During the 5 hours of testflying my Airbike, my instructor has complained about the low effect of the elevator during landing. He says he pulls the stick into his stomach, and the Airbike just barely flares. The rigging instructions calls for 30 degrees elevator up, and this is accomplished. Is this a known issue, or are we doing things wrong? Do we need to use engine power when landing, or land with higher speed? My C/G is at about 13" while the manual says it can be at maximum 16.2" back. Could this be a reason for the "nose heavy landings"? Your meanings would be much appreciated.
Home phone 602-999-3715/Mini-max with Hirth 2704 Ace
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Hi Petter, Try sealing the gap between the stabilizer and the elevator. I use cloth tape on mine and its held up for 10 years or more and there's a good selection of colors to choose from. With the elevator in the full down position, place tape thats wide enough(1.5" to 2.0") to cover over the gap and stick it to both the elevator spar tube and the horizontal stab spar tube. Just make sure that you have full travel in both directions. The gap seal will make a noticeable improvement in the elevator authority/sensitivity so you may want to try just 24" on each side to see how well it works and then fine tune it from there.
My cg is near 16” back. It will make the elevator more sensitive and will allow you to flare very easily at landing. You will enjoy your a/b a lot more.
As well as Dick's excellent suggestion, I suggest you add some temporary ballast to the tail to put the c.g. back nearer the aft limit. If this solves the problem, then you might want to think about fitting a small second battery as permanent ballast.
Great answers. I remember using the tape method on my model airplanes, and it worked, so I will try this. And then maybe try using some ballast to move the C.G. further back. I see that the flight manual recommends having the C.G. at 28%-29% MAC. This is surely for a reason. Mine is at 26% now. It is at 14 inches, not 13 inches as I said in my original post. Thank you for your answers, Dick, Monte and Bruce
I've had a similar problem with my Minimax. When I did the W&B calculations it turned out that my plane has a CG of 13.4" when the fuel tank is full. This is 1" forward of the recommended front limit for the CG of my plane. I intend to fit another fuel tank behind the seat, and doing the W&B calcs with a spreasheet calculator from the LAA website, I can move the CG back to around 14.8" just by doing this.
I have found that as the current fuel tank empties the plane gets easier to flare, and you'll probably find the same.
My fuel tank is located behind the C.G. so it actually gets harder to flare when the fuel empties. But I have installed tape over the gap at the elevator and it had a really good effect. So for now, I will leave the C.G, where it is. Unfortunately I haven't got to fly as much as I want, mostly due to weater, but I really like the Air-Bike in the air. It flies nice and straight without me having to compensate all the time, and it handles well. Have to practice cross wind landings though. I'm a bit scared of doing that.
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