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Old Oct 17, 2012, 10:41 AM
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USA, CA, Red Bluff
Joined Dec 2007
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Sparky79: It sounds like you have too much throw in your servo. Adjust your rudder links to compensate for that. You want full throw but not overriding. Then make adjustments in the gyro to make sure it do's not cause the servo to over ride. I have'nt used the gy250 for a long time so cannot remember how thats done Ed
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Old Oct 18, 2012, 04:26 PM
Registered User
Joined Oct 2012
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Hello olliw,
thank you very much for your interest to my issue.
I agree with your methodical approach to problem solving and I will answer point by point.

Quote:
Originally Posted by OlliW View Post
- The MKS480 can handle only 5.0V at most (it is IMHO also a bit "small" for a 450, but that's another cup of tea). I assume that you have checked that your BESC is not delivering more than 5.0V, and that the servo is working properly when e.g. attached directly to the reciever?
Of course, power supplies are ok, 5v leaves the bec and 5v enters into the servo
Quote:
Originally Posted by OlliW View Post
- According to the sepcs I found on the web the servo can handle 1520us at 333Hz. This should be perfect. Nevertheless, just as a quick double check, what would happen if you would set the gyro output to 70 Hz?
I confirm the characteristics of servo, if i set output to 55Hz (70 is not present), nothing change, the issue remains.
Quote:
Originally Posted by OlliW View Post
- You are sure you have connected the gyro correctly to the reciever? And that the reciever is set up properly (in particular failsafe settings can be a pain)
Of course, I checked all connections many times
Quote:
Originally Posted by OlliW View Post
- You are sure that burning the bootloader and flashing the firmware was really successful? (maybe you could post a screenshot of the output tab of AVRootloader)
I think so, I have not see any alarming message during flash
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Quote:
Originally Posted by OlliW View Post
- The GA250 has two Leds, a blue and a red one. What are the leds doing after you power up the gyro/heli? Try to look carefully and to report carefully what they are doing, the leds behavior can be a tremendously useful diagnosis tool. Repeat also with the gain switch at the transmitter set to heading hold and to rate mode. (in one of the first posts you find a description of what the leds are supposed to do, as well as in the pdf manual).
The problem seems to occur while the blue LED flashes, practically while bootloader is trying to establish a connection.

olliw ga250 firmware HH mode (0 min 21 sec)

Olliw GA250 rate mode (0 min 13 sec)

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Originally Posted by OlliW View Post

- Could you also post a screen shot of AvrConfig with the settings of your GA250? This too can be a most helpful info
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Originally Posted by OlliW View Post
- What transmitter and reciever are you using?
Transmitter is a turnigy 9x reflashed with er9x firmware
Receiver is a turnigy 8 channels 2.4Ghz

If I find something I'll let you know immediately
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Old Oct 18, 2012, 05:44 PM
OlliW
Joined Sep 2009
1,568 Posts
Hey Sparkie,

I first have to say that I'am impressed by the detailed info you gave, in particular the videos, good idea. I can confirm that you indeed have done everything expertedly, and that everything (except of course the servo) looks perfect. I also only now understand what your issue is. From your first post I was thinking that the problem is that the servo horn runs to an end position after power up and stays there. But looking at all videos the problem seems to be clearly in the initializing state.

There is actually one thing which I find confusing in the 3 videos, namely that the behavior of the servo after power up is not the same in all three videos:

video 1: servo in mid (?), power up, quick large deflection to the right, then big deflection to the left
video 2: servo mid (?), power up, quick large deflection to right just BEFORE the blue led goes on, ca. 1 sec in this position while blue led is on, return to mid after blue led goes off
video 3: servo mid (probably not exactly mid here?), power up, blue led goes on without any servo reaction, quick large deflection to right and back to mid position at the time the blue led goes off...

Not very consistent...

So, again some questions please:

- in the last two videos, if you would have let the power on, would the gyro and/or servo then have behaved as expected upon movements of the rudder stick and movements of the tail boom? (in short, once the initial deflection event is passed, does the gyro then seem to work?)

