- 9/9 -
maneuvers. The tail should not wag in any kind of flight conditions.
2) PID I
The goal of this step is to adjust the parameter PID I. Put your gyro into heading hold mode and
set Debounce CCW = 30, Debounce CW = 0. Increase PID I stepwise. You may have to reduce
gain a bit in order to avoid tail wag (with increasing PID I the acceptable gain tends to get
smaller). Do left and right piro stops. The tail will back bounce. For too low PID I the back
bouncing will be slow, which feels as if the tail is slowly pulled back shortly after the tail has
stopped. For too large PID I the tail will do two or more back bounces. The goal is to adjust PID
I (and gain) such that you get one, quick back bounce. It can be very pronounced, this doesn't
matter. The point is to find an as large as possible PID I while obtaining one fast back bounce.
You may have to play a bit with the gyro gain to find a best result. However, don't overdo, it
doesn't matter much if PID I is 9.5 or 10.
3) Debounce CCW/CW
The goal of this step is to adjust the parameters Debounce CCW and Debounce CW. Start from
Debounce CCW = 30, Debounce CW = 0 (see chapter 5.2). Lower first Debounce CCW in steps
(usually until below 15 nothing is happening). Do CCW piro stops. The tail will back bounce,
but with lower and lower value of Debounce CCW the back bounce should become shorter and
shorter. If Debounce CCW is too small, the tail will start to jump a bit ahead after the stop. Find
the best value for Debounce CCW. Now do CW piro stops. If you find that they need to be
improved, set Debounce CW to the same value as Debounce CCW, and start from there. The tail
may now show some very small wags at each stop. Reduce gain a bit.
4) Pre-Flight Tests
Go flying and adjust your gain until there is no wagging in any flight situation. Usually,
adjustments based on test maneuvers such as piros or pitch pumps lead to slightly too large gain.
Tip #1
: If the gain is adjusted via the transmitter (see chapter 4), the GA250-OW invokes a gain
stabilizer, which is needed to avoid noise and jitter from the gain input channel. However, it
results in a rejection of small gain changes, which can be confusing. It is hence recommended
that whenever the gain is changed in the transmitter to flip forth and back once the gain switch at
the transmitter. This will ensure correct gain setting in any situation.
Tip #2:
Remember my third comment in the introduction: For testing piro stop behavior do
never ever let the rudder stick just go.
Tip #3:
If in step (2) a pronounced asymmetry of the CW and CCW piro stops is observed, then
it may be worthwhile to check the mechanics carefully, and to play with the servo mid position
and servo end points (playing with the servo end points symmetrized the piro stop behavior on
my TRex-type 450). Also, other tail blades sometimes do miracles.
8. Further Resources
The firmware and further information is found on the project web page:
http://www.olliw.eu/2011/ga250-gyro-firmware/
. The excellent "Idiot's Guide to Olliw's GA250
Firmware" by
Holger Banko
is also recommended (available from Holger or
http://www.olliw.eu/uploads/OlliW-FW-Idiots-Guide-1.2.pdf
). Thanks to heroic work by
Mick
Steidl
also the German translations of this and Holger's document are available here
http://www.olliw.eu/uploads/Anleitung-GA250-OW-v016-v120607.pdf
and here
http://www.olliw.eu/uploads/OlliW-Gyro-Bauanleitung-1.4_DE.pdf
, respectively.
Thanks guys!
