lospeed

I have a pilot extra 260 with an MLD 28. It is balanced according to the manual but the problem is, when I cut the throttle it climbs? When I fly inverted, hands off the sticks, it still climbs? This makes it very difficult to fly and land this bird.
I was told it had to much down thurst, so I incrementally started to increase the up thhrust with washers...still no change after significant adjustments.

Has anyone else experinced this issue, if so what is the solution?

clarencem

Well it sounds to me as that it may be a little tail heavy to start with. I have had the "BOOK" be wrong on a coupe ocations. I always do the math myself and check and recheck it before I take to the air. I would start there befor going any further. I am assuming you know to figure out the cg for your self without using the book. If not its very easy to do.

Jezmo

I agree with Clarence. It's tail heavy. Slowly move the CG forward until it will fly inverted with just a very slight forward pressure on the elev stick. Should land (and fly) great at that setting.

da Rock

As mentioned, the chinese.... uh, the manuals aren't always right.

A quick, simple way to get a good start CG location is to measure the plane with a yardstick and plug the numbers into geistware.com's online application. It takes about 10 minutes and is foolproof.

lospeed

Thanks guys! I will go more nose heavy and see how that works...I will let you know next Sunday of the results

lospeed

Well, I got 3 flights in today and sure enough, the CG needed to go WAY forward. The manuel was way off. That is the last time I take the "manuals" CG recommendation without checking/verify its accuracy. Thanks for the advice guys, my plane flys like it should now...its like a brand new plane again

Jezmo

Glad you got it flying good.

JOHNS3D

My Feedback: (5)

thtas because sometimes companies use one manual for all the airplanes. You should take time and read the trimming charts and test. Those files are really good for people like you.

hutchi

lospeed how much did you have to move it

lospeed

Hutchi, I had to move it almost 2 inches forward. When it was balanced by the manual, my 5 cell NiMh battery was at the side of the fuel tank...now I moved it all the way to the top of the motor box. (under the cowl). I have it strapped to the X on the top of the motor box. Now it flys like an awesome plane. Before I had to use spoilerons (opposite of flaps) to get it to some what land, but after going extremmly forward with thre CG (according to the manuel anyway) it flies and handles like a champ now!

The 2 inches forward might seem extreme, but from my setup up, it was spot on

BMatthews

One way to test your new balance location is using a dive test. With the engine set to about 1/3 the max RPM and the elevator trim set for level flight nose over to a 60 degree dive and hold it there for a moment and then release the elevator stick. For a model of this type it should continue downwards in a steady line with no nose pulling up or pushing to a steeper angle. If it pulls up SLIGHTLY then that's fine too. But the goal for a model of this type is to keep the balance point very close to the neutral point. The dive test tells you if it's in the right area or not.

With the old setting it sounds like it would have certainly tried to tuck to a steeper angle. An instant sign that the CG is located behind the critical neutral point.

freakingfast

My Feedback: (3)

Lowspeed, you did well to get it on the ground with the CG that sick. Congats!

lospeed

It was a challenge belive me...I just cant believe I let it go for 3 weeks (12 flights) without moving it forward, thinking it was something else besides the CG.

hutchi

Thanks for the info lospeed moved some things forward an fixed the landing issue, now little work on thrust an be good to go.

lospeed

Hutchi, your plane may have the same issue as mine. Not only did the CG have to go forward 2 inches it also needed considerable right thrust put on the engine. I needed to add 2 washers thicknesst to get it to fly correctly. Before it would pull strong to the left in a vertical up line....put a couple washers between the standoffs and engine...that solved the problem.

millertym2000

My Feedback: (4)

after reading this I think My 50cc Yak is a bit tail heavy. When I bring it in and cut the throttle the nose always pops up like I bumped back on the stick. It makes it hard to get down when theres a little wind, but when theres no wind it will glide in like a trainer with the nose up just a little.,

BMatthews

Millertym, try the dive test I suggested to confirm the issue. If it passes but is still doing this then you may have a thrustline angle issue at play.

Jezmo

Yep, I agree with Bruce. Either tail heavy or a thrust angle issue. Also, like he said, the dive test should point you in the right direction for a fix.

rjkpic

Millertyme,

Try moving the CG forward incrimentally. If the aircraft pitches up when you reduce power it is probably a CG issue. For it to noticably pitch up when reducing power from a previous low power setting would be more indicitive of the CG being to far aft, or aft of the wings center of pressure (CP). I would try the CG first and if that does not rectify the situation progress to the engine thrust line. Assuming the model is an ARF from a reputable company, the likelihood of the built in thrust line being the culprit is statistically small compared to the placement of the modelers induced CG.

Jezmo

As Bruce mentioned in his post above, I would try the dive test before I moved anything, then you know what the problem is rather than guessing. It is quite probable that it is the CG but by testing first you are sure before you change anything.

AA5BY

I'm betting it lurched into the air on takeoff without any elevator to rotate.