HK401 gyro setup - SOLVED

[vlaporte]

HowTo – solve tail wag – HK401b gyro
09/18/11


Problem – After I installed a new gyro (switch from Logictech2100 to – HK401b) on my EXI452 - I noted good control in standard mode but severe tail wag in head hold (HH) mode.
So I tried two more new HK401b gyros with the same result.
I installed a new tail boom, belt, tail box and linkage – but no help.
I swapped receivers – HK orange FAST with original Futaba FASST – no improvement.
I finally tested my three brand new HK401b gyros on my old faithful EXI451 heli with original Futaba FAAST receiver – my original HK401b gyro (now about one year old) worked perfectly both standard mode setting A25 (on Futaba 7C 2.4) and HH mode setting N28. But, when I tried my three new HK401b gyro on this heli same problem perfect standard mode but terrible wag in HH mode.
So I tried decreasing gain settings on the Futaba 7C transmitter and discovered that the three new gyros work perfect with very low gain settings A7 and N21. For some reason the newer gyros (look the same to me) are much more sensitive than last years model.
Note – I used digital servos, (Corona 919) and setting on HK401b were DIGITAL SERVO, limit 100% and delay 0% and end point 100%.
I should have realized earlier that gyro hold perfection in standard mode and terrible wag in HH indicated an electrical setup problem and not spent time changing the whole tail.
I hope this is helpful to others.


Luck,
Vince

[vwchad]

I've been trying to get my HK 401 gyro set up in my HK 450 Pro for a while now. It is flyable, but the tail drifts a little and wags a few times when I do a piro. It just doesn't feel locked in at all. I've played with the gain all over the place and it never quite goes away. Not sure what the problem is at this point. I may replace the gyro soon if I can't figure it out.

[vlaporte]

Upon closer inspection of my EXI452 heli I noted that the bvearings in the HTX motor were very bad creating vibration so I believe that much of the bad behavior of this heli was due to bad motor and not bad gyro. But I still believe that the newer HK401b gyro must bet set to lower gain values to preform properly. I will replace the motor bearings and post again.
Luck,
Vince

[Glitch01]

I too had some serious tail wage on my Hdx300 with the Hk401b. After playing with the sensitivity on the controller, the tail wage went away.

Controller KDS 7-7xii
Started with -50 down to -20 normal and even with -18, tail wagged
Gyro worked fine at -15 normal.