The Naked Scientists

The Naked Scientists Forum

Author Topic: Can propeller-driven aircraft take off without forward motion?  (Read 16300 times)

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3823
  • Thanked: 19 times
    • View Profile
When a propeller driven aircraft is stationary on the runway with its propellers blasting back air over its wings and tail plane undoubtedly some lift is generated.
Are there any aircraft that can generate sufficient lift to get airborne without any forward movement.
« Last Edit: 23/01/2010 23:08:28 by chris »


 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
In theory, there's no difference between moving a wing through the air and moving the air across a stationary wing.  However, it's more complicated than that because you can't move the entire body of air.  The principle has been proven though, and is known as the Coanda effect.

Basically, air is drawn from above a (usually) circular domed surface and then blown down over the curved surface.  The Coanda effect means that instead of just hitting the top of the domed surface and then blowing out sideways, it follows the curve of the surface, as though it sticks to it, and this means that you're getting high-speed airflow over the curved surface, just as you get when a wing moves through the air, which generates lift in the same way.

Have a look at:

http://www.youtube.com/watch?v=KXVtUCABiv8
 

Offline Karsten

  • Hero Member
  • *****
  • Posts: 701
    • View Profile
    • Fortunately still only a game



That must have been a landing with no propeller movement. Or very little. It seems just the tips are a bit bent.
 

Offline Karsten

  • Hero Member
  • *****
  • Posts: 701
    • View Profile
    • Fortunately still only a game
Are there any aircraft that can generate sufficient lift to get airborne without any forward movement.

A kite?
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
That must have been a landing with no propeller movement. Or very little. It seems just the tips are a bit bent.

All the tips are bent so the props were still spinning when it nosed over.

What DiscoverDave says about tail-draggers is true though; is was common practice during WW2 for a member of the ground crew to sit upon, or more usually lay across the elevator of single seater fighters when the engine was revved up while being held on the brakes, or even on occasion while taxiing across bumpy grass fields, to prevent the aircraft from nosing over.  There was actually a documented incident where the pilot forgot about the female ground crew member laying across the elevator to keep the tail down while he revved up to check the engine and took off with her still hanging there.  Fortunately, she managed to hold on while the pilot did a quick circuit and landed again.
 

Offline Karsten

  • Hero Member
  • *****
  • Posts: 701
    • View Profile
    • Fortunately still only a game
Are there any aircraft that can generate sufficient lift to get airborne without any forward movement.

A kite?

Sorry, that was a stupid post of mine. Did not read that the vehicle had to be propeller-driven.
 

Offline doppler1

  • Sr. Member
  • ****
  • Posts: 156
  • Bazinga
    • View Profile
The entire key to success with lift is ensuring that sufficent wind speed is achieved across the surface of the wing. Thereafter, the Delta P increases and lift is created.
 

Offline doppler1

  • Sr. Member
  • ****
  • Posts: 156
  • Bazinga
    • View Profile
I have been in small aircraft, not tilt rotor or helicopter, that can manouvre into the wind and then tap off on the throttle until it has a ground speed of zero on the gps but manages to stay airborn so theoretically, if you had a fast enough headwind, you could take off with a zero ground speed.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3823
  • Thanked: 19 times
    • View Profile
Would that not only happen if you had some kind of tether to prevent you being blown back ?
 

Offline doppler1

  • Sr. Member
  • ****
  • Posts: 156
  • Bazinga
    • View Profile
NO, this is when the aircraft is already in the air and the propeller is keeping it from moving backwards but it is just that the air speed and the aircraft are in exact unison which results in a zero speed as far as ground speed is concerned. In actual fact, the aircraft is travelling at the required knots to remain airborn relevant to air across the wings. In essence the aircraft is matching the air speed exactly in the opposite direction
 

Offline daveshorts

  • Neilep Level Member
  • ******
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Can propeller-driven aircraft take off without forward motion?
« Reply #10 on: 26/01/2010 14:43:25 »
The people at fanwing have done something quite similar, but have a rather different design of propellor
http://www.fanwing.com
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Can propeller-driven aircraft take off without forward motion?
« Reply #11 on: 26/01/2010 21:47:32 »
It should be remembered that the Wright Brother's test gliders were often flown as kites i.e. tethered and controlled from the ground.  It was during such 'kite' flights that they found that the lift generated by their cambered wings didn't operate vertically but was angled forward; they discovered this by attaching spring balances to the tethers and could see that the force exerted on the tether was less than it should have been had the lift been purely vertical.

