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Assan GA-250, Quick Start Manual, Page: 9 / 9

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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!

 

Summary of Contents for GA-250

Page 1: ...t a fundamental level seems to be different from what is used in commercial gyros Many things of course do hold for any gyro also the GA250 OW and your previous knowledge on gyros is not worthless A second important comment is that this is NOT a tutorial on gyros per se There are many excellent writings and videos on the net and it is assumed that the gyro basics are understood by the reader This ...

Page 2: ...tup parameters are Gyro Orientation Servo Type Servo Direction Servo Mid Servo End Right Servo End Left Controller Parameters This set of parameters adjusts the behavior of the gyro or built in controller in fact Obviously once the setup parameters are set the controller parameters are the important ones to play with The nine parameters in this section are listed below However IMPORTANTLY not all ...

Page 3: ...w youtube com watch feature player_embedded v QvI nW9XcvU the movie is in German but it should be self explanatory 3 2 Servo End Points The next step is to adjust the servo end points such that the tail bridge doesn t bind maybe you want to leave 0 5 mm space but on the other hand the maximal travel range is available to the gyro Servo End Right determines the maximal travel range for the rudder s...

Page 4: ... 90 for the servo horn but rather have it tilted towards the direction in which it has to be turned less for the full pitch slider range TRex450 tilted towards the main frame 4 The Parameter Gain Input Function The parameter Gain Input Function determines what the GA250 OW does with a signal at the gain plug The behavior of the gyro does in fact depend strongly on this setting The Gain Input Funct...

Page 5: ...compensation as known e g from FBL units 5 The Controller Parameters It is important to understand that not all controller parameters are active at all times The GA250 OW can be set into different working modes and which parameters are active inactive depends on the working mode As the inactive parameters can totally be ignored this implies that in practice you usually don t have to deal with all ...

Page 6: ... Acceleration Limit Left the parameters Debounce CCW and Debounce CW are still active but should not be used and set to their default 30 0 Active Controller Parameters gyro gain set either via the transmitter or via PID Gain PID I De Acceleration Limit Right De Acceleration Limit Left If you have chosen Gain Input Function set gain mode which is assumed here the actual gyro gain is determined by y...

Page 7: ...l what the desired position was before a disturbance wind gust pitch pump etc occurred Such a memory is available in heading hold mode and enabled by the parameter PID I As before for gain the gyro could react aggressively to a difference between the actual tail position and its memory of it or could do so slowly The value of PID I determines how aggressively the gyro takes into account its knowle...

Page 8: ...d do the trick but finding a good one is obviously the challenge The debounce mechanism implemented in the GA250 OW firmware guesstimates how long the actual stop will take and cheats the heading hold such as to produce a stop without back bouncing The first method is so to say the textbook solution and to the best of my knowledge implemented in most if not all commercial gyros and FBL units and k...

Page 9: ...om 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 ...

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