You make some very good and succinct points, G-EMMA (Gemma, Emma?). To be honest I don't feel as though it's in my capacity to sufficiently debate either side of this one; Your points are entirely valid, but I also feel that there is a case to be made in purely logical terms for CFD and other associated numerical analyses being viewed as an extension to an understanding of lift generation.
Anyway, more pressingly, this all came to a head from a desire to find a theory of lift which could be related to PPL's. Personally, when I take friends flying, I prefer to relate the theory espoused by our military brethren.
When I advance the throttle and the engine begins to roar, lift pixies are attracted to the noise and flock to the wings. They stick on and up we soar;
Of course we can't pull the nose up too high, or manoeuvre too aggressively, lest they fall off.
And on landing, a touch of the spoilers to give them a gentle nudge off and let us return to the ground;
I've stuck with the thread in a rather cynical certainty that I might actually learn something that would turn on its head all my twenty years of explaining lift somewhat incorrectly.
Now having stayed up all night, ears pricked and eyes wide open, everyone appears to be taking their bat and ball home. Ah! well, its the way it goes. I'll just carry on explaining it all wrong - well why not, it seems to work and I aint heard anything better. Last one out turn out the lights and drop the latch please.
Good night, sleepy heads.
I'm with you - does it REALLY matter how lift is produced as long as we know how to use it?
It doesn't matter if it's Bernoulli, Newton or Basil Brush - more AoA = more lift up until the point when more AoA = less lift. As long as the pilot knows how to recognise, avoid and recover from the dodgy bits of the flight envelope the detailed aerodynamic theory doesn't matter.
This thread has turned into a p1ssing contest - "I can get it higher up the wall than you!".
I've found the old degrees=crosswind/nm per minute really handy of late.
So the other day I was given a diversion, cross wind was 6Kts, at 90Kts (1.5nm/min) I had an easy 9 degree correction angle, which did the trick - flew 279 instead of 270.
Though it took me more than 2 seconds, so your prepped sheet is probably better.
Sorry about the thread creep (though on this thread...).
Some of the commonly given theories are wrong though,
Now you're going to tell me that the lift pixies aren't real either, aren't you? You're a hard one to convince, you know.
I think every explanation of lift to a student should start with an empirical description: this is what happens with a flat plate, this is what happens when you change the AoA, when you introduce camber, when you introduce thickness, when you extend flap... That's a lot more use to the student than trying to explain why the lift is created. The rest can be saved for rainy days on PPRuNe...
I've just reversed engineered the whizzwheel and now have a spread sheet that will generate the sine and cosine waves for drift and GS for any given predicted wind so I can workout the heading to fly for diversions in 2 seconds in the air.
I don't think one needs to use the circular slide rule when airborne. One is not allowed to use electronic calculators in the ground exams or in planning the flight and there is thus an implicit assumption that you will have no option but to use the slide rule, but I don't think you actually have to use one.
What you have to watch is this: the CAA exams have tricks to catch you on common errors and if you get the answer 1 degree out you will fail that question. The multiple choices are rigged to catch this. The fact that not even a £20k autopilot can hold a heading within 1 deg is irrelevant.
The trig for wind calcs is trivial. There are also countless E6B programs around for PDAs. I have one myself, called Flightcalc or something like that.
I do wonder how they solve the turtle paradox aspects, as well as how they manage to stay comfortable while sitting on our vortex generators.
Of course it's a simplification of Shafer's Lift Demons which is unquestionably the truth as far as lift goes. S'pose you're going to say that that proves that lift has only been properly understood since 1994 then...
All will become clear when I write my paper on the extendable stick theorem.
I'll be very interested to read that.
Personally though, I believe that this approaches the problem from totally the wrong direction, and thereby propose the "string theory of flight". In this model, aircraft hang from high strength high tensile monofilament spidy-silk (which is why you can't see it). pitch, role and yaw movements are all based around the movement of the string at the attachment loops on the aircraft, and/or movement of the airframe within the loop. Turbulence is also easily explained by the interference of the string in contact with an external force or body that transmits as vibrations through to the airframe.
It's a monofilament above and a stick below. When the two are in balance you're straight and level.
Trimming shortens or lengthens the monofilament, which we call Lift, but you always pivot on the stick, which is called Gravity.
The stick is obviously connected to the aeroplane at the Centre of Gravity.
In my scientific paper soon to be published, I will draw on this theory to illustrate how nanopixies circulate from the wings to the Gravity and Lift with little parcels of air to keep the whole thing working - they run very fast indeed and have little boots that stick to aeroplanes
If you were using a CFD package to model the laminar flow over a wing how many individual cells (modelled pockets of air effectively) would be needed in order to provide a reasonable calculation?
I'm assuming you can alter the degree of precision by increasing or decreasing the number, would this be correct?
Linear Mode
