I'm just beginning to build an LT-40 kit. I've read many discussions on engines for this plane, and it seems that most people prefer putting a OS .46 FX in it (or something similar.. BB type). Many say that something like an OS .40 LA or even .46 LA is underpowered.

Why is this? the LT-40 ARF seems to require a .40 - .46 engine, but the KIT version, which seems to be the same dimensions, recommends .30 to .40... and says that anything over a .40 is too overpowered.

Although this is my first kit, I think I should do a decent job of keeping it lightweight.. I'm new to this hobby, and plan to stay in it.. but I think an OS .40 LA would be fine for my first choice. If I want to move up to something faster, I'd rather buy a 46 FX (or AX) and put that in the new plane, and keep the 40 LA in my trainer. That way I could take both to the field if I like.

Also, I'll only be taking off from ashpalt runways. There are three fields near me here in the Los Angeles area, and all are paved. So I won't need the extra power that something like the .46 FX would provide on takeoffs. The .46 LA version might also be an option, since the weight and dimensions are almost the same as the .40 LA - but they also seem to be the same performance-wise, so I'm not sure I see the point in spending $10-$15 for no noticeable difference. (or am I wrong?)

I'm sure others will have suggestions for other engine manufacturers, and that's fine. Feel free to suggest that too. But is there anyone out there who has had good experiences performance-wise from just putting a .40 sized engine in the LT-40 kit? (like the instructions recommend.

Nothing wrong with being overpowered.. but I'm trying to keep the costs down. Building tools and supplies are eating me up at the moment!

The .40 LA will be fine. It will require longer take off rolls and not fly into the wind as fast. The .46 LA does have a bit more power and would be my first choice for the budget minded. The .46 FX would be even better and possibly last longer. My son is currently flying an Avistar with a .46 LA that has seen at least 3 other trainers meet an untimly death, but the .46 just keeps on going! Good luck!!

A Mag 46 XLS is just right, the power of an OS and less cost. Don,t bother with the LA, a nice little underpowered engine, it runs well but doesn't do much else. ( Bet I hear about this?) From your remarks you think like I did when I first started, Got rid of that little plain Bearing engine rather quick! My thoughts.

Yeah, I think I might just go with the .46 LA. It's not too much more expensive, and has a little more power without being any different in size or weight than the .40 LA. By the way, how big of a difference would I notice between the .40 and .46 LA?

The .46 FX or the new AX would be great - but I still have club dues and a radio to purchase... not to mention a flight box and flight line accessories! It would definitely be a good investment for a future plane.. but like I said, I'd still like to keep and fly my trainer without having to switch engines.

I had an LT-40 with an LA-40. It was underpowered, but good for training. I think the LA-46 would probably work really well. I currently have the LA-40 in an LT-25, it's really at home there and balances perfectly. These engines aren't strong but are easy to tune and easy to start, good things when you're starting out.

My trainer has a 46la and I fly from grass. It is a Balsa USA Stick 40 and it flys it great. I put a set of home built skis on it and flew it off the snow about 6 inches of powder and it did fine. The LA runs good and is on it 8th gal of fuel but my father-in-law has a 46FX that runs so much better. It starts better,idles lower and makes a lot more power for just a little more money. I am keeping my trainer as long as it will last. I am thinking about putting floats on it next for snow and water.

There is nothing wrong with either of the OS LA's for your use but you need to look into the Thunder Tiger 42GP [$49.99] and the 46Pro [$79.99]. In my experience the 42 is more powerfull and at least as user friendly as either of the OS LA's.
Fred B

I have a LT40 with a 46 la - plenty of power for the trainer, but I wish I bought a 46 FX for it. I could then use it in many more different airplanes. The LA is more weight for its power and sport planes are more fussy about weight. When I first started I didn't know much (still don't) and was more worried about the Hobby store upselling me.

Either way you won't go far wrong with an OS engine.

You should definitely get a ball bearing engine. The .46 size would be better for the LT-40. You don't have to use it, but it's nice to know that the power is there should you need it.

