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A review by Clive Matthews. Pictures by Clive and Daniel Matthews
Having been delighted with my Blade mSR, when Horizon Hobby announced the imminent arrival of the world's smallest flybarless collective pitch micro heli, it was only a matter of waiting for the first stock to arrive in the UK. So what is it and what makes it so special?
There have been micro helis about for some time. Most are fixed pitch, which means that height is controlled purely by motor speed. More 'serious' model helicopters, just like the real thing, use collective pitch to control height. The rotor blades have a variable angle of attack to create more or less lift. Indeed, model helicopters, unlike the real thing, often allow large amounts of negative angle of attack in order to permit inverted flight. The variations in blade angle also allow forward, sideways motion and banked turns. Yaw is controlled by the tail rotor.
In order to dampen the motion caused by the collective pitch head a flybar is usually employed. This is a very efficient method of controlling the head but has the disadvantage of requiring energy to drive it through the air. They are also vulnerable to damage. For some years there have been flybarless heads available for model helis but they have been very expensive as they require three gyros to control the movement in bank, pitch and yaw. In the mCPx the three gyros necessary along with the receiver and speed controllers are incorporated in one tiny circuit board.
In the Bind and Fly model which I purchased, the model comes with two sets of blades, one for 3D and one for forward flight. Two 200Mah single cell LiPo's, a mains charger which is very quick (about 20 minutes), some spares and tools.
Enough about the gubbins, what is it like to fly? Unfortunately, I'm not able to talk about its 3D performance but I will talk about it's more 'sedate' flight performance. When I say sedate, this is probably a very poor use of the word! In transitional flight the mCPx moves very quickly indeed. If you expect it to stop when you let go of the sticks like an mSR, you are in for a shock. The model is most definitely not suitable for those taking their first steps in model helis! Take off is slightly unusual (for me at least), being flybarless, the model is 'fly by wire'. Any cyclic input on the sticks whilst the model is still on its skids will be amplified until the model tips over. The recommended method is to lift off before attempting any control. In practice I have found that small inputs as the skids lift will prevent the usual leap to the left beloved of collective pitch helis.
Once in the hover it is very stable, those three gyros look after you very well. It is very lively and I have removed any expo in order to give more direct control and reduce the likelihood of PIO- pilot induced oscillation! Initially it was a bit tame in the up department but increasing the pitch throws helped at the cost of tail wag. The tail is not quite up to extreme torque inputs, but still very controllable. Initial attempts at circuit flying require lots of space. I have found it quite difficult to do slow indoor circuits due to the lively response and PIO when nose in. Outside, circuits are relatively easy and the speed seems so much gentler. Unlike the mSR, the mCPx, is quite happy outside providing the wind is not too ridiculous. Duration, flying circuits and hovering, is just under 7 minutes before the head speed starts to decay. The battery protection circuit will pull the power after about another 20 seconds. This is impressive and shows just how efficient the flybarless design is.
Issues, within a day, one of the rotor blades flew off, fortunately without hitting anyone. The bearing in the blade holder had collapsed. Horizon Hobby have replaced these free of charge and issued a bulletin here. Don't ignore this bulletin! I also have to regularly reseat the main drive gear. However, generally the model is very robust if not totally Clive proof! Fortunately, Stanegate Flyers stock plenty of spares. There is a short video of my mCPx flying attemps on HMFC TV.
Words Clive Matthews, Pictures David Bridges and Clive Matthews
Fellow Hexham flyers Mark Siddley, Michael Ronan, Spud Milton and I have had the most amazing flying experience. In front of a crowd of about 15000 people, we performed a night time display, flying GoFlyKites supplied by locally based distributor Stanegate Flyers.
Joe Ronan, proprietor of Stanegate Flyers used to be an international businessman; he takes up the story.
‘When you're travelling on business you see a lot of things, but sometimes you spot the really unusual. In January 2008 I was in Singapore visiting customers and suppliers, and one night was standing on the balcony of my 20th floor room looking down on what I thought were kite flyers with LED's on their kites. This was rather cool I thought, then wondering how they managed to avoid tangling up the flying lines, since there were more than half a dozen in the air at any one time. A few more minutes watching revealed that these were not kites at all, but free flying radio control aircraft lit up brilliantly for night flying.Fascinated by now, I walked down to the field at the side of the Singapore river and stood with a crowd of sightseers mesmerised at the display of lights wheeling through the sky - this looked fun! Eventually I succumbed and came home with two of the kites. From there sprang the relationship that led to the formation of Stanegate Flyers and the distribution agreement with GoFlyKite. It took a while to find the right premises; Hexham is a popular market town, and suitable units are not easy to come by, but in April 2009 I opened up, stocking not just GoFlyKite, but additional popular model lines such as Silverlit and the Horizon Hobby range. Traditional stringed kites have also been a very popular part of the stock.
