B. Understanding Servo Travel vs. Function Travel (Multiple Rates)
What is the relationship between dual rates, exponential, AFR and ATV?
ATV:
ATV, or adjustable travel volume, is each individual servo's end point adjustment. ATV is
specific to each individual servo, so adjusting the ATV to the aileron channel will not, for example,
adjust the servo throw of the second aileron servo if you have flaperon (FPN) set up. ATV is the
“master” control. That is to say, it takes priority over all other items.
Since adjusting ATV will affect
everything else
– including rates, exponentials, and mixes –
it should only be adjusted during initial set-up
to avoid binding
, etc.
ATV/EPA/AST:
ATV is an older terminology for adjustable end points. It has been used to mean a
variety of combinations of adjustability. Futaba now uses the clearer EPA and AST terms. EPA is end
point adjustments, which provides a separate adjustment for each end of the servo. All 9Z ATVs are
EPA type. AST is adjustable servo travel, which is a single adjustment which affects the travel at both
ends of the servo.
AFR:
AFR, or adjustable function rate, is each individual
function’s
end point adjustment, or,
essentially, "primary rate" (or high rate) to go with the “dual rate (D/R)” (or low rate) function of the
radio. This is what the 8U and 6X consider the first switch position in dual rate, which most modelers
use as their high rate.
BUT
, AFR is available on all 8 proportional channels on the 9Z. AFR is active
until the dual rate (D/R) is activated, and it belongs to each
CONTROL
or
AXIS
of the airplane.
Therefore, adjusting AFR for ailerons in a model with flaperons (FPN) will affect the throw of both
servos.
D/R:
D/R, or dual rate, is essentially “secondary rate” (or low rate) to go with the AFR function. This
is what the 8U and 6X consider the second switch position in dual rate, which most modelers use as
their low rate. But, the 9Z offers three dual rate (D/R) circuits which can be used for any of the 8
channels. Find more information on dual rates, triple rates, and condition functionality later in this
chapter.
Why set AFR instead of adjusting ATV? Easy. ATV is your end point for
EVERYTHING
that
SERVO
does....mixes, expos, everything. So if you have low rate, mixes, etc., that you like, but you need a little
more (or less) on high rate, adjusting ATV will mess up all that other work. AFR is your “high rate”,
so adjust
it
to your liking. For an example of when to adjust AFR and not ATV, please see P. 2-11 in the
conditions section on trim effects in various conditions.
How do I set Exponential?
Exponential is set independently for your *high rate* (called AFR) and *low rate* [called dual rate
(D/R)]. So you have to go into AFR, set your high rate how you want it, then go to the NEXT screen
to set exponential. This is your expo setting for when your dual (low) rate is not activated for that
channel. Now if you also want expo on your low rate, then go to dual rate (D/R), set up your low rate
and its switch, and then set an expo here as well.
What does "Limit Mode" mean in the ATV function of my radio?
Normal ATV sets the amount of travel (how far a servo moves) in response to the primary control (ie
throttle stick, switch, knob). Limit Mode ATV (functional only in the World Champion editions) limits
how far that servo will move no matter what is making the servo move.
For example: In normal mode ATV you set your elevator servo’s travel, for example 1" when the
elevator stick is moved full throw. However, a mix/dual rate (D/R)/AFR that is set to, say 110%, will
take the elevator servo to 1.1". Depending on your installation, you may never want it to go past the 1"
2-2