- have you tried another servo? (you can use a cyclic servo, or any other servo, but have the frequency set to 55Hz)(yes 55Hz not 70Hz, my mistake, I forgot that exact number LOL)

- would the tail servo work properly if you would put it into a reciever slot intended for one of the cyclic servos?

- if you would put the tail servo in a cyclic servo slot at the reciever, would power up everything, would wait a dozen secs for everything to settle, what would then happen if you would disconnect ONLY the servo signal line (not the gnd and power line) of the servo? What would happen if you would have plugged in the servo but WITHOUT the servo signal line connected, would power up everything and would then connect the servo signal line after a dozen secs?
(I'd like to learn about the servos' behavior if it doesn't see a signal).

- have you tested/used the gyro BEFORE you did the conversion? If so, what did the servo do then?


I can currently see only three explanations
- the servo is a dude
- the servo output signal cable of the gyro is damaged (e.g. bad solder joint, insulation layer cut through, slack joint... the gyro is IMHO pretty well build, nevertheless I had all this before)
- there is indeed a sort of a compatibility issue in that your servo behaves with a running-to-the-right-end when it's powered but doesn't get a valid signal at its signal line

Looking forward to learn the answers,
Olli

EDIT: there is another thing which came to my mind (sorry that it didn't earlier)... during the blue led period the gyro attempts to find a programming box at the servo plug, and for that purpose it emits some particular signals and looks if it gets a reasonable response to them. The point is that the emitted signals are not conform to a PPM signal a servo expects. All my servos didn't had any problems with ignoring these invalid signals, but it could well be that the MKS tail servo behaves differently here. If at the end this indeed turns out to be the case, there are only these solutions

i) accept the deflection (wich is probably no option because of mechanical binding?)
ii) another servo (maybe no option either)
iii) I have to modify the firmware and provide an option to switch off the programming box (a programming box could then not be used, sad sad)
iv) I have to generate another firmware which uses another plug for the programming box (at the disadvantage of some inconvennience in using it)
v) I have to rewrite the firmwares and change the communication protocol between gyro and programming box

hmhmhm... solution (iii) would be the easiest... let's see what your answers are, in particular if the gyro is working correctly otherwise.
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Old Oct 19, 2012, 03:27 AM
Registered User
Czech Republic, Olomouc
Joined Sep 2011
126 Posts
Fixed plane

Hi Olli,
I used use your fixed plane FW in plane some time so I have experience to talk about.
In rate mode is awsome. Sometimes it whip with ailerons, rudder or elevator during flight. Its not wag and its hardly to see because it has no influence on stability of plane.
In HH mode (I used only twice) it has issues. It seem that gyro has too much "angle memory". When i hit full throw and plane has low speed that is not able to has such high rotation speed around particular axis, then release the stick gyro continues to rotate around axis. Yes, its the role of HH, but it continues to hunt the angle too far. Comercial gyro has about 45° in possition memory, so there is only 45° turn "overshots" in these cases.
I think that on heli could be the same in cases when tail has low rotation speed ability.
What is your oppinion?
Thanks
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Old Oct 19, 2012, 02:00 PM
OlliW
Joined Sep 2009
1,568 Posts
Hey ablack,

thanks for your biref feedback, much appreciated.

What setting are you using for the Controller Structure? Fixed Wing?

It's correct, my implementation works slightly different in some aspects than the commercial (heli) gyros (I don't have any knowledge for fw gyros). And one difference is that in default, as you observed, the HH "memory" is much longer than in commercial gyros. But you can adjust this via the I Limit and Gyro Limit parameters in the experts menu. I have not played around with them myself, but I would expect that e.g. reducing I Limit should reduce the angle memory (I don't know but you might have to lower it to something like 150 for a 45° memory).

