אני מפרסם כאן את הטבלה שהכין פיטר גולדשמיט.
הגיונית חכמה ועושה המון סדר באיזון הטיסן.
אני ממליץ ךכולם בלי יוצא מהכלל לקרוא אותה ואז להבין, שאנו מאזנים טיסן...לא מטוס, אלא טיסן.
האיזון הדינמי הוא חלק מאוד חשוב, והוא מתבטא בכמה נושאים...
קיראו והגיבו...
Balance
OK, how do I know the correct CG for my model? If in doubt, read your model’s instructions; that’s
usually a good place to start. For precision flying, forward is better, but… too far forward can be a
problem. I can’t put in writing what is the best feel for each pilot, other than it is a feel thing. I can,
however, give you some symptoms of too far back and too far forward, plus some simple tests I use to
check.
One of my favorite ways to determine the correct CG is spin entries. If, when entering a spin, your
model mushes, and kind of slides into the spin with no real stall visible, you may be too far forward.
Another sign of forward is excessive down elevator needed for inverted flight. This is not always the
reason but is a sign. Rear CG is probably easier to see for most pilots. Some obvious clues are the model
is sensitive in pitch, unpredictable around the stall, or climbs when on an inverted 45° line. Again, CG is
mainly about feel. The important thing is to determine your CG before you work on any other aspect of
trimming your aircraft. I would recommend at least 10 – 15 flights before making the commitment to
where the CG needs to be if it’s a new model.
Dynamic Balance
Ok, we’re happy with our CG. The next trim step is dynamic balance. This is really only relevant with
wing tip weight. Most other axes on a model aircraft are not affected too much by the dynamic effects
of high g loads. But the wings are. Just because they both weigh the same and don’t carry any aileron
trim doesn’t mean you can’t have a wing weight problem. I have seen a myriad of ways to test for wing
weight trim. Loops, pulling to vertical, and so on. My suggestion is to think about the sequencing
argument. If you do loops, or pull to a vertical upline, the engine thrust can have an effect. But we
haven’t trimmed our thrust angles yet, so how do we check this? Think about it, what could you do to
check your wing tip weight in flight that will not be affected by thrust?
Some of you may have figured this out already but what I do is put the model into a vertical dive with
the throttle back (minimum of 3 – 4 seconds) and pull a hard corner at the bottom. No matter where
your wings are in roll, when you pull to level, the wings must be level. Check this concept with your
stick plane. It really doesn’t matter where your wings are. As you pull to horizontal flight your wings
must be level. If you attempt to pull a hard vertical from horizontal, you must be absolutely sure your
wings are perfectly level. I don’t know about you guys but I am not that good!If you go from vertical to
horizontal, not only will the engine thrust have no effect, but your wings can be anywhere as you’re on a
vertical down line.
When you pull the corner, the aircraft may be pointing in a different direction than you planned, but that
is okay, as long as the wings are level. Now I know when some of you try this experiment you will
notice one wing will consistently drop. You may have to add some weight to the opposite wing tip. I
was never really sure if my tip weight was correct until I went to this method. Make sure you only use
elevator through the corner. Perhaps, just for the trimming process, you can increase the aileron stick
tension to ensure that you don’t accidentally input a little aileron with the elevator and the elevators
track correctly when you pull the stick back. Don’t be quick to make a decision!Have patience and
have a friend observe the proceedings. Do many pull outs and make absolutely sure before you move on
to the next step of trimming.
Thrust angles
OK, guys, it’s time to put aside esthetics and get that thrust correct. I sure see a lot of spinners perfectly
lining up to the cowl these days. One of the biggest deterrents to adjusting for the correct thrust angles is
once the plane is built and you make an adjustment, the spinner won’t line up any more. Once again,
when building your model, pay attention to the instructions. Chances are somebody has figured it out
pretty close. I like to test fly the model before I paint the cowl. Once I am happy with thrust, I can make
the appropriate cosmetic changes to complete the model before painting. For all the money you guys
spend traveling and time you spend practicing, do put good model trim ahead of esthetics!
Setting up the correct thrust angles is fairly simple. Well, it’s simple to identify, harder to adjust. Now
that we know our wing tip weight is correct, we should be able to, with confidence, pull to some
accurate vertical up lines. Number one issue with this is making sure your wings are level. Don’t guess.
Be absolutely sure your wings are level before pulling to a vertical. I have seen people add unnecessary
right thrust as they were not level when pulling corners, leaving an inside wing down (normal human
behavior) and the model would lean to the left. What I like to do is to fly directly overhead, into the
wind, where I can clearly see my wings, then pull to a vertical up line. OK, up we go, first 100’ is good,
next 100’ is good, moving through 500’, still tracking well, up over 1000’ now, still straight. If you
working at it, the best you can hope for is around 1000 or so feet – plenty for most figures.
