AAKEE
Senior Heliman
Location: Boden, Sweden
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| With a DX7 cant you use revo mixing ,that will fix it...
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No, dont do that. It just wont be right. The GY401 is a heading hold gyro and the rudder input tells the gyro to turn left or right. If revo mixing is used with a 401 it will cause the nose to move when changing pitch...and that´s already the problem, right ?
The problem is the nose going left on high pitch, and with revo mixing you also get a nose right input at smaller pitch values, so the nose will go right then.
If to do anything with the Revo mixing, it should be a check to make sure its inactivated 
I have a trex450SE with the V2 engine(430XL) running +/-10degree pitch, I have GY401 and a modified Futaba 9650 tail servo(same prestanda as 9257). This combination hold the tail VERY well.
If I run in normal mode(rahter low HS, about 2400-2500) and punch full pitch, then the tail cant hold. It´ll move about 10-15 degree nose left, the speed/rpm of the tail is to low. If I increase rpm by going into flight mode 1 i get a little more rpm and the nose/tail almost can hold...just minor movements. When switching into flight mode2 then it holds perfect. I guess it would be easy to use the gyro menu and have different gain in FM1 and 2, but i fly >99% in flight mode 2 anyway.
Tonic--> Use different flight modes with different head speeds to test this out.
First, your gyro setting? ...I dont use the gyro menu, I change the gain by changing travel adjust on the gear channel.
You should increase the gain in steps (of 5% or so) until the tail starts to wag. If gyro gain is too low, then the nose wont hold.
So by increasing it until its too high(tail wag) then that test should show us for sure that the gain isnt the problem( I dont think so, I´d put some money on the head speed.
Next, are you able to fly that ESC in 'not gov. mode' ? ..then set a normal flight mode curve with low throttle settings and see how the nose holds, then increase the middle stick setting rather much, perhaps 75-80%, and max throttle at 100%...and do the same test...my guess is that the nose holds now.
Step3, go back to gov. mode and change the head speed so the nose wont twist more than you can stand.
On the GY401: With a futaba 9257 the DS switch should be set to ON, and the delay should be set to Zero. Limit should be adjusted so you get maximum travel without binding.
I have one more tip, before the inc in my keyboard goes out 
Thats to manually adjust the mechanical rudder setting, start with booting the GY401 as normal(in HH mode) and the put it into normal(gain setting below 50% ?...I do it by flipping my gear switch).
Check rudder trim = zero before booting GY401.
Then adjust the pitch by adjusting the linkage rod length so the pitch is some degrees(about 6?) that will force the TAIL to the left.
You get about the right value if you fold the blades to same side on the hub and get about 1/3 inch (8mm) between the tail blade tips.
Then hover the heli, switch from HH to normal and check that the nose holds ok. If it turns left, increase the mechanical pitch value and vise versa.
This will help the gyro find the right tail blade after a rudder input...for me it made the tail stop faster/firmer after piros etc. |