For helis I can't see any problem with that (at least I never experienced any), since the maximum rate the tail can be turned is not very dependent on the flight condition. However, I understand what you're saying, that for a plane the max rotation rate depends strongly also on the speed of the plane.

Try plaing with the above limits (don't go higher than the default, but you can lower them).

Cheers, Olli
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Old Oct 19, 2012, 04:14 PM
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Quote:
Originally Posted by OlliW View Post
Hey Sparkie,

I first have to say that I'am impressed by the detailed info you gave, in particular the videos, good idea. I can confirm that you indeed have done everything expertedly, and that everything (except of course the servo) looks perfect. I also only now understand what your issue is. From your first post I was thinking that the problem is that the servo horn runs to an end position after power up and stays there. But looking at all videos the problem seems to be clearly in the initializing state.

There is actually one thing which I find confusing in the 3 videos, namely that the behavior of the servo after power up is not the same in all three videos:

video 1: servo in mid (?), power up, quick large deflection to the right, then big deflection to the left
video 2: servo mid (?), power up, quick large deflection to right just BEFORE the blue led goes on, ca. 1 sec in this position while blue led is on, return to mid after blue led goes off
video 3: servo mid (probably not exactly mid here?), power up, blue led goes on without any servo reaction, quick large deflection to right and back to mid position at the time the blue led goes off...

Not very consistent...

So, again some questions please:

- in the last two videos, if you would have let the power on, would the gyro and/or servo then have behaved as expected upon movements of the rudder stick and movements of the tail boom? (in short, once the initial deflection event is passed, does the gyro then seem to work?)

- have you tried another servo? (you can use a cyclic servo, or any other servo, but have the frequency set to 55Hz)(yes 55Hz not 70Hz, my mistake, I forgot that exact number LOL)

- would the tail servo work properly if you would put it into a reciever slot intended for one of the cyclic servos?

- if you would put the tail servo in a cyclic servo slot at the reciever, would power up everything, would wait a dozen secs for everything to settle, what would then happen if you would disconnect ONLY the servo signal line (not the gnd and power line) of the servo? What would happen if you would have plugged in the servo but WITHOUT the servo signal line connected, would power up everything and would then connect the servo signal line after a dozen secs?
(I'd like to learn about the servos' behavior if it doesn't see a signal).

- have you tested/used the gyro BEFORE you did the conversion? If so, what did the servo do then?


I can currently see only three explanations
- the servo is a dude
- the servo output signal cable of the gyro is damaged (e.g. bad solder joint, insulation layer cut through, slack joint... the gyro is IMHO pretty well build, nevertheless I had all this before)
- there is indeed a sort of a compatibility issue in that your servo behaves with a running-to-the-right-end when it's powered but doesn't get a valid signal at its signal line

Looking forward to learn the answers,
Olli

EDIT: there is another thing which came to my mind (sorry that it didn't earlier)... during the blue led period the gyro attempts to find a programming box at the servo plug, and for that purpose it emits some particular signals and looks if it gets a reasonable response to them. The point is that the emitted signals are not conform to a PPM signal a servo expects. All my servos didn't had any problems with ignoring these invalid signals, but it could well be that the MKS tail servo behaves differently here. If at the end this indeed turns out to be the case, there are only these solutions

i) accept the deflection (wich is probably no option because of mechanical binding?)
ii) another servo (maybe no option either)
iii) I have to modify the firmware and provide an option to switch off the programming box (a programming box could then not be used, sad sad)
iv) I have to generate another firmware which uses another plug for the programming box (at the disadvantage of some inconvennience in using it)
v) I have to rewrite the firmwares and change the communication protocol between gyro and programming box

hmhmhm... solution (iii) would be the easiest... let's see what your answers are, in particular if the gyro is working correctly otherwise.
here I am
I can confirm that the servo is working properly in other configurations.
I tried another servo and it does not suffer this the issue, I noticed, however, that during the blue led phase, this servo emits four distinct short ticks. Probably, as you say, these are attempts to contact the programming box. Also the mks servo is programmable The mks servo and probably these pulses immediately after power up will deceive him.
The programming box serach is done by the firmware or boot loader?
I'll give you this question because i thought that motivation immediately and so I tried to program the red gain plug bootloader alternative but nothing is changed.
Can you try to insert a 1 or 2 sec loop in the firmware before blue led procedure?
Another option might be an attempt to 'sense' servo on start up (I think that the servant has an internal pullup) and if it is detected, skip blue led phase.

