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HomeAircraftHelicopterHelicopter Main Discussion › Why have different pitch curves in different flight modes?
02-04-2010 01:26 AM  8 years agoPost 1
McKrackin

rrProfessor

Lucasville,Ohio

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I asked in another thread but I don't want to hijack the thread so here it is....

Why?
My pitch curve is a straight linear shot,0-100 in all three modes.
I take off in Idle up so no need to have NORM mode at all.

My throttle curve in NORM is at 80% at mid stick so I can actually hover inverted in NORM mode.It will be slow and twitchy(this alerts me that I'm not in idle up)but it will not just quit and fall.

So again,why have different pitch curves at all?
Just curious.

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02-04-2010 01:39 AM  8 years agoPost 2
jermo

rrNovice

Fort Mill, SC - USA

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so your throttle curve can have the entire range and not be full negative when you start...

Jermo

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02-04-2010 01:50 AM  8 years agoPost 3
McKrackin

rrProfessor

Lucasville,Ohio

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Why would you want any positive pitch if you don't have any headspeed?

What good is 8 degrees of pitch going to do at less than half throttle?

Again,just curious.

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02-04-2010 01:50 AM  8 years agoPost 4
jsenicka

rrProfessor

Eagle River, WI

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or shut down.
I run my normal curve with identical positive pitch to idle up, but have the curve below mid stick only take me down to neg 5 or so, so when I chop power to come off governor I am not trying to squish the bird in to the ground on shutdown.

Jim Senicka
Team Manager, GrandRC Flight Team

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02-04-2010 01:52 AM  8 years agoPost 5
McKrackin

rrProfessor

Lucasville,Ohio

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or shut down.
I run my normal curve with identical positive pitch to idle up, but have the curve below mid stick only take me down to neg 5 or so, so when I chop power to come off governor I am not trying to squish the bird in to the ground on shutdown.
No throttle hold?My pitch curve is even the same in throttle hold.

All my pitch curves are identicle.No surprises.Click click click no matter what mode,pitch is a constant.

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02-04-2010 01:55 AM  8 years agoPost 6
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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No throttle hold?
Same pitch curve as in Normal Mode. A real sensible setup especially when new to helis is just as JSenicka describes -- Normal Mode and Throttle Hold with typical pitch curves above midstick -- BUT with only a few degrees negative below midstick. This not only minimizes 'squishing' on the ground, but minimizes head deceleration if you accidentally go inverted before selecting Idle Up 1 or 2 -- and allows for finer collective control during autos.

Normal & Throttle Hold usually should have the same midstick (and up) pitch curve as Idle Up 1 & 2 to avoid jumping when switching modes.

My Idle Up 1 throttle curve is such that if the limiter/governor throws a magnet I can still fly without firewalling the engine. Idle Up 2 throttle curve is all 100's.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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02-04-2010 01:55 AM  8 years agoPost 7
JasonJ

rrKey Veteran

North Idaho

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I have full pitch range in all my modes. My engine comes off the gov at mid stick in Normal, so when I bring the stick all the way down it is full neg and it bleeds the headspeed off quick. I have to use the trim to kill the engine (DX-7) in Normal so it works out well. The rotor is nice and slow by the time I get to it so I don't have to stand there and wait for it to slow down. It never seems to want to squish it into the ground, it just bleeds off quickly.

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02-04-2010 01:55 AM  8 years agoPost 8
cdrking

rrElite Veteran

Seattle

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I have all 4 pitch curves 13/13 with my FBL N9. I like not having a jump/change in pitch when I switch modes/hold.

Jeff

To hover is divine, the alternative is rather PLANE.

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02-04-2010 01:59 AM  8 years agoPost 9
george0079

rrElite Veteran

USA

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St1, St2, and T-hold are all the same. Normal has no neg. I don't fly in normal. I only use it for spool up, and setup purposes

Hell... I can fix that.
Uh oh..
Nope.
It's ***ked!!!
RE-KIT!!!!!

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02-04-2010 02:00 AM  8 years agoPost 10
jsenicka

rrProfessor

Eagle River, WI

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I have top side of pitch curve the same in all modes.
Only bottom differs. I have neg 5 available in normal and hold. On hold it is a bit of a cheat, as I can grab hold and not have to worry as much about grabbing too much negative.

So I get zero jump between modes, as I am only going to switch when upright.

Jim Senicka
Team Manager, GrandRC Flight Team

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02-04-2010 02:11 AM  8 years agoPost 11
Steff Giguere

rrProfessor

St-Eustache, Quebec, Canada

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All the same here.

Team Synergy, Rail blades, Team Scorpion, V-Team

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02-04-2010 07:06 AM  8 years agoPost 12
finnegan

rrApprentice

Montreal, Quebec, Canada

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Same as Steffigiguere minus the Futaba of course!

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02-04-2010 01:24 PM  8 years agoPost 13
BarracudaHockey

rrMaster

Jacksonville FL

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So again,why have different pitch curves at all?
To your original question....to customize the way your helicopter flys and be able to change it quickly in flight.

Andy
AMA 77227
http://www.jaxrc.com

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02-04-2010 01:29 PM  8 years agoPost 14
ACKopter

rrApprentice

Florida

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As someone who is still learning and recently learned the value of doing auto's I see where it would be valuable to only have neg 5 or so degrees in T/H vs a linear curve to assist in not descending too fast during an auto. I think I'll give it a try.

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02-04-2010 01:48 PM  8 years agoPost 15
WJackson

rrElite Veteran

Smyrna, Delaware

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So again,why have different pitch curves at all?
To your original question....to customize the way your helicopter flys and be able to change it quickly in flight.
Exactly! For example, if you fly FAI you will want the abilty to make the hover very stable and predictable by having an "S" curve and esentially adding expo to your pitch. Then have the abilty to change flight mode to preform the aerobatic portion. The example others have used to keep the beginner pilot from belly flopping it when first starting is another common reason for changing pitch curves. Basically just what Andrew said " change it quickly in flight."

RIP Roman
Bill Jackson
AlignUSA

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02-04-2010 03:23 PM  8 years agoPost 16
Sillyness

rrVeteran

Little Rock AR

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So I don't suck up rocks and dirt when spooling up and so I can add extra pitch in throttle hold (autos).

Also, on my flybarless I wound up having to add a pitch curve to make it feel linear.

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02-04-2010 03:39 PM  8 years agoPost 17
cdrking

rrElite Veteran

Seattle

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Also, on my flybarless I wound up having to add a pitch curve to make it feel linear.
Could you explain this a bit?

Jeff

To hover is divine, the alternative is rather PLANE.

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02-04-2010 05:40 PM  8 years agoPost 18
Jim Patterson

rrApprentice

AREA 51 Roswell

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Could you explain this a bit?
Ditto

Highly addicted to carbon fiber.....

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02-04-2010 06:32 PM  8 years agoPost 19
dhc8guru

rrApprentice

Fort Worth, Texas

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I can tell you something you definitely need when its windy...atlest 5° of negative pitch in normal mode. Back when I was learning what to program in for pitch curves, I set normal mode with 0° from 0-50% stick..a nice gust of wind caught the heli and lifted it off the ground. Then while I was flying, I couldn't land without that negative pitch, my Trex 450 became a glider. I immediately corrected my mistake. Later I read that symetrical blades still develope lift at 0° pitch. Lesson learned with no damage.

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02-04-2010 08:43 PM  8 years agoPost 20
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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I read that symetrical blades still develope lift at 0° pitch.
Where did you read this?

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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HomeAircraftHelicopterHelicopter Main Discussion › Why have different pitch curves in different flight modes?
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