AVRO 539B – New Year Flight
Though the low Winter sun was a bit of a nuisance, conditions were near perfect for this flight. Winds peaked at about 7mph with only a little turbulence coming over nearby treetops.
For my own ‘flyer satisfaction’ I was aiming for slow flight in this session. Flying slow with this plane means less bank-and-yank and more controlled rudder turns - which I’m still far from comfortable with. Sometimes I ‘got it’ – quite often I lost concentration and reverted to bank-and yank - you’ll spot more than a few turns where I let the wings dip too much and the plane loses altitude and accelerates. Fortunately the plane is pretty stable, so it was easy enough to catch.
Overall it was a great morning’s flying. I think I managed to capture a few ‘scale-ish’ moments, with the plane ‘bumbling along’ serenely - which isn’t bad for a plane this size and weight. There’s no slo-mo film effects in the video – what you see is what it does.
CG is currently at 25% of wing chord, but I’m still trying to decide whether to push it forward a tiny bit more. I recently ‘munged’ the numbers through a CG calculator on this webpage;
http://www.willingtons.com/aircraft_center_of_gravity_calcu.htm
The results, depending on how ‘twitchy’ or ‘mushy’ I wanted the plane to fly (by adjusting the % static margin), were CG figures from 26% through to 22% - which was ‘interesting’.
On the maiden and first flights the plane was very responsive to the elevator, but I’ve tuned that right down, which has made the plane manageable and pleasant to fly. However there’s always room for improvement, so any comments on CG and the plane’s observed flight characteristics would be welcome.
Cheers, alibopo.
UPDATE 02/03/2014; the plane had a 1700KV 28A motor to start with, but current draw was quite high with the 9x3.8 prop I was using. Time in the air wasn't really that good. I tried a smaller prop, 8x4, to allow the motor to use its revs to produce the thrust - hoping for more efficient use of the motor - but I think too much thrust was lost pushing air against the blunt nose. A bigger prop pushes more air out beyond the blunt nose, so not so much thrust is lost. With all that in mind I decided to try a slower revving motor, better suited to turning a bigger prop. I went for an EMAX GF2215/20 1200KV which theoretically draws about 20A with a 10 x 4.7 slow flyer prop. I only had 9 x 4.7 prop around, so tried the plane with that. It flew fine, with plenty of get-up-and-go for the take-off. I'm guesstimating my max current draw from this 'under-propped' setup is somewhere around 15-16A. This should give me much better flight times, though I've still to get a chance to confirm this. Last outing, with the new motor and prop, shortly after I got the plane in the air the wind picked up and I was happy (relieved) just to get it down without mishap!
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