Re the Curtis Bleeker helicopter: it almost looks like a bi-plane chopper - Lol - but I suspect it was actually intended to work more like the Kaman servo-flap controlled rotor.  However, I can't see anything on that C-B to counter torque; unless the rotor also carried the engines and was effectively free-spinning (like an autogyro), you either need a pair of counter-rotating rotors, as on the Kaman and Russian Kamov helis, or the more common tail thruster/rotor to stop the fuselage from spinning instead of the rotor.
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Can propeller-driven aircraft take off without forward motion?
« Reply #12 on: 29/01/2010 00:17:30 »
Yeah - I think you might be right re the radial engine in the rotor.  Lol - it's like coming up with an even more Heath-Robinson solution to get around a slightly less Heath-Robinson problem  ;D
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #13 on: 15/03/2010 16:15:29 »
That fanwing was quite impressive. Seems very cool. How protected would it be to birdstrikes?
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #14 on: 16/03/2010 02:30:07 »
I don't think it would glide too well if the engine quit, but it might be possible to get the axial fan to autorotate during a steep dive and use the kinetic energy to soften the landing.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #15 on: 16/03/2010 04:17:23 »
Yeah it seemed a little clumsy, but to be able to travel at thirty miles an hour, or maybe slower?

I like :)
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #16 on: 16/03/2010 06:21:55 »
It's a very interesting invention - sort of halfway between a helicopter and an aeroplane, but much simpler than a helicopter at small scales. It might not scale up very well, but I don't think the inventor is very interested in large scale machines.

I think he sees it more as an "eye in the sky" surveillance platform. It looks really inexpensive too, which is a major plus for that application (a lot of them are going to be shot down).
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Can propeller-driven aircraft take off without forward motion?
« Reply #17 on: 16/03/2010 16:17:19 »
That fan wing is a very interesting design.  Actually, the inventor reckons the design becomes more efficient as it becomes larger, and wants to scale-up the design.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #18 on: 16/03/2010 16:45:44 »
That fan wing is a very interesting design.  Actually, the inventor reckons the design becomes more efficient as it becomes larger, and wants to scale-up the design.


That's true. He did say that. I'm just a bit nervous about the rotating mass of an axial fan in a large aircraft, but I suppose it could be implemented with several fans. I'm sure they could scale up their current model quite a bit for unmanned applications though.

The thing looks so simple. I might have a go at making one.

I don't care for typical RC model aircraft much. They fly too fast, so you need a lot of space to operate them. Come to think of it, are they flying at anywhere near their scale speed?
 

Offline wolfekeeper

  • Neilep Level Member
  • ******
  • Posts: 1092
  • Thanked: 11 times
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #19 on: 16/03/2010 16:49:18 »
Actually, I know this isn't what you had in mind, but a gyrocopter can do precisely that; it can takeoff vertically with the power of the propeller.

Basically what they do is put the brakes on and tilt the rotor backwards and put the air through the rotor from the pusher prop. Once the rotor reaches a high enough speed, they put the main rotor horizontal again and change the blade angle and it leaps vertically into the air.

The rotor is actually a wing- it is exactly what you asked for (but probably not what you wanted!)
« Last Edit: 16/03/2010 16:51:22 by wolfekeeper »
 

Offline wolfekeeper

  • Neilep Level Member
  • ******
  • Posts: 1092
  • Thanked: 11 times
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #20 on: 16/03/2010 16:55:50 »
The secret to vertical takeoff is you need to be able to make the airflow go straight downwards.

I vaguely recall that there was an aircraft that took the airflow from the propulsion system and via a system of flaps could turn it downwards; once in flight they could change the flaps and it flew more normally. There was some problem with it though; I can't remember exactly I think the aircraft was quite heavy and unstable during takeoff.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #21 on: 16/03/2010 18:48:09 »

The secret to vertical takeoff is you need to be able to make the airflow go straight downwards.

I vaguely recall that there was an aircraft that took the airflow from the propulsion system and via a system of flaps could turn it downwards; once in flight they could change the flaps and it flew more normally. There was some problem with it though; I can't remember exactly I think the aircraft was quite heavy and unstable during takeoff.


Were you thinking of the Hawker Harrier?

http://en.wikipedia.org/wiki/Hawker_Siddeley_Harrier
 

Offline wolfekeeper

  • Neilep Level Member
  • ******
  • Posts: 1092
  • Thanked: 11 times
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #22 on: 16/03/2010 19:50:59 »
No, anyway there's the amusing 'wheel of misfortune' that shows all the different ways that VTOL have been tried:

http://www.aiaa.org/tc/vstol/wheel.html
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #23 on: 16/03/2010 21:41:14 »
Can't get the link to load I'm afraid.

There was also something called "the flying bedstead". It was a early VTOL experimental testbed.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can propeller-driven aircraft take off without forward motion?
« Reply #24 on: 17/03/2010 23:11:24 »
The Wheel
first time I couldn't load it either? Then I copied the link and pasted it and it worked perfectly. But it seemed as if the first time I came somewhere else? Very weird???

Try mine and look where it gets you Geezer?
I forgot to 'save' where it took me first, although I did remember that it didn't fit the link location as I looked at it again, after?

Linknapping :)
 

The Naked Scientists Forum

Can propeller-driven aircraft take off without forward motion?
« Reply #24 on: 17/03/2010 23:11:24 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums