Vario JetCopter SX
Simon Lockington

One day at work Don had declared he needed to get a turbine helicopter. Naturally I was looking to encourage such thoughts, so we began investigating what options there were in the turbine market. Being totally unfamiliar with pretty much everything to do with turbines there was a lot to learn.

The big NH-90, honestly, how could you NOT want one?

At first we looked at scale machines such as the Graupner NH-90 marketed by V-East. The big NH-90 is a beautiful looking model and looked like it could be a good 'trainer' model for getting into turbines. I really loved the concept of this machine, big, scale, and it looked like it flew beautifully from the videos we downloaded. We chatted with Sandy from V-East at length about the NH-90 and what the options were, including the four bladed main rotor head and four bladed tail rotor assembly. Boy, you can get just about anything for these things, with Sandy proudly annoucing a Search And Rescue (SAR) package for the NH-90.

Ofcourse, the NH-90 is not the only option in the turbine market, I was particularly keen on investigating Bob Johnston's Turbine Robbe Cuatro, but it turns out that's not yet on the market.

One morning though Don announced he'd found a Vario JetCopter SX for sale on RunRyder.com and had contacted the owner regarding purchasing it. I didn't know a hell of a lot about the JetCopter so started a bit of investigation.

It turns out the JetCopter isn't directly marketed by Vario, rather it's packaged by VarioUSA.

Somewhere under there lies a JetCopter

Unpacked on the table waiting for the boom.

The business end of the JetCopter

Hovering in Don's back yard, it was a noisy, intimidating handful!

JetCopter in action at the field.

It's a Vario Benzine Trainer, modified to accept the JetCat HP5 turbine and all it's associated components. In addition, large, aluminium landing gear is fitted to keep the big heavy beast out of the grass.

The transaction completed successfully, and soon the JetCopter SX was winging it's way from the United States to Melbourne, Australia. Ofcourse, as we all do with any significant new toy, Don tracked the progress of the package every hour of the day until finally a knock at the door yielded a large, heavy box. Ofcourse the arrival heralded a stop in work and soon the box was torn open and we began scooping out all the polystyrene beans that had been used to pack the machine. The heli was well packed and secured, but unfortunately the landing gear had sustained a little bit of damage in transport, one of the struts had bent slightly.

The machine came fully equipped, all we had to do was add a receiver and set the machine up. Given I wasn't sure how turbines really worked in regards to throttle curves, I began research into setting the machine up.

The JetCopter SX uses four servo CCPM and had Futaba 9202's on the cyclic. It came with a GY401 and 9253 servo on the tail and ofcourse, Vario 810mm blades. With the 9Z, setting up four servo CCPM is pretty straight forward, however the servo installation on a Benzine trainer requires the dexterity of doctor's hands which makes things difficult. Also, with four servo CCPM, you have to be very precise in the servo subtrims and linkage lengths so that the servos don't fight each other and draw large amounts of voltage and burn out.

Now I began setting up the pitch limits and found that the head on a Vario Benzine trainer has stuff all pitch range. I could only really get about positive 9 degrees and negative 7. When you're running semi-symmetrical blades, this was obviously going to be a 'right side up' machine, not much in the way of inverted flight going on here. I have to say I was a bit dissapointed with the lack of available pitch on the machine, given that it's got a large amount of power, I was quite keen on using it. The limitation here is the rather large washout assembly that Vario installs here. Why, I have no idea.

Setting up the throttle on the turbine is pretty simple (once we worked it out). Firstly, you have to calibrate the Engine Control Unit to the pulses of your transmitter. Much like you do with a Futaba GV-1 governor. You tell the ECU when the transmitter and trim are at low stick and no trim, then when the throttle is at low stick and trim and full, then finally, when trim and throttle are both at full.

Setting your throttle curves is not like on an internal combustion machine. On the turbine, you nominate what power setting you want to fly around at (say 75% or 100%), and you simply put a straight horizontal line at your nominated power setting in your throttle curve and the ECU does the job of managing the fuel throughput to keep it there.

STARTING THE TURBINE
Ofcourse you must fill the fuel tanks first, the JetCopter carries just over two litres of Jet A1 kerosine mixed with Jet oil at an 80:1 ratio. The two aluminium fuel tanks are one litre saddle tanks mounted on each side of the main gear which feed into a header tank, then on via fuel pump to the turbine.

The turbine needs to use butane gas in the second stage of it's ignition sequence to get the turbine started before the kerosine is pumped in. The butane gas is stored in a cylinder by the main fuel header tank and is filled from common camp stove gas canisters.

With the machine prepped and ready (and a fire extinguisher handy), you're ready to crank.

The power switch is fashioned in the same way as a grenade pin which gathered a few comments from guys at the field about large explosions and fireworks. As yet, none of that has come to pass.

With the power on, it's time to advance the trim (with the throttle full down), to full. The helicopter will now start beeping in it's chase sequence which announces the machine is armed and ready to start.
Now, advance the throttle to full. You hear the electric motor engage the turbine and start spooling it up before the POOF of the butane gas ingniting cuts in and lights up the turbine and continues to spool up faster. Finally, the fuel pump engages and pumps kerosine into the turbine which ignites and the ECU continues to spool the engine up until it gets to operating temperature.
Once you hear the engine start on the kerosine, you reduce the throttle back to low. Once the ECU has stabilised the turbine, control is then handed back to the pilot.

