lighten up and enjoy this thread, I think it has been fun and educational. Yes it is relevant,, you just cleared up the drag
point. If you add power to counter turn drag, then reduce coming out, all you have left is the wind direction change.
I can't wait to get out and play in the PPC. (next spring).
Tim

The first mention of Doolittle here was probably putting words in his mouth, as he I think was referring to pilots not being able to 'feel' their aircrafts attitude which was the reason he pushed for more instrumentation and training w/ instruments.  If he were here now he'd be warning some of you to pay attention to the wind in your high drag machines especially.  I mean well but let's face it:  trolls beget trolls.  Though I personally like Doolittle for a life committed to aviation advancements, when Alec Baldwin played him in "Pearl Harbor" it was a tough pill to swallow because Alec Baldwin usually plays slimy bad guys... too well I might add.  Now I am going of on a tangent, but you get the drift, your war hero is on my and my airplanes side.

Again, guys, leave it alone.

Maybe he will go away.

Seriously, explain to me this scenario:
.40 size trainer flying into the wind and you pull up, with all that available airflow it loops easily. ok.
Now fly with the wind in say 20mph, pull up for a loop, notice how the plane has trouble, slows down and has troubles at the top of the loop, on occasion not even making it to inverted but hanging on the prop and then nosing forward either with the wind or towards gravity.  The issues at play again are drag and the airplanes non symmetrical design comparing front to back and how the machine behaves when the wind hits it from either the front or back.  The described situation plays out in slope soarers often too as I recall. 

Fully asked and answered earlier in this thread

I have never seen that in any of my aircraft, my .40 size trainer and slope soarers included. If it can pull a loop it can do it any direction, each time-every time.

There's no way to refute real world observations.  I realize too that I'm using a very specific type craft in certain manoevers.  Maybe what I'm explaining is 'an exception'.  But I see no reason to back down.  I'm already a pony, someone just needs get off their highhorse.

To replicate what i'm describing either power down or fly in more wind. I've seen the machines do this over a hundred times.

So you are saying that even though highly trained scientists in the field of aerodynamics say something is true, after decades of research and trial and error, you know better because you "seen it with my own eyes." Wow I want my taxes back. NASA has been wasting my money for years.

His planes are made by Harry Potter.

Your sig.- The three most useless things to a pilot, the sky above you, the runway behind you, and the fuel on the ground. ...how 'bout "air in the fuel tank"?

Yes there are a number of others that could be added. I just think those three cover it nicely

Pretty simple really.

You expect your downwind loop to "look" the same as your upwind loop with the same control inputs. It can't! If it does, then you are making corrections and the inputs arent really the same are they? The mass of air it is flying within is moving, so by default it can't look the same with the same control inputs. By trying to make it look the same, you are flying it differently upwind than downwind. Your .40 size trainer sees EXACTLY the same airspeed no matter what the wind is doing. YOU see a difference, but the plane doesn't.

It's all about your perspective from the ground, the way the plane "looks". If there were a way to program your control inputs for a loop with the flip of the switch, you could easily see this by simply flying one loop upwind and one down. The loops would look quite different in shape to you on the ground, but the plane (or a person in the plane) would see/feel exactly the same. The plane doesn't care about wind, YOU do on the ground by trying to make it look the same!

Many folks here are confusing what the airplane sees (IAS) and what you see (GS). These folks just wont get it no matter what.

Well, I think you're applying aerodynamic principles in an oversimplified manner or worse yet in an out of context manner, the same way Jehova's Witness's quote out of the bible.  If we can ignore drag, slippage, aircraft front to aft asymmetry, and skin slipperiness in an aircrafts design and performance it's like saying a 10-6 propeller advances 6" with every revolution - not only it doesn't advance 6" but the speed and efficiency and actual advance are effected by numerous variables.  While to real pilots of FS I bet we're splitting hairs of things that don't matter much, in our academic discussion these things matter greatly.  In summary, 2-3 equations have been applied to a 5-6 equation problem, you have an ok applied result but an absolute failure to prove the original premise.

I appreciate that some persons arguments were based on ground-reference to the pilot and agree that those arguments don't prove or disprove anything of the original premise as that's another subject entirely.

 

Then, if I may say so, you and sicklick give me the impression, maybe wrong and if so I apologise, , that you have little understanding of translational lift, (variation of lift as a function of airspeed across the disc which is why a heli needs most power in the hover on a calm day) ) retreating blade stall and the control and stability of helicopters. If there is ONE type of machine that I believe (and know from experience albeit many years ago) needs VERY careful handling when turning downwind, then a low powered helicopter at low speed near the ground is IT. A myth in these circumstances? I am not sure it is.

If you really want to learn about energy management in any flying machine then you can do little, no, better than try operating a low powered helicopter on a hot day ! Come to think of it almost any helicopter can be challenging at low speeds and near its performance limits.

Regards,

David.

How does the plane know whether it is traveling upwind or downwind if the IAS is the same? Hint" It doesn't! This is the part that is not debateable. It baffles me you can't grasp this simple fact. Please, provide ONE, just ONE verifiable peice of data to back up your claim of otherwise.

You can't because you are too closed mnided to accept the fact that your eyes are lying to you. Everyone knows that a 10-6 propellor doesn't advance 6" with every revolution, but you seem to think it depends on the direction of the wind.

HOLY BAT-LOOPS! So many phd's in aeronautical engineering, over 5000hrs in full scale with half of that being in stunts. Why don't you just go fly your planes, have fun, entertain the family with a crash or two, have some chicken, then go home and watch the ball game! OR, you could round up the young and old that would like to get into the hobby and teach them to fly and have fun WITHOUT the big loops of such non-sense as this! Now, you all could join the TSA and try to figure out how to be in touch with people without being in touch with people!

