Copyright © 2009-2010 Eagle Tree Systems, LLC
http://www.eagletreesystems.com
Page 14
IMPORTANT: if your receiver does not support failsafes, and your model has four or more flight controls, additional steps may be needed to use
the the Safety Mode features. Since the OSD Pro will take control of only three controls, the fourth control will be left connected directly to your
receiver. If the receiver loses signal, and does not support failsafe, the fourth control could move randomly or remain in its last position. For example, if
your plane has rudder, aileron, elevator and throttle, and you connect rudder, elevator and throttle to the OSD Pro, the aileron channel, which is connected
directly to the receiver, could move randomly if the receiver loses signal and doesn’t support failsafe. A possible solution to this problem is to purchase a
“servo fail safe unit” which is connected between the fourth receiver channel, and the fourth servo, which will provide failsafe operation if the receiver loses
signal.
For receivers which do maintain the last position of the servos when signal is lost, but with no failsafe positions programmed, Safety Mode is activated when
no servos move for a short period. This setup is not recommended, since Safety Mode will turn on if you don’t move your transmitter sticks for a few
seconds, even if your radio link is good!
For receivers with throttle failsafe programmed, Safety Mode is invoked whenever the throttle channel reaches the receiver’s throttle failsafe position (the
one you program into the receiver per your receiver’s instruction manual) for more than a brief period. To prevent Safety Mode from activating erroneously
during normal flight, make sure your receiver’s throttle failsafe is programmed so that the failsafe position is not encountered in normal flight. One way to
do this is to temporarily set your receiver’s throttle channel for “extended servo travel” or similar, and then program your throttle failsafe to an extreme off
position. Then, return your receiver to normal throttle servo travel, so that the failsafe position of the throttle will still turn the motor off, but cannot be
reached if you move your throttle stick off. The failsafe positions used by your receiver are detected during the Safety Mode Wizard.
For receivers with 3+ failsafes, Safety Mode is invoked whenever all three receiver channels (throttle, aileron/rudder, elevator) reach the failsafe position for
more than a brief period. The failsafe positions used by your receiver are detected during the Safety Mode Wizard. As above, it is recommended that you
adjust your throttle failsafe so that the throttle failsafe position cannot be encountered in normal flight.
Using the Return to Home with Stabilization Systems
The Return to Home feature can be improved significantly if a stabilization system, such as the FMA
TM
Co-pilot
TM
, is utilized. The stabilization system’s
servo inputs would normally be connected to the servo outputs of the OSD Pro. Then, the servos themselves are directly connected to the stabilization
system’s output.
If you are using the FMA
TM
Co-pilot
TM
CPD4
TM
, there are two problems you may encounter. The first problem is that the CPD4
TM
computer apparently
cannot handle receiving two or more servo pulses simultaneously. Futaba
TM
PCM receivers send simultaneous servo pulses, and FMA
TM
requires that you
use a “servo buffer” (which they sell) to slightly delay one of the incoming pulses.
The OSD Pro sends the servo pulses simultaneously by default (just as Futaba
TM
PCM receivers do), which might confuse the Copilot unless the “servo
buffer” hardware is installed on one of the servo connections. If you set the FMA co-pilot w/o servo buffer parameter in the Artificial Horizon
Configuration menu to “Yes”, it causes the OSD Pro to skew the servo pulses in RTH mode. Unfortunately, this causes the voice announcements to
automatically be turned off during RTH mode (including the “signal lost!” announcement that would normally occur when RTH mode is invoked). That’s
the only drawback of setting this option to “Yes.” Note that it is believed that the latest FMA
TM
Co-pilot II
TM
product does not have this shortcoming.
Secondly, another potential problem can occur with the Co-pilot
TM
, if you use a spare receiver channel to control its gain. If you use a spare servo channel to
remotely set the gain, and your receiver loses the signal, one of three things might happen:
a)
If your radio doesn’t send any pulses at all when it loses receiver signal, what happens with the Co-pilot
TM
is unknown. This is true with or
without the OSD Pro connected.
b)
If your radio is PCM and has failsafes, but you have not set the failsafe of the spare channel to something reasonable for the Co-pilot
TM
(or if there
is no failsafe setting available on that channel), stabilization will again be in an unknown state. Again, this is true with or without the OSD Pro
connected.
c)
Even if you have set the failsafe for the spare channel to a reasonable value for the Co-pilot
TM
, a problem can still occur, since the pulses from the
receiver to the copilot are not synchronized with the pulses from the OSD Pro to the Co-pilot
TM
, during RTH mode. The copilot can occasionally
glitch (moving the servos wildly) whenever the servo gain pulse momentarily overlaps with one of the RTH pulses. Again, this is due to the
perceived shortcoming of the CPD4
TM
in receiving two or more servo pulses simultaneously. If, during testing of RTH mode, you observe servo
excursions a few seconds apart, use the manual gain setting for your Co-pilot
TM
.
RTH Testing/Adjustment Procedures
Please follow these guidelines for adjusting the Return to Home feature to your plane.
a)
Initial setup and coarse testing of rudder/aileron control using the simulator (model on the bench with motor disconnected)
1)
With your model’s motor disconnected, and with the model on the bench, Run the Safety Wizard in the Configure Safety Mode menu.
2)
Select “Return to Home” as the desired safety mode in the Configure Safety Mode menu.
3)
Choose Receiver Type in the Configure Safety Mode menu.
4)
Indicate number of failsafe channels supported by your receiver in the Configure Safety Mode menu.
5)
Adjust the Cruise Altitude, Cruise Speed and Altitude Error settings in the Configure Safety Mode menu, as described above.
6)
Set the Turn Derivative Gain and Turn Integral Gain parameters in the Safety Mode Menu to “0”.
7)
Choose “Display Servo Deflections” from the Configure OSD Display menu. This will display the movement of the servos, relative to the “zero”
points established for level flight during the Wizard. These values are displayed both in normal mode, and safety mode.
