Ballooning Into The Wind

[Robin Colbourne]

31 minutes ago, Nigel Sharp said:

Or rubber bands give. Changing incidence.

 

Leading to weird things at the sticks.

 

Balloon was/is a simple one word description.

I've had that.  Flying fast and a sudden uncommanded loop when not expected!

[J D 8 - Moderator]

             As the loop ends you hear the slap of the wing reseating itself if lucky and if not wing wing flutters down like a leaf and fuzz does its best to join the Moles in my field. Got the T shirt on that one.

[Don Fry]

Wore mine out.

[Dickw]

1 hour ago, Mike Blandford said:

................................ When flying downwind and aeroplane does have more kinetic energy than when flying into wind......................

Why?
I am not looking for an argument, just an explanation.
The formula for kinetic energy is based on mass and velocity, and velocity is based on speed and direction.

 

(ignoring the actual turn for the moment) In the example you quote above the speed of the aeroplane from its own  frame of reference does not change, only the direction changes.
The speed only changes if you judge it from a ground based pilots frame of reference which is surely irrelevant to the aeroplane.
What am I misunderstanding?

 

Dick

[Andy Stephenson]

The answer seems fairly obvious to me. If the model has a lifting wing section or some  decalage ie incidence between tail and wing, if trying to push it into wind with increased throttle, the airspeed experienced by the model will be greater into wind than down wind. This ballooning or zooming effect is most obvious in vintage type models which were initially designed as freeflight or for single channel and meant to fly at constant power setting. The effect can be countered by adding down-thrust but it is only minimally effective on models with high lift design.

[RedBaron]

May I suggest that everyone go to their nearest gliding club (full size) and sign up for a number of basic lessons. Be sure that some of these are on strong wind days.

Seeing the effects of wind on ones circuits, airspeed, ground speed and landings will explain it all in a very basic way.

Good luck to one and all!

[Phil Green]

Who remembers Fred Deudney?  🙂

Edited August 12 by Phil Green

[Tim Flyer]

When turning from downwind into the wind the mass of air flowing over the wing initially increases due to the higher downwind speed and kinetic energy . This initially provides more lift.

This is soon balanced out by friction(drag)as the speed and kinetic energy drain during the up wind leg of the circuit. 

Edited August 12 by Tim Flyer

[john stones 1 - Moderator]

1 minute ago, Tim Flyer said:

When turning from downwind into the wind the mass of air flowing over the wing initially increases due to the higher downwind speed and kinetic energy . This initially provides more lift.

This is soon balanced out by friction as the speed and kinetic energy drain during the up wind leg of the circuit. 

 

Well that's how my head sees it, sounds like balloon to me.

P.S Can't afford to book the Glider lessons, but contributions welcome. 😉

[Robin Colbourne]

13 minutes ago, Tim Flyer said:

When turning from downwind into the wind the mass of air flowing over the wing initially increases due to the higher downwind speed and kinetic energy . This initially provides more lift.

This is soon balanced out by friction(drag)as the speed and kinetic energy drain during the up wind leg of the circuit. 

Tim, the speed which has an effect on the wing is the airspeed.  This is the wing's speed relative to the air around it.  In the absence of other information, the wing is moving through a body of air which is moving at constant speed over the ground.
If you did the flight above stratus cloud, with the cloud moving at the same speed as the air through which the model was flying, it would be as if the model was flying over the ground in zero wind.

[David P Williams]

11 minutes ago, Tim Flyer said:

When turning from downwind into the wind the mass of air flowing over the wing initially increases due to the higher downwind speed and kinetic energy . This initially provides more lift.

This is soon balanced out by friction(drag)as the speed and kinetic energy drain during the up wind leg of the circuit. 

You are still confusing groundspeed with airspeed. The aircraft has the same airspeed downwind, upwind, crosswind so it doesn’t feel an increase in mass of air flowing over the wing (or a decrease on the “dreaded” downwind turn). Only the groundspeed changes which the aircraft doesn’t know about, but you as a remote pilot on the ground only see groundspeed and probably consciously or subconsciously try to correct to keep the speed, as you perceive it, constant.

like others on here I have flown many circuits in light aircraft and never experienced “ballooning” turning into wind or stalling turning downwind. 

[Tim Flyer]

The wing may have the same airspeed up wind and down wind but the mass of air passing over the wing increases when it changes between the two. Exactly the same happens on a sailing yacht when you tack turning into wind. 

Edited August 12 by Tim Flyer

[Tim Flyer]

Imagine a 1kg plane travelling at 10mph ground speed with a 100mph head wind. 
it will have a kinetic energy of just 10kg . Its airspeed will be 110mph. 

 

When the same plane travels down wind and reaches 110mph  ground speed, its kinetic energy will be 110kg . If the pilot then decides to turn into wind he will have 110kg kinetic energy reduced to 10kg this needs to go somewhere . Either drag or lift. 

Edited August 12 by Tim Flyer

[David P Williams]

The mass of air doesn’t change. The aircraft is flying in a ‘block’ of air. If this block is moving relative to the ground, it is perceived as ‘wind’ on the ground. The aircraft doesn’t know the block is moving, it is just flying through it. Its groundspeed is irrelevant, and kinetic energy is irrelevant as its airspeed stays the same. The ground doesn’t matter other than to potentially generate turbulence if the block of air is moving over it, i.e the wind is blowing for a ground based observer.

