Month: September 2015

Lovely Weather for a Test Flight

The test flight in question was an A10 Warthog, not the Atom Autogyro, but more on that later. I wasn’t the first person at the field this morning. As I got there I met a youngster on his way home with a small Cessna type foam aircraft with a broken tail. I didn’t find out until later that it hadn’t actually flown, but he had put it on top of the bin out of the way of some dogs, then the wind blew it off and broke the tail. I hate it when that happens, but I told him to stick it back together and put some strengthening strips in and it will be good as new, so hopefully he will be back.

Anyway, when I actually got to the flying place, there was a Multiplex Heron in the air, an EFlite Advance on the ground and a big aerobatic helicopter about to take off and do some inverted tricks. Shortly after I arrived, another guy turned up with a DJI Inspire in its carrying case. He’s just done his BNUC practical assessment at a place in Wales, so we had a chat about aerial filming before I had my first flight of the day with the RS352.

After that the guy with the Dynam A10 Warthog arrived and I ended up test flying it for him. To be honest, you just look at it and think, “that could be tricky”. This is actually the first time ever that I’ve flown an aircraft with retracts and the last ducted fan I flew was either the Vampire or the Kyosho F16, which was some years ago. So, we did all the preflight checks, which button works the retracts, C of G, control throws and make sure everything is attached and looks right. Having exhausted all the excuses, I then had to fly it, so we picked a nice flat bit of grass and I stood there looking at it for a bit. It definitely had some power when I opened it up (slowly) and was tracking relatively straight on what is very rough grass. The rotation was more bump assisted and it was up, but pulling left heavily (felt that on the ground run) and also severely nose down. After screaming into the air, I found I could take it back to about half throttle and add some right aileron to correct the roll, but spent the whole of the first flight continually adding click after click of up to counteract its wanting to get back to earth more rapidly than I did. This was a bit of a handful for the whole flight and I was conscious of not letting the speed drop off as I was turning because it was wanting to screw itself into the ground. Aside from the still slightly left tendency, if you were to turn hard and use a lot of elevator to try and hold level, you would just lose speed and height rapidly. I think I’ve been here with ducted fans before. When I could feel the power going off I brought it in to land, which was uneventful, if slightly fast. It does fly very well when you cut the power back, but not for long. The wheels and U/C were still intact and it was at this point that I realised that I hadn’t used the retracts at all. The whole flight must have been about 4 minutes and left just 1% of power in the LiPo. You should never get this low.

Flight two was over very quickly as the LiPo just didn’t seem to have much power. The take off involved another dead straight high speed run along the grass, but it just would not unstick from the ground. I actually aborted as it was screaming along the ground into the distance, just when a bump caused the left wing to skim the ground and bounce it into the air. Select full power and it’s airborne. Not exactly how it’s supposed to be done, but any take off works for me. I spent the whole flight trimming again, but the power went so quickly I brought it in after only about 2-3 minutes.

The third flight lasted longer and was established using the same take off procedure. In other words it still wouldn’t unstick from the ground but now I knew where the bump was. It’s worth pointing out that this model has a nose wheel, but I never actually had to use it. The model just went dead straight along the runway and I was afraid that any correction I made with the rudder stick would see me over control and weave. This flight lasted about 4 minutes, during which time I was able to put the wheels up for the first time. It didn’t correct the, still massive, nose down moment, but it definitely felt cleaner and faster to fly with the wheels up. You could feel the reduced drag, but it did nothing to correct the fact that the up elevator trim was now on the limit. We tried a test where I went to full power and did a screaming fly past which was both fantastic to watch and terrifying for the person flying. I found that the excess power caused the aircraft to be sucked towards the ground, so it was really a high power turning dive, followed by a screaming flypast which was heading into the ground at the end of the field. The rather counter-intuitive way to avoid piling into the ground is to cut the power back to 50%, whereby I suddenly gained about 100 feet in height. After some more trimming and testing, it was time to land, so I remembered to put the gear back down and managed another fast run along the grass to a stop with no damage. That’s a relief.

