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HelicopterMain Discussion › Head speed/ throttle setting question
12-18-2003 11:54 PM  13 years agoPost 1
Helimex

rrApprentice

Oklahoma

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Went out flying this afternoon after having installed my new 401/9253 gyro/servo and as I was wringing it out and doing some tweaking I noticed that for some reason I wasn't holding engine rpm very well. I don't think the gyro/servo has anything to do with this issue because the gyro seems to be doing its job very well. No, I think I've got some other bugaboo nipping at me, although I may be wrong and the rpm issue may in fact have something to do with the gyro/servo. Here's what's happening: The heli seems to sound and fly right during forward flight at moderate speed, tail holds rock steady. It is when I start flaring out to return to a hover or when I am at a hover the engine rpm seems to drop considerably as is noticeable from the sound. The helicopter does hold a hover but it sounds like the rpm's are somewhat slow and the heli actually starts wobbling like it wants to kindof fall out of the sky, yet it does not. Tail hold problems, none. I'm kinda guessing that I need to do some tweaking in the throttle curve area maybe? Or am I looking in the wrong direction and tweak the pitch curve or maybe both? How about mixture settings? I don't have a tach to see what my head speed is so I'm winging it and going by sound alone. I'm flying an Ergo 30, OS32, 25%nitro, temp here is about 50 degrees. Pitch 0,5,9. Throttle linear. Thanx to all.

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12-19-2003 12:36 AM  13 years agoPost 2
d-n-jensen

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Bellevue WA

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Sounds like the engine is either lean or the throtle curve needs tweeking. Remember with glow power the fuel to air ratio is about 30% fuel to air and the air density can change a lot from the morning to the afternoon causing some engines to have to retweek the main needles. With gas engines it is about 3% fuel to air so the difference in air density does not make a big change to the overall ratio. First thing to do is richen up the main needle and see if this works if not add throttle to the hover position.

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12-19-2003 12:36 AM  13 years agoPost 3
Wisdom-Seeker

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Danville, CA

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What is your current throttle curve set to?

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Wisdom-Seeker
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12-19-2003 07:22 AM  13 years agoPost 4
Helimex

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Oklahoma

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dnjensen, when you say "add throttle to the hover position" do you mean that as in the throttle curve? If so, I'll sure give it a try, thanx. When I say I'm running linear throttle I mean 0,50,100. Should I try and tweak these settings? Shouldn't the throttle lead pitch?

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12-19-2003 07:18 PM  13 years agoPost 5
Wisdom-Seeker

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Danville, CA

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If you're running a linear throttle curve, you may be underpowering your rotor. My own heli uses a curve of 0, 60,100.

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Wisdom-Seeker
Protest letter to insurance co.: What do you mean "Act of God"?

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12-19-2003 11:43 PM  13 years agoPost 6
shawgl

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Murrieta, CA

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Flare

Helimex, you said it does it after flaring to stop forward flight correct, Well when you flare to slow down you are reducing collective/throttle in order to keep from gaining altitude. What is most likely happening is when you reduce the collective/throttle and flare you bleed off a good bit of head speed in the process which will cause lead lag problems with the head which will in turn cause your vibration. You just need to tweak your throttle curves to where you have more available at the low end. Example. I can see you are hovering at half stick by your post but you will see what I mean.

In my normal mode I have -3,0,10 for pitch and what I do is set my throttle curve to where my hover rpm is achieved at my mid stick postion (0 degrees pitch) and as I give more pitch it maintains the RPM up through hovering and so on up. What that is going to do is allow you to flare and slow down without reducing your throttle down to damn near nothing so when you roll it back over level you still have rotor rpm. You can do it by sound by pulling it into a hover and note the sound of the rotor, set it down and at about 1/4 stick you need to have the about the same rpm.

Hope it makes sense. Good luck.
Glad to hear the 401 is working for you.
Greg

In God we trust, everyone else we monitor.

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12-20-2003 07:19 AM  13 years agoPost 7
Helimex

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Oklahoma

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Thanx for the replies. I did some more tweaking this aft. and your suggestions paid off. It seems my pitch curve was a little off as was my throttle curve. After some fine tuning I got the heli running and flying pretty good.... I think. Anyway, I was a little puzzled at the onset of this problem because a week ago everything was fine and then all of a sudden the flying qualities changed. Oh well, what matters now is that all is ok again.

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12-20-2003 01:30 PM  13 years agoPost 8
shawgl

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Murrieta, CA

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Glad to hear it, remember that the weather can have a huge effect on the throttle/pitch curve because of the engine tuning. Rather than jacking with the curves, it can usually be solved by adjusting a click or two on the engine.

In God we trust, everyone else we monitor.

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HelicopterMain Discussion › Head speed/ throttle setting question
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