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.
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.