Landing at idle???
 

Hello,

I have been in this hobby for almost a year now and am still flying my LT-40(no crashes :D :cool: imagine that...) After my engine was initially tuned I never really attempted to change anything and therefore am still running at the same settings as when my instructor set it up. The engine is a TT Pro. 46, and the carb settings provided consistent performance throughout the year. The problem I am experiencing now is that before take-off, the engine idles well, at acceptable RPM(model doesn't roll at idle). But once I feel I have to land the engine is running at a very high idle causing the LT-40 to come in at a speed way higher than what I want it to be.(It is not necessarily my incompetence with the model as I can set her down smooth in the middle of the runway almost every time at a slow idle, but high idle and I make three landings/bounces in a row :rolleyes: :( ) A fellow flier told me that it could be caused by the engine achieving full working temperature in the air and hence working at a higher RPM at idle. He also suggested that I bring the throttle trim down a tad just before landing. I am wondering whether that is safe as I am running a chance of shutting the engine off if the trim is too far down(I tend to restrain myself from watching the trims). How do the more experienced fliers handle this? Carb settings? I love to fly but this is causing some frustration for me. :( Please explain how I should handle this type of idle setting fluctuation.

Thanks in advance.

RF

retune it
 

If the motor hasn't been tuned in a year, it is likely running at a setting that was determined in different weather conditions.

Try retuning it a bit. don't move the settings much....

Good Luck!

Landing at idle???
 

I've been in the hobby about 10 months myself. Glad to see that you're doing fine also. I'm no expert but there's times when I like to land a little hot. I used to balloon the plane alot also and break alot of props, but a friend of mine suggested...when I come in on the final, drop down and try keeping the plane just a few inches above the ground. Don't try to flare it everytime but just let it float as it comes in. You'll find that you'll have to gradually put in up elevator to keep it floating and soon it will just run out of airspeed. I used to drop it in and try to flare at the last minute to land it on a dime, but it would just about always balloon, and there would go another prop.
Try what my friend suggested and I bet you'll find you'll be landing alot smoother. And by the way, I have a whole lot of props that I don't need anymore if you need some.
Also, I retune my engine daily and sometimes several times if the conditions change very much. Again my friend suggested that I peak the engine, and then open the needle until you hear a considerable drop in rpm. Also, check your exhaust residue on your plane when you land. If it's the color of your fuel or slightly brown in color, you're OK. If it's real dark or black, you need to run it richer.
I hope this helps because it's been great advice for me this past summer.

Landing at idle???
 

:eek:

No dead sticks yet?

Thanks all!!!
 

:) Thanks for the speedy replies!

shradio:

Thanks for the advice. What your friend suggested is almost identical to what I am doing, but I just can't seem to get it right because the plane is going rather fast(not due to me attempting to bring it down from too high but from the high engine speed that actually still flies the plane). I am also changing the propeller from a 10x7 to a 11x6 to see if it performs better. I am wondering if the 10x7 prop would give enough thrust to maintain flying speed at such low RPM? Also, since I haven't really attempted to tune my engine, how would I peak it? Just lean it until it achieves the highest noise pitch(no tach here :( ) and starts to sag? Then richen it to the peak RPM and then some more until it loses some RPM? I am sure it is not complicated, just a little tense about screwing around with my engine. As for the unneeded props, I can unload a couple dozen myself (these were used/shortened before I started using Master Airscrew Nylons :D ).


Steve Guinn:
Well, yes I have had deadsticks (on the buddy box) before the engine was completely broken in and mainly because I ran out of fuel. Was having WAY too much fun.

Dead Stick Grand Total: 3 :D :cool: :devious:

RF

Landing at idle???
 

It's very common for an engine to run at a higher idle in the air, after warmup, than
on the ground after you've just fired it up. Learn to play with the idle trim for best results.
(Or get a computer radio which has "idle down", which takes care of this specific problem)
The prop is able to "unload" in the air, and you're probably picking up an extra
hundred or so rpm, even at the idle setting, in the air. This will be sufficient to keep it flying.
(The prop "unloads" by propelling the plane, which presents less resistance in air than grounded)

Also, don't expect that a carb setting should last a year. (even if it does, sometimes)
Given different weather, different batch of fuel, etc... it's not uncommon to retune often.
(I do this before every "first flight" of the day, and sometimes in between, to tweak)
Optimal settings may vary from day to day, or from morning to afternoon, by a few clicks.

