Myth busting! I MIGHT STALL IF I TURN DOWNWIND!

[pudestcon]

For me of little grey matter, it's just airspeed and angle of bank in the turn. KISS or am I wrong?

 

 

[Powerin]

I know how it feels. I just read this thread in it's entirety. Goes back a while. Windshear effects and visual illusions should be dealt with, as they are the things that cause angst. Nev

There was an article in Australian Flying magazine that dealt with all this quite well I thought...it's online here.

 

 

[facthunter]

To put it really basically Pud, a properly balanced aeroplane will only stall when YOU stall it. You make the wing exceed the safe angle of attack, (about 16 degrees) by "guess what"? The elevators. Nev

 

 

[Powerin]

You Einsteins are too good for me.So how did they lift 1100 tonne blocks of stone at Baalbeck in Lebanon and set them on a 2 metre high foundation?

Aliens of course!

 

 

[turboplanner]

Cerftainly not John Deere

 

Pud it will be easier for you; you won't have worry about airspeed.

 

 

[facthunter]

Some people have invisible means of support.

 

Incidently Pud, I'm not joking. In a turn you need more lift, the steeper even more, so you have to pull the stick back. More lift means more induced drag so add power to maintain or increase airspeed, and if you don't have enough power you MUST descend during the turn. Basic stuff but make it second nature. Most stalls happen in turns, in real life...Nev

 

 

[J170 Owner]

This is a math problem, not physics. Calculus and the subject of limits. The kind of stuff that drove me to drink....

 

 

[pudestcon]

Cerftainly not John DeerePud it will be easier for you; you won't have worry about airspeed.

Just one airspeed for the Thruster - 55kts easy

 

 

[Gnarly Gnu]

So how did they lift 1100 tonne blocks of stone at Baalbeck in Lebanon and set them on a 2 metre high foundation?

The info you seek is probably here and here.

 

 

[Powerin]

Thread Drift Warning!

 

Let's carry the thought experiment a bit further: we have a truck carrying a heap of pidgeons in a sealed shipping container.

 

1. If the truckie bangs on the side to scare the birds and they all start flying around in the container - will the truck weigh less than it did when the birds were standing on the floor?
    
    
   
2. Now imagine that, instead of flying, all the pidgeons are floating around in the container hanging from helium balloons. Will the truck weigh less?
    
    
   

 

 

 

 

[Guernsey]

Now that's a hard one and difficult to understand what you are trying to say.

 

Could you please refrain from talking in 'Pidgeon English'

 

Alan.

 

 

[Guernsey]

Further to the above.....if the pidgeons were flying around in the container which in itself was filled with helium...would the truck be heavier?

 

Answer....Yes because the pidgeons would now be 'dead weight' Alan.

 

 

[Guest davidh10]

One of my favourite " it depends on your point of reference examples" was from a book written by someone attempting to make Einstein's theories easier to understand.We all know nothing can travel faster than the speed of light right? So I'm standing here and a spaceship zooms past me doing 10Knots slower than the speed of light. Inside that spaceship, at the rear, a kid throws a baseball towards the front of the spaceship at 11Knots. To him the ball is travelling at 11Knots but to me the ball is travelling at the speed of light + 1 knot.

 

Not a very practical example and the ball can only travel "faster than the speed of light" for as long as the spaceship is but it makes you think.

Actually you will not observe the ball to be travelling faster than light because as an object approaches the speed of light with respect to an observer, time slows down for that object as seen by the observer.

This effect* has to be compensated for by the GPS satellite clocks which as observed by us on Earth, run a few microseconds slow each day. If not corrected, it would cause the computed position on the Earth's surface to be in error by an amount that would grow by about 10km/day.

 

*Actually there are two effects that have to be compensated; time contraction due to the velocity of the satellites and warping of space-time by the gravitational field of the Earth, which is greater at the surface than at orbital altitude.

 

 

[Guest davidh10]

Thread Drift Warning!Let's carry the thought experiment a bit further: we have a truck carrying a heap of pidgeons in a sealed shipping container.

 

1. If the truckie bangs on the side to scare the birds and they all start flying around in the container - will the truck weigh less than it did when the birds were standing on the floor?
    
    
   
2. Now imagine that, instead of flying, all the pidgeons are floating around in the container hanging from helium balloons. Will the truck weigh less?
    
    
   

The truck's weight will not change perceivably, but in theory the higher the birds fly, the less they weigh. Their Mass remains the same, but weight is mass X gravitational force, which decreases with distance from the planet... Have to be a very tall truck!

The helium balloons are floating in the air in the same way as a cork does in water, thus there is a downward pressure equal to the weight of the helium, balloon and pigeon acting on the air below it and through that to the floor of the truck.

 

 

[Tomo]

What if the birds were flying in a vacuum... would that be lighter on the truck..?

 

 

[turboplanner]

So how are the birds imposing weight on the frame/suspension/axles/tyres?

 

 

[turboplanner]

The info you seek is probably here and here.

Ed Leedskalnin was reputed to have used magnetic force lines in the earth together with sound to reduce the weight of the stone he worked with. When he died unexpectedly not much was found around his workshop which would provide too many clues except some speakers. This ties in with ancient stories of "trumpets", "sound of Angels" etc being related to feats of great lifting.

 

Wally Wallington is another story Gnarly. The principle he's using looks a very likely candidate for the beams in South America, the cyclopean type buildings such as the Oserion, and Baalbek.

 

He lifted and levered 10 tonnes, so upscaling to the 25 tonne blockas at Stonehenge would be well within the capability of his process.

 

It would be interesting to get an engineer to calculate whether timber could withstand the compressibity of 1,100 tonnes on the fulcrum, and whether the unreinforced stone blocks could withstand cracking from the point load, but a very promising possibility.

