Last updated: July, 2007

The trials and tribulations of buying, building and flying the Powercat Turbine Helicopter S1 – RRF

Ever since I was a teenager a very long time ago, I was always interested in aeroplanes especially helicopters. Back then radio control models were a thing for ‘rich kids’. A long time later when I used to walk my dog in nearby fields I sometimes met a neighbour (Ian or Genty as he’s known on the Runryder forum) flying a model helicopter, this started to get my interest going again and eventually I contacted him and said I’m going to buy a model helicopter, where do I start? I ended up with a Raptor 30.

After a short time with the Raptor I became hooked by RC Heli’s and started to look at Scale models and then I discovered Turbine engines which operated and sounded just like the real thing and the smell was just, ahhhhh! Great! Unfortunately the cost was still very prohibitive. Over the past few years the cost of turbine engines has dropped to within the grasp of most modellers, it just depends on where your interest lies, do I save and purchase one turbine or buy a few other models and kit them up with engines, Radio gear etc?

For anyone wanting to get into Turbine Helicopter models, you will still need to dig deep into your pockets for the initial outlay for the Turbine engine; this is the most expensive part of the setup as the turbine is a precision made part. The engine could set you back £2500 for the Jetcat PHT3 turbine or if you shop around on the Web as I did, you can purchase it cheaper abroad and still save money after paying postage and import duty.

ECU mounted in foam wrap

GSU

The PHT3 turbine includes the engine mount (mechanics) which is then installed into a suitable airframe kit such as the Vario XLV, Vario Trainer or MoBB. Also included with the PHT3 and as with most other brands of Turbine is the engine management unit (ECU), cables and a ground support unit (GSU) The GSU is connected by a cable to the ECU and is used for adjusting engine settings such as limits for the turbine speed, type of start up for the engine, it can also give engine data from the last run and fault diagnose. These airframes are standard model kits but have a turbine conversion kit available at an extra cost. The Powercat is slightly different which I will explain later. The big plus side of running a turbine is the cost of fuel. The turbines run on a mixture of Jet A1 (kerosene) and turbine oil. These are the same ingredients as used in full size Turbine engines. These can be obtained from your friendly airline operator (Thanks ‘Signature executive airlines’) for around £11 for 20 litres and around £7 for a quart (approx 900ml) size tin of Turbine engine oil.

The fuel is mixed with the turbine oil at a ratio of around 5% oil this just happens to be one tin of oil per 20 litres which just happens to be the size of my storage container, this makes mixing up my fuel simple, no calculations required, just open the tin and pour it in.

The actual Model Turbine helicopter kits are available from just a handful of manufacturers in the worldwide market. My Powercat is made by a combined effort from three German manufacturers, the well known ‘Vario’ brand, better known for their high quality scale models and a less known ‘MoBB’. The power plant is provided by ‘Jetcat’. MoBB provides the front frame structure, the fuel tank system, tail boom support and fin set. All the rotating parts (head, tail gearbox) are Vario parts.

The building of the Powercat was fairly simple; in fact it was a lot easier than building my Raptor as the engine and mechanics come already built, it took me just a few weeks to put together as I could only do 1 – 2 hours work at a time and this was not working every day. I think anyone who had a Meccano set when they were younger could build this kit in less than a week with a couple of hours work every night. The radio gear is standard Futaba kit using S9206 high torque servos for the 120° ECCPM head and a S9252 servo on the tail which works in conjunction with the mid range GY401 gyro. To power the model I opted for Duralite Lithium Ion batteries, one 4000mah powers the Receiver and one 4000mah powers the turbine ECU. The receiver battery is regulated down to 5.3 volts. The Duralite batteries have a built in cell balancer which makes them very reliable and safe to charge if used with a Duralite charger. Early lithium batteries were a bit unstable and had been known to burst into flames if not charged properly?

PHT 3 mechanics

At last the big day arrived to start up the turbine for the first time; it was a Friday night, weather perfect I had my able bodied! Assistant Ian there for moral support and to man the fire extinguisher just in case of the worst case scenario should occur? Did I mention earlier that a Co2 fire extinguisher is recommended to be on hand in case of a fire due to a fuel leak? We checked the charge on the batteries and setup the TX to operate the turbine ECU. This is done by connecting the GSU via a cable to the Engine ECU and following the instructions, simple really? The fuel capacity is 2.5 litres of A1 and a small tank of propane/butane mix gas.

The gas is pumped into the turbine and ignited by a standard glow plug then the turbine is started spinning by the onboard electric motor, at this point the fuel is pumped into the turbine and is ignited by the burning gas. When the fuel is burning and spinning the turbine, the gas is switched off, the starter motor disengaged and the turbine is now operating just like the full size engine. This start up sequence is all controlled by the ECU. If something fails or is out with the safe operating limits of the turbine? The ECU will automatically shut down the turbine.

Start up sequence initiated and we could hear the gas entering and the turbine start to spin and nothing, auto shut down. Everything was rechecked and a restart but the same thing happened again. The GSU gave no indication of a fault. After a couple of hours checking and rechecking we found the problem was with the glow plug. The GSU stated the plug was working and at the correct voltage but for some reason it was not hot enough to ignite the gas mix. A new glow plug inserted and we were ready to go again. By this time it was getting dark and Ian’s wife had arrived to see where he was and was now sitting drinking wine with my wife both thinking what a couple of Anoraks?

