speedracerntrixie

My Feedback: (29)

Correct, when I see people get into trouble with this one is when they make that downwind turn they try to maintain the same ground speed and not the same airspeed. From our perspective, the model needs to appear flying faster downwind.

I was instructing a guy to fly IMAC once and he was re- trimming his elevator everytime he would go downwind. I asked him about it and said that when he went upwind his airplane was climbing and downwind would dive slightly. During the next flight, I observed he was flying upwind at full throttle and downwind at half. I then flew his airplane and observed it to be nose heavy. We moved his batteries aft and I instructed him to fly both directions at 2/3 power. The trim change dissapeared.

Bozarth

My Feedback: (15)

Then what is your definition of "wind penetration?"

Kurt

speedracerntrixie

My Feedback: (29)

For me the only time where penetration would be a consideration is in the case of a sailplane flying at a slope or F3B where one has to fly a distance task and speed task. It is common to ballast up to convert potential energy ( weight ) into kinetic energy ( speed ). Wouldn't really apply to a motorized airplane .

hugger-4641

My Feedback: (6)

I actually disagree to a point. It's true that in a steady state wind, the plane doesn't care if you go upwind or downwind as long as you are not concerned about your ground track. In this case, given the same inputs, there's no difference other than percieved groundspeed. But if you are trying to follow a fixed pattern over the ground, as you must at some fields including some I fly at, then the argument changes. I engaged in this same argument in a thread devoted to the downwind "myth". I finally got things clear in my head as to what happens, but I never convinced some of them that flying a model over a fixed path on the ground is not the same as making an elongated turn in a full scale plane.

speedracerntrixie

My Feedback: (29)

OK Jerry, I'm listening. Can you elaborate for us?

hugger-4641

My Feedback: (6)

Ok, here's my best explanation of the confusion. When it gets down to it, the argument is really over two different events, two different perceptions, and two different cause and effect relation ships resulting from the same laws of physics. If you are flying either a model or full scale in heavy wind, and you are only concerned about airspeed, you can give the exact same inputs and the plane will turn just fine. However, the track over the ground will be elongated when making a downwind turn compared to what it would be making an upwind turn, or the same turn in calm conditions. Who cares in a full scale plane where you are not concerned about ground track? But maybe you are concerned about your heading, so if you are concerned about what your heading is going to be when you exit a downwind turn, you start the turn earlier to accomplish your goal.

The argument comes in when you try to apply this procedure to crop dusting or flying a model over a fixed pattern on the ground. For example, my club field has a row of trees beyond the runway, so unless I fly above tree level, I have to fly the pattern inside a box created by the trees. This box is about 800' x 250'. So if I want to fly below tree level, I have to follow a fairly fixed pattern over the ground and still complete my turns inside this box. In this case, I am mainly concerned about ground track, but I must also be concerned about airspeed. So if I try to use the exact same inputs for a downwind turn as I did for an upwind turn, I would find my craft heading into the trees. If I make the correct aileron/rudder inputs to prevent this, I will start losing altitude when I turn downwind. Take the next natural step and start giving "up elevator" input and I could crash if I did not have enough airspeed. To prevent this I must compensate with added throttle to make sure I keep enough airspeed or else I needed to have allowed enough altitude to accomodate the loss while airspeed is regained. The airplane did not loose airspeed because the wind changed or the laws of aerodymamics changed, it happened because I changed control inputs to accomodate the ground track I needed to follow. Call it a difference in perception if you want, but it is no "myth" that this happens to inexperienced pilots.

rgburrill

More power with an incompletely trained pilot (I hope this is PC enough) and get the aircraft to the ground much faster and with more destructive power.

Note: been there, done that, destroyed a $200 Saito because I forgot to throttle back in a nose dive.

speedracerntrixie

My Feedback: (29)

Ok Jerry, I think I understand where you are coming from. I have noticed when I am flying pylon that the upwind to downwind turns require less elevator then the opposite so I get where you are coming from about track. I still somewhat disagree about the downwind stall, the way you described it. To me it seems that the additional control imputs causes the stall and that happens wind or not.

Bundubasher

[quote]ORIGINAL: BMatthews

3. There is no skyhook that you can hook a plane onto tokeep it in the air..

If only....

