Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Page 3 of 3 FirstFirst 123
Results 51 to 72 of 72

  1. #51
    wzak29's Avatar
    Join Date
    Jan 2009
    Location
    lake peekskill, NY
    Posts
    763
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    You guys in here are experts in aerodynamics I am just a beginner I bought my first plane 3 weeks ago a G.P. PT-4-mkII. When I started the plane all I knew were that control services controlled the plane. I decided to buy a kit instead of a ARF or RTF to learn how a plane works you probably don’t remember, but it was hard when they used terms like L.E. T.E. aft. And what was a wing root? is this a plane or a tree. I really freaked out when I noticed my firewall was tilted down I thought I screwed up the plane good but I learned about down thrust. Throughout the build I learned about things like yaw, wing loading, lateral balance, tip stall, C.G. angle of attack Etc…
    Sounds elementary to you guys but it was a lot for a beginner to learn and know I have a lot more to learn and I will. Don’t think all beginners are just air heads that wand to fly a plane like playing a video game.
    Bill
    According to my calculations the problem does not exist

  2. #52
    Sandmann_AU's Avatar
    Join Date
    Mar 2008
    Location
    BrisbaneQLD, AUSTRALIA
    Posts
    648
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    Heya Bill... how's that PT40 going - close to flying it yet? Get that washout problem sorted?

    I don't think anyone here's accusing even the majority of newbies of being airheads (though there is definitely some that think it's just like a video game and want to start with jets etc)... this thread's more about the way RC flight is taught - some instructors teach basic flight principles like wing loading, lift vs drag and so on... others go with "pull up on this stick and the plane will head upwards as long as you've got enough speed" without teaching the "why's" of flight. You'll always get some students that aren't particularly interested in knowing why a symmetrical is better on an aerobatic model and a flat bottomed one on a trainer, but even those students can benefit from some basic theory - the trick is in knowing when to stop teaching before "basic" becomes "advanced and boring" for those uninterested ones. I've found that as soon as one or two pieces of "boring physics" start becoming useful for someone, they get a whole lot more interested in learning more.

    I was very fortunate to have always had an interest in flight and flight physics, had been using flight sims for something like fifteen years before touching an RC radio, and I had friends who were learning to fly full scale planes and were happy to answer my many questions so when the time came to fly my own models it came fairly naturally, but for many people (yourself included till recently by the sound of it) the way planes stayed in the air defying gravity is a complete mystery.

    Anyhow, keep us informed on how your PT40's going - I for one would be happy to see pics of it when you're done and to help with any advice you might need.
    Matt

  3. #53
    wzak29's Avatar
    Join Date
    Jan 2009
    Location
    lake peekskill, NY
    Posts
    763
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    PT-40 going great ready to start covering it using white on top red bottom with alternating red and white stripes, did not mount the Evolution .46NT engine as the manual says will do this last so I can use it to balance the plane. I have some wing washout built in but not as much as recommended It’s been a lot of frustration and fun.
    Bill
    According to my calculations the problem does not exist

  4. #54

    Join Date
    Apr 2003
    Location
    York, UNITED KINGDOM
    Posts
    1,214
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    There is an adage, which I have found to be true. It goes like this; "You fly with your head, not with your hands."

    Every RC pilot has developed a set of intellectual concepts, or rules, which allow him to control his model. Unfortunately, many RC pilots have developed concepts which are flawed. An example is the widespread confusion over the "effects of wind". These concepts generally result from a process of trial-and-error...a stony path to follow...and they are reinforced by flawed information from other pilots.

    You can become a competent pilot without the benefit of a theoretical background, but you are less likely to do so.

    Theory allows the new pilot to develop concepts which are accurate; that is, they represent the real physical world. And theory allows the pilot to develop those concepts more quickly.

    I think that so many flyers attempt to ignore theoretical aspects because they mistakenly believe that theory is unimportant and that the only way to learn a skill is to get "hands on". This approach would work better if we could actually "see" what is happening to our wings and control surfaces. We can't, so we have to deduce the effects of our control movements upon our aeroplanes. Theory provides a set of rules which can be applied to those deductions, and applied with great reliability.