Finally... the 10X7 isn't doing much to help slow you down.
On that engine, I'd suggest trying an 11x5. You'll trade off some top end speed,
for a greater static thrust, and a better "braking" effect on downlines and landings.

At the very least, try the 11x6 as you mentioned.
That's still quite a load for a .46, but it will give you better braking than the 10x7.

Landing at idle???
 

to set the high speed needle valve use a tach top reach max rpm,then richen the engine to 300 or 400 rpm below peak, if no tach you can use the pinch method. Run the engine max speed then pinch the fuel line, if engine is rich the rpm will increase,if the engine stops or slows as soon as fuel line is pinched that is the max,richen fuel so engine speeds up around 300 to 400 rpm as soon as fuel line is pinched,when finished point plane up, if engine dies then it's still to lean,if engine slows a bit when glow power is removed then time for new plug.

Have a goodun,John

Landing at idle???
 

Way back when I was at about the stage you are in flying, I was getting way low on my approaches to try to bleed off some air speed. A friend of mine was watching me one day and told me that if I happened to lose the engine on final, I would not make the field. He said always fly the approach so if you lost an engine, you could make the field. (Works with most trainers, but a warbird might be a different story.) I thought it was good advice and have practiced it ever since.
As far as a dead stick on an LT-40, don't be afraid of it, it won't fall out of the sky. I also believe that learning to land dead stick is important to practice, since the odds are you will experience one sometime. Of course, that's just my opinion. I learned to fly RC on a two channel Cox Centruion, which was hand launched, and every landing was a dead stick since I had to fly it till it ran out of fuel. I became pretty proficient at flying, but when I went to a 4 channel Senior Falcon, I had to learn to take off!
As far as tuning the engine, don't try to get every last ounce of power out of it on the ground, as the prop will unload once in the air as C_Watkins said, and the engine might go lean. Running a little on the rich side isn't going to hurt the engine. These guys above had some good advice. Go Flyin'!

Good Luck,
Randy

Landing at idle???
 

here is what i do to tune/setup etc

fire up the engine, then when its in the restraint (you do have a tie down dont you?) stand behind the plane and bring it to full throttle.

(note i do this part by ear... you may want someone with experiance to help you with and maybe a tach.)

I then lean out the needle valve till i hear a drop in RPM .. i then back the needle out until i hear it peek again then drop a tiny bit. thats how i know its running just a tad rich.

i then bring it to idle and let it sit for a few seconds. then "pop" the throttle t full ... if it hesitates its running rich at the low end if it comes to full bore quick i bring it back to idle as its running right... i then set the idle down to were it just about to quit and bring it up a tad to keep it running.

then i fly.

if you still have it running "hot" when your on approach bring the engine idle down a click or two .. you can always throttle up a bit if the engine starts to die.

Landing at idle???
 

oh ... and if you want to hear about high idles at landing ask marc (rcadmin) about his cap today ..

came in ... idle to high ... went around brought the idle down a click or two. .. still to hot .. went around .. etc etc etc ... till went around... ran out of fuel, stall, bang, bye bye cap. :rolleyes:

Landing at idle???
 

It's likely that your idle mixture is a tad on the rich side when you first start up which gives your nice idle revs but at the end of the flight you've used up most of your fuel, the level has dropped and now the idle mix is leaner which is increasing the revs.

Landing at idle???
 

More diameter and less pitch alone will probably bring about the change you are looking for. I also agree with changing the needle setting unless you are flying in San Diego where the weather is the same 97% of the time you are not getting all out of the engine you should.

Landing at idle???
 

I keep my Saito 56 idle setting so low it just about quits before a flight, I keep the throttle up 2 clicks to keep it running. After I fly around for awhile and the tank level drops the engine leans out and the idle is perfect for smooth slow landings.

tuning
 

There was a thread on here a week or two ago about the pinch test. Search for it, and you will read several opinions about it. I think it is the best way to check your settings. I am NOT a fan of needle tweeking. I like the err on the side of caution, as a lean run really hurts the engine. It seems to me that the ones always neddle tweeking are the ones always changing engine parts.

