Engine RPM keep increasing

[mave]

Hi all,

recently I have this problem:
when I push my throttle stick for the heli pass Mid stick, the engine will start to increase speed even though I have held the stick in position. It keep increasing even while I tried to land it.

the following are what I did to try to rectify the problem but to no avail:
1) I changed my main fuel tank
2) changed the fuel line in the header tank
3) change all the fuel line.
I did all the above, but the engine problem still persist
4) finally I resorted to pressure testing the carburator and I notice air leakage at the circle area. Is it normal to have a bit of air escaping from there?
If it is normal, where is the place that caused the problem?
If it is not normal, is there a way to "patch" the leakage?


Please advise.

[Ghostfit]

...I suspect you're having this problem only when yur heli is decending from height ? ...quite common with a non-governed nitro heli when the main rotors are unloaded.

Could be a sign that your mid-range needle setting is a tad lean.

[mave]

I will have this problem once my stick past the mid point. Then the rpm will start to go up no matter if it is descending or ascending.

[gilera180]

I think your engine is getting leaner and leaner when pass mid stick. Check your main needle O ring and your mid range needle O ring make sure they are not wearing out, meaning when you turn them you can feel a little bit of restriction. Of cause for the main needle you have to remove the ratchet before you can feel the restriction. Hope it helps.

[mave]

Hi, I have changed the high end needle o-ring, but the problem still persist.
Also, I did a pressure test and those places with o-ring is not leaking air. The only place leaking it the region around the mide range needle which can slide in and out when you throttle. That is the only area that is leaking which I am not sure if it is normal.

I think your engine is getting leaner and leaner when pass mid stick. Check your main needle O ring and your mid range needle O ring make sure they are not wearing out, meaning when you turn them you can feel a little bit of restriction. Of cause for the main needle you have to remove the ratchet before you can feel the restriction. Hope it helps.

[Blackite207]

Did you do anything to your pitch and throttle curves? Without a govener, it will take some time for the blades to stablise with a fixed throttle setting. When decending from foward flight you may experience a sharp increase in headspeed with reduced throttle prior to landing. This is normal but can be corrected with a good throttle and pitch curve

[mave]

I get what you mean, you are saying that during the initial hoover, the heli is bog down but as the engine spool up the engine gather speed... Is that what you meant?

I have consider that factor too. bu tht rpm keeps increasing way passed 3000rpm when my throttle curve at that point is only 65%.(holding the stick at the same position.

So, I don't think it is the throttle or pitch curve even though I am not totally disputing that possibility.

Did you do anything to your pitch and throttle curves? Without a govener, it will take some time for the blades to stablise with a fixed throttle setting. When decending from foward flight you may experience a sharp increase in headspeed with reduced throttle prior to landing. This is normal but can be corrected with a good throttle and pitch curve

[Blackite207]

Please Dont fly if your head speed is 3000 rpm!
You risk ripping the blades off your heli and flying off at the speed of sound!!!!!
Looks like you need to seek the help of someone who can inspect the engine, throttle, servo and linkage. Could be fuel mixture setting. Perhaps you should start fresh with the power plant. Remove the engine and chek for overheating. Redo the linkages, reset the servo. re-tune the engine high speed needle first then low speed needle.
This will be a process of elimination and trial and error.

[mave]

Yup, there are too many possibilities....
I'll try with a new carb and see what happen

Please Dont fly if your head speed is 3000 rpm!
You risk ripping the blades off your heli and flying off at the speed of sound!!!!!
Looks like you need to seek the help of someone who can inspect the engine, throttle, servo and linkage. Could be fuel mixture setting. Perhaps you should start fresh with the power plant. Remove the engine and chek for overheating. Redo the linkages, reset the servo. re-tune the engine high speed needle first then low speed needle.
This will be a process of elimination and trial and error.

[mave]

Finally solve this probem!

I richen the mixture and high end needle a lot(3.5 turn for this TT50 engine).
at the same time I changed the fuel filter. Now the engine runs cool and with ample power!

Save myself buying another engine.

[HotDogBun]

Handsome. Let me know when you fly again. Want to know more about setup for nitro heli

[mave]

What about thursday?

Handsome. Let me know when you fly again. Want to know more about setup for nitro heli