Align DS510

You will be disappointed with the DS510 if you aim for a decent servo. But it will be a good one if one looking at the price initially.

1)It strips EVERYTIME there is a minor blade strike crash. Most of the time, at least 2 servo. Gear set are not sold cheap as it packs with bearings.
This annoys many of us despite there are "good comment" of this servo by some "supporters"
I think this is the same for 9650, but 9650 gear set is sold cheaper in my LHS.

So after replacing 2 sets, you will be regret not to use metal gear servo, as the price will be similar.

2)The slop of the 510 gear is horrible. There is absolutely no slop in the 9650. The slop cause delay in cyclic response despite good-looking spec. One can acutually see the swashplate rocking when the rotor is spinning on ground. My actual experience in during 3D when the pitch is moving precisely from + to - near the center, there is "deadband" response - meaning the stick should command a -ve pitch but yet no response because the "effective pitch" lost in the slop !!

The gear set of 510 and 520 are the same for the 1st, 2nd and 5th gear (count from the horn side). Majority of the crash will break the 2nd and 3rd gears.