What do you think about that?

Thank you
Cosimo
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Old Oct 19, 2012, 09:54 PM
OlliW
Joined Sep 2009
1,568 Posts
Hey Cosimo,
thanks for the info

Once the blue led goes off, does the gyro then behave as expected, i.e. once the initial deflection event is passed, does the gyro then seem to work?

Quote:
The programming box serach is done by the firmware or boot loader? ... so I tried to program the red gain plug bootloader alternative but nothing is changed.
smart idea, but its in the firmware, the bootloader has finished by then (it runs only for ca 0.3 secs)

Quote:
Can you try to insert a 1 or 2 sec loop in the firmware before blue led procedure?
not sure what your real intention is here. From your tests do you have evidence that the servo would accept false signals once it has gotten correct signals for a short period? That is, this
Quote:
- if you would put the tail servo in a cyclic servo slot at the reciever, would power up everything, would wait a dozen secs for everything to settle, what would then happen if you would disconnect ONLY the servo signal line (not the gnd and power line) of the servo? What would happen if you would have plugged in the servo but WITHOUT the servo signal line connected, would power up everything and would then connect the servo signal line after a dozen secs?
(I'd like to learn about the servos' behavior if it doesn't see a signal).
would not lead to a deflection of the servo but would work?


Quote:
Another option might be an attempt to 'sense' servo on start up
well, the box would also be a load, would be difficult to distinguish whether its a "servo load" or a "box load"...

Generally the implementation of the programming box feature gave me headaches... because many things have to work hand in hand... (and I had some specific goals such as for instance that you don't have to reprogram the programming box when you install a new firmware on the gyro, that you don't have to modify the hardware of the Robbe box, etc. pp, otherwise it would have been much easier)(also, the GA250, or better the Spartan Quark, is ill designed for that purpose... even Spartan apparently had issues with the design, otherwise they would not have had to "invent" the fancy need of a special inconvennient linker)

At one point I decided that the gyro has to be the active player. But this came from another project (the GA250 coax gyromixer project) and I wonder if, for the GA250 alternative firmware, I could not have made the box the active player... (which would avoid the issue)... can't see a problem at the moment, but might miss it... and it would need some substantial work

Another, easy to implement option would be to look for the rudder signal at startup, and jump into the blue led mode if it is e.g. fully right or left. This would be easy and not too inconnvenient for a user, but bears the problem that you can construct situations where the servo again would see a false signal (and deflect and bind), e.g. then you start with rudder fully left but have the servo still connected... should happen rarely and if must not be totally destructive... so, this approach is relatively safe but not totally safe

The best solution in some ways would be to modify the hardware of the GA250 by soldering a servo cable to the GND, VCC, and maybe SCK pin of the ISP pads, i.e., to kind of build a special programming port.

The ultimative solution would be to switch off the blue led phase at the cost that a mobile programming box can't be used anymore.
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Old Oct 20, 2012, 01:36 AM
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Joined Oct 2012
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Hi Olliw
Quote:
Originally Posted by OlliW View Post
Once the blue led goes off, does the gyro then behave as expected, i.e. once the initial deflection event is passed, does the gyro then seem to work?
Sure, the gyro works wery well after blue led goes off. Occasionally it happens that the servo does not respond at all (probably it has entered the programming mode) but after disconnecting and reconnecting the servo, it resumes operation immediatly (the gyro is ok)

