autogyro

Autogyro Flies!

After starting the build in Autumn 2014, I can finally say that I’ve fulfilled my ambition to fly my own autogyro. It didn’t all go completely to plan, though.

Last night I added a bit of extra shim to the blades to help with the spin up:

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LiPos charged, I was ready for the first flight of the day, so, here we go again…

 

I decided to use the wind to spin up the rotors and then hand launch, which worked last week when I got my first 10 second flight. This week it was a bit windier at around 8mph, which I figured was perfect. This time I had the trims zeroed, so the head head was at 90 degrees to the mast, which is the recommended position. I tipped the aircraft back so that the nose was vertical, the blades spun up to a speed where there was a definite “lifting noise” from them, increased the throttle and rotated to the horizontal launch position and released the aircraft into the air. Immediately it wanted to go backwards and I spent most of the 20 second flight with the elevator stick all the way forwards trying to control it. Anyway, the landing wasn’t too bad, in long grass over to my left and downwind. On recovering and checking the aircraft, I discovered that the right fin had snapped in the landing.

 

I borrowed some cyano and patched it up with sellotape, then I moved the elevator trim all the way forwards and gave it another launch. I had a four minute flight with it this time, flying backwards and forwards in front of myself, demonstrating some semblance of control.  This time I was actually flying it, even if it was a bit of a handful to start off with. The thing is, it was pulling badly to the right, so I spent the first few minutes gently dabbing in a couple of clicks of left aileron trim until it was flying more comfortably. That’s 25 clicks of left and about the same on the down elevator prior to flight, which explains my earlier comment of, “a bit of a handful”. Especially when you’ve never flown an autogyro before, and it is a very odd thing to fly. Also going through my mind was the fact that the fin was held on with sellotape. That’s why I was very reluctant to use the rudder, but I did  give it a go near the end of the flight.

As for the flying, the elevator controls the speed, while the throttle controls the height. I did actually get up quite high at one point, but I was very careful not to let it get too far away from me as the orientation is a problem. I had a couple of moments when it was turning towards me and I lost orientation. What really surprised me was how much height I was losing on the turns. I was flying off to my left, turning 180 degrees, losing half my height, then picking the height back up again as I flew in front of myself, only to lose it again on the turn at the right hand side of the box I was flying in. It didn’t seem to matter if I turned left or right, the height loss was the same, and there were a few points where I couldn’t turn tight enough to fly in front and had to do a big circular circuit around my head. There didn’t seem to be much authority in the turns, but I can live with slow and docile at this point. Like I said before, I did very gingerly try the rudder out at one point and it was effective in bringing the nose around, but I was too scared of the cyano and tape on the fin giving way to do very much. Anyway, that was the battery exhausted, so I had to think about landing. This proved to be very easy and I touched down with almost zero speed and so lightly I’m sure my pilot in the red baseball cap never even realised. The only thing to mention here is that it’s very important not to reduce the speed too much. I was on the point of doing this and could feel it rolling left as the speed was decreasing. Post flight analysis of the battery showed that it only had 10% left.

Four minutes of autogyro flight! I’m only saying that again because it goes a bit downhill after that. On the next flight, the launch was fine, but it just didn’t seem to have any power. I can’t understand it because I did two launches, and both times it didn’t want to climb, landing about 20 seconds later. On both occasions, there was ample power when the aircraft was recovered. I decided to charge up one of the new 1300mAh packs and see what difference that made, but I’m fairly sure I made a mistake launching. There wasn’t enough speed in the rotor when I released it, the aircraft went away, but climbed too fast and rolled to the left. It was like it did a stall turn from my hand and I almost managed to recover it, but it hit the grass quite hard on the two wheels and tail skid simultaneously. This had the effect of partially splitting one of the spruce longerons and put paid to any more flying.

 

I always suspected that a hard landing would cause a break like this, but it’s easily fixed with some glue and a couple of plywood doublers. In my defence, I think the rotors were spinning at the right speed, right up until the point where it left my hand. The wind dropped at just the wrong moment, causing the rotor speed to drop as I brought the aircraft up to the horizontal and applied throttle.