Afterwards the verdict was that the high position of the fans above the vertical C of G and the fact that the fans blow (low pressure) air over the top of the horizontal stabiliser all contribute to the power induced tendency towards negative pitch. The fact that I couldn’t find a safe operating point and the obvious up position the elevators ended up in when at neutral are a worry. I can’t see what you are supposed to do to make this aircraft work. The only thing I wasn’t told until afterwards is that it was designed for a 3S, not the 4S that I was flying with. It might be a C of G correction that’s required, or maybe it’s the excess power? I think it needs some more flights to ascertain what the problem is, but I’ll have a look on the forums and see what experience other people have had as Dynam have a reputation for making some really good aircraft. This strikes me as being something which falls into that category. Any retracts that can survive one of my grass landings have to be good. I need to get some.

The Dynam A10 Warthog, proving that the nose wheel will unstick from the ground

The Dynam A10 Warthog, proving that the nose wheel will unstick from the ground

After that I had two more relaxing flights with the RS352 while everybody else tried to work out how to make the Warthog work.

That’s all the flying for this week, I’ve been a bit lax with building the ATOM at present and hope to catch up as I’ve got some holiday to take this week. I’ve been a bit pre-occupied with the quadcopter simulator I’ve been writing, though, so building has taken a bit of a back seat.

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How to Replace a Hubsan Q4 Battery

I’ve flown my Hubsan Q4 rather a lot now as I’m currently on my third battery. For the benefit of anybody also looking to fit a replacement, here’s how easy it is. You don’t even need any tools.

All you need is a Hubsan Q4 battery, part number H111-04. I got mine from Robot Birds for £3.95: [link]

The Hubsan Q4 and new battery

The Hubsan Q4 and new battery

The first step is to remove the white plastic bodyshell, which is done by gently prising the two plastic clips at the front of the Q4 free from the PCB.

Look at the four small white plastic clips holding the bodyshell to the green PCB

Look at the four small white plastic clips holding the bodyshell to the green PCB

Gently push the white clips out and over the PCB

Gently push the white clips out and over the PCB

It’s easiest to remove the front clips first as they can be gently pushed out and up over the PCB. You may be able to move the white plastic body backwards which helps a little.

Once the front clips are out, slide the shell forwards and up to free the two clips at the back, taking care not to break them.

The white shell is lifted free

The white shell is lifted free

Now pay attention to the orientation of the battery and the wiring which we are about to remove.

The battery is exposed, ready for removal

The battery is exposed, ready for removal

Now unplug the existing battery from the PCB, making a note of the orientation. It does have + and – printed on the PCB to help though.

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The battery is attached to the top of the PCB using nothing more than a sticky pad. Take a last look at how the battery is fitted, then just gently pull it free.

The old battery is removed (right) and the new one is ready for installation (left)

The old battery is removed (right) and the new one is ready for installation (left)

Remove the backing paper from the new battery. At this point I put the waxed paper onto the old battery so that it wouldn’t stick to anything. Please dispose of the old battery responsibly, don’t just bin it as it is lithium.

Peel the backing off and get ready to place it on the PCB

Peel the backing off and get ready to place it on the PCB

With the new battery all ready to fit, this is the point where you think, “where did it actually go on?”. My advice is to place the battery where you think it should go (look at the earlier pictures), but DO NOT press it down firmly. In other words, trial fit it, then put the white plastic shell back over the top to check that you have it in exactly the right position. There isn’t a lot of spare space, so it needs to fit right.

Trial fit the battery, making sure the white shell fits over the top

Trial fit the battery, making sure the white shell fits over the top

Once you’re happy with the fit, push it down on the sticky pad and connect the power lead. Make absolutely sure the polarity is right as it is very easy to break the connector if it is the wrong way round. There is a + and – printed on the PCB, plus you can have a look at the old battery as the leads are very stiff and it will have kept its shape.

That's the way to plug the battery in

That’s the way to plug the battery in

Then tidy up the wiring by doubling it up as in the picture, or just copy how the old battery looks. There isn’t much space, so it needs to be neat and tidy.

