Flying the Tempest
My last article on the Tempest covered the building and setting up of it, this article is going to cover the flying characteristics. However before I do that, I want to cover off a few points that came up in the final stages of the building.
The mounting process came to an abrupt halt when I slid the canopy on to find it hit the exhaust which is just a fairly run of the mill Hatori 990. The rear mounts were fine, but the forward mounts were too low. I found that by attaching the rear mounts and lifting the nose about 5mm, everthing fitted up nicely. Another trip to Darryll's mill and some blocks were made to attach to the canopy mounts to relocate some holes about 5mm higher and everything came up fine.
I hadn't bothered to get the canopy cut to see the fuel tank or an opening for the switch given that I wasn't able to mount in the stock location anyway so I didn't see the point. As soon as I mounted the canopy I realised that not getting them cut out wasn't a good idea. The canopy covers a hell of a lot. A lot more than the CS one does. You can pretty much only see the engine and little else. Without the fuel tank windows cut out you have to make a concentrated effort to look up into the canopy to see the tank.
In regards to the switch, I changed the mounting so the switch now points downwards and is easily accessible with the canopy on.
I have to say I'm pretty impressed with the canopy, it's nice and strong which is one part that disappointed me about the CS canopy which in places is thin and fragile.
The initial flights were done before the canopy came back so they were only hovering and autos. I did the first flight at a slow headspeed but Darryll reckoned the clutch was slipping which was backed up by the very warm clutch bell. The headspeed was increased to about 1500RPM where the heli felt very nice. The first impressions was that the muffler was doing a very good job of keeping noise to a minimum. The whole helicopter is certainly less noisy than the CS which has got a loud tail gearbox.
At 1500 the heli had a very 'locked in' feel to it and required only a couple of minute trim adjustments before it was hovering hands off.
End of the flight brought about an inspection of the heli to see if any issues might have cropped up. There were none.
Cline equipped C-Spec
All of the flying today was just doing the F3C hovering routines and the occasional auto to break up the boredom. It soon became very apparent that this heli has an attitude that when it comes to hovering, it knows best. For example, it's best if you don't try and counteract for the wind too much because the head is already going to do that and so you're just making trouble for yourself.
In the climbing piroette of the vertical rectangle the heli definately requires less correction than the CS. I used to have a lot of trouble getting the CS to 'settle' at the top of the piroette, however the Tempest is best if you let it figure itself out. This head is very proactive.
I found that with my blades, 720mm Rotortechs, the best hover speed was 1500RPM, any less and the heli would start to wobble or 'mast bump' as some call it.
I did notice a small tendency for the heli to slowly slide into the wind which to me means that the flybar is too powerful which can be a combination of too high a flybar ratio or the paddles are too light. I had no weight in my paddles, but didn't want to put any in either cause I felt that would dumb the heli down too much. I decided to leave any changes until I had done some aerobatics with the machine to see how it felt.
There was no tendency to pitch up and the heli autoed at least as well as the CS.
I had set the GV-1 for 1800 in ID1 and ID 2. On the initial climbout of the day the engine was very rich, much richer than it had been the previous weekend. I therefore spent a couple of flights setting the needles again. I seemed to have to lean off the top needle A LOT to get it to run clean again. I'm now down to one turn on the top needle and 1/3 turn on the mid range.
Once the needles were set again, I proceded to try a loop in what was quite windy conditions. In FFF into wind I felt that the heli wanted to nose down noticeably, pulling up slowly produced a huge loop which was no doubt aided by the windy conditions. Next up was a roll which I had to make a concious effort to pull the nose a up little for first. Once that was done I started the roll which was slowler than I had expected, but crisp nonetheless.
The rolling stall turn proved the tail had more than enough power for what I was doing and although I felt the aileron cyclic was a little slow, it was more than enough for this maneuver.
Please remember that a lot of this is just personal preference. I prefer to have a machine that rolls fairly quick.
This is the beauty of this machine. I changed flybar ratios in less than 20 minutes.
I expected now that the heli would start to get blown 'with the wind'. This means that the flybar is not compensating enough for the wind because now for each degree the flybar moves, the blades are only moving 0.65 of a degree.
