Ballooning Into The Wind

[Dickw]

8 minutes ago, Chris Freeman 3 said:

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.   

So the speed has increased because you have increased it (throttle up or slight dive), and hence once straightened up at the increased speed it will climb - unless you decrease the speed as you straighten up.

 

Yes, I fly gliders and you learn a lot by flying slowly 😀.

 

Dick

[Tim Flyer]

There are probably additional factors to be considered with models vs full size e.g Reynolds numbers etc. Model planes have some different characteristics to full size. The turning radius made by models is also likely to be far sharper than full size where smooth turns are the norm. Air density is not scaled with model size as we all know. 

[Tim Kearsley]

1 hour ago, Mike Blandford said:

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

My take on this is that, since kinetic energy is given by the formula E = 0.5mv^2, relative to the fixed ground frame of reference the kinetic energy is zero in both cases, as its velocity in this frame of reference is zero. The italics are important!

[Phil Green]

Einstein says the faster your model flies, the more mass it has. So when it slows into wind its lighter and so balloons 😂😁

 

 

 

 

[joshing of course!]

 

[Steve Dunne]

Could I suggest an exercise that we did back in the eighties as part of this discussion?

 

We flew Ebeneezers, small profile cartoon warbirds, about 18" span, free flight (No radio, so no pilot interference!), powered by small diesels.

They were trimmed to fly low and slow in circles. They were observed to balloon somewhat when turning into wind.

We found experimentally that the wind over the golf course that we flew on did not flow in a straight line, but tended to roll upwards or downwards.

This shows that the idea that the wind is a constant, straight mass of air is wrong, and confuses all arguments on ballooning.

Please experiment yourselves rather than assuming constant masses of air. The results should be ver interesting...

 

Steve.

 

[Martin Harris - Moderator]

Are you sure it wasn’t a visual effect due to the diminishing size while flying downwind changing to getting larger temporarily as the models started coming back towards the launch point?

 

Turbulence will, of course, affect a model’s height and angle of attack, as will thermal effects and localised wind shear but these are incidental to the false assertion that turning into wind causes ballooning. 

[john davidson 1]

many models balloon coming out of a turn, up or down wind,  perhaps due to up elevator held in the turn? and more noticeable when turning into wind

[Andy Stephenson]

3 hours ago, Chris Freeman 3 said:

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!

I see someone agrees with me. Rather than discussing the theory, this is a simple practical explanation, see my post above.

[PatMc]

1 hour ago, Andy Stephenson said:

I see someone agrees with me. Rather than discussing the theory, this is a simple practical explanation, see my post above.

It's not an explanation, practical or otherwise. It's completely at odds with the experience with my Jnr 60 that I described yesterday.

[Christopher Wolfe]

10 hours 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.

 

As for kinetic energy, don't forget that we are on a planet that is rotating at 1000mph and orbiting a star which is moving along with our galaxy.

These people got it pretty right Monty Python - The Galaxy Song 🙃

 

About twenty years ago a fellow aeromodeller had permission to launch some free flight HLG's (chuck gliders) from a hot-air balloon (Canowindra, Australia) to settle a similar debate.

 

The models flew around the balloon basket in perfect circles. A VHS video exists, I shall try to obtain a copy.

 

* Chris *