    Maybe.

  5. #55
    Moderator da Rock's Avatar
    Join Date
    Oct 2005
    Location
    Near Pfafftown NC
    Posts
    11,132
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    OK, devil's advocate here...........

    If you believe that aerodynamic theory is beneficial to a pilot, would you be so kind as to expand on that idea. For example, pick a bit of theory and explain how your average pilot would exploit the knowledge to fly better.
    Good flying wit ya today

  6. #56

    Join Date
    Aug 2006
    Location
    Denham Springs, LA
    Posts
    1,175
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    One thing that I see plently with inexperienced and experienced R/C pilots alike is the failure to understand bank angle and it's relationship to G-forces/stalls. Most people don't realize that the increased bank angle results in higher G forces, requiring more lift to maintain altitude. Many people try to just bank and yank when they have a flameout, not realizing that it will usually cause a stall that is very difficult to recover from. With the same angle of attack, the airspeed at which the stall occurs will be increased by the square root of the G force. Airplane pilots would call this an accelerated stall. Of course, proper training on dead-stick procedures could eliminate the need for the student to understand these principles, but in my opinion people learn better when they understand the reason behind doing something rather than just understanding the way things are done. Maybe I'm just the inquisitive type, but I prefer to understand the "why" behind what I do. I hate being told "that's just the way it's done."

    mjfrederick AMA 275874 NSRCA 4134
    Hebert Competition Designs

  7. #57
    dolanosa's Avatar
    Join Date
    Oct 2005
    Location
    geneva, IL
    Posts
    265
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    Here's a simple one, basically using the original poster and many other people who decide to learn by themselves for one reason or another.

    Let's say some guy decides that rc airplanes are fun and he should give it a try. $500 dollars later, he has the plane, radio, and starting equipment. All he knows at this point is how the control surfaces should move is the sticks are pushed or pulled which is basically all they give you in kit or ARF building manuals. After reading the engine manual, he finally is able to start the engine reliably. Butterflies in stomach, he throttles up...and the plane noses over...several times. He finally gets the plane to go straight and pulls on the elevator. The plane goes up nearly vertical. In a panic, he puts the engine to idle. You can guess what happens.

    If he knew just a little bit, like stalls, and MCA, he would be fighting the plane correctly.

    Here's another one for the same people who are building their airplanes...large hinge gaps. You see them at least several times a summer. They decide that it's ok as long as the control surface moves and nothing happened the last 10 times they flew their airplanes. They take off, decide to do a high speed run. You hear a buzz and the plane re-kitss itself in midair sans the box it came in. A little knowledge on airflow would make him at least close that gap.

    And another...beginners who don't understand CG placement will blame the plane for erratic behavior resulting in a crash, "I think it was my batteries died when the plane went vertical."

    Another...non-beginners but semi-noobs with fighter planes suddenly see their planes drop a wing when coming in for a landing. "I grease in my trainer all the time, what happened?" A little knowledge on wing loading.

    Another...powered airplane pilots trying to land a high performance glider. The glider stays at 1 foot above the runway...never landing until it crunches tall grass or something harder at the end of the field. Ground effect, anyone?

    You also get the guy who already knows how to fly and loves to firewall his engine. His planes hold up, thankfully but he doesn't know why his planes' tails move from side to side. He thinks it's a servo but no. He can't fix it so he just says jokingly that his plane is wagging its tail to make it go faster. What could it be, hmmmm?

    You also get the guys who is trying their hand in extreme aerobatics. They have their own signature crazy tumble that they practiced over and over to perfection during the fall and the spring. Summer rolls around and it's hot and humid. All his fair-weather friends want to see him do this incredible maneuver but he can't seem to do it for the life of him? Hasty retreat to the shade, tail between his legs. What happened?

    One more...the designer. We all know one of these lads. These are the guys that never seem to get a break when they design their own airplane. They come to the field with 5 or 7 new airplane designs and one after another, they fly like they hate the air. Some crash, tearing HS-55 servo gears and bending expensive LiPo batteries, sending sheets of tattered blue foam all over the field. Notice that the planes they made that are copies of successful designs actually fly a little better that their own creations? They need to at least understand basic design principles.