Your sailing analogy is also irrelevant as the boat is ground based not air based.

[David P Williams]

Just to add - kinetic energy only matters if the aircraft encounters the ground, where it’s groundspeed can vary enormously depending on the movement of the air relative to the ground (i.e wind), hence why we much prefer to land into wind.

[Geoff S]

13 minutes ago, David P Williams said:

The mass of air doesn’t change. The aircraft is flying in a ‘block’ of air. If this block is moving relative to the ground, it is perceived as ‘wind’ on the ground. The aircraft doesn’t know the block is moving, it is just flying through it. Its groundspeed is irrelevant, and kinetic energy is irrelevant as its airspeed stays the same. The ground doesn’t matter other than to potentially generate turbulence if the block of air is moving over it, i.e the wind is blowing for a ground based observer.

Your sailing analogy is also irrelevant as the boat is ground based not air based.

 

A sailing vessel isn't ground based - it's water based and moving water at that in some cases. It is certainly analogous to flying in moving air.  The only ground-based elements are the shore and, when racing, turning marks.  Obviously not reservoir sailing but certainly river and tidal sailing. 

[Robin Colbourne]

1 hour ago, Tim Flyer said:

The wing may have the same airspeed up wind and down wind but the mass of air passing over the wing increases when it changes between the two. Exactly the same happens on a sailing yacht when you tack turning into wind. 

In your example, the water is providing resistance to the boat moving with the wind. 

Now imagine the boat in a river flowing north to south at at 10 knots, the wind is blowing from the North at 10 knots.  The boat is drifting South at 10 knots relative to the river bed, but it has no movement relative to the wind so the sails have no effect.

[Mike Blandford]

Kinetic energy is calculated using the ground speed. It doesn't matter whether the moving object is on the ground or flying. If the mass is the same and the ground speed is the same then the kinetic energy is the same.

An aircraft moving at a constant airspeed through air moving at some, non zero, speed WILL have more kinetic energy when travelling downwind than when travelling into wind.

If an aircraft changes direction from into wind to down wind it WILL have to gain kinetic energy and if it changes from down wind to be into wind it WILL have to lose kinetic energy.

 

Mike

[Tim Flyer]

Kinetic energy matters for all moving objects . When  they change direction the energy needs converting. It doesn’t just matter when planes hit the ground. Gravity is closely related to kinetic energy . It is with all moving objects. and it is very important manoeuvring aircraft. As a plane dives potential gravitational energy is converted into kinetic. 

[Simon Chaddock]

Mike

Where does it say the kinetic energy is only calculated relative to the ground? Its all to do with relative velocity.

Kinetic energy is measured as the relative velocity to the space in which the object is travelling.

We all agree, I hope, that a plane circling at a constant radius in a wind has the same air speed regardless of whether it is travelling up, across or down wind thus relative to the air it has the same kinetic energy all the time. No energy is gained or lost during the turn although from the ground the apparent velocity will change dramatically.

Of course if you hit something fixed to the ground there will be a big difference in the plane's velocity if travelling up or down wind. Always crash travelling directly into the wind. The repairs cost less.  

 

[David P Williams]

Sailing is ground based compared to an aircraft.

Once again, please don't confuse airspeed and groundspeed.

If you are flying in a full size aircraft, into wind, throttle set to cruise and trimmed for straight and level flight, you will have a constant airspeed. If you look out, you will see you are moving over the ground at a particular rate. If you turn cross wind your airspeed will be the same after the turn so you will neither climb or descend and you will have a different movement across the ground - you will be moving diagonally across it relative to the aircraft's heading. If you turn downwind the same applies but you will observe that the rate you are moving over the ground is now greater than on the upwind leg, and so on as you complete the circuit.

Your airspeed and height will remain the same (ignoring the compensations for the lower lift in the turns).

The aircraft does not "balloon" turning into wind or descend turning downwind because it doesn't know about the wind.

Wind speed is the measurement of the movement of the air relative to the ground, which is important to an observer on the ground but irrelevant to an aircraft in that air apart from navigation considerations.

 

[Chris Freeman 3]

Having done a lot of sailing, flying gliders and old timers I am not sure I can add much to this discussion but I do know that the ballooning terminology was often used in the sales pitch for trainers with semi symmetrical wing sections saying that they would not balloon like the flat bottom wing sections. A high lift wing on a slow flying airframe will use speed to create more lift. This is why turning from downwind into wind and the airframe has increased its airspeed, it will climb or balloon!     

[Dickw]

1 minute ago, Chris Freeman 3 said:

............This is why turning from downwind into wind and the airframe has increased its airspeed, it will climb or balloon!     

Why has it increased it's airspeed?

 

Dick

[Mike Blandford]

An aeroplane is flying at 40kts into a 40kt headwind and is 1 foot off the ground (a runway). What is its kinetic energy? The aircraft now lands so it is on the ground, stationary, facing into the 40kt wind, what is its kinetic energy now?

 

Mike

[Chris Freeman 3]

When turning more speed is required than when flying straight. How many aircraft crash when trying turn to get back to the runway? We are also talking about slow flying aircraft.