Quote:
Originally Posted by OlliW View Post
smart idea, but its in the firmware, the bootloader has finished by then (it runs only for ca 0.3 secs)

not sure what your real intention is here. From your tests do you have evidence that the servo would accept false signals once it has gotten correct signals for a short period? That is, this
would not lead to a deflection of the servo but would work?
Not a good idea, i thought that the servant in the first seconds might be more sensitive to impulses. I do another test:
- servo power connected directly to receiver
- gyro power (red plug) disconnected from receiver
- plugged in battery
a this point servo doesn't see any signal and won't initialize but if i shortly touch the +5v pin with the signal line, servo start to move towards right end
- plugged in gyro power
same old problem

Quote:
Originally Posted by OlliW View Post
well, the box would also be a load, would be difficult to distinguish whether its a "servo load" or a "box load"...
But programming box comm line is not normally down? If servo has a internal pull up, on startup you can do a quick:
Line low -> check for programming box
Line high -> nothing

Quote:
Originally Posted by OlliW View Post
The best solution in some ways would be to modify the hardware of the GA250 by soldering a servo cable to the GND, VCC, and maybe SCK pin of the ISP pads, i.e., to kind of build a special programming port.
This can be a good alternative.
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Old Oct 20, 2012, 02:32 AM
OlliW
Joined Sep 2009
1,568 Posts
Quote:
Sure, the gyro works wery well after blue led goes off.
ha, LOL, this wasn't very clear to me from the beginning

OK, I guess we have nailed down the problem, that's a good thing (and your diagnosis efforts where very helpful)

Now we only have to hammer out a solution...

If (and only if) you would like to go with the extra programming plug option (it needs some soldering and some modifying the gyro case, both would be obviously a piece of cake for you, but I am not sure you like to go this route), I should be able to quickly send you an modified firmware (I should have to change only one line in my code and recompile).

Otherwise I guess I would go with the rudder stick left/right procedure. It's the easiest to do and nearly safe.

Äh, I should have asked actually beforehand, do you actually have or plan to use a programming box?

good work, Cosimo


PS: the line of the box is normally high impedance (=nothing) since its an input, but it has a pull up resistance, both similar to what a servo would have (but it was another good thought!)
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Old Oct 21, 2012, 10:00 AM
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Czech Republic, Olomouc
Joined Sep 2011
126 Posts
Quote:
Originally Posted by OlliW View Post
Hey ablack,

thanks for your biref feedback, much appreciated.

What setting are you using for the Controller Structure? Fixed Wing?

It's correct, my implementation works slightly different in some aspects than the commercial (heli) gyros (I don't have any knowledge for fw gyros). And one difference is that in default, as you observed, the HH "memory" is much longer than in commercial gyros. But you can adjust this via the I Limit and Gyro Limit parameters in the experts menu. I have not played around with them myself, but I would expect that e.g. reducing I Limit should reduce the angle memory (I don't know but you might have to lower it to something like 150 for a 45° memory).

For helis I can't see any problem with that (at least I never experienced any), since the maximum rate the tail can be turned is not very dependent on the flight condition. However, I understand what you're saying, that for a plane the max rotation rate depends strongly also on the speed of the plane.

Try plaing with the above limits (don't go higher than the default, but you can lower them).

Cheers, Olli
Thanks Olli for advise.
Im using fixed wing controler structure.
I will try to experiment with I limit asap.
I also have a remark to switching modes of gyro by gain signal and RUDD RATE multiplier. From my experience it would be nice if each gyro mode (rate, HH, OFF) could have its own RUDD RATE multiplier. Now I have some not easy solution by using complex mixing in TX, but its not transparent at all. Im using all 6 mixers only to tune RATE and OFF mode. I miss mixers for tunning HH mode.
Fo explanation, in RATE mode roll is slow, in HH fast, in OFF insane fast. Dual rate helps only a little because I cant program my TX to switch modes and D/R by one switch.
What do you think about this?
One more question, when I use RUDD RATE 2.0 do I loose any resolution?
Thanks
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Old Oct 21, 2012, 12:17 PM
OlliW
Joined Sep 2009
1,568 Posts
hey ablack
Quote:
it would be nice if each gyro mode (rate, HH, OFF) could have its own RUDD RATE multiplier
I understand what you're saying. But to be honest I am not going to implement it. The firmware has increased in complexity quite a bit because of the fixed wing support, and introducing further parameters wouldn't be convenient at all for all others. I mean, if there would be 20 fixed wing pilots jumping out of the woods and wanting to use the modded GA250, then it could be worth a thought to branch off a fixed wing version, but that's not what it is (remember, that's my hobby and not my bussiness, and I don't have any fixed wings...). So, this is mainly a heli gyro.