I thot I was done for the night, but i can't leave this one alone.

I'm going to shock everyone, not the least of which will be P51Dpony, and cover his back for one observation.

What u are seeing there in the highlighted scenario, Pony, is this:

In an effort to make a VISUALLY (as opposed to aerodynamically) round loop you are forced to spend much longer in the 2nd quarter of the loop as you fight a headwind , and during that time the under-powered 40 sized trainer's energy is played out, to the extent that it "flops out" before it can recoup some energy in the 3rd quarter. And yes, the flat-bottom trainer wing which flies so ineffeciently inverted is a major factor. U would see the very same flop if in a zero wind condition you flew a very ugly out of round loop that spent the same protacted time in the second quarter and "leaned" well into the 3rd quarter. The protracted AERODYNAMIC flight path of the 2nd quarter in the case you mentioned is where your energy is being spent to exhaustion.

What you are NOT witnessing, however, is the headwind or tailwind affecting the airspeed of the airplane...which is the subject of this thread.

A 10x6 prop travels exactly one inch, no more no less, on earth as well as Mars. It ia called pitch and has nothing to do with air, mass, density or whatever factor you want to pitch in. It has nothing to do with Fluid Mechanics either. It is just a simple measurement of angle, similar to threads on a bolt. Or did you think a model with a 4-40 bolt instead of a prop would travel 4" every 40 revolutions?

Screw Jetcat I want a 4-40 bolt on my Bandit!

And furthermore, yes it would travel 1" if it was incompressible fluid. ;-)

The problem here is the laws of relativity. F=MA on earth and F=MA from a fixed point, and F=MA relative to the windis not the same. We are always moving on spaceship earth. The Sun is pulling us in, but we are circling around the sun to cancel out the pull of gravity, we are pulled toward the earth, and the earth is rotating trying to sling us back out to space. To say that the turn is causing acceleration relative to the earth is not a valid point, because the plane is flying relative to the air. The acceleration of the turn is affecting the stall speed in the positive G in the turn, but has no effect in the down wind turn. It is like saying we are accelerating faster when we run to the west than we do to the east. But we do not feela differance in G force because we are moving relative to the earths surface.

Ever hear of slip? A prop does not travel its distance measured in pitch, but something less. More drag is more slip, thinner air is more slip.

You are desciribing the apparent ground speed not the airspeed of the plane. The plane is simply slowing relative to the ground and you are interpreting that as being at or near a stall. It is actually not having any more trouble, if handle the controls the same the result will be an egg shaped loop instead of a round loop. If there is any trouble it would be when flying into the wind and you back off the trottle at the top to slow it down so that the loop is rounder. Because you slowed it down you may enter an inverted stall and spin.

Ah, great stuff for a new guy looking for explanations.  Between highhorse and rcjets63 I have my explanation of why we takeoff into a headwind.  It very logically reduces the take-off roll and the amount of runway needed.  It is not that you can't or you will lose control on a downwind, but a longer roll, perhaps substantially longer, will be required to get to the proper airspeed for take-off. 

While some of this stuff can stray off on tangents it is very useful to new guys (this one in particular) who are not full scale pilots and are really looking for explantions of the dynamics of flight to become a better pilot.  And if you don't know why something works or doesn't work you have a much harder time properly managing the effects.

Your best bet is to get a good book on flying such as "stick and rudder." If there is anything you need help with after that get with an experienced flyer. Even some of the "experienced" flyers don't have a good understanding of aerodynamics as seen here. If they are contradicting the textbooks then I would be wary of their "experience." Years of doing it wrong is still experience, just bad experience.

p51Dpony, rjbob, Tim (parachute example) make my point better than I did.....and true, perhaps folks in the a/c do not detect minor accelerations(maneuvers), though they would if abrupt enough (my 100-200mph, for example, and much less extreme ones).

All posited frames of reference 'making a difference' are moot...they cancel out, so long as there is constant speed or such minor accelerations as to be unnecessary to consider (earth/sun/universe). Comes down to the simplest frame of ref that has meaning and where there are actual/significant speed changes: a mass in the air that changes direction. Our model. And if that mass changes direction or speed, then there is an effect on it.....whether being observed form the ground or aboard. And so it will slow, or speed up, drop or rise, as conditions change (going from UW to DW, etc.), unless actively compensated for.

Recall: the original issue here is the effect on the mass (a/c) of a maneuver...not necessarily what folks observe...though it's certainly observable. You (the wind or prop/turbine thrust) simply cannot bring that mass back up to the same AS instantly, there is a lag, and that lag can produce (for one) the effects of 'the dreaded DW turn'. Sorry, but again (in our classical conditions, anyway), F does equal Ma.

Mike, I meant to answer earlier: I'm a retired mechanical engineer, though that's hardly a credential here. Commonsense and an open mind suffices. The aero phds/books are not wrong...but most often they are speaking of specific cases/conditions, eliminating variables/difficult quantities in order to clarify/solve an aero problem, etc.

Really.....just go out and observe it. Turn fast from UW to DW, esp w/ a heavy highly WLed model. Do nothing but get it to turn...and watch it drop. POV does not matter (someone said correctly inertia is a property of the object/the a/c). It will drop because it has to, as it has lost AS.

Ray

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You are incorrect.

The pitch number on a propeller is NOT an indication of blade angle. It is a measurement, in inches, of how far the the propeller will travel forward in one revolution if the propeller is 100% efficient. Both numbers describing a propeller size are in inches...not degrees. In other words, a 10-6 propeller is 10 inches in diameter and will travel 6 inches forward per revolution.

Since, as pointed out in an earlier post, there are many variables to consider, the pitch is used as an approximate value. A highly efficient propeller, such as an APC, will come pretty close, however.

BTW...Where did you get that "one inch...no more, no less" measurement from?