Just bought a TT pro 46 for my trainer,I wonder which propeller will be the best fit?Thanks.

11/5 is a good size for a 46

Take a look here:

http://www.rcuniverse.com/forum/m_10386274/tm.htm

CGr

"best fit" is what we all wish for. The best we can hope for is one that works good enough we don't know right off it's the wrong prop for that plane/engine/fuel/and flying site's altitude.

The best prop for YOUR model really winds up being (pun intended) one that lets the engine run in it's best rpm range while using the fuel you bought to pull the model you have in front of you (ARFs vary in weight off the assembly line and straightness and quality) at your flying field on the day you're out there flying. One size prop can be the answer, but it's not guaranteed.

So you look at the mfg recommendations for the engine. You'll see a huge range most times for the reasons already mentioned. Every one in that range has a good chance of working well on that engine. The best thing you can do is start with what you see working on your engine on your model at your field IF someone out there already has that combination and is flying it.

But all that aside, for a beginner's trainer, you want "more" prop diameter and "not so much" pitch.

The diameter gives thrust. It also, when "enough" for the engine, will actually help make that engine easier to adjust and smoother running in the air. 46s can run 10" diameters, but often are screamers with more sensitive needle settings with that dia. They'll turn 11" diameters just as easily when the pitch matches the airplane, and with a trainer that'd be both 5" and 6" pitches.

Once upon a time, glow .35s had the power to spin 10x6s and that's what you'd see on almost every one of them. Today's engines are a bit more powerful. A good .46 on 10% fuel pulling the average trainer would be underpropped with that.

Try either an 11x5 or 11x6 first off, and plan to try more than one brand. BTW, there is no magic prop manufacturer. Advice to the contrary is actually a clue that the advisor hasn't really tested different brands to know they all work very well when dia/pitch/blade area match up with the test plane/engine/field altitude/etc.

It's actually valuable experience for anyone who has just learned to fly by himself to start right in trying different props. It teaches them to better observe what the plane is doing etc.

Have fun, but that's the easiest thing to do in this hobby.

I had a TT pro 46 in my trainer and I used a evolution 10x6. It was a pretty good screamer with that prop on 15% nitro, but in my opinion, it was a great combo. Mine would roll 20 and take off at a really steep angle at full throttle. If I left it on the ground to build speed it would go striaght up much farther than a trainer should be able to! On landing it it slowed down enough to make it managable on apporach. I tried a 11x4 and 11x5 on it as well and it slowed the plane down quite a bit in flight and helped slow the plane even more on approach. I just didnt like the lack of top speed with the lower pitch prop. Again it is my opinion but I really liked the 10x6 evolution for this engine on a 40 size trainer. Good luck!

The good'old Master Airscrew black colored G/F series 11X6 is great for beginners because it doesn't always shatter if it just nicks the ground. Always keep some spares ready.

For better performance step up to the dark grey colored Master Airscrew S-2 series 11X6, but this one is more brittle with impact. This prop speed and engine load fits between an APC 11X6 and 11X5. In some sport/trainer applications the M.A. S-2 may actually exceed those APC props in performance.

APC makes excellent very high performance props, yet they are among the least forgiving of a minor prop strike.

I have an 11x5 APC on mine in the nose of a Saratoga 40.  Beautiful match up.