Futaba GY 611 & 701 Tail drift issues

[Ozflyboi]

Hi guys,

I require some assistance from those who are well versed in Futaba gyros as I am having ongoing tail drift problems in two of my Align Trex 700E F3C Machines.

Both of these machines are identical as to the electrical components ie: Motor 800MX 440KV, Spektrum Receiver, Castle Creations IEC2 HV 120AMP ESC, Align HV 800 series digital Servos

Here is a run down of the gyro equipment I am using.


GY611 w/ BLS 251 & Alternate unit GY611 w/BL251 & 9256

GY701 w/ BLS 251



Gyro Settings as read from the controller box

68% Gain in HH
55% Normal Rate mode


GDir: NOR

Gyro Gain Adjustment: 100% both AVCS and Normal

ACG & NCG : 120% & 130%
D1L: 0% both directions

D1D: 0% both directions

Trk: 0%

Mode: CMT

Fmod: F3C

AVS: 100%

Lmt: 110% Left and Right



What seems to be my problem is having setup each of these machines in Rate Mode (Hands Off) and setting the neutral position for heading hold via toggling the switch when in Heading Hold mode I am finding the helicopters are pirouetting left very slowly. What I do actually notice is that when the helicopter is even just light on the skids the machine already begins the slow pirouette and continues as the machine is lifted up off the ground.

This pirouette can be so slow that it is not even constant and it would seem that the tail slowly works it way around having a few stops along the way.

Just to confirm a few details for you as I am an experienced modeller. I have no sub trims programmed in my transmitter nor do I have any active mixes. I have verified numerous times using the servo monitor screen of my transmitter just to make sure there is definitely no output on the rudder channel. I have also confirmed the neutral position for heading hold by moving the rudder stick back and fourth several times to get the linkage to rest at center then toggled back to rate mode and the linkage remains stationery.
I suspected vibration may have been the culprit however both machines are electric and running quite smoothly with minimal vibration.

Even so I relocated the Gyro Sensor which did not make any difference. I have even tried different mounting foam and even Align PU adhesive gel which I also known as Zeal tape.

A little information about my radio equipment, I am using JR 12X (Please forgive me) and Spektrum receivers. I have tried several receivers thinking it could be the neutral point is being incorrectly read at power up however this has not been the case.I have even rebound my receivers numerous times to ensure the correct failsafe is being set.

I have 100% Dual Rates and ATV in both directions of travel though I am using 20% - 30% exponential.

The ultimate test on the weekend was when I flew my machine fitted with the GY-701 that upon entering forward flight and at speed I could see the tail creeping around slowly. This as you know should not be happening.


As to my other machine I tried changing both the gyro Amp and sensor to another brand new 611 unit. Both units are reacting the same and the only thing that I can think off is that the gyro is receiving some kind of offset from my transmitter somehow.

I suspect that this has something to do with the gyro incorrectly reading neutral either at power up or for when the neutral point is being set via toggling the AUX channel. Is there any way I can prove this and how would I go about correcting this?


If anyone is or has experienced the following and knows how to overcome it I would be extremely greatful.

I have already sent emails to both my local Futaba dealer as well as to the US dealer, however no responses received.

Steve

[Ozflyboi]

Hi Guys,

Well I wanted to prove a point in that this tail drift is a localised problem to Futaba gyros so yesterday I installed an Align GP750 gyro to my Trex 700 F3CE and went to fly it only to find that the tail held consistantly throughout all hovering manouvres.

I even pitch pumped the collective to watch for any wag or tail swing and there was none whatsoever!!!

This does not leave me feeling very confident about Futaba gyros, that said prior to this tail drift I have never had any problems with Futaba gyros.

Perhaps the sensors Futaba use are more succeptible to a harmonic frequency or range that is present in the Align T-Rex 700E F3C mechanics, than the Align sensor.

I have since contacted Futaba to inform them of this and awaiting a reply.

I will be sure to post any further findings here.

[kamarthinsen]

hey. when i had my 700F3C i used the GY-701 gyro on it. could not get the align gyro to hold when giving id hard collective .
the 701 worked flawless
i just set up neutral hower in rate mode. (i did this mechanical ) Servo horn 90 and lifted the model up in AVCS switched it to norm and observed . turned the tail rod link until it as close as possible sat still in the ear in rate. set new endpoints and god to go
didnt want to have the trim and neutral trim setting active .
Try it out

[Ozflyboi]

Hi kamarthinsen,

As to your suggestion trimming the tail mechanically in rate mode is something I do on all my helicopters prior to even going into heading hold.

I have even travel (end points) of 110% on the gyro and servo horn is perpendicular to the servo linkage/servo case.

I will be test flying both F3C machines fitted with Align GP750's tonight and will report back with my results.

Still no reply from Futaba as to my last email I sent them. Go figure!!

[Ozflyboi]

Well I have tested both my F3C Machines now and installed the Align GP750 gyros which are connected to the Futaba BLS 251 servos.

At this stage of the game my findings are very very interesting.

Would you believe it or not if I said that both machines (TAILS) are locked in and holding without any drift.

I actually could not believe this as I have previously used the Align 750 gyros and was not impressed with the tail holding ability, however that said this was using the stock Align DS650 tail servo.

It actually amazes me how much a difference the BLS 251 servo has had on the performance of the Align GP750 gyros.

They are holding as good as what I would have expected from my Futaba Gy 611's and 701 gyros.

I tested not only in the hover at varying governed head speeds but also in forward flight. The heading of the helicopter was locked in throughtout the entire flight.

So where to now??? Do i continue just running the Align 750 gyros and not spend anymore time troubleshooting the futaba units??

I have just one more test to perform on the GY611, one change I made to both machines was upgrading the cyclic servos to the Align BL 700H High Voltage Brusheless Servos. Perhaps there is an RF issue here that the Futaba gyros do not like?

I will post my findings here.

This is my last straw for Futaba.

[Ozflyboi]

Hi Guys,

Well I tested out the 700 F3C last night with the stock Align DS610 servos to see if a 6Volt setup would make any difference as to the potential for electrical RF noise affecting the tail gyro..

Having re-installed the GY 611 back into this machine I discovered that the tail drift was still present but only very small.

I also decided to test out my other F3C 700E which is running the 110T black main gears and 13T motor pinion and is fitted with an Align GP750 gyro and noticed an ever so slight tail drift in this machine now as well. That said when I previously tested out the machine I could not detect or see any tail drift present.

Also I might add that a friend had his 700E F3C running a GY611 and test flew it last night only to find it has the exact same left tail drift that I have been battling from the beginning!!

I first encountered this tail drift in June 2013 and have been trying to resolve it up until now.

So where does this tail drift come from? Can anyone help us? PLEASE?????

Steve

[kamarthinsen]

Ok , just a thought!
I remember when I had my F3C with futaba all the way. I read in the instruction manual to the futaba RX that if you use sub trim In the RX you wil need to re bind them. (Performance issue )
Maby worth a try

[Ozflyboi]

Hi,

Yes I have rebound the TX to RX several times and obviously each time I changed receiver whilst trying to resolve this problem.

If there was sub trim in it the tail would move one direction whilst the heli is on the ground stationery. It is not doing this.

I am now chasing the possibility of a harmonic frequency or vibration that is causing the gyro sensor to experience a position error.

I will keep you posted with my progress.

[Vlandercosta]

Hello Guys
I have a TRex 700 converted to gasoline and a gyro 611. The sensor gets hot after each flight (50 C). In the beginning, it was inside the canopy. Now, it is near the tail but the temperature is the same. Getting this hot is normal? Any help? Any clue?