As for your problem, I agree with the too rich on the low-end adjustment. BUT I would not change that. You are REALLY close. If you are too rich, the engine will load up and die on final. If you are too lean, it will not run a smooth idle. While I have seen various things said on here about how much to turn your low-end needle, the consensus seems to be in small increments. (1/8th of a turn). In my mind, that is not worth the trouble so that you might end up creating a problem.

I seem to have the same problem with one of my engines as I get more runs on it. However, it is under a cowl, and I don't want to go in there for a few more months when the weather really changes. So yes, I do drop a few clicks on final.

There is a guy at our club (very experienced and qualified pilot) who dead sticks all his landings on purpose with his new engine for this same reason. So if you come in hot, go around once and just kill it when you are on final. I think this better that what happened to the guy who talked about losing his CAP

Zee

Landing at idle???
 

I fly my LT-40 with an APC 11X4 prop. This works really well. It jumps off of the runway. Also, you don't want high speed with an LT-40, so the 11X4 prop is a great choice.

Landing at idle???
 

I do the same thing rc-sport does. It works every time.

Thanks everyone!
 

Thanks to everyone who replied,

After reading the replies I decided to enlist the help of a more experienced flier at our club to learn how to tune the needle valve this weekend and see if the problem is eliminated that way. I am still very uncomfortable about being so close to the spinning propeller and trying to direct attention to adjustments which causes me to limit my tinkering with the engine :rolleyes: . I will also practice reducing the throttle trim inflight if the problem persists, so I would not be caught in a situation I am not prepared for.

Thanks again for all the help.

Houston Weather: 85% of year consistent weather, 15% Rain.

RF

Landing at idle???
 

The best prop for that plane and engine that I have found is a master airscrew 11 X 6. you might need a bit of re-tuning, but it in my opinion is that in the air the prop is not loaded like it is in flight. the larger prop will help that a bit, and will also help with a bit of aerodynamic braking at idle. You may also want to put a piece of fuel tubing on the needle valve where the needle meets the carburater. The last two of those motors i have had (and my students have had) were leaking, and would lean out the motor in flight. good luck!

FW

Landing at idle???
 

Continue to be uncomfortable about getting your fingers around spinning props. You'll save yourself a lot of pain!
Some of those composite props remind me of spinning steak knives!

Randy

Re: tuning
 

Well, "proper" needle tweaking prevents the lean runs you fear ;)
Lean runs DO hurt the engine, you are correct.

I'm not a fan of tweaking, either, if it's leaning to the last nth rpm.
(For others, it's fine. High performance comes at a price they're willing to pay)
I do like for my engines to run happily, and not surge, sag or bog.
If given the proper oil, in the proper ratio, there's nothing wrong
with tweaking the needles to maintain stoichiometry. (for power AND economy).
This could be needed several times per day, as temp, barometric pressure, or humidity changes.

As for always changing engine parts...
I've never wasted one yet, outside a crash... and I tweak almost every time out.

Landing at idle???
 

If you find you are still bouncing when landing, try to push in some DOWN elevator when the wheels first hit the tarmac. That will press the nose wheel down and keep the bounce to a minimum or not at all. (Tricycle gear only, of course!)

Happy Landings.

Pat

Or just...
 

Or land only a wee bit above stall speed, with an adequate flare....and you'll do fine. :)

Landing at idle???
 

I like to have lots of thrust thus I fly with an 11/5 on my mvvs 40.
would like to try 12.25/3.75 what do you think?
the plane is a house of balsa extra 300L.
ps the mvvs runs great (It has that mini tuned pipe)

Landing at idle???
 

I have a little great planes cap 232 with an OS 46 fx, and I swing a 12X5 Graupner prop on it. It gave me the best low end thrust and good speed to carry inertia through IMAC manuevers. with that smaller motor that 12.25X3.75 might work pretty well. you will need to be careful with your landings. with that low of pitch and long blades, the airplane will slow down ALOT faster than your used to.. you might even have to carry power all the way to the gound when landing. Have fun and try lots of different props. you will be amazed at the difference they can make in your plane.

FW

Landing at idle???
 

I agree with Fourthwind it is better to carry a little power on the approach than to go hopping down the runway like a bunny.