Hey, it is probably not what you thought it was... see pics...(airships somewhere around 1929)



Here is a couple of more true/untrue myths...

13. "V tails" have less lateral stability than normal configuration "upside down T tail" planes.


14. "V tails" stalls easier than normal configuration "upside down T tail" planes.


15. "T tail" tailplanes stalls at lower speeds than normal configuration "upside down T tail" planes.


16. All flying tailplanes (such as on a Cherokee 140) are more efficient than normal configuration "upside down T tail" planes.


17. The dustbin nose shape of radial engined powered planescause air to dam up as not all the air can pass through the cowl, thus dam up and flow in turbulent flow over the fuselage at high speed...

18. While on topic of dust bin noses - air that is forced into the cowl during flight creates a higher pressure in the cowl and air is "jetted" out through the ventilation gills/holes, causing a force that could affect the handling of the aircraft...

19. Tree trunks are not aerodynamically shaped and thus cannot fly..

What says thee about these myths?

Cheers

Bundu

rctech2k7

My Feedback: (1)

These statements are correct. Weight makes the energy, momentum and inertia of an aircraft higher. However high wing loading aircraft are challenging especially those with lower power to weight ratio, by making them more stable will reduce work load of the pilot therefore becomes easier. My addition to this is to make the aircraft more aerodynamics and highly efficient by reducing drag coefficient, also equipped with retractable speed brakes.

Load distribution on rectangular wing aircraft creates higher stress and moments at the wing root. In ideal airplane it is difficult to make wing chord constant all throughout the span.

Most high wind comes with gust, aircraft with higher stability, energy, momentum and inertia has bigger capability to overcome change in surroundings. These aircraft performs better in most weather condition.

jeffEE

My Feedback: (5)

Bigger flies better.

And if a plane is in level flight and flies with its tail down is tail heavy, are all cubs and B-52's nose heavy?

GerKonig

Not only bigger flies better. Also: Much bigger flies much better...

Gerry

acdii

True, surprisingly enough my Apprentice flies pretty stable in gusty cross winds of up to 15 MPH with very small corrections. Ispent a lot of time trimming it, balancing it, and squaring it. It weighs in at only about 4 pounds tops. OTOH my T-34 is 6 pounds and a little more squirrly in the same wind conditions.

BullardRM

My Feedback: (39)

A shorter left wing will make left turns easier and quicker.

Frank Ts Stuff

My Feedback: (130)

I'm here to disprove a few busted myths (that's a double negative)!

These are TRUEisms:
1. Planes with heavier wing loadings do fly better in the wind. Refer to Master Modeller Dave Platt's laws "big planes fly, small models flit" http://www.daveplattmodels.com/
2. Given enough power, any airfoil will fly. My UMX Beast flys excellent and the wings are made from 1/16 (or so) flat foam!
3. A shorter left wing will turn left faster. Well, kinda sort of... Look at the MAcchi 200/202/205 Italian WWII fighter series. Designed on purpose with a shorter right wing to compensate for torque!
4. Turning downwind downwind is no different than turning upwind. Ask any dead pilot who got too slow in a downwind turn what they think of that statement...

-Sean

hugger-4641

My Feedback: (6)

You are correct. As I pointed out near the end of my prior post, the control inputs are what caused the stall, not the wind. If there were no wind, the control inputs would be the same, no problem, and no argument there. Even in the wind, if we weren't concerned about ground track, there would be no need for those control inputs to be different. My point of contention is that it is deceitful to tell a student pilot that there is no difference between an upwind turn and a downwind turn. He will find out the hard way that there is a difference when you are concerned about ground track, and most model airplane flying does indeed require some concern for gound track.

jquid

Maybe with a Moo-ki engine up front? I know, I know Udderly impossible to attach.

Bundubasher

That would depends on whichdirection the prop is turning - some are going clock wise, some goes anti clock wise.




Here is is myth to be proved/busted:

20. Politicians makes good aircraft designers because they understand the concepts of deflecting air very well....

Cheers

Bundu

MTK

Hmmm...

