Gasser ... throttle & pitch curves

[tidalwave]

can anyone help with this - setting pitch and throttle curves for a gasser. what should be the right amount to begin with. where to begin, and where to go from, from there. thank you!

[rbort]

There is no pitch curve programming, it stays linear (0, 25, 50, 75, 100) in all flight modes including hold so there is no jumping of the heli when you switch modes. You setup your top end and bottom end range so the heli climbs at full collective and maintains your headspeed without bogging. Normally mid stick is set to 0 pitch for 3D flight and you hover upright around 2/3 stick and inverted around 1/3 stick. Top end is from 12.5 degrees in summer to 13.5 degrees in winter on average with 716 blades, more with 690 blades maybe 13 to 14 degrees.

Throttle curve varies with your linkage setup but for me something like this:

0, 25, 38, 48, 100 (normal) 1700 head speed
100, 51, 41, 51, 100 (idle up 1) 1800 head speed
100, 56, 43, 56, 100 (idle up 2) 1900 head speed

The way my throttle arm size and geometry is with these setting if I hover at 1700 head speed with governor on and turn off the governor then the throttle curve allows for the same rpm just about. Same thing with idle up 1 and 2 so governor on or off head speed stays about the same. If you turn off governor and rpm goes up, throttle curve too high lower the points. If you turn off the governor and the rpm goes down, throttle curve too low raise the points. Also check midstick by landing from a hover to 0 pitch on the ground center stick and turn off the governor and see if rpm is about the same, if no lower or raise the mid point to match or be close.

If you retune engine you will have a different speed between governor off and on unless you go back and redo throttle curve numbers, but as long as they are close it doesn't matter you can still go fly OK no worries.

Hope this helps, see what other people tell you to do also and go from there.

-=>Raja.

[dshriver]

I’m pretty much the same as Raja. I run a linear pitch curve. -12.5 0 +12.5 for IU 1/2 and Hold. In normal I don’t run as much negative. It’s more like -3 0 +12.5.

For throttle, my normal curve is nearly identical to Raja’s. However in IU 1/2 I just run a V (well more of a U) f
curve. The gov on my Futaba 760 FBL ignores the throttle curve and I don’t fly without the governor. I only have the curve in place in case the governor fails.

[ChrisMatthews]

You guys are pulling 12.5 to 13.5 degrees pitch on your gassers? What engines are you running and rpm? You don't get a lot of engine bog pulling 12.5+ degrees? 12 degrees seems a lot more stable to me as far as engine load. I was running the MS Composit 710mm gasser blades which performed very nicely and precisely... until I trashed them recently Ill be trying the Rail 716 very soon.

[rbort]

I am running Hanson 300 motors in my Whiplashes with the zimmerman long mufflers and typically I run between 1800 and 1900 rpms when I fly. I set the top end pitch so I can maintain my rpms and I can climb at full collective at 1800 governor on and it will hold the 1800 all the way up to the moon if I let it go that far... But if I turn the governor off the the engine will "run away" accelerate the head to a faster headspeed until it tops out wide open.

Normally it tops out somewhere around 1900 rpms so it can maintain also idle up 2. In the winter time it gets up even more topping out closer to 1950 rpms. I add some more pitch in the winter to "consume" that power and get an even faster climb at full collective as the governor otherwise it holding it back all the time.

Rail 716 very nice for me they auto super and track nicely in the air. Ms Composite are lighter more for stick banging if its the black ones with the red tips I'm thinking of?

Best regards,

-=>Raja.

[dshriver]

I’m running an OBR 310 with the ReVo 720 blades. My engine is still breaking in so I’m on the low side for RPM right now. 1500/1600. Once I get more flight time my target HS is 1600/1800.

[tidalwave]

Originally Posted by rbort

There is no pitch curve programming, it stays linear (0, 25, 50, 75, 100) in all flight modes including hold so there is no jumping of the heli when you switch modes. You setup your top end and bottom end range so the heli climbs at full collective and maintains your headspeed without bogging. Normally mid stick is set to 0 pitch for 3D flight and you hover upright around 2/3 stick and inverted around 1/3 stick. Top end is from 12.5 degrees in summer to 13.5 degrees in winter on average with 716 blades, more with 690 blades maybe 13 to 14 degrees.

Throttle curve varies with your linkage setup but for me something like this:

0, 25, 38, 48, 100 (normal) 1700 head speed
100, 51, 41, 51, 100 (idle up 1) 1800 head speed
100, 56, 43, 56, 100 (idle up 2) 1900 head speed

The way my throttle arm size and geometry is with these setting if I hover at 1700 head speed with governor on and turn off the governor then the throttle curve allows for the same rpm just about. Same thing with idle up 1 and 2 so governor on or off head speed stays about the same. If you turn off governor and rpm goes up, throttle curve too high lower the points. If you turn off the governor and the rpm goes down, throttle curve too low raise the points. Also check midstick by landing from a hover to 0 pitch on the ground center stick and turn off the governor and see if rpm is about the same, if no lower or raise the mid point to match or be close.

If you retune engine you will have a different speed between governor off and on unless you go back and redo throttle curve numbers, but as long as they are close it doesn't matter you can still go fly OK no worries.

Hope this helps, see what other people tell you to do also and go from there.

-=>Raja.

much appreciated Raja, thank you!

[tidalwave]

Originally Posted by dshriver

I’m pretty much the same as Raja. I run a linear pitch curve. -12.5 0 +12.5 for IU 1/2 and Hold. In normal I don’t run as much negative. It’s more like -3 0 +12.5.

For throttle, my normal curve is nearly identical to Raja’s. However in IU 1/2 I just run a V (well more of a U) f
curve. The gov on my Futaba 760 FBL ignores the throttle curve and I don’t fly without the governor. I only have the curve in place in case the governor fails.

thank you dshriver!!