Will it fly?
 

The mythbusters on discovery tonight answer the question. Will a plane take off on a conveyor belt?

yup- little to no resistence on the wheels.

As long as it gets & keeps enough air movement over its wings...

Yes...as long as the treadmill is long enough.

Sure it will. I want to see the massive conveyor belt.

Some people have far too much time on their hands.

Does a carrier catapult ring any bells? Given enough airspeed, a brick will fly.

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All the plane needs to take off is sufficient forward airspeed.
As long as the prop is driving the plane forward the the airspeed will be just the same whether the ground is moving relative to the plane or not. If the plane had to get to take-off speed by driving throough it's wheels then that would be a different story.

Can someone please explain the physics of that video. That plane should be stalling and falling right out of the air. Is it defying bernulli's principle? Come on people why is that happening?

When is it on?

I say 'no fly'.
The engine will run fast enough to keep the plane standing still. No air will move over the wings.


KT

Headwind and a low stall speed...... Love it! If you get a fast enough headwind and a low enough stall speed you can actually land with zero groundspeed or while moving backwards over the ground. Did this with an r/c airplane, never did it with a real one though.

Yeah it looked like the video was shot in a valley with the mountain on the otherside. I guess thats exactly the reason why carriers launch into the wind? So the plane doesn't have to physically be moving? Just the air has to be moving fast enough over the wings to produce lift?

This is too cool.

I was actually dissapointed by the mythbusters. it is just too obvious that a plane still could fly, b/c the ground has nothing to do with lift.

The plane above can take off b/c there is a strong enough head wind. Thats why an aircraft carrier points into the wind when planes take off

Airspeed (speed of the air moving over the wings) is everything to the physics of flight, groundspeed (speed relative to a fixed position on the ground) is meaningless to the physics of flight.

You are correct. It is the reason carriers launch into the wind, also why they land into the wind.

So theroetically, yeah I gotta use that word atleast once when talking physics, if you had a constant headwind moving quickly enough to produce instant lift. The plane would just take off? I.e that video?

Don't want to ask the dad. He is the physicist and he will give me meaningless physics scenarios. I want lift speeds. Come on 450, you fly an Embraer, I fly on one once a month. At what speed Mph/knots do you get enough lift to sustain flight?

Sounds like I am talking gibberish.

The plane will take off with the wheels turning Zero mph!
Think rope theory :D

another reason why they have to tie the wings down when not in use.

Yes, but you will need the engine to keep the airplane moving relative to the wind. It would appear from a position on the ground that the airplane is rising vertically.

WIND!?!?! See those big Ballon wheels? they're filled with helium. ;)

Pretty cool video, eh?

This is really interesting stuff. Keep it coming guys

If a wing is very efficient in producing lift, and if the airframe attached to that wing is very light, and if the wing is very large compared to that airframe, then enough lift will be produced to fly at a very, very low airspeed. There are a few very specialized bush planes built that can get airborne with as little as 35 mph of airspeed over the wings. If one of theose airplanes were to be pointed into a 35 to 40 mph wind, it would levitate.

To answer your question, BRPORSCHE, normal liftoff speed for an Embraer is in the vicinity of 130 knots (150 mph or so). Within 15 seconds, however, it has accelerated to 200 knots, and within another minute it's climbing at 250 knots. Five minutes later it's climbing at about 300 knots. By the time it levels off at 37,000 feet 20 minutes later, it's finishing its climb at about 420 knots (true airspeed) and will cruise at about 445 knots or so.

Yeah I figured a half of my one hour flight from Houston to Baton Rouge was ascending and descending.

So once the wing takes flight, you need the engine to keep the wing moving foward? Even if the headwind stays the same? Or will the plane just levitate in place?

the propellor creates lift too. rev the **** out of the ngine and it will take off like a helicopter. provided you don't care that it will stall and crash two seconds later.


the show is coming on now, l.a. time. we'll see if i'm right.

For those of you who are not pilots or aerospace engineers, here are a few ideas to ponder:

Once you are in the air, you are moving within it and wind speed is only relative to the airplane itself. In other words, let's just say that the airplane is being pulled along by its prop through the air at 80 mph, the speed of the wind over the wing is then 80 mph. Let's also say that that airplane is pointed West for this discussion, so it's westbound. Now, lets say that the air itself is moving over the ground at 100 mph, but it's moving East. In other words, it's a 100 mph wind over the ground moving eastbound (common at altitude in the winter, btw). So what do we have? We have an airplane moving at 80 mph through the wind westbound, but that wind itself is moving Eastbound at 100 mph. The net result is that the airplane will be moving over the ground eastbound at 20 mph (80 mph into a 100 mph headwind equals 20 mph the other way). To someone on the ground, the airplane will seem to be going backward.

Yes, the engine of any airplane is simply there to pull or push it through the air. The wing itself does the flying. If the engine quits, the airplane will not suddenly fall out of the sky, rather the pilot will simply need to start a gentle descent to use gravity to keep the speed up, exactly the way a car can roll endlessly down a hill without the engine running.