Was talking with Bob Hunt recently about light versus heavy CL aerobats. Bob stated in no uncertain terms that he builds to a weight due to feel. His super light planes simply can't handle wind as well as his slightly heavier models. 'Cept, CL is a whole 'nother way of flying aerobatx that really doesn't apply to "free" flying planes

BMatthews

Models flown in judged events also need to deal with appearance of the model's flight to the judges. In any outdoor event this means some days will be calm and some windy and choppy. To impress the judges this means that a design is needed that will smoothen out the choppiness of the air on the bad days. But you don't want it so heavy that it affects the calm days to a high degree. But if one could have models for each conditions range then there's no doubt that a calm weather model would want to be built very lightly.... Well.... at least "maybe". The problem is that what the judges like to see and what the rule books call for are often somewhat different.


An example of this. Many years back a CL stunt guy measured the radius of the square corners of the then popular and winning stunt designs. Seems they were all turning with something like a 10 to 12 foot radius corner at best in the square maneuvers. The rule book called for a 4 foot radius as "ideal" from a scoring standpoint. He created a model of superb lightness and advanced design that would actually do this. I believe it was called the "Humbug". Or it may have been another one. There was the Humbug and there was another which was stupid big and stupid lightly built using sliced ribs and jap tissue with clear dope to achieve something like a 32 oz model on 60 foot lines. In any event this whole story was published in American Modeller as I recall.

He measued the radius of the turns of his new world beater and got the model so light and so big that he was actually able to do an honest 4 foot radius corner. He went off to the next contest to prove his point. Seems the model didn't do well. The super tight corners were just too jarring to the judges' perceptions and too far from what their experience base.

This same sort of impression judging showed up in RC pattern to a big extent around the time of the change over from the old style "way out there fast and big" to the closer in "turnaround" style. Our own rmh was there during this time and likely he can add something to all this. Dick?

So sometimes what is technically better isn't always what wins.

speedracerntrixie

My Feedback: (29)

Great post BMatt. That is pretty much wat I wanted to put out there in response to Hugger but you beat me to it. Being judged adds a whole new level to ones flying. If I could take one guy and show him flying a strait line with a turn around manuver at each end with an airplane he felt was well set up and then show him after some tuning and coaching, most would be amazed by the difference.

MTK

I would argue that too.... Having flown and judged at the highest levels of pattern for going on 35 years now I can say with certainty that we have come a long way from full imprssionist judging of yesterday. However, we have not nor will we ever eliminate it no matter how much we try to legislate downgrading.

What Robin was saying was that light versus heavy is not as much a technical conundrum as much as it is a Physics and reality variable. He is skilled enough to build models supremely lightly. But they do no good at the top of his hemisphere where his lines will go slack if the model doesn't have enough momentum at the speed he wants to fly. That requires mass to achieve if the speed is constant. Throw in wind as a variable and there you go

We don't have that problem in Pattern. Weight hurts us in every practical way

rmh

The closer in turnaround -strangely -never happened
I designed planes for it thinking it would be the future approach
Nope - the present F3A is flown at distances exceeding the previous ones. However the indoor pattern -restricted by building size IS flown by the extremely ght but very accurate electric powered models flown at a walking pace
evolution at work
no heavy wire lines (CL) no wind
produced a different cat -
Darwin was spot on

MTK

I don't think I totally agree about where models are flown (current F3A models). These can be flown pretty close in. We have specific downgrades for flying past 175 meters. We also have side limits which have their own downgrades when violated. Pattern's footprint is not any larger than it ever was even when we flew "smallish" 60 sized models in pre-TA. I'd qualify it by saying that the small models of yesterday were too small to see easily at 175 meters so maybe distance out was slightly less then, but not the footprint

Throw in current SOA electric power and one can really fly about as slow as the wing loading will permit. The key thing about electric power is the large prop disc it enables. The thrust is there at slower speed. To achieve the same with wet power, one has to use pretty large engines, larger than what's currently available on the shelf. It's a technical challenge, one I really appreciate

rmh

We occasionally fly with electric powered FAI flyers
Jesky and Pierce -fly HUGE patterns and I was told that was what the World championship contest wanted to see.
I flew 40% IMAC models and was Line Chief at last TOC-
Those sequences were unbelievably large .
Close in is possible with current models No question - but the preferred distances are waaay out there.
I simply can't see well enough to fly out there -
e