 

My work revolves around calculating dimensions and moments on trucks, and I frequently have to change dimensions to change axle loadings, and sometimes add ballast to replace weight lifted off an axle by cantilever.

 

Wally's principles are close to one ancient description of how the 2.5 tonne stone blocks were rotated up the 48 degree sides of the pyramids using a simple wooden lever.

 

Another mystery in the Great Pyramid is how the 85 tonne tuned granite slabs were raised about 200 feet for placement above the King's Chamber.

 

Thanks for that Gnarly.

 

 

[Guest davidh10]

What if the birds were flying in a vacuum... would that be lighter on the truck..?

We'll assume they all have little space suits and oxygen to preserve internal pressure and life. As there's no air, they are fitted with little jet packs in order to provide the thrust to counter gravity. The emission of gasses creating the thrust hit the floor of the truck and .... the weight of the truck remains unchanged.

It is just the same as if they were jumping into the air. The added force required to both launch them into the air and arrest their downward motion when they land mean that averaged over time, the weight of the truck would be the same, albeit that it would be lighter if all the birds jumped in unison during the interval that they were in the air. Take that measurement NOW!.. Quickly!:big_grin:

 

So how are the birds imposing weight on the frame/suspension/axles/tyres?

Regardless of the method of keeping the birds in the air. Ballooons, flying, jumping,... they are exerting a force (thrust) downwards equal to their weight to maintain altitude within the truck. (The same as the forces on an aircraft.) Because the truck is a closed system, the thrust acts on the floor of the truck.

To achieve the objective of having the flying birds exert almost no force on the truck, the roof and floor of the truck could be a mesh that does not impede airflow. Now, if the truck is weighed by measuring the weight on each wheel (ie. single wheel scales), there will be no bird generated thrust force against the scales or the truck. If, however the truck is on a weighbridge then some of the downward force will be on the weighbridge, but some of the airflow will escape around the edge of the truck and not exert all of the force on the weighbridge. Thus the weight would be reduced by some amount, but not completely the amount of the birds collective weight.

 

 

[Gribble]

This thread reminds me of a question I got asked during my BAK. What effect does a headwind, tailwind or crosswind have your rate of climb?

 

I cant believe how simple the concept of travelling relative to the parcel of air is but people seem to get it confused all the time.

 

 

[facthunter]

You got the answer Davidh10. Nev

 

 

[Bryon]

We'll assume they all have little space suits and oxygen to preserve internal pressure and life. As there's no air, they are fitted with little jet packs in order to provide the thrust to counter gravity. The emission of gasses creating the thrust hit the floor of the truck and .... the weight of the truck remains unchanged.It is just the same as if they were jumping into the air. The added force required to both launch them into the air and arrest their downward motion when they land mean that averaged over time, the weight of the truck would be the same, albeit that it would be lighter if all the birds jumped in unison during the interval that they were in the air. Take that measurement NOW!.. Quickly!:big_grin:

 

Regardless of the method of keeping the birds in the air. Ballooons, flying, jumping,... they are exerting a force (thrust) downwards equal to their weight to maintain altitude within the truck. (The same as the forces on an aircraft.) Because the truck is a closed system, the thrust acts on the floor of the truck.

 

To achieve the objective of having the flying birds exert almost no force on the truck, the roof and floor of the truck could be a mesh that does not impede airflow. Now, if the truck is weighed by measuring the weight on each wheel (ie. single wheel scales), there will be no bird generated thrust force against the scales or the truck. If, however the truck is on a weighbridge then some of the downward force will be on the weighbridge, but some of the airflow will escape around the edge of the truck and not exert all of the force on the weighbridge. Thus the weight would be reduced by some amount, but not completely the amount of the birds collective weight.

One of the factors most of you guys have missed is the excrement factor.

 

Pigeons are notiorious poopers and the weight of poop must be included in the equation

 

This can be easily calculated by using a simple formula based on the following

 

a = number of pigeons

 

b = number of poops per hour x weight of average poop

 

c = time in truck

 

d = fudge factor (believability)

 

so therefore, to determine the EWT (Eventual Weight of the Truck) we must apply the following

 

EWT = a(b/c) x d (multiplied by Intelligent Quotient of calculator)

 

A factor in all this is the weight of the average pigeon and poop proportionality to body weight

 

A true analysis of this equation will be posted in the NES in the Forums on this site within the near future

 

 

[Powerin]

Think of a truck carrying a big container of water. Now float a 1 tonne boat in the water. You would expect the weight of the truck to increase by one tonne because the water is holding up the boat (even though it is floating) and the truck is holding up the water.

 

Sorry for the thread drift....now....back to supposedly losing airspeed when you turn downwind!

 

 

[Guest davidh10]

wouldn't the helium ballons reduce the effective density of the gases in the container, thereby reducing the weight??

You are absolutely correct.... The lower density helium has displaced an equal volume of higher density air. I missed that one

 

 

[Guest nunans]

There was an article in Australian Flying magazine that dealt with all this quite well I thought...it's online here.

That's a very good and informative article which I found helpfull, Except for me I found the myth of the "downwind turn temporarily reduces your airspeed" and the Real issue of wind shear a bit of a contradiction.

 

I think they are both real but in the downwind turn is the loss of airspeed due to inertia isn't realised because the turn isn't rapid enough so the turn on it's own doesn't pose any problems. (not including the other influences like apparent increase of airspeed while viewing the ground etc).

 

 

[Powerin]

I'll let you work it out cfi.....air weighs roughly 1.25 grams/litre and helium around 0.18 grams/litre. So if a balloon contains roughly 4 litres of helium it would reduce the weight of the truck by roughly 4 grams for every balloon...but you have to take into account the weight of the balloon too!