At all times, you need to have a guy standing by with a fire extinguisher incase of a hot start (ie flames shooting out of the back).

FLYING
With the turbine idling on the ground, I click the transmitter into Idle Up One which is set at 75% power. The ECU is set to ramp up to this speed over 10 seconds, then onto Idle Up Two which is set at 100%.

As always, hearing a turbine wind up is a stimulating experience. The roaring of the exhaust combined with the whistle of the turbine and the thumping of the big blades makes for a great sound.

The first time I flew the machine was in Don's backyard, I lifted the machine off ground and it was on for young and old. The damn thing wouldn't sit still and was like a cat on hot bricks. It was very difficult to to hover steadily and kept wanting to make a run at the rose bushes. Hmmmm... It was going to need some work...

FIRST MODIFICATION
The first modification we undertook was to fit Futaba 9252 servos to the machine. I'd hoped that these servos would go some way to fixing the percieved 'slack' in the control system. In reality, there is very little mechanical slop in the machine, it just felt terrible to fly.

Ofcourse, as I discussed, working on the four servo CCPM system on this machine is not easy. Infact, it's a big job requiring flexible hands, pliers and a fair bit of thought and persistance to do correctly.

CERTIFICATION
The following day was to be the day Don and I were going to be assessed by guy designated by the Australian Modelling Association as a turbine instructor so that we were able to fly the machine legally. Here, the machine has to be certified, but so do the pilots.

The certification process is very much plank oriented, so basically just flew the machine doing a few simple loops and rolls. All of which wasn't easy given the machine's propensity to pitch badly at speed and in a dive. The addition of the 9252's had made an improvement, but we still had a long way to go before the machine was going to be any fun to fly. I reduced the flybar ratio which also helped too.

The machine passed it's certifcation as did I, so it was back to the drawing board on what to do to get it to fly well.

CHANGING HEADS
The more I looked at the head on the JetCopter the more I disliked. The dampening was far too soft and there was just no way of getting more pitch. Once I had got the machine to fly stable, I was going to be looking for more pitch to get some more speed out of it. I started toying with the idea of putting a different head on just to see if that would make a difference.

I looked long and hard at the Sylphide head which I think would have been great, it's vastly over-engineered very adjustable. However, I wasn't overly keen on disassembling one of the Sylphides to try this out. Don recalled having a spare Robbe Millennium II head at this place so I got this and went to work at fitting it.

Ofcourse, one thing I had forgotten about, is that the Robbe head has a 45 degree phasing offset whereas most other machines are offset 90 degrees. This would mean that if I put in forward elevator, the machine would nose down and roll to either the left or right as well, rather than pitch forwrd. This meant, I'd have to use a seperate washout and phasing ring assembly. Again my eyes turned to the Sylphides which had a suitable setup, so one of them was robbed of the necessary bits and installed onto the JetCopter. I rebuilt the Millennium head with new dampeners and bearings where required and installed.

The test flight with the Robbe head went well and certainly yielded more pitch but didn't really give us the stability improvement I was looking for. Back to the drawing board... Don wanted to go back to the Vario head and I couldn't really argue with that as the Milly one hadn't given us much.

The Vario head went back on, but I kept the Sylphide washout and phasing ring on so that we could keep some of the pitch we gained when putting the Milly head on. So now we're back to the drawing board again.

NEW BLADES
By now the SAB 810 blades that Don had ordered had turned up and it was time to try these out in comparison to the Vario blades. These blades were also semi-symmetrical so we still weren't gonna be doing much in the way of inverted.

The SAB's did make a bit of a difference to the hovering stability, but we were still a long way off. By now I would have tried heavier paddles, but the big Vario has to be different in yet another way by having a 5mm flybar so nothing I had would fit. At the moment, we have some weights being milled up, so hopefully we'll get to test them soon. I really feel that a heavier rotor system will help. The current weight of the blades is 250grams which in my opinion is probably a bit on the light side.

HEADSPEED
We had always known the big Vario would fly around with a pretty low headspeed, but we'd never had the tachometer on hand to measure what it really was. I had a feeling that if we increased it we might be able to tame the big beast so Don went off to investigate what needed to be done to get the turbine to run a little harder and get the headspeed up.

After a bit of research Don entered the parameters into the ECU and we went about testing it on the Turbine Testing Ground of Don's front lawn. By now the neighbours were used to the noise of the big noisey vacumn cleaner from next door, but they still came out of their houses to watch anyway.

Certainly the increase in headspeed had yielded a positive effect. Don announced there was a speed up gear which effectively lowered the main gear ratio so we'd get more head RPM at the same turbine RPM.

FLYING
By now the turbine had had quite a few outings and I was beginning to get used to the flying characteristics of the big heavy mother. I knew if I put it into a dive or went to fast, the thing would porpoise around the sky, so I learned to fly to keep it happy and began looping and rolling it. The thing has an amazing roll rate that really belongs on a Fury, not a big lumbering bus like this. Hopefully the new paddle weights will settle it down some.

While some of you might now be thinking that I'm focusing on the negative part of this machine, it should be remembered that this is still a turbine, and turbines equal cool. The sound of this thing from the time the little electric motor starts winding it up for the start sequence, to when the same little electric motor is spinning the turbine over to cool it down in the shutdown sequence is pretty thrilling.