    These examples are all real and if you've been doing this for a while, you see this pattern every summer. It's easy to say that they need a tutor to help them fly. What if they don't have one or can't afford another $200 for a video game? This is where learning just the basics of the physics of flight will help immensely after shelling out half a thousand dollars of hard-earned money.
    Regards,

    Butch

  8. #58

    Join Date
    Dec 2002
    Location
    USA
    Posts
    2,035
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    ______and it would seem that we could teach young children what 'hot' is and therefore they could avoid being burned.

    Doesn't work that way.
    The ground reached up and smote my airplane

  9. #59

    Join Date
    Jan 2002
    Location
    San Bernardino Calif
    Posts
    3,757
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    I am not so much involved with actual flying as for making up plans for model aircraft.

    Essentially, got into an argument with a young fellow this weekend. He came up with a whole new design of model that looked like a late model Jet, and was powered by an electric D.F. unit. That's nice.

    Then he mentioned he ran the whole thing through his employer's computer and had it do the testing. Ought to fly excellant he thought. He now wants to go into business in the worst way. Expecting to get rich quick selling this model. He says they can be made for pesnuts, and he then walks away with a huge profit.

    But, my simple question was.... are you going to manufacture "everything" or shop out, source out some parts?

    It looks to me that you got too thin of a wing? A nine percent at the root will not enable the new model A/C to handle commercially available tires. But, but, but, I will make my own then. Then they will be thin enough to fit the wing. How about if I go to foam or wood to let them fit?

    Are you also intending to manufacture your own retractable landing gear units? Normally, they are pretty thick in height, and unless you have a thick wing, they will bulge out the top then. Remember you cannot infringe on anyone's patent if you do this domestically. He was planning on getting them made in China, where they do not have a problem with USA patents....etc.

    Now, this thing is still on the hard drive of some office computer, but he is all ready to hand in a resignation and go into business producing this.

    Tells me he put in the weight of batteries, the D.F. unit and receiver weight and it ought to fly and be fully aerobatic. Is he missing anything other than experience?



    Wm.
    Thousands of Laser Cut parts, thousands
    And plans too

  10. #60
    rmh's Avatar
    Join Date
    Dec 2001
    Location
    , UT
    Posts
    12,597
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    This type of folly is all too common
    Libby is still watching you

  11. #61
    Moderator BMatthews's Avatar
    Join Date
    Oct 2002
    Location
    Chilliwack, BC, CANADA
    Posts
    11,980
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    ORIGINAL: da Rock

    OK, devil's advocate here...........

    If you believe that aerodynamic theory is beneficial to a pilot, would you be so kind as to expand on that idea. For example, pick a bit of theory and explain how your average pilot would exploit the knowledge to fly better.

    For sailplane pilots the idea of adverse yaw to aileron inputs when flying slow seems to be "out there" until they get it explained to them. Even then I think some of them still think it's magical. Same with high speed/high loading stalls and snaps into the ground due to excess line tension coupled with a really wussy or NO throw upward pointed model at launch. Some get it but others just never do.

    When I've taught new pilots I try to toss in such nuggets. But there's no point teaching a Gentle Lady or GP Spirit with polyhedral owner about adverse yaw. It'll just confuse them and it has no pertinence anyhow. But I DO teach them about high loaded stalls and why they need to do an Olympic style javelin throw each and every time at the launch.

    Specific items of need for the moment I totally agree with. But to try to run them through a complete ground school? Even if it's simple and generic it's not needed and I doubt many would get much of it until they've flown a bit and can relate cause to effect more directly.
    Witty saying to be plagarized shortly.....

  12. #62

    Join Date
    Mar 2008
    Location
    Waterford, MI
    Posts
    133
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?