In my experience (I am also a beginner), the .40LA is just fine. The LT-40 is a big trainer, so if you want fancy aerobatics, I would recommend the .46FX. My LT-40 flies just fine with the .40, and I can still fly it through some basic aerobatics. I waited on the .46FX until I had a plane that would suit it better. I would say if you're just learning the basics, go with the 40LA. Hope this helps, good luck

Use any ball bearing .46 and run an APC 11x5 or 11x6 prop on it...it doesn't get much better than that! When you start with the forward-most CG it will be a puppydog, go to the intermediate CG you'll have an advanced trainer...go to the rear CG and it'll do stuff you never thought it would

Build it strong, build it light but more than anything build it straight!

Mtisdale, I am teaching my kids with an LT-40, GREAT AIRPLANE, but its BIG for a .40 size airplane. It will fly with any .40, but there are a couple of things you have to consider. First, in windy days, with a small engine on a big airplane, you`ll be in trouble. Second, with the LT-40 you will learn to fly rather quickly since it`s an awesome trainer, then you WILL want a faster bird soon, the LT-40 is not aerobatic at all, so get an engine that you can later put in an aerobatic plane. We have an .46FX and thats a sweeeeeeet one, and will power a good aerobatic plane with easy. If I may, let me recommend you a Superb 2nd plane , the do-it-all SIG Kavalier, a Kavalier with the .46FX and you will never forget this advise ever. If you get a .46FX, get the new .46 AX ABL BB, it`s even better.
If you need to get something more economical, get a Supertigre G-45 or a Tower H. .46 ABC BB. Anyways, GET a BB engine. Do not hesitate to contact me with any questions, I`ll be more than glad to help you. You can e-mail me too. GOOD LUCK !!!

I have the LT-40 and have the OS 46 FX It turely is a great combination..I learned on it in less then 4 tanks of gas last September as a beginner. They couldn't believe i could learn that quick. I did cheat a litte with the fight G2 flight simulator. Cobberbob

Hey Gene tell me more about the CG on the LT40. How far back can you go and what sort of tricks can it do?

I thought I would have to take the dihedral out of the wing to get anywhere. I haven't done that yet because I still want to teach my kid with it.

The first one I built was per plans except for being a tail-dragger. I had a TT PRO .46 on it and used an APC 11x5 prop. If you check the directions they will show you three different CG locations. At the rearmost CG it wasn't a pattern plane, but it would do snap rolls and other aerobatics impressively for a 'trainer-type' plane. As I built the plane and didn't glue in the servo tray...never do on any plane until the last thing. I get all equipment in/on the plane and then set-up the CG by moving the tray as needed to minimize, or not need, any additional weight. On this plane I initially set it up to balance perfectly on the rear CG and then added weight under the engine to move the CG forward. That way when you finally 'advanced' to the rear CG you lost weight in the process. That was the first LT-40...it died one day when I was really wringing it out and was a bit too close to the ground...oops!

The second LT-40 has a flat bolted-down wing (no dihedral) and one-piece fir main and rear spars...you could practically beat someone with this wing! This plane was also built as a taildragger and a tailwheel was made to be steerable by running another pushrod back and rigging a control horn on the tailwheel...works great! Initially I had TT FS .54 up front...it flew, but it didn't have the umph I wanted so a Magnum FS .80 was put on it...that made it almost like a tractor pulling through almost anything I wanted to throw at it. Presently it has a TT FS .91 up front though I haven't had time to get it fully set-up and test-flown. I also plan on using two servos on the wing, side by side, for the torque rods on the ailerons since that was the way the plane was initially built. If I had it to do over again I would put the servos out on the wing and get rid of the torquerods. I bet it will be even more fun to play with using the FS .91...time will tell!

One definite 'to do' tip would be to ditch the Dubro pushrods supplied with the kit and go to Sullivan Goldenrods...they don't expand and contract as much with temperature extremes. Install pushrod supports at every fuselage former and relocate them from stock locations so as to minimize bends/friction...you'll get more out of your servos that way and not use as much battery current in the process. Also, make sure hinge-line gaps are as tight as possible or if nothing else, seal them with additional covering...your control surfaces will work much better that way. Oh, BTW, I dialed up the throws somewhat from 'stock' recommendations, too. Please keep in mind that the second plane is by no means a 'basic' trainer anymore...there is NO self-recovery to it...screw up and it is crash and burn time!

I've got the ARF LT-40. I first flew it with an Irvine 39 which worked perfectly for this plane and enabled me to solo first time out (this was not my first trainer).

