down thrust
 

My flying buddy is relatively new to the hobby, but flies well. He has a sig 4* and it flies very well, and he has mastered the take off and the basic maneuvers. It seems to be properly balanced. His problem is in the landing. If he slows it to a reasonable speed, it wants to baloon and stall, otherwise he has to come in too fast. I recommended he try some down thrust (this worked on a plane I used to have with the same problem), but am now wondering if this is good advice. Any thoughts on this, or another solution? I recently added tail weight to my Kaos, and this greatly helped the landing, but am slow to recommend tail weight to his airplane since it flies so well except for landing.

RE: down thrust
 

It's possible he's just pulling too much elevator on flare. Four stars land like kittycats. If the balance is right on, as you suggest, check your throws.

RE: down thrust
 

Recent experience leads me to believe balance on a 4* is sensitive as it relates to landings. A spinner recently broke and was replaced with a prop nut. The weight difference was only 1oz less but elevator trim changes were necessary and landings were different. Also the airplane has a very light wing loading and wants to continue flying if the idle is the least bit too fast. Bouncing seemed to stop but there is always the possibility that I simply had a good day.

Bill

RE: down thrust
 

Downthrust will make it worse. You would need up trim in the elevator to offset the down thrust at high throttle settings, and that up trim would still be there when you throttled back for landing.

Having the tail drop on landing approach is a classic sign of tailheavyness. Make sure that it balances no more than 30% of the wing chord behind the leading edge with the tank empty.

Or it could be simply pilot technique. He may be flairing too early in the approach. As BillS says, 4 Stars are famous for floating on landings. Clipping one bay off each wingtip helps a lot.

Jim

RE: down thrust
 

It could be simple. It "seems" to be balanced right, but try putting the plane in a dive and then suddenly cut the power to idle. If it begins to pull up and level off on it's own, then it is too nose heavy. Move the CG back some, retrim for level flight, and try the dive test again. It should then continue in the dive or just pull up ever so slightly.

Now that it has been retrimmed for really proper CG, the balooning on landings should disappear!

Ernie

RE: down thrust
 

If the plane balloons over the runway when throttle is cut it means that downthrust is excessive. Adding more will make the problem worse. Shim the engine UP to alleviate this problem, but only after you have tried expo in your elevator settings and ensuring the plane is indeed balanced..

A nose heavy plane won't balloon, a tail heavy one will.

That plane should darn near land hands off.

DP