Hexham is a very close community, and the Bonfire and fireworks display in November has always been a very important part of the town's year as well as an important fundraiser for local charities. The show opens with the large bonfire being lit at 6.30pm, and the fireworks at 7.00pm. The large crowd can become a little restless, especially if the fireworks are a little late starting. Soon after opening, I had one of the organisers in the shop, and suggested that it would be a useful warm up act to throw the night flyers up for a short display. This suggestion was enthusiastically taken up, and after further discussions with the organisers, and the fireworks company to ensure the safety angles were covered, we had the go-ahead and so this year, the event was started with our flying display of the SB42 GoFlyKites.
The SB42 is named after the 42nd birthday of Singapore. Joe had demonstrated one to the Hexham club a few months earlier. Looking like a kite, the SB42 has a central spine onto which is mounted the outrunner brushless motor. The receiver, 2 servos and battery are mounted on this spine.
The 2 servos operate two large control surfaces at the tail. Utilising delta mixing, these operate as elevons. They move independently for roll control and together for pitch control. There is no rudder. The motor control is via an Electronic Speed Controller with a battery eliminator circuit to power the receiver and servos. A separate feed is wired to the coloured LEDs, red for port, green for starboard, white at the front and blue on the body. These LEDs were far brighter than I had expected. A pair of tail fins is easily removable and the whole model fits into a very convenient bag.
It showed a surprising speed and agility, but as Joe fly's mode 1 and we were mode 2, we had no opportunity to try it out at the time.
It was to be a week before the display that two mode 2 models became available, Michael already flying mode 1. Mark, Spud and I were thrown in the deep end and had to quickly get used to this new type of flying. We needn't have worried the SB42 handles very similar to a delta. Very soon we were ripping up the sky. The incredibly thin section means there is very little wind resistance and flown as deltas they can get very fast. The controllability of the airframe is outstanding. The SB42 fly's very crisply, in fact too crisply for us. We were soon looking for expo and reducing throws, these would make perfect 3D trainers! In fact apart from rudder initiated manoeuvres, there is little that they are incapable of. Orientation took some getting used to, and a couple of prangs resulted. Whilst embarrassing, Joe had a comprehensive stock of spares and repairs when necessary, took minutes.
Practice makes perfect.
Joe had assured us that the orientation difficulties would disappear as soon as we started night flying. I found this difficult to accept but with so little time to the big night, every suitable moment had to be grasped for practice. The first time I saw the SB42 switched on in full darkness amazed me. It seemed even brighter than I had remembered. Immediately after launching I accepted that Joe was right. They were actually easier to fly at night. Joe then dropped the bombshell that in order to maintain safety, we were to confine the display to the area the size of a football pitch. I wanted to slow the flight speed down, but when I did so, maintaining height required such high alpha that I was anxious of stalling. It took some time to get used to the fact that with such a light wing loading, the SB42 was more than happy to fly like this. It was actually possible to fly at little over walking pace if needed. Just like a Delta, these things have an impressive speed range. For peace of mind, Mark and I also substituted the 9 x 7 prop for a 9 x 3.8. This didn't seem to limit top speed much but certainly made it easier for us to keep the display with the area required. Aerobatics could be accomplished within a very tight space using this prop. Michael decided to stick with the original prop that he was used to rather than learn a new set of characteristics at this late stage.
Rain rain go away!
Saturday the 7th of November, the day of the display and it was pouring down. We met at Joe's shop an hour before we were due to perform and things were looking doubtful. We checked over the equipment and walked the short distance to the Sele park in Hexham where the display is held. As we arrived, the rain stopped and there was very little wind. Someone was on our side! Quarter of an hour before the fireworks were due off, we all launched together. The concentration levels for the next 8 minutes were such that it seemed like seconds. I could hear the wows and cheers of the huge crowd behind me as we flew our hearts out. The plan for the display was to fly anti clockwise and in line as much as possible. We had also decided that unless we felt completely comfortable on the night we would shy away from aerobatics, for fear of embarrassment. In the event, with the boundaries of the display area perfectly back lit, all of us felt comfortable to ‘wring' them out a little. Rolls, loops and freestyle weaving and diving gave the crowd quite a treat, and with the spectacular backdrop of a flaming bonfire, was a memorable experience for the pilots too. The unique SB42 proved well up to the job with a precise flying style and instant response to controls.
Then, all too soon it was all over. We had to quickly pack away and clear the area before the fireworks started. As we walked clear quite a few of the crowd came across to show their appreciation and to ask about the kites.