I am having the same problem as errolw98 described, except they are HiTech 5625 digitals. Only on the ailerons on my H9 Funtana, with 12" extensions. The rudder and elevator are analog HiTech 625s.

When I do a range check, the digitals on the ailerons start fluttering wildly with the antenna down at about 35'. 1/4" to 3/8" each direction. The analog 625s remain rock solid. If I pull up the antenna, the digitals stop fluttering, until I walk out of sight of the plane.

I too don't think this should be "normal", and find it interesting it seems common to digital servos on large control surfaces on our 3D planes, not just JR DS811s.

Voltage measured at each servo is good.

I am going to try:

1. Heavy duty extensions;
2. Twisting the extensions;
3. Torroids on the extensions.
4. 4.8V NiCad vs. the existing 4.8v 2100mAh NiMH

1 is more a current/voltage drop related cure, 2 & 3 combat noise/cross-talk. 4 is an off-chance test that the NiMH is having a current supply problem - not likely with only 2 digital servos that are not in stall.

If the problem is simply the weight of the ailerons at rest, or other non-noise/current issue, I don't expect any of these tests to have an effect. And if so, I'll replace the 5625s w/ 625s.