    ORIGINAL: dick Hanson

    From experience:
    AmongThe worst model flyers I ever tried to teach:
    An ex fighter pilot
    A commercial multi jet airline capt
    a civil instructor
    These three guys simply "didn't get it -and said as much.
    Among The best flyers I know
    An ex fighter pilot
    a commercial multi jet airline cap't
    A civil instructor.
    The most astounding and ,adept flyers I know , all started as kids who knew nothing about theory but "got it " INSTANTLY.

    Starting out at 7 years of age as a clarinet student and playing with various bands in high school / college - I sa the same thing .
    Some "got it " with little or no formal training - just ' naturals ".
    An old jazz group gag is the side man who was asked if he read.
    "yup," he replied " but not enough to hurt me".
    Studying aerodynamics before learning to fly models is like giving a dead man an enema.
    It may not help but it can't hurt.

    I can see this thread is getting a little dated. But I have to give my $0.02 on this statement of Dick's. I went thru 9 months of FAA ground-school in a high school program that included over 40 hours of flight time. I received my private pilots license at the age of 17. I completely understand nearly every aeronautic and mechanical theory of flight. Really truely understand and could teach said theory.

    I race 1/10th scale RC off-road and can't hardly make the A mains.
    I know I will never, ever, no matter how hard I try, be doing rolling harriers with my RC airplane. Because I cannot do it.

    I am living breathing proof of Dick's point. Knowledge is not everything. I did, however, trim my first rc plane, make it's first maiden voyage as my first solo, and landed the plane every flight since. I contribute that to knowledge. But, I understand how to do a rolling harrier too. *chuckle*

    That's funny thing about RC. I can and do manuvers in a real vehicles (airplanes, snowmobiles, motorcycles, you name it) that make most people puke, I do manuvers with my RC and feel like puking while standing on level ground.

    Go figure.

  13. #63
    JNorton's Avatar
    Join Date
    Jan 2002
    Location
    Coopersville, MI
    Posts
    4,291
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    I used to be involved in the Lockheed Explorer scouts in the 60's. We had an excellent aerodynamic engineer teach us the basics. He was heavily involved in the AH-56 Cheyenne helicopter. Great times.

    I understand basic aerodynamics though like String Cheese I couldn't do a rolling harrier if my life depended upon it. My hand to eye coordination sucks.

    Did understanding help me learn to fly? Not really what helped most was understanding depth perception and training on Real Flight Version 2. Depth perception so I could figure out where the runway was in relationship to the airplane and real flight to figure out how to fly without crashing. I still had an instructor and soled in two months.

    Just my two cents,
    John
    Have desk ... Will Fly.... Saito Member #467
    Ultimate Brotherhood #11, Ultra Sport Brotherhood #90

  14. #64
    apwachholz's Avatar
    Join Date
    Oct 2007
    Location
    Silver Spring
    Posts
    408
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    Cheers Everyone -

    It's been a month or two since I decided to check in on the status of this thread and I have to say that the responses have been, to put it mildly, very interesting and extremely insightful. It's interesting to see such a variance of interest in the topic of 'understanding flight physics' but more-so what strikes me is the overall tone:

    If it works for you, then stick to what you like.

    After all, isn't what the hobby is all about is individual experimentation and satisfaction? A hobby is meant to bring you enjoyment and give you a chance to 'get away from it all' and meet up with good friends and have good times. And just like personalities, we all share different views on how we achieve our own successes.

    As for myself, I'm still very interested and very intrigued in flight physics and will continue to dive deeper into it as it has helped my skills for flying in so many ways. Currently I'm in 'training' if you will, for my first aerobatic competition and have for my part, found a better understanding of flight physics knowledge to be so helpful in my learning and avoiding situations that, hopefully in the end, will be rewarding in both experience and perhaps a trophy!

    Again, Cheers everyone and happy flying to all!

  15. #65
    P-40 DRIVER's Avatar
    Join Date
    Apr 2005
    Location
    Cedar Park, TX
    Posts
    1,464
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    I know a guy at my club who complains that people are flying RC airplanes with no idea of how they fly. When I asked him some details on how they fly, it was obvious he did not know much about it. All knowledge is relative and if a guy knows enough to do what he wants to do, so be it. Once you get the point that you realize you know nothing, you might actually know something.