Finally, put the body shell back on, reversing the procedure you used to get it off. Push the back clips in first, slide and clip the front ones in.

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That’s all there is to it. You should now have a fully working Q4 again.

All back together and no pieces left over

All back together and no pieces left over

It was at this point that I switched it back on and wondered why it didn’t work any more. Obviously you need to charge the new battery before you can use it.

30 minutes later and I’ve got a zippy new Q4 flying around the room again. No more heavy throttle stick and 2 minute flight times. Like I say, I’m on my third battery, so they must be a bit marginal on the current drain to be wearing it out so quickly (or the charger is rubbish). Either way, at £4 at time I can’t really complain as this one will last a few more months.

Rugby and Running

It’s a lovely bright and sunny morning, but there’s no flying today due to a running race and the rugby World cup preventing me from getting to the flying field. My lift is also on holiday this week, so it would have been the bike and the flying wing if they hadn’t closed the roads.

Anyway, I’ve got some time off work so I’ve been doing some more building on the ATOM.

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That’s looking almost complete now, but I’ve still got to finish the tail section, glue the fins and horizontal tail on and make the rudders work. Everything else should then just slot into place.

 

Three Weeks Running

I think that’s three weeks running that I’ve been able to fly on a Sunday now. That hasn’t happened in a while, which just shows you how bad the weather has been.

Anyway, we had seven people this week, including myself, flying a combination of a Dynam Smart Trainer, EFlite Advance, Parkzone Radian glider, Hyperion Sniper II 3D aerobat and a smaller CAP231 (?) profile 3D EPP parkfly plus a small helicopter. The final guy was the aerobatic helicopter pilot, who I haven’t seen for quite a while, but he was doing his thing upside down and right way up with a big electric helicopter.

As for me, I only had the RS352, which I managed to fly three times, along with a long flight of the Radian and three trimming flights with the Sniper, which I had flown a few weeks ago. Neither the Sniper’s owner nor me could understand this, but it was completely out of trim for some reason. He managed to do a really interesting ground snap roll before handing me the transmitter and saying, “you have a go”. OK, so first attempt at take-off resulted in the prop hitting the ground and the nose digging in. I cut the power early, so no damage, but I did check the prop remembering what happened last time. Attempt number two and holding in a little up, it took off. Oh dear, that’s VERY sensitive, so find the operating point, fly the circuit and come back down again. After turning down the amount of movement on elevator and aileron (the TX said 135%, but we don’t know why), and also re-centring the surfaces, I was back in the air again and everything seemed a lot better. That was until I pointed out that the rudder was actually reversed. I really don’t know how I didn’t notice that before as I had done all the checks, but perhaps it got reversed when the rates were changed and I just didn’t notice? Anyway, back down to earth again, reverse the rudder put it back into the air and everything was more or less right.

The most impressive flight of the day was probably watching the Dynam Smart Trainer, which looked absolutely perfect. Apparently it was only his second flight with it, the first had bent the nose leg on landing so he had to straighten it out. For a trainer, taking off from rough grass, it went up absolutely dead straight, like it was attached to rails on the ground. He then proceeded to fly it around the sky and execute a perfectly good landing about 100 metres down the field. Any landing where you don’t have to bend the nose leg back counts as a good one, so he got a second flight before packing it up to go home. Apparently he’s waiting for some new LiPos to turn up so he can get more flights in. The thing we all found astonishing about this aircraft is the sheer size of it. The entire tail section is removable to enable you to get it into a car and both wings unplug.

That’s it for flying this week and I really haven’t done anything more on the ATOM since last week due to the amount of work I’ve been doing. One thing I was playing around with yesterday, though, is the Quadcopter simulator which we’re writing. I’ve just built a Windows 10 machine so I can run Unity and managed to get it flying using my old Great Planes Real Flight Transmitter joystick controller for the first time. This was originally an analogue gameport device, but I’ve connected it to a SiteCom gameport to USB adapter which I got from Maplin years ago for about £10. I now use it for all my simulators.

