A couple weeks ago i threw a prop and lost it out in the bushes. I thought the prop was a MasterAirscrew 11-6, so that is what i replaced it with. Well, somethings wrong because now it flies more like a pylon plane than a trainer. It flies way faster on 1/2 throttle than it did before. It is an old Great Planes Trainer 40 with a OS .46ax. I would perfer a lower top speed with good climb. I like the durability of the MasterAirscrews. What would be a better prop for a trainer?

skeeter

That's actually a very good prop for that engine. If you want to get quicker acceleration and slow the plane down a little, go to an 11x5.

Hmm.... the plane definately is faster and i can't think of any other reason than that.

skeeter

With that engine...

I'd recommend the APC 12.25x 3.75...

works perfectly with the .46

I'll second that, lots of pull, will slow down for landing and being a trainer it won't float across the entire runway.

There is a such thing as too low a pitch for trainers. If he gets in some wind with that prop, he'll have a fun time trying to get it to go forward. Me personally, I'd stick with the 6 pitch and throttle down as needed for that reason alone.

I third exeter_acres suggestion to get a lower pitch prop. Only get a 12x4 or 12x5. Note that the larger prop will turn slower and offer a little better engine life. It will also offer good accelration and lower speed.

But frankly, a 11x6 should be quite OK. I flew my own 65" 40 size Explorer-40 with a 55AX on 12x6 for a long time and 11x7 when I progressed to aerobatics. I didnt transition to a lower pitch prop till I started hovering on my 3rd airplane.

Ameyam

APC 11X6 would rock on this motor, IMO, I'd always go for this.


Best of Luck to you.


Mody

4 pitch props are for hovering and pulling slow uplines in aerobatic birds. A trainer needs to keep some speed up to keep its controls effective and to deal with wind. I learned that as a student, and have now seen it as an instructor. If the OP will give the 11x6 a chance it should perform well and be a good compromise between speed and acceleration.

I also fly a 40 size trainer with a OS 40 engine my instrutor told me to us a 10x6 prop on it . with is prop the plane flys vary good fast or slow all will loop and roll .I use a master airscrew like itlot better they don't break as easy. be sure to balance them before you us them.

I would try a 11x5 apc. . The 13.25x3.75 or 12x4 will also work well but you may run into prop clearance problems with the PT40 . Master Airscrews are also good if your flying off a rough feild and prop strikes are an issue.
My trainers are all taildraggers with after market main gear and have plenty of clearance for the bigger props. If the feild I,m flying has a tight landing area I switch to a lower pitch prop mainly to help slow it down on landings. 13.25x3.75 works the best and the wide flat blade acts like a brake when pulled to idle. But for an overall trainer prop the 11x5 seems to give enough top speed and also a little more pull for loops and such.

The GP Trainer 40 is not what most would consider a primary trainer.
It has a fully symmetrical airfoil, very little dihedral, and is more like a "stick" than a trainer.

Skeeter,
If the 11x6 is too fast for the way you like to fly, and you want to stay with MA, here are two options
12x4 http://www3.omnimodels.com/cgi-bin/w...I=MASQ1359&P=7
12x5 http://www3.omnimodels.com/cgi-bin/w...I=MASQ1251&P=7

As far as speed, the calculated number at an arbitrary 10,000 rpm is
4 pitch 37.9 mph
5 pitch 47.3 mph
6 pitch 56.8 mph

Quite sorry for my rather incomplete post earlier.

Skeeter, a lot of people will suggest a lot of things (that includes me). For a sports trainer (as I think you have), you should either put 11x6 or 12x6 if the model has the ground clearence. 4 and 5 pitch props are also good but use them as a last resort if you are most uncomfortable with the above.

By any chance, did you adjust your throttle pushrod linkage about the same time you lost the prop? Or you may have lost the throttle alignment. Meaning, what you think is 50% throttle on the stick may not be 50% on the carb. Just check by observing your carb while operating throttle on your TX. It the alignment is lost, readjust. You will find a lot of info on other threads on how to do this.

Normally for your app, 11x6 should be quite good

Ameya

Recheck CG location; advanced location imposes higher load to the wings.

Check prop ground clearance (allow ~2"), for max diameter; then adjust pitch accordingly.
You could use this chart as a guide:

http://www.top-flite.com/accys/topq5000a.html

Isn't your plane a PT-40?

Shh.. don't tell this to my LT 40 that I learned on and am teaching my son to fly with.. as it flies perfectly with the lower pitch prop....
I would hate for it to find out and stop flying well....


Either works fine...

props in that range are cheap.
Have an open mind and try a few out and see which one you like best....

My plane is actually a Trainer 40, not a PT40. It is over 20yrs old and i pulled it out of storage, restored it and started finishing learning how to fly. I converted it to a taildragger awhile ago to learn how to handle one since my next build on the table is a SS60.

Just to give the full story. I threw the prop and upon inspecting the engine noticed the front hub damaged and the front bearing rough from what looked like rust. I replaced them and the engine seems to run great again.

I wondered about the throttle linkage adjustment the other day but when i checked it it seemed to be ok. But now that i think of it when flying on saturday it seemed to idle lower than normal and had to use a couple of clicks to idle smoothly. If the 11-6 is the normal prop recommended for that engine then it is probably what i had before. If i adjust the linkage to idle a little higher like it was before it would run even faster than it does now at half throttle.

Maybe it's just me! Any suggestions?

skeeter

I will make one comment that seems "too obvious"
If the plane is going too fast at your "normal" throttle stick position, pull it back a little bit.


I do not move the throttle much while flying and occasionally wonder why it's going so fast (or slow); and it takes a while for it to register that I can control that.


But, don't be afraid to change props. If you put on a lower pitched prop, the plane will not fall out of the air. You might find yourself at full throttle all the time and wanting to switch back. If so, just land and make the swap. The MA 12x4 and 12x5 props are about 4 dollars each. If you have a LHS (and if they have them in stock) you can try both for about 10 dollars including tax.

Thank you, and yes i do realize, as others have mentioned, you can just pull back on that left stick to slow it down. My question was more around the subject of why does it seem to be flying faster now then before with the same stick setting. i believe it might have to do with the throttle linkage. I did remove the engine during all this so maybe it's just adjusted differently. Unfortunately i have not had the time to check it out closely. When i do i'll post my results.

skeeter

I run a 10x6 scimitar on my Nexstar, works fine, and at half throttle I can go for 20mins.