At this point it's worth noting that the Irvine 39 is about 2ozs heavier than the 46LA and is more powerful, although not as powerful as the OS46FX.

I bought an OS 46FX to go in another plane so I thought I'd put it in the LT to get used to it and break it in. I moved the battery back to keep the CG in the same place. When I made the change I noticed two things:
1. There was practically no difference in performance
2. The nose would drop noticably more when power was removed.

So, if you can find an engine that has similar power to the 46FX but is about 3oz's lighter, this would be the perfect match.

BTW. I am now running an OS FS70II in the LT with an 11x6 4 blade prop. This is an interesting combination that will pull the plane straight up almost out of sight, but I think this engine is too heavy for this plane.......

As you pointed out with your comment on paved runways, I think the choice of engine depends a lot on where you fly. I first flew my LT40 with 46LA. At our field, you have a fairly short runway and then have to make an immediate climbing turn to clear the trees at the far end of the field. You then have to continue climbing and turning to get above the trees on the downwind leg. Takeoffs with the 46LA were a little more "exciting" than was really comfortable given my experience (or lack thereof!). A missed approach was definitely pucker-time if you left it a little late. I changed to a 46FX and it made a world of difference. Takeofs were all of a sudden a lot more comfortable. Either will work. Go to field(s) you plan to fly at... there's almost sure to be an LT40 or two. See what motor they're using... ask the instructors which motor they would recomend with an LT40.

I've got an LT-40 Flew very nice with a 40 la the 46 la has more power and runs Great as well. Go with the 46LA to start out with. You will love the Plane and the Engine! I have had the Plane 4 Years now and I do alot with it. I have a bombay door in it and I Pull Banners with it! I also put a Magnum 91 four stroke in it after three years of refreshing my flying skills. Go with the 46 LA or a 70 Four stroke you'll love it!

I have to disagree with the idea of heavy 4 stroke engines in this plane. See above, I think the weight of the FS70II ruins the sedate flying characteristics of this plane, maybe a Saito 72 might be better.....

As for the 46LA, that's the other end of the spectrum. It's probably just adequate for power and is a bit light. It's 2oz's lighter than the Irvine 39 for example and not as powerful. I had to move everything forward with the Irvine.

On the new LT-40 ARF's (with the bolt on wing) you may have to add nose weight with a 46LA.

My preference would be a decent BB 40-46 2 stroke or Saito 72 4 stroke. Anything heavier will ruin it.

Well here we Go! Opinions are for everyone! This Plane would fly very nice with a four stroke OS 70! I have the Ninty Magnum in mine. It will fly ultra slow and on a brezzy day you can actually fly it backwards into the wind! I had a 40 LA in it it flew nice. I had a Magnum 52fs in it. It also flew nice. I had the Ninty Magnum fs I had to try it! It's perfect the plane will do anything you want it to!
Check this post out
http://www.rcuniverse.com/forum/m_13...tm.htm#1394294

If a four stroke is your cup of tea. A nice 50 size engine is all you need. I reccomend Saito, I have and use them. Get an OS if you like. They are good engines as well. As for an OS 2 stroke I would say the 45 FX. Only because you can use it in later models. If your heart is set on an LA then the only real choice is the 46. I feel from what I have read the 40 is just not enough. Whatever engine you choose this plane will please you a lot.

Mark Shuman

Last summer I put an OS 52 FS on a LT40 I repaired, and it flew beautifully. I can't recall what size prop I used. But it didn't take much throttle to get it airborne.

OK OK OK... Don't go for the LA range! Think about the future! I really regretted getting a 40 FX instead of a 46FX...

Although it may seem that 40 LA/ 46 LA is a better choice now, because of price and power, if you get into 3D flying, you'll need all the power you can get! Beginners usually think that they need the basics, and that will last them down the road ( take me for an example). Nope!

At first, when I was starting out I started, I bought a Skysport 4 and a 40 FX. I changed the Skysport 4 after I got sick of it's short range and limited channels.

You really NEED a 46 FX! You won't need to change the engine for any other .40 plane for as long as it will run! Long term savings...

Mmmm... my friend runs a GMS .47, its full of power and is fuel effecient... it flies for 25 minutes non-stop. Wow.

Oh and the new 46 AX is great stuff. I took off a beginner's trainer after rolling out about 200cm. LOL! Should try that again...