Weight, lift and what keeps things in the air.

[flying dog]

I am probably going to regret asking, but here goes:

 

A long time ago there was a question posed about a truck carrying pigeons inside.

The gross weight is 5 tons.

If all the pigeons fly - inside the truck's area - does it (the truck) weight any less?

 

(Don't answer that yet)

 

Then there is the story I heard a long time ago about falling objects.

I don't remember the specifics, but it was something like:

 

A rock is sitting on the ground.  It weighs 2 kg.

You pick it up and drop it.

As it is falling how much pressure is on the ground below it?

Supposedly 2 kg because of the pressure below the rock.

(Beats me.)

 

And there is a question about hovercraft and how much weight do they have (on the ground) when "flying" compared to when they are just sitting there engines off.

 

Just recently I've seen this youtube on "How do plane fly" - which is not arching back to a SHELL movie from decades ago.

This new one

 

So what is happening with all the "weight"?

I know weight is a concept - controlled by gravity - and it should be MASS that is measured.

 

I'm not the sharpest tool so maybe don't use too many long words.

I really don't like it when I get bored and ask hard questions that are well above my knowledge.

 

So now my little brain is curious about what is going on with that sort of thing.

 

 

[Thruster88]

As long as you understand that pulling back on the stick puts more load on the wing and pushing forward puts less load on the wing you will be fine.😁

[facthunter]

IF some thing is moving the air, to STAY airborne, it has aero DYNAMIC effects which offset the MASS times G  = weight G is gravity  of this earth which will cause an accelerative force of 32 feet/sec/ Each second IN A VACCUUM.

     A falling object will continue to speed up till it reaches it's terminal velocity where the drag equals the weight when it's in air or water or  any fluid. If you are below it you won't feel the weight till it hits you.

  IF a big plane flys over you and is very low you may feel the downwash that supports it but if it's say 2x wingspan of height it's likely you won't. 

   Birds flying in a  sealed cage will not affect the weight of it unless they hit the top or bottom of it (Inertia). There would be  a complex energy  Dynamics and pressure going on there when they were in flight but consider it contained.  Nev

[flying dog]

Thanks.

 

ITMT I did some digging and have kind of resolved the question.

 

Thanks for the info.

 

6 hours ago, facthunter said:

you may feel the downwash that supports it but if it's say 2x wingspan of height it's likely you won't

 

Is this part of ground affect?

 

[facthunter]

Has to be doesn't it.? Ground effect is a known and accepted phenomenon.  There are those who say when the air is away from the wing there can be no effect. The "interference" between the wings of Bi Planes and the wind begins to move a long way ahead of large curvature wing leading edges.   The "down wash" behind a wing is the necessary reaction to producing lift.   At a zero Lift angle of attack there is NO down wash  and a large resultant reduction of drag while that situation lasts. Nev

[coljones]

No One Can Explain Why Planes Stay in the Air

Do recent explanations solve the mysteries of aerodynamic lift?

By:Ed Regis

 

https://www.scientificamerican.com/article/no-one-can-explain-why-planes-stay-in-the-air/?fbclid=IwAR2H7_ys5T1O-53SrKKnRu4OVbhmoqvbewk-sNun9vkZ1yHJnob5R6nXC1g

Edited May 18, 2023 by coljones
Edit for title of link

[facthunter]

I've never found Bernoulli to be anything but a convenient question for an exam. Aeronautical  design Knows a hell of a lot about subsonic and supersonic air flow, lift and drag  so it's just sensationalised article for taking up space somewhere.   Nev

[Ian]

On 19/05/2023 at 10:40 AM, facthunter said:

I've never found Bernoulli to be anything but a convenient question for an exam.

I know it's easy to be dismissive however I think that a half decent understanding of Bernoulli can lead to a significantly better understanding of how things like radiators should be designed and installed on planes. Just sticking them out into the airflow or trying to force air into it may not lead to the outcome you want. A little bit of theory can help you avoid some of the more obvious mistakes however aerodynamics is complex, add a bit of detail or parameter into a CFD model and you run time can go from days to years.

[facthunter]

It's simple Newtonian Physics. Gases flow from high to lower pressure and if you shove them they shove you in return.  If an air current is curved the lower pressure is in the inside of the curve. The universal GAS equation is P1V1/T1 is a constant. Know what effect Reynolds number does. You don't have to design a plane, Just fly one.  Even though they look as if nothing is holding them UP but it IS aero-DYNAMICS we are dealing with.   Nev

[derekliston]

On 11/3/2023 at 8:27 AM, flying dog said:

I am probably going to regret asking, but here goes:

 

A long time ago there was a question posed about a truck carrying pigeons inside.

The gross weight is 5 tons.

If all the pigeons fly - inside the truck's area - does it (the truck) weight any less?

 

(Don't answer that yet)

 

Then there is the story I heard a long time ago about falling objects.

I don't remember the specifics, but it was something like:

 

A rock is sitting on the ground.  It weighs 2 kg.

You pick it up and drop it.

As it is falling how much pressure is on the ground below it?

Supposedly 2 kg because of the pressure below the rock.

(Beats me.)

 

And there is a question about hovercraft and how much weight do they have (on the ground) when "flying" compared to when they are just sitting there engines off.

 

Just recently I've seen this youtube on "How do plane fly" - which is not arching back to a SHELL movie from decades ago.

This new one

 

So what is happening with all the "weight"?

I know weight is a concept - controlled by gravity - and it should be MASS that is measured.

 

I'm not the sharpest tool so maybe don't use too many long words.

I really don't like it when I get bored and ask hard questions that are well above my knowledge.

 

So now my little brain is curious about what is going on with that sort of thing.

 

 

Regardless of how much you quote physics, at the end of the day it is money that keeps planes in the air! Cynical!……me?……. Never!