I would think that any programmable transmitter should provide at least two flight modes. Not sure why yours doesn't.

Quote:
Fo explanation, in RATE mode roll is slow, in HH fast, in OFF insane fast.
Is this actually a commonly known issue with fixed wing gyros?

Quote:
One more question, when I use RUDD RATE 2.0 do I loose any resolution?
I think that this should not be any problem.

cheers, Olli
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Old Oct 21, 2012, 12:33 PM
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Quote:
Originally Posted by OlliW View Post
Now we only have to hammer out a solution...

If (and only if) you would like to go with the extra programming plug option (it needs some soldering and some modifying the gyro case, both would be obviously a piece of cake for you, but I am not sure you like to go this route), I should be able to quickly send you an modified firmware (I should have to change only one line in my code and recompile).
this might be enough to solve my problem. I would not have difficulty to modify my gyro to get new programming port

Quote:
Originally Posted by OlliW View Post
Otherwise I guess I would go with the rudder stick left/right procedure. It's the easiest to do and nearly safe.
This may be the best solution in a general vision of your project. I think it may be more difficult for you but this solution might solve my problem to other people in future.

I leave you the decision.

Quote:
Originally Posted by OlliW View Post
Äh, I should have asked actually beforehand, do you actually have or plan to use a programming box?
No,my computer it's enough for me


Thanks Olliw!
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Old Oct 21, 2012, 12:53 PM
OlliW
Joined Sep 2009
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Quote:
No,my computer it's enough for me
if you don't need the progbox support I also could just switch it off (i.e. no blue led seqence)... have send you a PM
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Old Oct 21, 2012, 01:19 PM
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Quote:
Originally Posted by OlliW View Post
hey ablack
I understand what you're saying. But to be honest I am not going to implement it. The firmware has increased in complexity quite a bit because of the fixed wing support, and introducing further parameters wouldn't be convenient at all for all others. I mean, if there would be 20 fixed wing pilots jumping out of the woods and wanting to use the modded GA250, then it could be worth a thought to branch off a fixed wing version, but that's not what it is (remember, that's my hobby and not my bussiness, and I don't have any fixed wings...). So, this is mainly a heli gyro.

I would think that any programmable transmitter should provide at least two flight modes. Not sure why yours doesn't.

Is this actually a commonly known issue with fixed wing gyros?

I think that this should not be any problem.

cheers, Olli
Olli,
yes I see. I hope there will be more fixed wing FW version users because it could be well parametrized and still is smaller than KK 2.0.
Yes I can program 3 modes (gain), but only 2 modes (3 gain channells) I can mix in my DX7.
I dont know because I use only 3 GA-250 in plane.
As far as I know cheap 3-axis plane gyros uses only rate mode and are not even switchable from TX.
Thats not a problem. I only have to find compromise between modes.
With I limit I would solve the main HH flight issue.
Thanks
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Old Oct 21, 2012, 01:29 PM
OlliW
Joined Sep 2009
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the 3 flight modes of the DX7 do not allow to also set the D/R independently?

I understand that you can't set different D/R easily depending on the gyro gain switch, but why not using the 3 flight modes for No gyro, Rate gyro, and HH gyro and set each for your specific wishes... (and kind of inactivate the gyro gain switch)

looking forward to hear if the I Limit has allowed to get your HH behavior right
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