Start up sequence initiated again and as if by magic the turbine burst into life, what a relief as I did not fancy sending the turbine back to Canada. Ian and I just stood there watching the turbine as if it was going to do some magic trick before our eyes!

Over the next couple days, I would just run the turbine in my back garden, watching, listening and smelling the exhaust fumes, this is the effect turbine power seems to have on people!

The big day arrived; it was a Friday afternoon when Ian and I went down to the club field at Bonchester. The weather was dry, overcast and the usual wind was blowing across the strip. I fuelled up and carried out the pre flight checks at least 10 times? I think most model flyers do this with a maiden flight of any model but with the turbine costing 20 times more than most Heli kits and weighing around 9Kg I did not want anything to go wrong. Ian was ready with the camcorder (look out David Bailey)which made me feel more nervous than ever!

I initiated the turbine start sequence and could hear the familiar sound of the ECU beeping and the LED’s flashing, this is a good sign! The turbine burst into life and settled back to idle (33000rpm). I let the turbine run at idle for around 30 seconds to make sure everything was running as it should. I then turned the engine control knob (standard Tx rotary dial allocated by me to control the turbine) on my Tx to full power and raised the pitch to just under hover (+5°) as the down force of the blades could damage the landing gear.

The engine ECU is set to build up the turbine speed to around 94000rpm over 20 seconds as the torque is so high, the sudden power could twist the main shaft on the rotor head or cause worse damage. Nervously (Pound signs flashing before my eyes should anything wrong) I raised the pitch up to hover and the Heli lifted 4ft off the ground and jumped around, shit!! This shouldn’t happen? I immediately landed again and tried to figure out what had happed? A nervous Pilot error was decided and I raised the pitch again and the heli lifted into the air and again the control seemed to be very sensitive.

I immediately landed and turned the turbine back to idle. I then heard a voice shouting “what expo have you set?” I checked and replied +34%, Ian then shouted “it should be -34% for Futaba”, smart Alec! When I had set up the pitch in my TX I had input positive values instead of negative values, no wonder everything was sensitive. I changed the values and off we went again, this time the Heli lifted into the air and immediately felt more stable. When I turned into the wind, the heli would start to climb this is due to the 800mm long blades with 80mm chord width. These blades give a great amount of lift when facing into wind. I hovered around for the rest of the tank while Ian filmed

The next few flight, I just hovered the heli, I think this was 90% due to Pound signs in my mind should I crash and 10% getting used to the feel of the heli, Ilearned that I needed to predict how the heli would react to stick movements, there seemed to be a time lag from giving a stick input to the heli actually reacting and when you bring the pitch down I had to anticipate when to give positive pitch to stop the heli continuing into the ground.

Large heavy turbine Heli’s do not fly the same as small, light and fast Raptors. One day when I was hovering around again with the Powercat the turbine seemed to momentarily drop rpm; it did this a number of times during the flight. During the post flight check I could find no visible sign of anything wrong with the setup. On the next few subsequent flights the same thing happened. As the turbine is quite expensive I decided to go onto “Runryder” (RC Helicopter web forum) and post the problem in the Turbine section. I would recommend anyone starting out in the RC Heli hobby to visit this site. It is a wealth of information about RC Helicopters. After a few days I received a message from a gentleman called “Roman” it turned out that he worked for Jetcat in Germany and had seen my post on Runryder. He asked for my home telephone number so as he could call me to discuss the turbine problem and sure enough he called me at the agreed time and date. He suggested that I connect up the turbine ECU to my Laptop computer via a special cable and the Jetcat “Jetronic” software program (alternative to using the GSU) and run the turbine saving the engine management data in a file and e mailing him the result. I did this and within 24hrs I received an e mail from him stating that the fuel pump was most likely faulty and a new one would be in the post. I received a new pump within the week and once fitted no more rpm fluctuations. That is what I call customer service. Anyone wary of spending a fortune on a model turbine engine and then being left without backup is worrying over nothing. I have also read that Wren turbines have also a very good customer back up.

One morning, mid week I decided to go down to the field at Bonchester and just go for it! I thought “what the hell, I will have to do it sometime!” flying circuits with the turbine can’t be that difficult? I went through the pre flight safety check, push rods, links, fuel tubing, batteries etc at least three times, if I was going into circuits I did not want to crash due to something that could have been easily prevented. A pre-flight safety check including Tx range check should be carried before every flying session regardless of what you are flying. The turbine started faultlessly as usual, they seem to very reliable. Hands sweating! I increased the pitch and the heli went up into a stable hover, I then dropped the nose as I gave more positive pitch and the heli started to move forward increasing forward speed very quickly. At around 50yards out and approx 40 – 50ft in altitude I turned the tail around and the heli came back down wind as fast as ever and again around 50 yards out I turned back into wind and came back. I completed a few circuits and thought to myself “what was all the fuss about; this is easy I can now say I can fly a turbine?”

I hope anyone reading this is not put off going down the turbine powered road. The nervous fear of crashing is felt by everyone when they take a new heli out for the first time? The difference with this one is the cost of spare parts. I would not recommend a turbine as a first RC Helicopter unless you have loads of spare cash as you will crash at some point when learning to fly. As your skill increases you start to push yourself a little further. You can practice flying by using a computer simulator and it does not cost a penny when you crash! There are a few good simulator programs on the market such as Realflight, Reflex and Phoenix. I would recommend using one to everybody, it will save you £££?

If you want further information regarding turbine Helicopters or any other RC Helicopter don’t hesitate to contact the club in the first instance.

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