[Area-51]

What keeps anything in the air, or upon water, is the "stickyness" of the fluid medium and its ability to support a specific mass divided across the surface area of both object and fluid (this is called the "wetted surface"... a boat floats because all these individual items have reached a point of equilibrium i.e everything has cancelled out to zero, so the object floats; (equal force against force equals zero) the vessel may be 100kg, and the volume of water it displaces is 100kg, so it floats at the zero point... if any single factor is altered the "buoyancy" will alter.

 

A 100kg fixed wing aircraft moves through the fluid of air.. if the volume weight of sticky air it tries to drag along with it is 100kg the aircraft will float at the zero point (this aspect and angle of drag is complex, however the combination of this angle and the stickyness of air allow the aircraft to float)... When the stickyness of air is torn away from the surface of the object acoustic noise is created. When it is severely ripped apart the aircraft falls from the sky. High and low air pressure, fast and slow air velocity are all a symptom/result of the "stickyness" of air...

 

Air does not like being seperated; it is chaotically lonely, and violently codependent...

 

 

 

 

[old man emu]

To be really honest, is there any reason to spend time trying to get an answer to this question? For an aeronautical engineer the question to be answered is how to obtain maximum lift and minimum drag. One can start with a mathematical model, but that only directs you to a design to test. Therefore,  the design of a wing is an empirical process. One doesn't need to know how the desired lift is created, just that the design produces the desired result.

 

Next we have the poor wingnut trying to utilise the aeronautical engineer's design to the best effect. The wingnut doesn't need to know the How of the situation, merely the how  to use the tool the aeronautical engineer has provided. 

 

That said, it creates a great argument for dispensing with all the guff 'n' stuff we are fed about How Lift is produced, and replacing it with study of how to use the tool. We practice how to use the other tools that have been provided for efficient flight, so why not practice using the wing? I wonder how many people who spend ages arguing the two common theories of Lift generation ever spend time washing and polishing their aircraft's wings to reduce the drag associated with unevenness of the wing's surface? Reduce drag, improve the L/D ratio.

[Area-51]

Agree... that's why the only important everything answer to remember to explain everything imaginable is the word "electricity"... that should screw the wingnut's brain for a few hours... after the fourth hour the wingnut's memory has reset to zero, and it has an empty brain again...

[Carbon Canary]

10 hours ago, old man emu said:

To be really honest, is there any reason to spend time trying to get an answer to this question? For an aeronautical engineer the question to be answered is how to obtain maximum lift and minimum drag. One can start with a mathematical model, but that only directs you to a design to test. Therefore,  the design of a wing is an empirical process. One doesn't need to know how the desired lift is created, just that the design produces the desired result.

 

Next we have the poor wingnut trying to utilise the aeronautical engineer's design to the best effect. The wingnut doesn't need to know the How of the situation, merely the how  to use the tool the aeronautical engineer has provided. 

 

That said, it creates a great argument for dispensing with all the guff 'n' stuff we are fed about How Lift is produced, and replacing it with study of how to use the tool. We practice how to use the other tools that have been provided for efficient flight, so why not practice using the wing? I wonder how many people who spend ages arguing the two common theories of Lift generation ever spend time washing and polishing their aircraft's wings to reduce the drag associated with unevenness of the wing's surface? Reduce drag, improve the L/D ratio.

Yep ! Just ask a roofer, who’s tried to lay corrugated iron on a windy day. They’ll readily give you a theory of lift, complete with adjectives as coefficients.

[spacesailor]

When a set of plan's , gives you the choice of ' fat or thin ' airfoil rib dimensions,  do you think ,

.I'm fat ( overweight) !.

SO

I' LL HAVE TO BUILD THE FAT ONE !. ( more lift less speed )

OR 

I'm skinny I'll build the FAST one ,  ( more speed less lift ) 

Spare skinny wing ribs for sale.

LoL

spacesailor 

 

Edited May 21, 2023 by spacesailor

[Mike Gearon]

Oshkosh 2023. We had a very interesting chat with Randy Schlitter (designer of the Rans aircraft) Rfguy and Thruster88 on wings and lift.

 

 

[BrendAn]

On 21/05/2023 at 7:28 PM, spacesailor said:

When a set of plan's , gives you the choice of ' fat or thin ' airfoil rib dimensions,  do you think ,

.I'm fat ( overweight) !.

SO

I' LL HAVE TO BUILD THE FAT ONE !. ( more lift less speed )

OR 

I'm skinny I'll build the FAST one ,  ( more speed less lift ) 

Spare skinny wing ribs for sale.

LoL

spacesailor 

 

my doctor said my bmi would be perfect if i was 9ft 6 tall

[flying dog]

Don't you lot think this has gone a bit off topic?

 

[Litespeed]

Back on topic.

 

What keeps aircraft in the air?

 

Tricky but I have seen a lot fly but look very awkward doing it...so it must be ...

 

Ugliness - the earth repels them from disgust.

 

And since I live under the training area for the F-35, it is ugliness, huge sound and billions of your 💰 

Edited July 27, 2023 by Litespeed

[old man emu]

On 27/07/2023 at 10:58 PM, Litespeed said:

What keeps aircraft in the air?

After all the discussions of this topic, especially Bernoulli -v- Newton, and hundreds of person-hours of research by NASA and others, I think that the conclusion reached is "We don't know how, but wings work. Live with it." 

[coljones]

But it is the conspiracy theorists who most stridently defend the indefensible - the difficulty with leaving them unchallenged is that, emboldened, they will come out with more outrageous claims which will be raised to the level of holy writ by their fellow travellers.

[derekliston]

I don’t care what physics proves or what conspiracy theorists or anyone else say, what keeps aeroplanes in the air is money, lots of it!