Speed will have a huge affect on your thrust angle on a vertical up line. Entry speed, compared to speed
under load after climbing to 100’, will be as much as 30 – 40mph slower. My goal is to trim as best I
can for the first 1000’. If I go for 2000’ then I typically end up with too much right thrust at the start of
the climb and not enough at the finish. Play the numbers, look at the figures we fly and set your model
up accordingly.
Here’s a great little tip for making the adjustments. Let’s say, after many pull ups you really need more
right thrust. As you pass through 500’ you can clearly see your model drifting to the left. Here is the
haven’t trimmed our thrust angles yet, so how do we check this? Think about it, what could you do to
check your wing tip weight in flight that will not be affected by thrust?
Some of you may have figured this out already but what I do is put the model into a vertical dive with
the throttle back (minimum of 3 – 4 seconds) and pull a hard corner at the bottom. No matter where
your wings are in roll, when you pull to level, the wings must be level. Check this concept with your
stick plane. It really doesn’t matter where your wings are. As you pull to horizontal flight your wings
must be level. If you attempt to pull a hard vertical from horizontal, you must be absolutely sure your
wings are perfectly level. I don’t know about you guys but I am not that good!If you go from vertical to
horizontal, not only will the engine thrust have no effect, but your wings can be anywhere as you’re on a
vertical down line.
When you pull the corner, the aircraft may be pointing in a different direction than you planned, but that
is okay, as long as the wings are level. Now I know when some of you try this experiment you will
notice one wing will consistently drop. You may have to add some weight to the opposite wing tip. I
was never really sure if my tip weight was correct until I went to this method. Make sure you only use
elevator through the corner. Perhaps, just for the trimming process, you can increase the aileron stick
tension to ensure that you don’t accidentally input a little aileron with the elevator and the elevators
track correctly when you pull the stick back. Don’t be quick to make a decision!Have patience and
have a friend observe the proceedings. Do many pull outs and make absolutely sure before you move on
to the next step of trimming.
Thrust angles
OK, guys, it’s time to put aside esthetics and get that thrust correct. I sure see a lot of spinners perfectly
lining up to the cowl these days. One of the biggest deterrents to adjusting for the correct thrust angles is
once the plane is built and you make an adjustment, the spinner won’t line up any more. Once again,
when building your model, pay attention to the instructions. Chances are somebody has figured it out
pretty close. I like to test fly the model before I paint the cowl. Once I am happy with thrust, I can make
the appropriate cosmetic changes to complete the model before painting. For all the money you guys
spend traveling and time you spend practicing, do put good model trim ahead of esthetics!
Setting up the correct thrust angles is fairly simple. Well, it’s simple to identify, harder to adjust. Now
that we know our wing tip weight is correct, we should be able to, with confidence, pull to some
accurate vertical up lines. Number one issue with this is making sure your wings are level. Don’t guess.
Be absolutely sure your wings are level before pulling to a vertical. I have seen people add unnecessary
right thrust as they were not level when pulling corners, leaving an inside wing down (normal human
behavior) and the model would lean to the left. What I like to do is to fly directly overhead, into the
wind, where I can clearly see my wings, then pull to a vertical up line. OK, up we go, first 100’ is good,
next 100’ is good, moving through 500’, still tracking well, up over 1000’ now, still straight. If you
working at it, the best you can hope for is around 1000 or so feet – plenty for most figures.
Speed will have a huge affect on your thrust angle on a vertical up line. Entry speed, compared to speed
under load after climbing to 100’, will be as much as 30 – 40mph slower. My goal is to trim as best I
can for the first 1000’. If I go for 2000’ then I typically end up with too much right thrust at the start of
the climb and not enough at the finish. Play the numbers, look at the figures we fly and set your model
up accordingly.
Here’s a great little tip for making the adjustments. Let’s say, after many pull ups you really need more
right thrust. As you pass through 500’ you can clearly see your model drifting to the left. Here is the
I’ve broken down the Program Mix (P-mix) topic into 2 sections. The first is the downline torque offset
or throttle offset mixing. Second is the traditional rudder elevator/aileron mixing. Most pilots have a
fairly good understanding of the latter, rudder to elevator/aileron, but not many are using throttle offset
mixing. I have seen some, but only in the pitch compensation. Pay attention to what your model is doing
on a down line, or at reduced throttle (idle) in the roll or yaw axis. One of the side benefits of judging
our events is that you see a lot of strange trim situations. I can clearly remember models at the Nationals
rolling on down lines, and yawing off axis causing some strange looking down line rolls. It’s almost
impossible to have perfect trim in roll at all speeds. All you can hope for is to mix in some compensation
to help reduce your workload.
Both the yaw and roll axis, in most cases, have a bigger affect on your model tracking on down lines
than any other situation. Imagine what the effects of a 5° error on every down line would mean. Over the
height of the box you can drift in or out by as much as 150’. The same applies to the roll axis. Ever
noticed how hard it is to get your wings level when approaching a pull corner with little time? With your
model rolling and yawing at different speeds you will never be consistent. It is hard enough to be
absolutely sure if your wings are level, let alone chase an out of trim situation. Good news is that it’s
fairly easy to compensate for.