A glider can remain airborne indefinitely by descending down through a column or wave of upward moving air that is moving upward faster than the glider is descending.

Just a few basic tidbits.

thanks for all the great info 450!

When I started my career in a small tower in the very early 90's I did witness a Belanca land on the numbers and take the taxiway at the threshold......

Last year we had a C182 IFR over the interior of the province GOING BACKWARDS on radar. He turned around and went back to his departure point grounding about 260kts in his 182..... I still may have the file stored on disc.

Cheers

http://forums.pelicanparts.com/uploa...1201762661.gif

something to cogitate on....

Think of it like a boat on a river.

Think of a fast moving river and a boat tied to the dock. The boat 'feels' like its going as fast as the water- say 5 knots. If you untie the boat the boat floats away and 'feels' likes its going zero, but if someone was on the shore with a radar detector they would say you were doing 5 kts. Next fire the motor up and set it to 5 kts speed and head downstream. The boat would 'feel' 5 kts, but the person on the shore with the detector would read 10kts. If you turnws the boat around and went up stream, the boat would 'feel' 5 kts but the person on the shore would show 0 kts.You'd be sitting still.

A boat (airplane) tied to the dock (ground) is subject to the surrounding water (air) but as soon as the boat (plane) is let loose (airborne) it's now a part of the river (airmass).

An old instructor used to say if you had a balloon and there was an ant on it and it was a windy day, the ant would feel the wind as long as you held the balloon in your hand. The momemt you let the balloon go, the ant says "hey the wind stopped", while in actuality the wind is still blowing, but the balloon and the ant are a part of the airmass floating away.

Same as what Scott is saying.

If is pretty scary how much that chart would change with a little ice on the lifting surface....
Right Scott?

Just got of work after a pretty bad night of iced up aircraft..... sorry for the sidetrack :)

Cheers

http://forums.pelicanparts.com/uploa...1201762715.jpg
http://www.custerchannelwing.com/
Repost, but if there's air moving over the wings, there's lift.

http://forums.pelicanparts.com/uploa...1201762922.jpg
http://en.wikipedia.org/wiki/Fieseler_Fi_156
The Storch could fly as slow as 32mph, and land in 60ft.

http://www.slepcevstorch.com/
An improvement on the original design:"The aircraft will fly at 22mph at full flap and 30% of power. Take off run into a 16mph wind is vertical with no forward roll."

My Minimax "ultralight" will hang in there at indicated airspeeds in the vicinity of 20-25 mph.

I have taken off on cold windy winter days while out ski flying in 30' or less.
For fellow tail dragger pilots: 1 full throttle + 2 stick forward + 3 stick back = airborne (in the amount of time it took you to read the procedure :eek:)

http://forums.pelicanparts.com/uploa...1201784163.jpg

You can hear the wind ripping in that video. Absolutely a case where there is a huge headwind component (probably just below the stall speed of the aircraft) and all the guy needs to do to get airborne is give it enough power to generate a little prop wash and a small amount of ground speed.

I've actually seen situations where certain airplanes would have a negative ground track at Vso due to high headwind components. You'd be flying backwards, in effect.

It's all about the airspeed.

Our J4 Cub stalls at about 38mph, I was out over Lake Michigan a few years ago, there was a nice steady wind, it was about 40mph and I could pull the nose up and let the plane hang and actually back it up slowly, its a strange feeling seeing your GPS ground speed around zero!

Do you have heat in that minimax Tim?

Ugh.

My wife still doesn't understand why it works. No amount of explanation from me or from the TV show will make her "get" it. I couldn't post this last night. ;)

Yep! 30 degree weather requires removal of coat, 15 degree weather...coat stays on, but gets unzipped.

The engine is essentially a fan cooled snowmobile engine and for winter flying, I simply wedge a 4" dia dryer vent hose into the engine cooling tin outlet which then snakes back into the cockpit and blows out under my panel. When I first hop in and while taxiing, I can simply stretch the hose and direct it at the canopy to quickly defrost it. Crude system, but very effective ;).

so it flew off the conveyer belt? i was at school and missed it!

I can see how people might have a hard time understanding the concept of airspeed vs ground speed and what actually lifts a fixed wing aircraft off the ground, but was there really as much debate on this topic as was alluded to on the show?
Seems like several posters here were able to make a concise and logical explanation of the situation, which I would assume would put the issue to rest.

Yes, Grant... plenty of debate has raged on this topic.
I've even seen it discussed some here on PPOT.

I'm always surprised at the pilots who get the answer wrong.

I think people tend to miss the most basic element of the experiment. The propeller tractors the plane forward, not the wheels. Running a conveyor belt under the plane only affects the wheels, while the prop pulls the plane forward completely unaffected.


But try this... Given a plane with a 30mph takeoff speed, and an runway with a 30mph tailwind, will the plane fly? If so, what will the takeoff speed be?

30mph IAS


Cheers