LT 40 climbs forever!
 

Hi.
My father has an LT 40 that he is training on. There two problems we have encountered with this plane: It wont stop climbing at anything above idle and its a bear to land.
Dropping the engine speed doesnt result in the plane settling down to earth, you have to FORCE it down to the ground. I have had some floaters but this thing is insane.
Idle is set properly, CG is correct, engine is an OS .40LA.
My suggestions to him were to either shim up the rear of the wing a bit or add small washers to the top screws of the engine mount to add a little down thrust.
Anyone agree, disagree or have any other suggestions to offer?
It is very difficult helping my Dad learn to land a plane that is so difficult to land. I can set that sucker down fairly easily but, as I said, I have to force it down to get it to land.
Makes him so nervous that its near impossible for him to land it and landing practice is what he needs the most right now.

RE: LT 40 climbs forever!
 

I have a student that has one. It is definitely a floater and flies well.

We have had to add a bit of downthrust to get it to fly right. Originally it needed a lot of down trim with the plane flying with power, but when it came time to land it needed up trim. Downthrust should help solve your problem.

RE: LT 40 climbs forever!
 

Put 2 popsicle sticks under the trailing edge of the wing when you put it on. This will reduce the incidence and ease the climbing problem.

RE: LT 40 climbs forever!
 

I have had 2 LT-40s (first a kit then an ARF) and the charicteristic you are describing definitely isn't normal for this plane. When reading your post my first thought was that the plane may be tail heavy buy it seems you have ruled that out. These planes do float forever since there is so much wing area. I can't tell you how many times I watched mine float on by and had to go around for another try while learning to land. They simply cover a lot of air space for every inch that they drop closer to the ground. A flat bottom air foil will produce more lift when you increase speed but it sounds like your plane is excessive. I have flown other trainers that have this charasteristic and it can be really annoying as you feel like you are constantly trimming and correcting the plane.

I would give the above suggestion to raise the trailing edge of the wing a try. It may not be the exact answer to the problem but it could very well help. If the balance is OK as you say my next guess would be a wing incedence problem. Of course the problem may not be with the main wing as the horizontal stab could also be the culprit. If you fly with a club you may try asking around to see if anyone has built the kit version of the LT-40 and borrow their plans (assuming yours is an ARF) so you can check the thrust line and wing incedence of your plane against the plans.

RE: LT 40 climbs forever!
 

Raise both ailerons a bit?

RE: LT 40 climbs forever!
 

I have to ask if you balanced the plane correctly. A tail heavy plane will fly like you describe.

RE: LT 40 climbs forever!
 

Jim Trainor's suggestion is usefull (reflex the ailerons up a little). I also suggest that you deliberately increase the nose weight somewhat. This will raise the landing speed a little, but it will smooth out the handling & reduce the floatiness.

RE: LT 40 climbs forever!
 

Yesterday I took my LT-40 out for its flights # 5 and 6. For some reason the trainer box idle was a lot higher than it was the previous flights, and I had a hard time getting it to come down (but I landed it myself because I wanted the challenge). It currently has a fair amount of down elevator trim. Later with the low idle (we reset it mechanically) the instructor had me doing downwind landings, and I went from an average of 70% landings-per-approach to less than half. It just loves to float. My CG is towards the front of the range the instructions dictate. I don't really have to give it much down elevator on approach unless I'm coming in too high.

-Jeff

RE: LT 40 climbs forever!
 

Thanks for the advice, guys!
I will have my father re-check the CG to make sure we can positively rule that out. I had suggested he make it a bit nose heavy a while back but am not sure if he did or not. I suppose I should have mentioned that we always have to land downwind due to the set up of our "field". There is only one approach direction available due to a highway being near so up wind landings are not possible.
We fly where we do because there is very rarely anyone else there and are not restricted to landing on a specific runway. Landings are NOT his thing which is why we do not fly at the club I belong to or the public field at Sepulveda basin.
At the club field, you either stick it on the runway or kiss off your plane. there is no kind of median strip either at the ends or along the sides of that runway and the sucker is lined with boulders to keep the 4X4 jerks off the pavement. It is kind of like carrier landing in a paved trench.
I know that once I get him able to land with confidence we can move to a nicer field.

Thanks again!

RE: LT 40 climbs forever!
 

He might have bought an early version of the LT-40 kit? Mine (many years ago now) had the (unmodified) wing saddle cut-out at too high an incidence. Factory error. Everything including thrust lines were as per plan. Even the engine was as depicted per plan. Despite the significant amount of additional lead noseweight required to balance the characteristically tail heavy build of the LT with a similar lighweight powerplant up front, the consequence was that with the OS 40FP at full power, it'd climb abnormally requiring abnormal down elevator trim and the associated problems with decalage amongst other things. Your primary problem sounds very similar. I corrected mine by shimming the trailing edge up about 1/8" to correct the incidence and decalage issue. If that is your problem, that will stop the climbing and any associated pitching instability issues.

As to the landings. The LT-40 is an acknowledged floater, but - propping that engine airframe combo right is the key. It's a high drag (slow) airframe with a (relatively) low power engine - which is though, just fine and arguably the ideal combo for the training task. Too high a pitch prop will give you poor airframe acceleration, slower engine accleration and importantly poorer braking at flight idle. After much experimentation I found a Master Airscrew 11x5 suited the engine/airframe combo well. The blade is slim and light allowing good mechanical and aerodynamic acceleration, and the pitch/diameter combo is right for this airframe engine RPM range. A 10x6 won't work well. You might try a wider bladed 10.5x5 Bolly Sportsman which I think would work well. They weren't available when I had mine running an MA 11x5, but I think that particular Bolly would probably work well for your purpose.

You can research the aerody of it all at your leisure, but you'll find those two suggsetions will probably fix the climb rate/angle at full power and address the descent rate at flight idle issue as well offering good aerodynamic braking for a slow good angle approach with superior engine and airframe acceleration should a missed approach be necessitated. PS: Just read your mention of downwind approachs. This is of course an aviation no-no both IRL and R/C. Expect a floater to extend on approach & float much further on a downwind approach and landing. This exacerbates the importance of correcting the salient factors previously mentioned

Hope this assists.

RE: LT 40 climbs forever!
 

He has had this LT ARF for less than a year and had the LHS order it from Sig so it should be from the latest batch. My father doesnt do kits even tho I keep suggesting he do so now that he is retired. He had to replace the wing due to a chance meeting with a tree but the climbing thing was happening before the wing replacement and continued after.
It flies very slow and sedately but whether facing into the wind or flying downwind, you still need to force it down to land even at idle.
Anyway, I will have him re-check the CG first. If that is correct or correcting it doesnt solve the problem I think we will try the popsicle stick shims at the trailing edge.

RE: LT 40 climbs forever!
 

Let me confirm the popcycle sticks under the trailing edge, that Ed Moorman suggested.
It was on my LT-40 that Ed & I were flying, that had the same climbing problem. He said to add the sticks....which adds a negative (or reduces the positive) incidence to the wing and reduces the climb tendency. You may even have to add another stick depending on the CG. A little nose heavy is a good thing ! Now I had a manageable airplane.

Try it, You'll like it !

Ugo

RE: LT 40 climbs forever!
 

My father informs me that it is nose heavy according to the instructions. We will try the popsicle stick idea as that seems to be the most advised adjustment to try.

Thanks Guys!