SnitGTS

Hello all! I've been posting on rcuniverse for almost a week now and I've gotten some great advise and good answers so I'm hoping my string of luck will continue!

I just took my Graupner Tipsy out for my maiden flight, and I think I might have a balance problem, however I'm not sure. I've been very careful to follow the instructions and I've made a few modifications that was recommended to me to correct the most common problems I found about the Tipsy. The mods were to add a couple rows of reinforced packing tape to the wing to strengthen it and to upgrade the motor from a Speed 280 to a Speed 280 Sport. According to the instructions, the CG is slightly forward of the middle of the wing, and as far as I can tell when I balance it on my fingers, that is exactly where it is. I had planned several flights today, each longer and more challenging then the last. For my first flight I got the plane up to about 25 feet and circled, then I cut power to glide back to Earth to check its balance and how well it glides. It flew well under power, but as soon as I cut the motor it nosed down about 15 degrees and full elevator up was barely able to pull it out before it hit the ground. It was a rough landing, but no real damage. Before I launched it again, I adjusted the trim to lift the nose, but when I cut power the second time I got the same result. Thankfully only very minor damage to the front of the nose.

The thing that bothers me is when it was under power, it flew well. I was surprised how strong the controls were and how little throw I needed to make the plane go. This leads me to my second theory as to what caused the dives, pilot error! When I got it up in the air, things started happening real fast! I didn't panic, but the plane drew an audience (unwanted for my first flight!!!) and I feel like my mind was racing.

All help is greatly appreciated!!!

Jay

aflipz

My Feedback: (10)

it sounds to me more like you stalled than anything else. If you were not having problems handling it before the incident. Allways trim for level flight on power then don't mess with it, their is no sense in changing the trim for off power glide characteristics because these same inputs will have a huge influence on your on power flight characteristics. (you noted yourself that full elevator was not effective to raise the nose at low speed)

Planes need airspeed to stay aloft and influence the control surfaces, lower the speed too much and your wings no longer provide lift and your control surfaces have no effect, most of the time on a "normal" cg either the nose will go down or it will drop a wing and then the nose goes down. In your case the tipsy has dihedral in it so i'd immagine it went down and your elevator had no influence because of the lack of airspeed, had you let off the elevator and input some power then pulled out it would have come out of the dive for sure. Don't beat yourself up you sound like you'll get the hang of it.

Try this next time; trim your plane so it flies straight and true under power then climb up at a good altitude, say 100 feet, let off throttle and bring the sticks to center; your plane should be loosing a little altitude (15 degrees sounds about right) and carrying some speed gliding in a relatively straight line depending on wind, add just a little elevator and you will see it climb a little but loose speed, when it looses enough speed and stalls you'll see the nose go down and all the elevator in the world is not going to help that until gravity has given the plane back enough speed. Input down or no elevator at all until you get some speed, pull up... Figure out exactly at what airspeed it stalls by lowering the throttle and trying to stay flying level with as little power as possible all the while taking into consideration wind speed and direction and voila, you understand how your plane glides and stalls, you are ready to land.

Now the trick is to touch the ground just a tad faster than the stall speed so that it lands straight and level and doesn't suddenly point 15 degres down at 2 feet from the ground.. Come in low but at a nice stable speed and start slowing down If you feel it is about to stall you can add a little bit of throttle. Look in the hobby lobby video of this plane; the pilot inputs a little power when coming in for landing. If for any reason you don't feel confident with your approach then input throttle, climb up, circle the field and line it up again and again until everything feels just right.

Dead sticks (no power) landing are another story; you need to line up your descent and maneage your speed as close to perfectly as possible because you only get one go and there's no turning back; "what goes up, must come down"

Hope this helps


@flipz

SnitGTS

@flipz - Thanks for your advise! I don't think I stalled, but I agree that is what it sounds like. I attributed the lack of elevator control to the motor not pushing extra air over the controls, but a stall would explain it too. As far as I can tell, I was moving at a pretty good clip when I cut power, but I was coming out of a turn and heading in my relative direction so maybe I was going slower then I thought. Is it possible that stopping the motor could have cause the plane's nose to drop? (similar to a car hitting the brakes) I'm going to try again tomorrow if it's nice out, and I'll climb to a higher altitude to have more room for error.

Thanks again for your help!!!

Jay

aflipz

My Feedback: (10)

No prob SnitGTS. No cutting power no matter how suddenly would not cause the nose to instantly dive, If anything it would cause a hardly noticeable roll to the left if the prop is big and heavy and the brake is on. So eliminate that from the possibilities.

Another possibility remains wind; you can fly into it at a much lower speed in relation to the ground (airspeed remains same) So when you fly slowly into the wind and turn 180 degrees you go from increased airspeed relative to the ground speed all the way to a slower airspeed compared to the ground, with a transition that can be a little tricky at first. You should definitely get a simulator if you don't allready have one.

say you have a 15mph stall speed, and fly into a 10mph wind, you only need to be travelling at 5mph into the wind (5mph in relation to the ground) to stay aloft, but when you turn 180 degrees you will need to fly somewhere around 25mph ground speed in that direction to offset the airspeed difference (if you go 10mph with the 10mph wind at your plane's back the air around the airfoil is pretty much standing still, no lift at all, you can be sure the nose will drop right about then... )