Anyway, I’m very happy now that I’ve achieved my lifelong ambition to fly an autogyro, so I’ll fix it up and have another go soon. Oh, and by the way, there should be video of the event, assuming the camera worked. I haven’t had time to look yet. Post-flight analysis of the flights were there was no power could be interesting. I’m wondering whether I was pulling back on the elevator more than I realised, rather than giving it throttle? I really don’t know, as I definitely had 100% throttle and had to back off to land. Would forward tilt have increased the speed and built up lift? What I would really like is some sort of telemetry to record my transmitter inputs along with the flight video.

As for the rest of the day, I had a single flight of my RS352 right after the final flight with the autogyro. I buzzed around the sky with an old Corsair, which was a lot of fun. We were dogfighting with each other, but pretending that we weren’t. Him and his father between them had a fair few aircraft, including a Lazy Bee and a UMX Beast, which I’ve flown before and which he threw around the sky very convincingly. There was another guy who helped me with the autogyro last week, but this time he had brought his son and was teaching him to fly with a buddy box. I haven’t seen that for a long time, but together they were flying a Bixler. I also discovered that the aircraft I maidened last week wasn’t a Bixler, but actually a SkySurfer. The same guy was here again this week, but with his Nieuport biplane this time. Unfortunately, the Nieuport had a bit of an incident on its first take-off, then got into the air, completely out of trim, gradually settled down into flying, but suffered another incident on its second flight. This time it looked like the top wing was damaged, so he went back to his car and brought back a contra-rotating helicopter. This also flew, but it looked like the wind wasn’t its thing. When I had to leave at the end of the session, I left him with my sellotape fixing something on it. We also had a lady with a micro drone, brushless, and made from carbon fibre. I think I last saw her on the autogyro’s first outing a few weeks ago, but a couple of her friends also turned up with drones. There were also another couple of drones at the opposite ends of the field not wanting to talk to us (I wonder what they made of an autogyro flying past?). Finally, the guy with the Bixler also had an own design, small, agile, high wing plane that he spent the best part of a decade building. He asked me to have a fly of it and see what I thought. Well, it’s actually very nice to fly. I thought it was going to be very sensitive to roll, but actually, the controls were very well balanced. It was fast, agile and aerobatic, without being overly so. Anyway, he’s got a SIG Cobra pattern ship type plane that he’s just finished and wants to fly next week.

That’s about all there is for this week, except that I’ve still got the video of the autogyro flight to have a look at and edit, plus some repair work to do. I’m still determined to make the autogyro a regular flier.

Post Autogyro

The weather wasn’t very good this week, so I didn’t get to do any flying. The forecast was for heavy localised showers and, right on half past twelve, it rained. A lot. I might have got wet, or I might have got lucky, but, either way, it was just as windy as last week. If the weather had been calm, then I would definitely have had another go with the autogyro, but there didn’t seem much point with the weather like this.

I’ve been looking into the problems with the autogyro and come to a number of conclusions. Firstly, the video I captured was rubbish and didn’t tell me anything. If I try that again, then I’ll have to get the camera higher up. The next thing is that I don’t think I got the rotors up to flying speed as everything I’ve read says that there is a characteristic “whirring” when this happens. It’s supposed to take off at walking pace, which I achieved, but I think there might be something wrong with the rotor head. I went round all the factory fitted bolts and discovered that some of them were quite loose, which was causing a lot of play in the head. In addition to this, I’ve been reading the “Cruiser” autogyro build article from the November 2015 RCM&E, which is basically the same design as the earlier Atom. There is also the larger “Panther” autogyro article from the Model Flying Workshop Special, published in 2015, which contains all the original articles which were serialised in RCM&E from March 2013. These all contain basic instructions on the design of the head and how to test fly an autogyro. However, while they advocate short hops to ascertain the trim, I’ve seen a video on YouTube where an Atom was hand launched in almost gale force wind. This is something I’d never seen before, but you can apparently hand launch an autogyro very easily: https://www.youtube.com/watch?v=OdrfQxKu1Ik

This video is also interesting, as it suggests that the left wheel sticking to the ground is normal and that you can power on past it: https://www.youtube.com/watch?v=9OVpcZOvsOs

If the camera I was using had worked, then this is a carbon copy of my experience last week, except that I wasn’t brave enough to get it into the air. After some playing around on the ground, my feeling is that the left wheel coming up last is due to the anti-clockwise direction of the main rotor.