Here is a quick screenshot of my attempt at drawing a quadcopter in Blender for use in the simulator:

A model of a quadcopter being built in Blender

A model of a quadcopter being built in Blender

Also, I must put a new battery into my HubSan Q4 as I’ve completely worn out the old one flying it around the bedroom. A post on how to do that will follow later.

A Very Busy Morning

We had near perfect conditions this morning which meant flying two weeks running. That hasn’t happened in a while.

Lots of people flying (at a distance) and lovely sunny weather.

Lots of people flying (at a distance) and lovely sunny weather.

I was the first to arrive again, but was shortly followed by my two friends from last week who brought a Multiplex Extra 300S and a very realistic looking foam Stinson Reliant. I had already had one flight earlier, after talking for some time to a couple who were walking past and saw the aircraft on the ground. They were really interested and actually asked some good questions, like “why isn’t the wing flat on the bottom and only curved on the top?”.

Later on in the morning, the first flight of the Extra showed that it really is a fantastic aircraft. It was using a 2200mAH LiPo and weighs about the same as my old Extra, but flies so much better. I really do have to resurrect mine and give it another go after seeing this one fly. I just seem to have a thing about Extras and this one looks fairly close to scale. I would fault it on the taper ratio being less insane than the real 2:1 and the teardrop fuselage is a little too straight, but that’s being really very picky as it is fantastic. Unfortunately, part way through the flight there was a strange noise which sounded like the three blade (fantastic) prop slipping on the shaft. The landing was then a bit too fast in rough grass and ripped off the undercarriage. It looks like Multiplex deliberately made this a break off part that’s easy to fix as it’s not glued into the fuselage with any inherent strength. In other words the wheels are designed to break off without any damage to the fuselage. A bit of epoxy and it will be fine again. After that the pilot then went off to retrieve a Whipit that he had left behind.

The Stinson Reliant (this one? [link]) just looked fantastic in the air too. I’ve always loved DH Beavers and this is a similar looking aircraft, but with a much more iconic wing shape. Apparently, they’re no longer available, which is a shame. It also flew really well, taking off from the rough grass almost effortlessly. I still remember the first grass take-off with an electric plane, which used most of the field before getting airborne. These days we have much higher power to weight ratios and this is a much more popular option than the hand launch.

Anyway, I managed four flights with the RS352 again and part way through the morning the guy with the pure balsa gliders turned up and set up his bungee. You don’t see many pure gliders on flat fields these days using bungees as most people have opted for the power assist. He’s dabbled, but resisted going over to the dark side yet, still preferring the bungee launch.

After that, we had somebody else with a Hobby King Easy Star clone and a 3D Yak foamie which was slightly smaller in size to my RS352. He had problems with the control throws being too big and it being hard to control, so I suggested how much movement he should have, which was duly dialled in on the Spektrum transmitter and the aircraft was transformed. Then, round about 12 o’clock, lots of people turned up with a small quadcopter and quite a number of foam Cessna type aircraft. One of these had a rather nasty end when the wing bands failed completely and the wing parted company with the fuselage, rotating down to the ground gracefully while the fuselage hit the ground like a javelin. It does look like it’s repairable though, despite the damage to the motor mount and front of the fuselage, plus the fact that the body has split vertically just behind the wing. The others seemed to be flying OK, but by that point I had to leave them to it.

I haven’t had the time to do any ATOM building this week, but last Sunday I started on the pilot, so that’s the project for the rest of the day.

My ATOM pilot starting to take shape.

My ATOM pilot starting to take shape.

With all that clear canopy, it really needs a pilot and console, so I’ll have to see what I can carve. I am particularly useless at carving pilots, though, so I’ve opted for the helmet approach. I might experiment with adding some smoked plastic for his visor, but I was really impressed with my use of leading edge stock to make the top of the torso. Then I just stuck some sheet onto the sides to make the arms and some 5mm square inside that to fill them out. The head started out as laminations of scrap 3mm sheet cut into rough circles and sanded to a helmet shape, then stuck on with a cocktail stick. I’m a bit stuck with what to do about his hands though.

It does look like the ATOM is coming along, and I’ve still got a lot of work to do, but I want to fly it this September.