  16. #66

    Join Date
    Apr 2003
    Location
    York, UNITED KINGDOM
    Posts
    1,214
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    Every pilot is using a theory as the basis for his flying. There ain't any other way to do it.

    In some cases, that theory is developed with the help of proper instruction and a sound theoretical basis. In other cases, the pilot has developed his own set of concepts and applied these.

    If he's very smart, his "home-made" concepts will accord with accepted aerodynamic theory; or pretty much. So, he'll be a competent, self-taught, pilot.

    If he's not so smart, you'll hear him crying "radio failure" from time-to-time.

    What I'm saying is that no competent pilot ignores the physics of flight. All competent flyers are applying the same set of behavioural rules. They must be, since the physics of flight are constant. It's just that some flyers will have benefited from formal instruction and the rest have done things the "hard way".

  17. #67
    rmh's Avatar
    Join Date
    Dec 2001
    Location
    , UT
    Posts
    12,597
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    And -
    The entire concept is intuitive to some.
    Libby is still watching you

  18. #68

    Join Date
    Apr 2003
    Location
    York, UNITED KINGDOM
    Posts
    1,214
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    I'm struggling to see how such intuition could evolve within humans.

    Since I've been around flying for a good while, and never met an intuitive pilot, I can only conclude that such people are vanishingly uncommon.

    Discuss.

  19. #69
    JNorton's Avatar
    Join Date
    Jan 2002
    Location
    Coopersville, MI
    Posts
    4,291
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    An example - Chuck Yeager. I've been flying since 2001 and only seen 3 pilots that were.
    Have desk ... Will Fly.... Saito Member #467
    Ultimate Brotherhood #11, Ultra Sport Brotherhood #90

  20. #70

    Join Date
    Dec 2002
    Location
    USA
    Posts
    2,035
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    While hardly common it does indeed happen.

    Similar to a person sitting down at the piano, playing with the keys and then simply launching into whatever musical piece came into their heads.

    I witnessed that one with my best friend in grade school. He went on to teach music and composition at the College level with a PhD. I am obviously still amazed at that display.

    In RC I have not seen one quite that dramatic but I have had a student who went from a tentative circling of the field to competent basic flight in one day.


    Regardless of the field of endeavor there are those who are simply 'naturals'.
    Locally we had a five year old who became quite adequate as a 3D pilot. Yeah, I thought it was trash too until I witnessed a performance at a Fly In.
    He was then six!
    Not world class but better than 50% of the field at that time.
    Allow for the "Wow" factor and he was the hit of the meet.

    EDIT ADDITION:
    bogbeagle

    I think "evolve" is the wrong word. 'Gift' seems more adequate to me.
    The ground reached up and smote my airplane

  21. #71
    aeomaster32's Avatar
    Join Date
    Nov 2006
    Location
    Maroochy River, AUSTRALIA
    Posts
    156
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?


    ORIGINAL: apwachholz


    lnewqban / dick Hanson -

    But based on some of your responses to this particular thread, should there even be an Aerodynamics forum for radio control then? If the reason for the forum is, as it states, to "Discuss the physics of flight revolving around the aerodynamics and design of aircraft." why are there arguments defending why you should not need to understand it as an rc pilot? Therefore wouldn't statements against pursuing further knowledge of flight physics be detrimental to your arguments when they are posted within this very Aerodynamics forum?

    I'm not trying to engage, rather, I'm just trying to wrap my head around why there is so much resistance to the idea of how understanding the basics of flight physics would be damaging to any new rc'er...
    I'm with you on this. Ignorance is no help when flying, and I have seen many scratch their heads wondering what happened, and even then have trouble understanding the explanation given them. Here are some myths I have heard floating around the field:

    A Dozen Aeronautical Myths


    Myth 1:
    A model will tend to weather cock into wind during flight.
    Assuming a steady (non gust) wind, the aircraft can do no such thing, short of being anchored to the ground in some way. A fuller explanation follows below at myth 4.