This is the other hand launch video of an Atom that I found: https://www.youtube.com/watch?v=5bVkgLwmBAc  I’m just not sure I’m that brave.

Anyway, I’ve checked the balance by measuring the hang angle using some rulers and a bit of trigonometry. By my calculations it’s 18.5 degrees, which is spot on. I’ve also modified the 0.8mm shims on the underside of the rotor mounts as they were getting caught every time the blades got tangled up last week. I’ve now lengthened them and covered over them, but I suspect that this might be where my problems lie. When I spin up the rotors on the ground, I just don’t feel like I’m getting much movement of the air. Now, the HK head has a known problem in that it’s constructed upside down and shipped in a state where the rotors would give no lift (souce: modelflying.co.uk Atom build thread). I took it apart as directed, fitted the fibreglass triangle to replace the plastic one which breaks and rebuilt it the other way up. I’ve added the shims as instructed, which put the blades at a more negative alpha and aid in spinning up the rotors. I’m not convinced that this is right, though, so I’m going to do some more investigating before I try and fly again.

That’s it for this week, but work is taking over again, so I’m not sure how much I’m going to be able to do on the autogyro. I’ve got this close to getting it in the air though, so I’m not going to give up now.

Remembrance Sunday 2016

It’s Remembrance Sunday this week, so what we usually do is to put an aircraft up and wait until we hear the cannon. Not having a Spitfire or Hurricane (or Tempest), I had to resort to flying a Taylorcraft.

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The weather was perfect, with lots of sun, no wind and not at all cold. I had one flight with my RS352, then the Taylorcraft, followed by a Hobby King Bixler (EasyStar clone). The Bixler had an issue with its flaps not being connected to anything, causing them to flap around on their own. After the owner had flown it, he asked me to have a fly to see if I thought it was behaving oddly. Not surprisingly, the free flaps were causing it to fly in a rather erratic fashion. It was flyable, but you had to constantly correct it. Also, he didn’t tell me until afterwards, but he had the rudder trim and aileron trim on opposite sticks. I had been feeding in right aileron during the flight, which was actually right rudder. I can honestly say that I’ve never seen that type of setup before and can’t think why on earth you would do it. He said that the idea was to be able to trim it without taking your hands off the sticks, but it’s just confusing. I also did a dive test to determine the centre of gravity, which turned out to be round about neutral. It didn’t quite tuck under in the dive, but it sure wasn’t stable, so we suggested adding nose ballast until he’s comfortable with the flying characteristics. Thinking back, I did fly one of these a few months ago which was very tail heavy and was a real handful to fly. It must just be down to the kits. As for the flaps, I suggested he put the hinges in and glue them so they can’t move. There are cutouts and horn positions if you want to add flaps, but apparently no instructions or obvious way of fixing them if you don’t.

After that I had three more flights with the RS352. In between all of this, there was a guy with a drone filming a keep fit group. He was interesting to talk to as he’s just got his permission for aerial work. Talking to him, he said it was really easy to get and just required a lot of paperwork and a flight test. Near the end of the morning a family turned up with a white Piper Cub (see picture). The older kid was actually quite good at flying it, but it’s the little one launching that got me. The picture shows him having just thrown it into the sky.

We also had the EFlite advance and, just as I was leaving, another guy turned up with a flying wing. I only saw it flying from a distance, but, given the small holdall it came out of and the FPV kit, it may well have been a Bormatec Ninox?

I’m back to building micro drones now, when I really want to be finishing the AutoGyro. You can see the parts I’ve just had delivered above. I’ve got two sets of F3 EVO Brushed flight controllers and the generic FrSky receiver that the Eachine QX90 drone uses. I’ve also got four sets of our modified HubSan quads with 3D printed frames repaired and ready. This is for the “Drones Masterclass” that we’re running at the end of the month. The parts above are intended for an FPV micro drone that we’re going to try running a 3D reconstruction from.

Here’s an example I captured of the ATOM autogyro:

http://www.123dapp.com/fullpreview/embedViewer?assetId=6342729&size=medium

Here’s a link in case the 123d Catch embedding doesn’t work: [ATOM Autogyro]

Hopefully there’s going to be more on this project later.

