AR7300BX Strange movement

[jverhaeren]

Tell me what you think of this.

I have a 7300 on a Goblin 770C, the other day during some test flights I pulled a dumb move and left my hold switch with a wide 50 pitch curve( for setting zero pitch and collective limit) IE 0-50-50-50-100. anyway I came down to land and flipped the switch about 10 inches up and it really wasn't a bad bump but a bump nonetheless. nothing broken, I have seen worse landings for sure.

Anyway for some reason I took it into the garage and went about checking pitch again ( had a wobble that I am still working on). anyhow set zero pitch and checking pitch limits I had not removed power from the receiver.

This is where it happened, I put the collective all the way down and it only went to -10( I had set it at -12) but very slowly without any input it was moving down....WTF so I looked at the swash and it was nowhere near level and moving further away from it. move the collective up and swash stays all skewed and strange. Servos moved in odd ways

unplug the power and power it back up and no problem.

Has happened one other time after another test flight but no strange things in flight but same thing if remove power and start it back up its fine.

Anyone?

[crashcopterman]

Was this in flight mode or in step K where the swash was moving while checking pitch?

Steve

[jverhaeren]

It was in K the first time, but it has done it in flight mode once as well. spectrum didn't think it was a problem but I have not had one do it before.


Just looking to see what the masses think, if I need to scrap it or not worry.

[jverhaeren]

Both times it has been after a flight, with no odd behavior during such flight

[jverhaeren]

I think I know what you may have been getting at


I checked zero pitch in flight mode, but when I was in menu K if I was to put it all the way down or up the swash wasn't level and the servos kept moving with no input.

That's when I finally had enough and pulled the plug

Restart and .....Fine

[jverhaeren]

Originally Posted by Frenchdress

Hi,

reason for the heli moving forwards can either be a stick command or a command due to sensor movement.

Are you sure you did not touch the stick trim of your radio, i.e. when carrying the heli to the start place? The system does learn stick center positions each time when it does init sequence. So when you changed the stick trim and power it up the next time, everything will be OK again, as the trimmed position will then be taken as center position.

Other than that this maybe due to poti drift or bad poti centering of your radio's stick potentiometers. On some radios the sticks do not center perfectly when moving the sticks and centering again, which will cause some slight movement just as you would trimm the sticks. Also the potentiometers might jitter slightly or change values, i.e. due to temperature change. If you've been flying some minutes and the transmitter did heat up/cool down to outside temperature this effect may have disappeared as the system did learn the new offset position when powering it up again.
To compensate for the pot jittering you can increase the stick deadband in the Microbeast's/AR7200's paramter menu at menu point E. The unit then will be more insensitive to stick movements and stick jittering may not cause any effect.

Last but not least a random movement also may be caused if the gyro sensor of the unit does drift into an offset postion. Same as the stick positions the unit learns the sensor rest positions when powering up the unit. When the internal temperature changes (similar to the stick potentiometers as mentioned above) the sensors (which are mechanical devices!) may start to drift slightly and the system "thinks" the heli is moved even if it is not. If the system is nearly at operating temperature and you reinitialize the spook will be gone as the rest position will not change anymore.

Also such drift behavior can occur when there are high frequent vibrations on the system, i.e. when the heli does not run smooth. When you meet a frequency that causes the sensor to get in resonance, it may produce positive sensor output although the heli is not moving (well somehow it is). This can be the case i.e. when you use different flight batteries which produce different motor rpms or when the battery has different charge. At one flight nothing happens but in the next flight the system will drift as you hit a specific rpm which is not good and which causes "bad" vibrations.

OK so this makes me feel better, I didn't have a stick out of place but as far as getting drift from sensors changing temp or something similar, this is what I was hoping to find.


Thanks for your help Crashcopterman, im looking forward to getting all the bugs out of this G770C didn't want to have second thoughts about the AR7300

[crashcopterman]

In step K the sensors are 'turned off' so to speak and should not give any servo movement, in this step it's all collective and rudder sticks only. Trim does do some weird stuff in flight mode, but I'm not certain it would contribute to the problems you have described in setup menus. It's definitely a good idea to zero and or lock out any trim functions, just in case.

Hope you get it figured out!

Steve

[sutty]

Was it a very hot day, or is your Beast positioned in such a way that it could become warm as a result of any other components?

[jverhaeren]

No trim set, it wasn't a hot day. Maybe 75-80. its mounted on the fbl bench behind the anti rotation guide.

Like I said I haven't had any of the others that I have do it before.

[sutty]

Sorry about the delay, I was at work. After I posted I noticed Stefan had already posted a detailed reply which mentioned temperature. The reason I asked about temparature is because it has been historically documented in this forum that you get severe drift, and post flight regulation artifacts when the temperature of the unit gets above approximately 50 degrees C, if I recall correctly. There are some good videos detailing this. However, this is not going to happen on a moderate day such as you describe.

That isn't even going to cause a temperature stability issue such as Stefan described, as there would be little variation from inside to outside at that temperature.

That brings you to what he mentioned with regard to accurate stick centering (pot drift) etc, trims, or vibration. You have ruled out trims, and you can rule out poor centering by increasing the deadband setting in the flight parameters section to see if that changes anything. Vibes of course is more tricky to track down, but you could try a different mounting tape and see if the behaviour changes.

Good luck with it.

Cheers

Sutty

[jverhaeren]

Ya I redid the tape and we will see what happens, if it happens again I will take video.

General Consensus then.... I don't need to be in a rush to replace this unit so long as preflight reveals no wandering?