main module is mounted with unusually soft 2-sided tape to keep vibration to
a minimum. For nitro helis a thick steel
plate is included for additional vibration
damping. The GPS sensor is mounted on
the tail boom using the supplied platform
and clamps (clamps are included for all tail
booms from 450- to 800-size). Because the
sensor unit contains a sensitive magnetometer, non-magnetic stainless screws are
included for mounting the bracket. Make
sure no ferrous metal is in the vicinity of
Supplied ribbon cables connect the GPS
sensor to the main module and the main
module to the 3GX unit. Be sure to leave
slack in these cables so no vibration is
transmitted to the main module. That’s all
there is to it; you’re now ready to program
;e APS main module and GPS sensor are compact and light, making the system suitable even for smaller helis.
and follow the steps carefully and in linear
fashion. The complete manual starts with
the setup of the 3GX system. Even for an
existing heli, you must go back through the
3GX setup sequence, as the APS’ throttle
and collective curve requirements are different from a conventional flybarless heli’s.
You should set up flight modes for
Normal and Idle-up. In Normal mode, the
throttle curve should be a straight 0-50-
100, and in Idle-up mode, it should be a
flat line for whatever head speed you want
(I chose 70%). In both flight modes, the
pitch curve must be a straight 0- 50-100.
You should adjust swash travel to get the
recommended eight degrees of cyclic and
negative 12 degrees to 12 degrees of collective travel.
When calibrating elevator and aileron
travel, be certain to push the stick forward
for elevator and to the right for aileron. If
you do this incorrectly, you’ll effectively reverse the APS’ sensors
... with dire consequences.
You must assign a
three-position switch to
control the flight mode
from 3GX to APS to GPS. This can be done
either with the Gyro menu or with Aux2,
depending on your radio. The manual gives
recommended settings for major radio
brands, and the status LEDs will tell you if
it’s switching correctly.
Programming For my test flights I installed the ver- sion 1.1 firmware upgrade. In addition to tweaking the unit to work better with a wider range of radios, V.1.1 adds some nice features like the ability to adjust heading hold gain while in APS mode and “descent deceleration,” a feature that slows the rate of descent the closer the heli gets to the ground. Programming the APS system does require a degree of care and discipline. Pick a time when you’re free of distractions
For accessibility, I installed the main module on a small carbon-fiber
plate so that it extends back from the T-Rex 500’s frame. ;is allows
easy access to the “set” button and visibility for the status LEDs.