Throttle to Aileron Mixing
Let’s do the roll axis first. You can do this either of two ways and both work well. In fact, I would
suggest you try both to get the best input. Version 1 is to climb to a high altitude, simulating a typical
top of the box altitude, and fly directly over your head and into the wind. About 50’ - 100’ out from
yourself, push down. Watch carefully to see if the model is rolling on the down line. Most models will
roll slightly to the right as the aileron trim set for full throttle will be too much at low throttle as the
torque effects will be greatly reduced.
Okay, I know many of you fly with no aileron trim. That’s great but I bet you are carrying trim at
reduced throttle. Personally, I have never had a model that hasn’t needed a little left aileron mix on low
throttle. The second way to check for throttle aileron mix is to fly along at level flight, medium height,
and reduce the throttle. Watch carefully and see if your model is rolling; chances are it is. Ever
wondered why you always have to lean a little left aileron entering spins, or why your model always
falls one way? Perhaps it’s because your low power trim is not correct.
Throttle to Rudder Mixing
The second P-mix is the throttle to rudder mix. Again, it’s hard to get your model to track correctly in
the yaw axis at all speeds. Your only hope is to apply a small amount of “left” rudder on low throttle.
To check for this, use the same technique as the throttle to aileron (above). Fly above yourself, directly
into the wind and push down in front of yourself and watch carefully. You will be amazed, especially at
the start of the down line. If you haven’t got any throttle offset to rudder, you are most likely flying
around the problem and where I find it most challenging is in figure 9’s and vertical and horizontal 8’s.
Any time you are using elevator and are off on the yaw axis, it’s a bad day. I can hear all you guys
thinking, yes it’s true, your model perhaps could need a little rudder mix on low throttle. Give it a try
and you will be amazed.
I know of some fairly experienced modelers that use the same theory but reverse where the mix is. They
use little to no right thrust on the engine but have right rudder mixed on full throttle. That works well
too, I’ve been told, but haven’t tried it myself. One thing you may want to experiment with in both these
scenarios is where the mix is activated. For a low throttle left rudder mix, I like to have the stick offset
start at least above half and let it progress from there as you reduce the throttle. It seems to be the best
balance, plus I am not getting a sudden mix input -- it progresses more or less with the speed of the
model. This will vary from model to model but try to keep the mix activation well above an idle setting.
Rudder Aileron Mixing
Earlier I made reference to pilots applying programmable mixes in their trim program. Notice that this
is the last thing you do. Looking through the sequence, each trim adjustment has complemented the next
stage. In most cases, for rudder aileron mix, a linear P-mix is all that is required. What I mean by linear
P-mix is that you don’t need a progressive value to the mix, i.e. less at the start, more at the ends. The
mix will be linear. What causes adverse roll or proverse roll coupled to the rudder is the incorrect
dihedral. Most modern designs, with the exception of biplanes, are real close and only require a small
amount of rudder aileron mix. Some like to put their model on knife-edge, but I like to just do flat turns,
simulating rolling turn inputs.
Rolling turns require more precise mixing than sustained knife-edge flight. In fact, in a contest you don’t
do much flying on your side at all, but you sure do a lot of rolling turns. So, I like to do the flat turn
thing. Doing a simple inside rudder turn to the left, using left rudder, the model should just yaw, with no
roll affect. If the roll rolls to the left, then you need to mix 2-5% right aileron to left rudder. My Cap is
a little unique as it has adverse roll. When I apply left rudder the model rolls right, so I need left aileron
mixed with left rudder. Repeat the process with right rudder. Now what I want you to do is vary the
speed in which you do you flat turns. If you find, as you increase your speed, the mix becomes too
much, you could be getting surface blowback. Sorry to keep harping about this but it is important. With
insufficient rudder power, when you apply a P-mix for roll, or pitch for that matter, the mix value will
become too much as the rudder throw reduces due to aerodynamic pressure. I see a few lights going on
again. Could this be why you have your mix perfect for knife-edge, but you chase your aircraft all over
doing rolling circles?
Rudder elevator mixing
I think about three times in my entire life I had a model that didn’t need rudder elevator compensation.
As with the previous rudder aileron, start by doing a flat turn to the left and see what happens. If your
model pitches down when rudder is applied then mix a small amount of up elevator, or if it pitches up,
apply a small amount of down elevator. In some cases, even without blowback, the mix value will not be
exactly correct for all throttle settings. Don’t panic as with most modern radios suitable for aerobatics
you can use what is called a curve mix. This mix allows you to have multiple points along your mix
curve to increase or decrease your mix value at different rudder inputs. My Cap is a good example of
this. At low rudder throws, I only need 1-2% mix, but as the throw increases I need up to 10%. If I just
have a 10% mix it will be too much at small rudder inputs. The curve mix is designed to solve this
problem.