    Myth 2:
    A model will stall if it flies too slow.
    This one can be correct, but not necessarily so. It is not speed that causes a stall, but separation of the airflow from the wing. This means an aircraft can stall at high speed, e.g. a snap roll, or not stall at zero speed, e.g. the top of a hammer head (sometimes called a stall turn despite no separation burble). Think of stalling as an angle of attack (usually around 16 degrees), rather than speed.
    (By the way, a 60 degree level turn increases your stall speed by 41%). It is the higher angle of attack in a turn, that can cause a stall, leading into a low speed snap roll.
    If you lose power, you are unlikely to stall if you get the nose down below level flight. Warning signs to get the nose lower come from having a lot of up elevator applied. It means you are approaching 16 degrees.

    Myth 3:
    The more stable an aircraft, the better it is at aerobatics.
    Quite the opposite. A stable aircraft wants to keep doing what it is designed to do, normally regain level flight if disturbed from it. You don't need this stability fighting you if you are trying to make the aircraft follow your commands. A good trainer should be stable, but few are these days.
    Neutral stability best serves the aerobatic pilot since the machine keeps doing what was last commanded to, with no deviation.
    Unstable aircraft are usually beyond human control, as they increase any deviation input given to them. Too far back a C.G. can make a simple up command turn into an unwanted loop for example. Modern fighter jets are unstable in order to attain rapid response, but need a computer to fly them.


    Myth 4:
    Turns down wind are more dangerous than turns upwind.
    In some ways this is true, but not for the usually given reasons. In a turn downwind, a gust will tend to roll you on your back since the high wing usually presents more under wing area to the gust, than the protected low wing.
    Secondly, that gust also decreases your airspeed if you are going downwind. Generally your increased ground speed downwind makes a prang take place at higher ground speed than turning up wind.
    Thirdly, the increase in ground speed gives the illusion of a higher airspeed, tricking one into slowing the airspeed, perhaps to the stall.

    That said, the aircraft has no way of keeping track of it’s relationship to the earth below it. This is an important point to remember and this enlarges on the explanation on Myth 1. Assuming a non changing wind, once the machine is airborne, the ground relationships cease. It is in a river of air, and the motion of the river over the earth, doesn't affect it's flight characteristics.
    One way to get this clear, is to imagine you are in a free floating balloon watching a model circle around you. The balloon may be doing 100 kph over ground, but you won't fell a breath of wind. Neither will the model circling you, other than it’s own airspeed.
    Only when a machine reemerges from the "river" of air, and touches the shore do we need to worry about the earthly relationship.
    Another example: Imagine you are on a train moving at speed. As you walk in the direction of travel, your speed over the ground is increased by the speed of your walk, and conversely, if you walk to the back of the train, your speed over the ground is reduced. The speed of your walk in the train, is not affected by the speed of the train. If you bump into someone, your momentum is relative to the train, and it doesn’t matter which way you walk.
    Just as you are in the moving train, the aircraft is in the moving air mass. In the example above, the aircraft speed is equivalent to your walk speed, and the air mass (wind speed) is like the train moving over the ground.

    If you want to delve deeper, consider a 180 degree turn in still air. It involves reversing ground speed from say + 100 North to - 100 South, a relative speed change of 200 within the time of turn.
    Now imagine you are flying into a headwind of 100 going North,. Your ground speed is now zero. You now again do a 180 degree turn, in the same time frame. Your final ground speed is 200. Once again, a relative speed change of 200 within the time of turn.
    Notice, the aircraft undergoes the same accelerations within the time of the turn. It make no difference because the wind is blowing. As you turn down wind, it may help you to visualise the wind is helping carry the aircraft down wind and accelerate it over the ground.


    Myth 5:
    The model can make a tighter turn if it slows down.
    Look at our pylon champ for an answer to that one. It again comes down to angle of attack and it is the stalling angle of your machine that determines it's minimum radius turn. You can turn at the minimum radius at more than one speed, but the faster the speed, the more bank is required which in turn means you increase angle of attack. If one stalls at these speeds, a snap roll usually results. The increased angle of attack required in a level turn will slow you down if you don’t add power.

