I recently took a trip to the local flying club for the first time and met the crew. After talking with them for a while, the general consensus was that if my wallet allowed, continue my flight training with another trainer rather than my newly completed J3 Cub. So I just ordered a Sig LT-25 (I heard it is better than its 40 sized counterpart) and my question is this:

Can I put my OS .46AX 2 stroke on the LT-25 and fly it safely? It has a 62" wingspan and I figured this will have UBER amounts of power but it wont be too much.

Any comments?

It will take off nearly immediately and pull out straight up. If that's what your shooting for then it's perfect.

I think you'd be better off with a setup the floats like a butterly rather than one that stings like a bee.

For learning, I'd select a smaller engine.

Just curious, how big is the Cub? Was the .46 engine for that?

The cub is a H9 80" Cub (ARF). I went ahead and bought a Saito .56FS for it. The .46AX was on my Airmadillo Kombat 40 (48").

Trainer's typically have larger wingspans than sport planes for the same size engine displacement (and combat planes like I fly, are even bigger, 64-72" wings with .15 size engines, but I digress). I'd stick with a recommended engine, putting that much power and weight in the LT-25 will take away some of the desired flying qualities. The LT-40 is actually a very nice flying plane, well liked at my club, several experienced pilots here have them for goofing off with.

I have a LT-25 which has an Os 32Sx and I think that is almost to much engine for that plane.An LT 40 would be much better for your power plant.

That's way too much engine. I have a 40FP on mine and it's sickly overpowered.

The Saito FA 30S is a perfecrt match for the LT-25.
A guy at our field has this set up and it flys great
just like its bigger brother the LT-40. Yes i know
the saito is probably more than your willing to spend.

I'm no expert (I always start a post where I'm disagreeing with the consensus that way) but I really see no reason not to use the .46 if you've got it, especially if money's tight. I built my LT-25 with a Fox .40BB on it, and it has no negative flying characteristics that I can determine resulting from this engine choice. It does climb like a ROCKET, though! 1/2 throttle is all that's needed for takeoff. Mine balances without adding any unneeded ballast, and really, the LT-25 has similar wing area to most .40 size trainers at slightly less weight. It can also still slow to a crawl and just lope around the sky in a trainer-like fashion.

I can give you three good reasons NOT to use the 46AX
1). The LT has a flat bottom airfoil and will balloon as you increase the throttle.
2). You will be more likely to get into a situation that will over stress the airframe.
3). The AX is an AAC engine and reaches its optimum running conditions at a given temperature. You won't reach that temperature because you LT will be able to fly level at idle. The engine will run cool and that's hard on this type of engine.

Come to think of it reason number 4). You won't be able to get the thing down to land w/o cutting the motor.

The LT is really a floater. A .25 is ample power for it. Either buy a bigger plane to go with the .46 or get a smaller motor.

The LT-40 would ba an ideal trainer for that 46AX, the best trainer I've flown. The only way I can see that the LT-25 would be better is that it would give you some tail dragger experience to prepare you for the J3....

If you haven't already got the LT-25, then the best option I think would be to get the LT-40 or similar. It could be converted to a tail dragger later. If you have got the LT-25 then you have a mismatched pane and engine and may need to get a smaller engine. On the bright side, a decent 46 2 stroke is always handy to have laying around...

I have an LT25 with an 32SX engine. This is more than needed and shows up at takeoff and when you try to land. For fun I go to full up elevator and and then go to full throttle! The plane will take off in about 10 feet and climb like a rocket almost straight up! On landing however at idle the plane takes a long time to lose altitude and doesn't really want to stop floating over the runway. I have learned how to deal with this by throttling down to idle on the downwind leg before turning to final to kill speed and altitude. With a 46 size engine, even at idle the plane will probably just keep cruising along making landing very difficult unless you dive for the runway or cut the engine completely. Neither one is the preferred method of landing! For an engine I would go for something cheap and reliable such as a Thunder Tiger Gp25. Its good for the LT25 to have its own engine anyway and the smaller motors run a lot quiter and use way less fuel![8D

i run a 46 LA on my kadet, and it is the best combo out there. this engine was made to be put on this plane. plenty of power to learn to fly with, and to goof of with. put a 12 or so oz. fuel tank in the plane and get HUGE flight times!!!

Way too much power.

Either buy an LT-40 or a suitably sized engine for that LT-25. Assuming you're a beginner, being guided by SIG's recomendation will afford you the optimum training result. Learn to fly properly in the first place so you don't end up like so many here who never really advance beyond 'learning' anything much other than how to crash consistantly.

The most common mistake most students make is overpowering their model at the ill-informed if well meaning advice of self-proclaimed 'experts', mistaking forcefully delivered enthusiastic opinion for expertise. For a myriad of reasons I won't expand upon here which just a little genuine research and reading will reveal, the ideal trainer is best powered by an inexpensive simple air bleed carburettored plain bearing engine. Thunder Tiger, Enya and OS are just three manufacturers of many who offer proven reliable engines ideal for the task. Provided you also have a competent instructor, the money spent on such an engine and trainer combo is truly an investment which will save you a bundle in the long run in terms of the emotional and financial pain of crashing, crashing & more crashing as well as avoiding, until you're better informed, falling into the trap of buyer excitement driven wrong engine choices.

