So comparing a Boeing with a 60 metre wingspan to fit in the usual hangar, with an Eta glider, having a wingspan of 30.9 meters from wingtip to wingtip, the Boeing is not that much bigger, just a lot heavier!

before I had operated into Vargar Fareo's I thought I had experienced moderate turbulence........

After VArgar I realised I had only experienced light chop.

I can't help suspect that has a lot more to do with the quality of the simulator than it does with the perception of the pilots, in the particular instance.

G

You got me curious there, but I could not find such a place on any map... Must be a very exotic and/or elusive destination!

****e spelling which auto correct doesn't pick up

have a look at the brief

https://aim.naviair.dk/media/files/h..._2_EKVG_en.pdf

If you take the full range of aircraft to include model aircraft, then I can say that the smaller they are, the more wind gusts can disturb them, especially in bank angle.


The smallest airplane I have ever flown weighs just about one ounce, think of it in terms of a paper bag with a very thin carbon fibre framework. It is impossible to fly this model in any wind over 3 knots. Even when flying indoors, if someone opens a door the draft will cause it to quickly roll over.


So I suppose the Moment of Inertia is the proportional factor that you are looking for, and this increases with Mass and aircraft size.
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its wing loading and speed

lift varies with the square of speed and directly with the coefficient of lift.

low speed and low low Cl then not much increase or drop in force.

Loads of both and its a huge change in lift.

@tescoapp: thanks, I had a kind of suspicion there...
None like the Brits, though, for mangling up nouns proper! :)

Truthfully it doesn’t take a pilot to understand a little plane experiences “bumps” differently then a big airplane....
:}

I once considered that the air surrounding a model aircraft was effectively more dense than the air around a full size aircraft, I did say "effectively" not actually.
The analogy of the model ship looking as though it is sailing in thick oil rather than throwing up fine spray.
The big aircraft must fly faster to maintain lift.
The wing loading (area--weight) doesn't consider relative (effective) air density, the density is considered constant.
Maybe I'm all wrong, the instructor I mentioned it to told me to bugger off!

What about the scale of the air movement?
Alternating lift and sink, repeated, (wave?) when flying a Pa28, would possibly appear as turbulence in something with more inertia and much more speed?
What throws a Jodel about would cancel out over the wingspan of an airliner?

your getting into none dimensional numbers which are used for making comparative models Crash one.

The number in aviation is the Reynolds number.

And the one for boats is called the froude number.

Unless your instructor was an Engineer of some form they won't have a clue.

or maybe they were and they thought you were about to launch into a discussion about Navier-Stokes equations.

I have heard of the Reynolds number but no one has explained how to apply it.
So building a model just by scaling it down isn't going to work.
Anyway how can you scale the density of air? Depressurise the test flight building?

For a model to be comparable you need to match the Re number density is a bit difficult to change but I suppose you could heat/cool the fluid. Also change the pressure in a closed system.

They tend to change the velocity of the fluid.

For wind tunnel stuff you need to match the Euler number as well.

That is exactly what we used to do when I worked in high speed wind tunnel testing back in the early 90s. It was a very slow and expensive process.

The use of non-dimensional variables exists throughout engineering analysis, and there are all sorts of variables in various applications. The two most pilots are likely to familiar with are Cl and Cd; Reynolds Number is another, mainly used for matching wind tunnel results to full scale flight results - particularly the Cl.v.AoA and Cd.o.v.AoA curves are likely to be a function of Re, although don't change much (usually) within an order of magnitude change. Two orders, and it starts to become quite important.

The formulae for gust response are a function of lift curve slope and wing loading. Lift curve slope in turn is a function of Reynolds Number (and Mach Number, another nondimensional variable of-course).

G

See BBC website for this video:

"Plane tries to land in Austria storm... takes off again"

Just shows that even the big ones can have trouble landing in turbulence!

PS If there was any power to kill at the actual touchdown, it might have worked out but going around and back to Frankfurt was almost definitely the right decision.

To muddy the waters, there's the squared and cubed scale factor.

Thus a half scale a/c has 1/2 length, span etc., but only 1/4 the area and 1/8 the mass.

In practical terms e.g. a 2/3 "Spitfire" replica has 4/9 (44%) wing area but merely 8/27 (30%) the weight of the real thing, all other things being equal.

Different construction materials, and a full size 1:1 space for the P1 make more differences when comparing "the same" shape with the original a/c.

mike hallam

Thank you Gengis.
I'm no mathematician, so much of it is going over my head.
Asking a gliding instructor once for the formula to calculate lift, he said "Half Ro V squared". Yes all very well, what units? Pounds? Kilogrammes? Miles per hour? Feet per minute? Not very helpful. It took me a while to guess at the speed of light?
No wonder my car doesn't fly like bird at 60!

Hi Guys, I think we need to consider the two different types of turbulence...

The first type is lift related, and is the type that makes you bump your head on the cabin ceiling. That can be explained by how much more Cl you have left before the wings stall, or the speed of the downdraught.

The other type of turbulence is caused by the rotor effect of say, flying into your own wake turbulence when doing tight turns with the wings already near their stall speed. This can soon turn you upside down and spit you out of your radiused turn. These rotors can also occur behind very large airfield buildings, and behind mountain ranges. I am just thinking that an airplane with full tip-tanks would be less susceptible to this type of turbulence than the same aircraft with the fuel in its inboard tanks. It all depends upon the distribution of Mass, and it's distance from the centre of gravity.
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Hi Crash One, If you use the same units in the lift equations you will get the correct answer (use all metric, or all imperial.)
There is a simpler way of finding out the lift. As an example... K8 Glider Lift=350Kgs, Cessna 172 Lift=1050Kgs, Airbus =60,000Kgs.... It is simply equal to the aircraft's weight, in level flight. You can also work out the drag force easily... K8 glider has a 35:1 L/D. Therefore Drag = 10Kgs.

As for your car not flying at 60mph. It would if it drove off a cliff. hi hi.
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That's not flying- it's gliding very badly!


Not much affected by turbulence though....