I have a tower trainner 40, and I put a O.S. 46 AX in it. The manual recommends a 10.5X6, 11X6-8, 12X6-7 size prop. I have a 11X6 on it now and my club trainner would like to slow it down. any recomendations on how to do it without buying a new engine? he recomended a 11X5 prop and thought a longer prop may not be very good for the engine. Oh, the O.S. manual has the props listed as sport and dosent list any other recomendations.



all recomendations are appriceated and will be tryed, thank you.

Yes, you can use an 11x5 prop or even an 11x4 prop. This will help to slow the plane down as compared to a 11x6

you should reduce the pitch on the prop that would help big time i have also shortened the prop by one size and left the pitch the same

Ditto on the recommendation to drop to an 11x4 prop. That will slow the plane down quite a bit.

Ken

Another one for an 11X4 APC

Depending on ground clearance, you could use a 12x4 and slow it down even more.

I don't see why any trainer of the usual size should ever have more than 4 inches of pitch, yet you see 10x6s routinely. Just makes landing harder.

Jim

An 11-4 will help. However, an 11-4 is light for a .40 and a .46 AX is overkill. You are going to be turning MORE RPM, Tell your instructor that the throttle does NOT have to be full forward regardless of the fact that he can push it there.
With a Tower trainer 40, a good .29 will fly it well. A .46 AX is real overkill. Simply throttle back to a comfortable cruise speed and work from there.

i agree with the last statement. a 46 flying an 11 x 6 on a trainer is slow enough. there is no need to fly any slower than that. i flew that combo on my first flight and it was easy breezy. moving to a 12 x 4 may slow it down but really there is no need. i can't imagine a situation where that kind of prop would be needed for training. as hossfly said, throttle control will be the way to go IMHO.

Also they make props that are wider that will help slow it down and no need to fly it as fast as it will go. Fly about half throttle if you need to. I had a 40 and a 46 and not all that much difference really that cannot be compensated by throttle and prop pitch. You could also limit servo travel to a set point by working with the linkages.

After you fly it for some time you will be ready to rip the sky up with it anyway. If it is the club trainer a different prop might be the best way to go.

G'day The main advantage of using a lower pitch prop on an overpowered model is to allow the model to slow down when the engine is idling to let you land more easily.

For this reason I usually use 5 pitch props on my trainers.

The AX 46 will happily spin a 12 x 6 (a friend has quite a heavy model of a PC-9) flying really well with this combination) so a 12 x 5 would be a good start. The engine will happily swing the 12 inch prop and this will keep the revs and the noise down too. Or you could try an 11 x 5 as well.

There really is only one way to find out. Try some props and see which you like.

For that .46AX I'd also recommend an 11x5 or a 12x5. It would depend on ground clearance. An 11x4 just sounds like too little a prop (pitchwise) for this engine and you risk over-reving.

Changing the prop will help, but you might also consider moving the CG back a little.

If the plane is nose heavy, it will fly faster than if it is balanced properly

An 11x4 will spin faster than a fast spinning thing. If you want to drop the pitch then opt for a 12x4 to keep some load on the engine.
The increase rpm of a 11x4 may actualy make you fly just as fast but slow you down like a chute was deployed when you throttle back.

I find on the OS 46Ax, the 11x6 provides excellent throttle response and a 11x7 even better and landings are fine.
 When I fited an 11x5 my rpm increased and the plane actually flew faster and the vertical was better too.

I find this is more clearly noticed on my GP Escapade. With the 11x6 she flies fine, fit an 11x5 and shes a lot more lively.

Try changing prop pitch?

Put the prop on backwards. That's an old free flight trick to slow the plane down for testing.

I agree with many here. You should look at a 12x4 so that you dont over-rev the engine, provided of-course that you have the prop clearance.

However, I believe, its better to fly a trainer with a medium pitch prop. It will prevent you from slowing down too much and stalling at landing. I learnt on a trainer with a 55ax and 12x6 prop. I broke the prop after 6 months and by then I wanted to leanr aerobatics. So we put in a 11x6 then and it flew aerobatics much better (it had a 65" span semi-symmetric wing). On my second airplane, Tiger-40, I went all the way upto 11x9 before I settled on a 12x4 mainly because it isint that stable at landing (Its a Phoenix Tiger not CG). I now use 12x4 or 13x4 on my Reactor because it remains controllable at a speed lower than a trainer.

Better would be learn on the 11x6. To slow down the airplane, you just need to go to idle a bit earlier

Ameyam

Go to a 3blade for slowing it down. 

I agree with Hossfly. There's nothing that says you have to use full power if you don't want to. You can adjust your throttle linkage so that you can't get full power from the engine. Or if you have a computer radio it's very easy to adjust your travel limits. I would rather do that than put too light of a prop on there.

Agree with Hossfly, changing props, putting them backwars, set limits in the transmitter, change the CG. Putt the  throttle back, back on the elevator a little and the plane will slow down without any changes.

Spider, I have a Tower 40 trainer with an OS Max 25 on it. It came out very nose-heavy and landed too fast. Thanks to help from this forum, I figured out the CG problem and moved my battery toward the tail. It made an amazing difference on landing speed.

Lower pitch props will make sure your idle (which is great on the engine you have) doesn't develop too much thrust so the 11-4 suggestions are good ones. Here is a link to a bigger wing I built for mine to slow it down even more. The Tower Hobbies Trainer 40 is a tough bird and a good flyer once the CG gets in the right place.

http://www.youtube.com/watch?v=4EkaU9emYWU

BTW, my CG is 8 cm back from the leading edge of the wing.

Does that OS .45AX have a carburator, and does the throttle stick on the transmitter move it? If so THROTTLE BACK....!!

12 x 4 should not be needed on that plane and that engine unless you are trying to hover with it. I'd go with an 11 x 5 or a 10 x 6, but you can really rev up a .46ax with a 10 x 6 if you insist on pushing that left stick all the way foward. I'll also second Minnflyer's suggestion to move the cg back a little. It will help the plane land slower and it will be more fun to fly as long as you don't go too far back on the cg.

We typically use an APC 12.25 x 3.75 or 12 x 4 on a trainer...unless prop to ground clearance is an issue. If that's the case, then maybe an 11.5 x 4 or an 11 x 5

Naturally, proper throttle management is part of the learning curve....as some have already mentioned, that's why they put carbs on the engines...

If you run a 10X5 three blade Master Airscrew you will have fantastic aero-braking for low, steady descent speed and lots of power to pull out of trouble without over revving. A side benefit is more ground clearance. Do not confuse this prop with an Evolution trainer three blade, I refuse to teach with those on a plane and install a APC 11X6 or black MAS 11X7.

11x5 is a great prop for that engine and plane. Hold a little back pressure on the elevator to set a slower speed approach.