrier due to these reasons.  The speed of the carrier itself generating headwind over the deck + the thrust of the engines + the thrust imparted by the cat.  The plane being launched is indeed moving relative to the air itself unlike the plane oon a stationary belt with the belt speed exactly matching the forward thrust of the plane.  In the case of the carrier the thrust of the engines + the thrust of the cat = a fixed headwind velocity.  The variable is in the velocity of the headwind across the deck.  The navy knows exactly how much assistance will be required of the ship itself for any given aircraft type to achieve vref.  It's very basic math.  On a calm, windless day the ship can provide at least 30 + knots of additional lift.  More than that actually but I'm forbidden to say how much more in the case of a Nimitz class carrier.  And, remember that it is SOP for a carrier to steam upwind during both launch and recovery operations.  The real variable is the naturally occuring headwind velocity. Just the same though, the cat + the ship are able to emulate 120 +kts. of over the wing air velocity.  Ever been on a carrier at flank speed? It's like standing in a gale.  But, trust me though.  Except in cases of extremely light payloads if any of those three quantities are taken out of the equation that plane isn't going anywhere except in the drink.  Therefor, the plane on a treadmill with the rearward pull of the belt matching the forward thrust of the plane is totally not the same as there is no way any air velocity is going to be generated.  That would indeed require forward motion of the plane.

[Delta_]

You do know the conveyor belt is not moving the aircraft anywhere don't you???.  Just spinning the wheels really fast.  If you read back at the other posts you will realise this.

[Woodlouse2002]

"Anyone who doubts that the plane will lift off should ask themselves what happens aboard an aircraft carrier. If a CVN is travelling at 30 KTS does a plane have to reach normal takeoff speed plus that 30 kts? Of course not...all that mattes is the planes airspeed, not it's groundspeed."

The difference here is that the carrier is moving in the same direction as the plane. If it's doing 30kts then the aircraft is doing 30kts before it's even released it's breaks so it would only have to reach take off speed minus 30kts in relation to the carrier if you get what I mean.


I still maintain that in the case of the conveyor belt the wheels of the aircraft would fail due to excessive stress due to having to go at speeds that are potentially infinately more than they are designed.

[Jakemaster]

Yes, thats exactly right.  The conveyor wouls allow the plane to run at full throttle and roll without flying, which would probably overstress the tires, wheels, and gear.  If you go to the airport and walk slowly the wrong way on a moving walkway, you will not feel any wind.  A plane wouldnt experience airflow rolling in the same place at 300MPH.

[TacitBlue]

Aaagh! It wouldn't be rolling in the same place. The airplane moves by thrust generated by either a propeller, or jet engine. This thrust pushes against the surrounding air in order to move the plane forward.

Now that we have that established, lets look at the conveyor/tredmill/moving runway thingy. It is set up to automatically move at the same speed as the aircraft, but in the opposite direction.

understood? okay, now the wheels of an airplane spin free like the wheels on roller skates. These wheels have very good bearings, have you ever seen someone move a light plane weighing over 1500 pounds all by themself? If a little skinny guy like me can pull a Cessna out of a hanger all by myself from a standstill, then it stands to reason the the engine running at full power could easily overcome whatever additional stress is placed on the wheels by a conveyor belt moving in the opposite direction.

That being said, the belt will make no difference. the airplane will still reach takeoff airspeed.

... I ran out of steam back there somewhere, but it's plain and simple. The airplane will takeoff. The conveyor doesn't matter. Somehow I don't think this discussion will end until OTTOL confirms someones answer. I'm done.

[Chris_F]

[quote]Yes, thats exactly right.

[C]

Charlie's input:

Thank heavens I've been away all week! I'll give this discussion a miss!

[jordonj]

Yeesh!  How can you make a rhetorical question an arguement?!  ::)

[H]

Yeesh!  How can you make a rhetorical question an arguement?!  ::)

C'est la guerre de la vie. We can make such a battle over self-delusion.

[OTTOL]

..... Somehow I don't think this discussion will end until OTTOL confirms someones answer. I'm done.......

I didn't realize that I was morally obligated to answer the question.

Actually, I sourced the scenario from a thread on the FlightInfo website (which I referenced earlier) and don't have a confirmed answer.

I would like to try an R/C model on the treadmill downstairs but, unfortunately, I'm stuck in Kuwait and the closest R/C shop that I know of is in Dubai.(where's Rifleman when you need him?)

What really cracks me up is the number and type of equipment references which are used to justify one's argument (rockets, rollerblades, strongmen, toy cars, aircraft carriers, super braking devices.....)!

In my opinion, the problem was best resolved with this scenario:

......imagine the opposite: a plane landing under these conditions same conditions.  The plane is moving relative to the air and REALLY fast relative to the belt....

Let me use a light Cessna for this scenario.

It's been awhile, but I think 60kts would a reasonable touchdown speed.

If my theoretical Cessna touches down on a giant treadmil whose belt is moving opposite the direction of the Cessna at 60kts, will the Cessna immediately come to a stop when the wheels touch the belt?

OR.....

Stated another way.....

Let's say that you have an aircraft carrier with a giant conveyor belt for a main deck. It's traveling through the water at 30kts, while traveling directly into a 30kt headwind. Sitting at the back end (the stern) of the main deck/belt is a Cessna. In front of the Cessna is a strong man, wearing roller blades,  with a rocket (which is capable of accelerating a strong man on roller blades to 300kts) strapped to his back. A bungee cord is tied to one of his roller blades and around the prop spinner of the Cessna. If you start the Cessna, hold the brakes and increase power to 1700rpm, light the rocket and have the strong man skate at his own personal  best roller blading speed of 20kts, while the Captain of the ship steps on the "super brake pedal" what will happen if you place a toy car with wings at the front end (the bow) of the deck/belt?

or....

You could just watch a bunch of professional pilots argue about it endlessly....

http://forums.flightinfo.com/showthread.php?t=66860