UGTTS CNC Complete Tail Assembly fits Pidgeon 12mm boom fit
HeliDirect T-Rex Complete Tail System V2
Overview
The following is a review of the HeliDirect T-Rex Complete Tail System V2 supplied courtesy of www.helidirect.com.

Unlike many other tail upgrade offerings, this all inclusive tail system incorporates the tail gear case and gear, rotor blade grip assembly, pitch slider, bell crank, belt pulley and output shaft. Basically, it's everything that you need to fit to the end of the tail boom, excluding the tail blades.

The first thing that strikes you when you open the packaging is the overall beauty of the whole thing. It is simply stunning and is certainly a winner in the bling stakes. Everything about it screams quality and it looks like it will be a solid performer. Lets take a look around it.





As you can hopefully see, it looks superb. The machining of all the parts looks excellent as does the quality of the anodised finish.

Most of the bolts into the body of the unit are 1.5mm hex headed bolts. There are also three philips (cross) head screws in the assembly which are all on the lever that connects the tail pushrod to the tail pitch slider. All three are countersunk but one really shouldn't be as it doesn't sit into the metal part it screws into and therefore looks a little odd - perhaps a bolt would have been a better option?

The blue anodised tail belt guide pulley looks like it is sitting in mid air due to only being mounted to one side of the casing. But, as we will see next when it comes to fitting, there is a purpose to this design and I have to say, it's well thought through!

My overall first impression of this assembly is very high indeed and I can't wait to get it fitted to the T-Rex and fly it. So, on with the show.

Fitting
The first job is to fit the tail belt into the unit. A superb touch here is that undoing three of the side bolts removes a panel allowing very easy access to fit the tail belt. As mentioned earlier, only mounting the tail belt guide pulley to one side of the housing means that the other side panel can be easily removed without disturbing the whole assembly. This greatly simplifies putting the unit back together as the sometimes awkward job of positioning the tail belt guide pulley has been removed from the task altogether.



With those three bolts threadlocked back in place it makes sense to just go over the remaining bolts to threadlock them in for peace of mind. The bolts that go through bearings are very well secured so I left them alone, not wanting to get threadlock into any bearings!

The next task is to fit the unit to the tailboom and to get the belt tension right. The unit has a bolt that goes right the way through it on the underside and, when tightened, will draw the gap it spans ever so slightly closer together and clamp tight to the tail boom - although this will hardly be noticed as the tailboom is such a tight fit into the unit anyway. When fitting, I removed the long bolt completely and put it through the other way so that it was driven from the same side as the one above it - i.e. from the side that the tail fin will attach to. There are also two ball links on these two bolts that will act as a suitable spacer to keep the tail fin away slightly.

With that done all that remains of this very straightforward build is to attach the tail rotor blades and the tail fin. Sadly, the tail blade spacer washers that are supplied are too wide to fit inside the blade grip holders with either the standard white plastic tail blades or the carbon tail blades that I use. Fortunately, my old tail rotor setup contains spacer washers that fit, so I swapped them out to complete this build. The bolts for the blade grips are a 1.5mm hex headed bolt with standard nuts to attach to the other side and hold everything securely in place. It might have been better to supply a nyloc nut here but a little dab of threadlock should be fine.



Flight test
Flight testing made use of an HDS 577 servo on the tail in conjunction with a GY401 gyro. I always use heading hold mode when flying and the rate is currently set to 45% which produces no wag on the tail at all. This combination gives the tail an incredibly locked feeling in both forward and backward flight.

The tail response is crisp and fast and pirouetting manoeuvres are very smooth and controlled. Increasing and decreasing the pirouette speed is also very smooth as the mechanism slides very freely. It all feels very precise.

I have flown this tail with both carbon tail blades and the standard Align white plastic blades and both blades felt nice and responsive with a slightly noticeable edge in favour of the carbon blades. This is to be expected though as the carbon blades flex less than the plastic ones.

I did not experience any noticeable lag in response to my inputs on the transmitter and even small inputs translate smoothly into minor turning movements as would be expected.

Conclusion
This is a great looking tail assembly which is also easy to fit and flies very well. The tail is responsive in flight and operation is very smooth providing a lovely pirouette and a great locked in feel. Having had some bad experiences with wagging tails and sloppy feeling from tail inputs in the past, this system really does inspire confidence. Of course, a decent Gyro and servo combination are a major factor in getting that setup right, but this tail assembly just finishes it off nicely.

Having had several test flights with this tail assembly, there is no sign of anything coming loose anywhere on the unit and the tail blade grips are still holding firmly on to those tail blades with no sign of changing anytime soon.

There aren't many negative points with this assembly, but the issues I found that niggled me slightly were the use of a philips (cross) head screw on the lever that connects the tail pushrod to the tail pitch slider - I think a short bolt would have been better used there. Also, the tail blade grip spacers were too thick making them unusable with either the carbon blades or the stock Align white plastic blades. Beyond that, when you consider the complexity of the unit in terms of moving parts, I'm quite impressed.

For those of you who are looking for a tail system that gives you more precise control, is a very straight-forward upgrade to add to your heli and looks great too, I would not hesitate to recommend this assembly.