Buy what you need now, not what you desire, think you will in the future or others want.

I train studs with an LT-40 powered by an OS 40FP. You might find an equal, but you won't find a better training combo. Though properly engined, the LT-25 rates as a pretty good alternative. With sound reason, similarly IRL studs train & learn on a C152 or Piper Tomahawk, not a C-210 or Malibu.

My powerplant recommendation for the LT-25 in the training role would be to power it with a TT GP25. Cheap as, robust, simple and adequate. Once your skillset (not to be confused with confidence) grows beyond that, although you could up-engine the LT-25 with a ballraced 25 or even a 32 which will fulfill any desire for more power when you can hande the extra speed, but more so you'll more want manoeuvering capability. You will benefit yourself best by advancing onto another model type better suited to role.

I agree the 46 is serious overkill. I would reccomend a 25. I hear the 25 LA is actually a good engine. This is only repeating what I have read. There are many good 25's out there. Irvine,Fox,OS,EnyaTT all come to mind. It is all you will need. It is a great plane. Good luck with it.

Mark Shuman

You already ordered it and you already have the plane.. Just go for it and be careful with the throttle. When you want to start getting crazy with this thing or are in high winds you'll like the power. My OS 46FX is not enough power for my LT40. Need much more!! Can't even do a 500 foot loop, geesh.. Need some ponies!! Remember, NO FEAR!

So.. what would you guys reccomend on the LT 25 for someone who was planning on just making it a ton of fun to mess around with?

IE No diheadral, etc..

Tram? Whaddayoudoin'here?(I won't tell anyone...) Mine is bone-stock, except for the Fox .40 on the nose. The structure can definitely handle the extra weight and power. Were I to build another LT-25, here's what I'd do:

-Build the wing flat--no dihedral
-Set up the ailerons to allow 45* of throw(I've maxed out the throws as built stock at both horns and it still rolls too slow for me)
-Enlarge the rudder about 20%
-Install a good .40BB 2-stroke or a .50 class 4-stroke

It's a great plane built stock, but it's so forgiving i wind up fighting it a lot, so my goals are to neutralize it a little and speed up the reponse. I suppose if you made the modifications listed above, you'd have something resembling a kit-built .40 ultra stick. Maybe that's what you're looking for, maybe not.

I have mine set up with dual aileron servos, maxed out control throws on all surfaces, and a TT GP 42. It will hover, does rolling circles, just doesn't look right since people don't expect it, gets a lot of laughs. Can dial down the throws and anyone can fly it. It still weighs very little, and I didn't sacrifice slow speed handling. I'm a big fan of this cheap little motor. Lots of power for the price $ 45 USD.

I just picked one up on ebay.. Gonna put... something in it.. Maybe a nice 32..

Someone was stating that they couldn't see how the LT25 would be a better trainer than the LT40. I trained on an LT40 and my son won an LT25 at one of our club meetings. The LT40 is a great trainer and will land at very slow speeds. I found out however that when the wind suddenly got really gusty, the LT40 had a real problem penetrating the wind and almost stopped moving forward. This is pretty fast winds we are talking out here! We landed in a few minutes out of frustration and then put the LT25 in the air. The LT25 penetrated easily, was easily controllable. It didn't ballon in the turns and and was actually a blast to fly. We put the LT40 up for sale after seeing this and kept the LT25!

I'm trying to understand why I see so many people who are no longer beginners making recommendations such as overpowering the plane, adding way too much throw to the surfaces, removing the dihedral from the wing, etc. The OP was looking for information on setting up a trainer, not en extreme trainer. Any chance we can all work to keep him on a track that will lead to success, not excess?

RCRainman, your best bet is as others have said, follow Sig's recomendations. The ideal trainer is one with a little extra power, but light weight. Adding the .46 will probably work, but it'll end up heavier than necessary. Get yourself a reasonably priced .25, build the plane light, and learn to fly it on the wing, not the prop. When you're done learning, keep it for practicing landings, testing new radio equipment, etc. Or, if you do a good job building it, and it's in good shape when you're done, sell the plane and engine to another new beginner.

That's why.

In addition, the original poster put this question out in March. Most likely, he long ago decided what to do, and our comments now are moot to him. In my March 10 post, I merely told the orig. post author how mine was built (on the advice of our club's instructors). Adding the power of a light .40 had no ill effects on the flying characteristics of my plane, so why not? I had the .40 on hand, a .25 I did not. The weight difference between the Fox .40 and the OS .25 FP I had is only about 2 ounces. Turns out I needed to move radio weight forward even with the .40. So, not net weight gain, as I would've needed about 2 oz. of ballast anyway.

Piper Chuck- I solicited ideas.. Matt just helped answer my "newer" question..

A friend of mine has a LT25 that flys on electrons rather than slime and it is a ton of fun to fly, I'm sure I can get the same flight characteristics out of mine on a nice .32 or something like an LA 40..