Ok I have an LT-40 with an O.S. 46fx on it.. I have been running an APC 11 X 6 on it, but it seams like the plane just doesn't want to slow down for landing. The idle is as low as it will go. when on the ground at idle it will barely move. If you change to a different pitch prop, what affect will it have. would a shallower pitch prop increase idle drag on approach? Or should I go thicker to make the speed of the prop slower? Thanks in advance.

FW

Assuming the idle rpm of your setup is where it should be or at least close,the prop size is OK,and I think you just need a little more practice on your approach and landing techniques.The LT 40 like most good trainers is a "floater" to give you time to get your height right as you pass the edge of the field,set up your glide path as you slow the plane with the elevator and do a perfect "10" flare and landing!

Hey fourthwind

I understand your problems on slowing the plane down on approach. I have had the same issues. Check out the posts and explainations that Harry gave me on my landing woes. The threads were titled "getting the hang of it" and tail dragger setup. The whole problem is around confusing throttle with speed, and the game is to use your elevator to control speed, and throttle to control elevation. Harry gave a really good explaination there, and I have been really practicing it the last couple of times out, and his techniques really work.

Good luck ... Bo

I don't have any problems with landing the plane. I can compensate for the plane's floating tendencies just fine. I would however like it if it didn't take a 300 foot final after a lockeed turn from base to do it. I talked to an high time flyer today at lunch, and have decided to try a 12 X 6 prop to give a bit more drag when at idle. I will lose a bit off the high end speed, but we are talking about a trainer.

Cheers,

FW

If you had already made up your mind why ask the question?If the plane is floating for 300 feet and your idle is OK,then you are doing something wrong and a different size prop isnt going to fix it.

actually I hadnt made up my mind when I wrote the post. I didnt talk to someone till AFTER. so no need to get pissy. I'm no rookie to this sport. just trying to get this plane set up to teach my father inlaw.. The idle is as low as it is safe to do.. I was just looking to see if anyone could tell me what the affects of different props would be. not my landing abilities. There are also facters of the alititude. 5750 feet to be exact.

Cheers,

FW

I would think you should go to a smaller prop, such as a 10x6. The bigger prop at the same idle speed will grab more air, causing you to go faster. let us know how it works out.

Ditto on the smaller prop. Reduce the pitch should slow you down. But remember there is a lot of wing out there to give you lift. Dont be too overly cautious about stalling. The LT is hard to stall. Practice how slow you can fly at a high altitude before slowing down too much on the deck.

I will have to grab a few props and give them all a try. I am just used to planes that bleed off energy faster. (Kaos, sticks, patterns. ect) I can get the LT slowed down with lockeed turns, but I would rather get it so that it bleeds it a bit faster without high bank manuevers on base to final.. (yes im impatient) lol. I think it comes from my father telling me how much my fuel bill was costing me for all the time wasted in the pattern with full scales as a kid.. I will post up after I try a few props.. going to try both extremes and record the results.. good excuse to burn some nitro in the father in-laws trainer.

cheers,

FW

I have an LT40-46FX-APC 11/6.

No problem slowing it down for landing.

Sounds like you are just keeping the plane level until it lands. Try adding in some up elevator on the final approach. It will raise the nose and start to slow the plane down. An LT doesn't need much speed to keep flying and you can control how fast the plane flys forward by the amount of up elevator you put in. You will be amazed at how slow you can bring it in. Add the up elevator slowly and watch how the plane slows down. You will get to the point where the speed is comfortable and at that point just continue to hold the elevator stick at that position until its ready to flair. Then add in the rest of the elevator as the plane is touching down. This method also prevents bounce on landing.
I have a low wing that has to be landed this way or it use the entire runway to slow down after touchdown. Have fun, Fast!

Something else you could try is a side-slip ( I think that's what it's called). On final, give rudder in one direction and aileron and elevator to keep it straight. So you give right rudder and enough left aileron. This will increase the drag and should slow the plane down. I've done this before to lose altitude. If your trying to slow the plane down so it will be easier for you father in-law to land, this wouldn't be the best thing to do. In any case, good luck!

down both elevators and then trim the elevator for level flight. This should generate more drag and slow you down faster.
Thoughts?
Steve

Do you mean "down both ailerons"?

I'd be willing to bet that the plane is nose heavy. It may be balanced exactly where the MFG suggests, but every plane is different. I once had 2 Goldburg Cubs. When I built the second one, I balanced it exactly where the first one was balanced, but the second one was nose heavy and wouldn't slow down for landings (or spin very well). when I added tail weight, the plane was as good as the first one.

CG is right in the middle of the manufacture spec. I will play with that as well. thanks. adding a bit of flaperon might be worth trying just for curiosity sake. a few degrees might be what im looking for.

FW

FW

cut some flaps ....they will slow you down...and are fun to play with!