Testing the theory
Picking the helicopter up in what was again ANOTHER gusty day revealed that the heli now did not want to fly into the wind. Instead it showed small signs of being blown with the wind which is what I was expecting.
The hovering performance became more accurate as a result of this. I eventually settled on -40% exponential and 70 AFR/Dual Rate limit on the cyclic controls. I was interested to see how the heli would fare in aerobatics. In FFF into wind the heli no longer displayed any tendencies to nose down. Rolls became easier due to the fact that I didn't have to lift the nose any longer and also the increased roll rate thanks to the increased cyclic pitch. All in all, very happy with the change to the lower flybar ratio. However I feel I might also try one of the intermediate settings such as 0.75:1 to see if I can get rid of the small tendency to get blown by the wind. It's a small thing, but I want to see what happens.
It should be noted too that what flybar ratio you use will depend on your paddles and also your blades.
Rotorhead Update - 13/10/03
I had some spare Hirobo Freya paddles lying around which had worked well on the CS so I installed them with the brass weights. I had set the flybar ratio to 0.75:1. While hovering the helicopter showed that it was being blown with the wind which I take to be a weak flybar system. I then removed the weights and tried again. This time the heli sat still in the wind or if anything, ever so slightly, flew into the wind.
Now I tried the rolling performance and found a much better improvement. However the machine still demonstrated a tendency to slightly pitch up while inverted during the roll so I added a PMX in the 9Z to add 8% of back elevator as the pitch goes into the negative value in Idle Up Two (don't you love 9Z's???). This rectified the situation.
Now the only issue I wish to address is the tendency for the helicopter's nose to 'fall back' slightly at the top of stall turns (ie doesn't stay vertical). For example, the heli will climb vertically in the stall turn, but when it does stall, the nose slightly goes back over the tail and as a result the heli doesn't stay vertical. I'll work on this and see what I come up with.
Engine Update - 13/10/03
This was starting to annoy me. The shimmer wasn't serious, however it wasn't good enough for a top level F3C machine. I wanted to investigate what adding an additional shim to the engine would do. I wasn't up to speed with what shimming did for engines, so I did a bit of research and found an article written by Ron Lund and Ben Minor (click here) which seemed to explain things for me. The C-Spec already comes with a 0.008 thou shim included. I decided I would add another 0.008 thou shim so I would see a distinct difference. To my delight this rectified the shimmer in the horizontal shim and then allowed me to tune the engine to a clean note rather than to try and get rid of shakes.
The engine is now pulling the Rotortech 720's through 11 degrees without too much problem and is running smooth with it.
The helicopter is very stable even in very gusty conditions. We have had some of the most crappy weather ever here lately, but it got to the point where I just had to fly no matter what, so initial flying conditions for the Tempest were not favourable, but it performed admirably even so. It's very quick in FFF which results in large vertical maneuvers such as loops and stall turns.
180 autorotations are a no brainer like you'd expect from a machine of this Caliber.
Will I notice a huge improvement over the CS in F3C flying? No I don't think so, I think the slightly better hovering ability of the Tempest will help, and with hovering worth double the points, that's worthwhile. However in the aerobatics, all bets are off.
Has the CS lost it's standing in the fleet? Hell no, it's still the best machine I've flown so far, it's just that now, I have two machines that fly equally as nice.
Update - 7/11/03
Adding about 60 grams of weight to the nose of the heli REALLY helped the loops and the verticals such as stall turns on the pushover with 360.
The other day I had a small mishap where I lost track of time and was flying fast backwards down the flying field when all of a sudden everything went very quiet... I managed to auto it down, but as it was far away, it was difficult to see what was going on and I ended up cracking one of the Rotortech 720 blades. I replaced these blades with MS 710's the same as the ones I've been using on the CS for 3D. I was pleasantly surprised to see I could immediately reduce the hovering headspeed from 1550 down to 1450 with no decrease in performance and no wobbling/mast bump. I've only done one session on these blades, but have always used them with the CS. I'll let you know how I get on.