This is Autumn

It’s blowing a gale this morning. Then it started raining. The type of light misty rain that means if you have to wear glasses to see the aircraft, like I do, then you need windscreen wipers. I’ve missed three weeks running because of the weather now.

Anyway, I’ve finally covered the AutoGyro. At least I think I’ve covered it. I’ve never know an aircraft like this. Normally you cover the bottom of the fuselage, then the sides, top, bottom of wing and top. There are so many awkward bits to cover on this that it’s taken ages, plus the 35 degree ambient temperature hasn’t helped. When I put it all back together I keep finding bits to cover that I hadn’t realised needed it. The front face of the main former holding the mast is a case in point. It’s highly visible because of the cut-out for the head control rods. I didn’t know whether to do it black or the silver blue colour, so I opted for blue in the end. With all the exposed wood, I don’t know what to cover and what to leave, so I’ve just been doing a bit at a time and then seeing how it looks the next morning. This is why it’s been taking so long, but it’s been quite fun to do.

I really like the silver blue, but I think I need some white trim in places. Now I need to put all the radio gear back in and make it work again. That only leaves the balancing and covering of the blades as the last major item.

Red Autogyro, Blue Autogyro

I’m a bit late this week as I’ve spent the day covering my ATOM Autogyro. There’s no flying this week as yesterday it was blowing a gale and this morning isn’t much better. It’s taken me a long time to get to the covering stage as it’s just been so hot recently that I couldn’t bring myself to plug the covering iron in.

As you can see, it’s taken me a long time to get this far and I’m not quite there yet. Normally you cover the bottom of the aircraft and it’s a nice and easy way to start, doing something that isn’t terribly visible and is square and flat. Not with this fuselage. I hadn’t realised how many compound curves there are to go around on the bottom. The sides were a piece of cake by comparison. It seems you never lose the knack for solar filming though, even after you realise that the blue metal flake film is partially transparent and is going to magnify every tiny little mistake. If you look at the tail closely, I’m disappointed at how visible the joins are. I was covering it using up my very last scraps of old (20+ years old) film and ran out on the top horizontal stabiliser surface. You can see the overlap where I’ve had to join three pieces together in a funny position. Oh, well, I’ll just have to get creative with the trim graphics. I still haven’t decided what colour to do the fin end plates or the blades, but that can wait for a bit. What worried me a little when I was covering the fuselage is just how top heavy it is. I’ve never covered anything like this before and it was so difficult to hang on to the thing as I was smoothing out the film as it kept trying to twist out of my hands. There’s just nothing to hang on to or rest flat on the work surface.

OK, so that’s the autogyro, but I’ve actually spent most evenings this week working on the quadcopter simulator. I’ve had a play around with a control system that could be used for automatic navigation. In the simulator I could just tell it to head in a particular direction at a certain speed and height and the controller would just get on with it. I was thinking that I could try out some of the synchronised manoeuvres that I’ve seen the GRASP Lab at Penn University put up on the Internet. I’m thinking of simulating it first as I’m currently lacking a vision system, but it would be interesting to explore what’s possible with some of the cheap hardware that’s around. In addition to this, I’ve been improving how the quadcopter flies in the simulator. It’s well worth having a look at the MultiWii rewrite controller in the Cleanflight code to see how it’s done on a real aircraft, but there are some subtle differences between that and how it’s done in a flight simulator. It’s all very interesting once you get into it and it’s making me think about whether I could construct something novel out of all this automatic control theory.

Definitely Building an Autogyro

We’ve got weird weather this week, so no flying. Bright and sunny, rain, wind, very hot, humid, then cold, heavy rain, back to Summer again. It’s completely mad. I would have got both drenched and roasted if I ventured out.

Anyway, I’ve got all my work out of the way now, so I’ve got my weekends and evenings back and I am definitely building the Autogyro. There’s just one little idea I’ve been thinking about for a while that I need to try first. I’m going to spend the rest of today looking into the feasibility, so it’s either going to work brilliantly and be the subject of the next post, or we never speak of it again. The plans are below.

IMG_20160710_173623You’ll never guess what it is. All I’m saying is that it’s got five rotors.