Just for those that are curious. I got some flight time in today, and did some experiments on props. To try and keep all things as even as possible I did all tests in the first few minutes of flight with a full tank. ran engine till hot before take off. engine at one click rich from peak. idle as low as it could go without quitting. I tested master airscrews 10X7 and 11X6. and APC 11x6, 11X7, and 12X6. The master airscrew 10X7 was just too small for the plane.. It did make it a bit easier to slow down, but at the same time took away huge amounts of performance. remember I live at 5700 feet in elevation. air thickness is an issue.. I should also state that density altitude was 8300 feet because of the warm temps. next I tried the 11X6 master airscrew. This prop really gave me the best performance overall with my set up. Good take off and maneuver power, and still slowed down for smooth landings. The APC prop of the same size (11X6) had as good of pull, but for whatever reason it just didn't want to slow down when idled back. maybe the APC are just more efficient and have less drag than the airscrews?? The final prop was the 12X6 APC. really just to big for this plane unless you add larger main tires and extend the nose gear a bit. it definately greated LOTS of drag at idle speeds, but did reduce the take off and maneuver power. anyhow.. after all is said and done I am keeping the 11X6 master airscrew on the plane and putting the other props away for the multitude of projects I have on the table.

Cheers,

FW

you may be an experienced model pilot, but you should pay attention to what is being said in this thread.
I am an instructor in our club and have flown many LT40's.
Yes the plane does like to float. And with a bit of head wind, it just doesn't like to land...... (good trainer)
One thing I have noticed with this airplane, is that Sig's suggested elevator throws are a bit small. This is because it is meant for the novice.
If your idle is set right as you say, then you are just not slowing the plane down as much as you should...... maybe add a bit more throw to the elevator to get that nose up...... and like the one of the other posts....check the balance.

And I instruct as well and have been a licensed full scale pilot for 17 years .. wooopy! I have no fricken problems landing the damn airplane. This was not the intention of the post.. my intention was to LEARN about PROP sizes and effects so that I could optimise the airplane.. Yes I am being picky, and yes I didn't like the way this plane floated. Different props make a small difference in handling. this was my goal to learn what difference it made. I hadn't played with this part of models. I put them together. put the motor on and went with the recommended props and flew them till I wore them out. Now I have something else I can play with on my other birds.

FW

Then why are you posting in the "Beginners" section?

Interesting thread.....

Generally the smaller the prop diameter, the higher the idle RPM. That is why the 12 x 6 slows the plane the best. The bigger prop will act as a bigger flywheel with higher rotational inertia. It will idle slower than the 11 x 6 or 10 x 6. The 12 x 6 will have a lower "pitch speed" at idle, pitch multiplied by RPM, and will slow the plane.

I fly at 4200 feet and have flown at Evanston with a density altitude of 10,000 feet. The 12 x 6 is too much prop for these altitudes. I run prop sizes of 10 x 6 to 11 x 6 on the .46's.

If you really want to slow is down, try the APC 12.25 x 3.75 or 12 x 4 prop. It will keep the plane slow as well as act as a good air brake. I have tried the prop on a .46 powered plane and have to land with a little power on.

One of the big problems with high altitude flying is over 'prop'ing the motors. There is a difference in power up here and sometimes the recommended props on the high end are too much for the engine. The engine will run, but not very well. It will also overheat in some cases.

The LT-40 is a floater. I've flown one once and it reminds me of a powered glider. I had to throttle down early to land it compared to other planes.

I figured there would be people that moniter this forum that had played with different size props before and it would be a source of info for my own experiment. It is just something I hadn't done yet. so I guess you could say I was a beginner at the effects of pitch and length of props. I should have worded the original post differently.

FW

And Thank You AQ500. finally some imput I had been looking for. any difference between the APC and airscrew props that you have noticed?

I take a collection of props I have collected over the years out with me whenever it comes time to fly a new plane. I fly a couple of flights and then change the prop. I do that until I find the best prop. It is a lot of work and a couple of trips to the field, but pays off.

I have found that in some cases the MA will perform better than the APC. The best prop will differ from person to person depending on the way people want their planes to perform.

I'm a speed freak and love unlimited vertical. Most of my planes have APC's. For me, my fast planes all have APC's and the slow ones MA's.

I can't say one is better than the other. Props for the smaller engines are around $2 so experimentation is cheap. I guess if you read between the lines, I have found APC's perform better on faster planes and MA's on slower planes. I'm sure someone else would come up with a different conclusion.

Thanks for your imput AQ. I have bought a few more props for a few of my planes. Just another aspect of the hobby to keep me busy. like I needed one, but being the tech tweak that I am, I love playing with all aspects of the flight envelope. gives you something to do other than practice maneuvers all day.

Cheers,

FW