    Myth 6:
    A high wing gives pendulum stability.
    This is misleading, because a pendulum is fixed to a support, whereas the aircraft is not fixed in any way. What happens is that as the aircraft banks, It sideslips towards the low wing, and it is the retarding effect of this relative airflow on the top wing that rights the plane (see myth 7).

    Myth 7:
    Dihedral works because the horizontal lift component of the lower wing is greater than the other.
    Yes, partly but more is involved. Imagine you can slide the model along a wire through it's C.G., and it's not hard to see that while the above effect will slow a rotation, it won't stop it, and certainly won't bring the model upright. Once again, it is the sideslip that increases the lift on the lower wing and levels it. As the wing drops, the model slides in that direction, causing a greater relative angle of attack and lift on the lower wing. The opposite wing has a lesser angle to the relative airflow.

    Myth 8:
    "Dual servo rate should be low for strong winds and high for light winds". (After hearing this, I assume the proponent thinks that strong winds give more airflow over the controls and less control deflection is thus required.)
    If one realizes that an airplanes "wind" is due to it's motion, and not the wind speed (when airborne, remember it is in a river of air), then different rates of throw are not involved with wind speed although they are with airplane speed through the air (relative wind).

    Myth 9: Big vertical stabilizer (fin) means directional stability.
    If we remember that an aircraft will sideslip towards the lower wing in a bank, the relative air stream creates side forces either side of the C.G. These can either yaw the model into the slip or out of it. Too large fin acts like a weather cock during the slip, and tightens the turn. The end result is the nose dropping and a spiral dive. The perfect size fin will balance the area ahead of the C.G., so that the yaw is appropriate for the sideslip involved. Too small a fin will yaw a machine out of the turn.
    It is the rudder effect that turns (yaws) the airplane (else it would crab in a straight line but wouldn't turn), despite the fact you may only use aileron input. The bank causes the machine to sideslip, which brings in the rudder yaw effect.

    Myth 10:

    A model will glide farther if it is light.
    Assuming no wind, the angle of glide relates to the lift and drag of the machine. Without drag you would glide horizontal indefinitely and without lift, you have a vertical descent (don’t we know). The actual glide angle is thus a ratio of these two (Lift to Drag), and not related to weight. Wind has an effect on the angle over the ground, but not through the "river of" air. The heavy model will reach the ground sooner, since it glides at a higher speed, but both will glide the same distance in still air.
    The minimum sink speed of a model is flown slower, near the maximum angle of attack (not the faster best distance speed), since one is more concerned with lift than speed. Here a light model will glide a longer period than a heavy one.

    Myth 11:

    A model will gain the most height in a given time, if we climb it at the best angle of climb.
    There is a difference between angle and rate of climb. The first compares altitude to forward distance and is affected by wind, the second compares altitude to time and is not influenced by wind. Best rate of climb is done faster than best angle of climb.

    Myth 12:

    A headwind will slow a model more than an airliner.
    If we go back to the "river of air" concept, one will find it easier to grasp the picture that everything in the "river" is carried along at the same speed. Hence a ten knot headwind will take 10 knots off the model and airliner speed, equally.
    Now let the arguments begin.
    It\'s better to break ground and head into the wind than to break wind and head into the ground.

  22. #72

    Join Date
    Jun 2003
    Location
    Oakmont, PA
    Posts
    32
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: Loaded Question: Why is it that rc pilots ignore flight physics?

    I thought everybody knew aerodynamics by the time they were old enough to fly. If you are interested in planes, isn't that the first thing you learn? At least by age 10 right? Do kids not make paper airplanes anymore? I am amazed by the lack of practical knowledge in some people, everybody today wants to have instant gratification so they don't build or design first anymore, they just buy an ARF and go to town, trying to learn backwards.


Page 3 of 3 FirstFirst 123

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
All times are GMT -6. The time now is 01:34 PM.

SEO by vBSEO 3.6.1 ©2011, Crawlability, Inc.