 

 

Weather Again

It’s quite bright and sunny this morning, but there’s a strong northeasterly breeze which means that it’s not worth venturing out of the house to fly. I’m also grounded for other logistical problems and have a mountain of work to catch up on before Monday.

Despite this, I’ve made some more progress with the autogyro, to the point where I’m now looking at it thinking, “what do I still need to do before I can cover it?”. The pictures should give an idea of the current state of progress.

I’m currently making the tail skid as you can see that I’m having to balance the back end on an old 2v glowplug battery. The weird thing is that part of the balsa skid had been cut off, so I must have thought it was scrap 6mm balsa at some point and cut the top off to make something else. Now, not having any more 6mm sheet to hand, I had to find another scrap and stick it to the top to make a complete piece. The fibreglass bit is going to get stuck on soon, after which I can attach it to the underside of the tail. The aileron and elevator rods all work, but I’m still in the process of trimming the canopy so that they can poke out of a hole. Carefully and little bits at a time is the way to do this so I don’t cut too much off. I just keep fiddling with it and gradually improving the fit until I’m happy with it. Also, the pilot needs painting, so that’s something else I can do.

Last weekend I spent far too much time on the quadcopter simulator which we’re going to need for a workshop in three weeks’ time. It’s about ready for release, once I’ve done a few final tweaks. I’ve also ordered a replacement PCB for my HubSan X4 which is currently sitting in a custom 3D printed frame. That’s due to arrive next week, so I should be able to resurrect my little HubSan in another body.

Hopefully next week we’ll get some better weather.

RCM&E Atom Build

I woke up to thick fog and freezing conditions this morning, so no flying this week.

I really need to get on with building the RCM&E Atom as I haven’t touched it since before Christmas, despite the required spruce and plywood supplies turning up from SLEC the week before. Their mail order service was certainly very prompt as I was worried about getting caught up in the Christmas mail order chaos, but it arrived in a couple of days.

My main reason for writing this article, though, is to prevent other people from making the same stupid mistake that I made. Now, I’ve built a couple of dozen aircraft from ARTF through to scratch built own designs, so I’m not a complete novice, but I must be getting out of practice. I could try and blame the lack of 3D construction diagrams with the ATOM plans, but the truth is I measure the wood wrong. The photo below shows the problem:

Looking from the back at the sandwich of B1, B3 and B4, plus sides

Looking from the back at the sandwich of B1, B3 and B4, plus sides

Back view of the fuselage with the sides removed

Back view of the fuselage with the sides removed

The base piece, B1 is 5mm balsa, along with B3 which sits on top. Then the top piece, B4 is 3mm. In the photo you can see B1+B3+B4 in the centre with the pencil drawn vertical datum lines visible going up along the end of all three pieces for alignment when glueing. The two sides aren’t glued at this stage and you can see the doublers, D1, left and right sitting on top of B3 and forming a nice square box. It wasn’t always like this though.

My mistake was that B1 and B3 are from the same stock, which isn’t exactly 5mm deep. Either my eyesight is going, or I didn’t measure it properly, as it’s about 0.75mm thicker than it should be, so 2×0.75mm is 1.5mm and the extra height meant that with the doublers, D1, glued to fuselage sides, the sides didn’t reach the bottom. Without any construction drawings on the plan, it took me a long time to work out what was wrong and how everything was supposed to fit together, but then that’s half the fun anyway. I like the idea of the plans being a bit “open ended” as I always like to tinker with things, so this isn’t a criticism, just a bit of advice for anyone else building it – measure B1+B3 together!

Anyway, my solution was to place the base on the flat building board and offer up one of the sides. Then I drew a very fine pencil line along D1 using the top of B3 as a guide. Placing the fuselage side flat on the worktop, I cut very carefully just inside the thickness of my line to remove about 1.5mm from the bottom of D1 so it now fits as in the photograph above. Then I repeated the process for the other fuselage side.

OK, so everything now fits together and I think I understand where all the remaining pieces go, so the everything should just fall into place. I won’t forget to double check all the angles, though, as the modified D1 might have some consequences for the former and mast angles. And the hole is obviously slightly bigger than my 5mm square spruce strip.

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