HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Sep 09, 2013, 04:51 PM
Auntie Gravity left me hangin'
Uncle Gravity's Avatar
United States, CA, Los Angeles
Joined Nov 2007
640 Posts
Question
Any advantage in using idle-up for scale/sport flying?

A bit of background: I've been flying CP (Walkera Super CP and V120D02S V2 with a Devo 10) for around a month, though I have almost a year's worth of micro FP and quad experience. My goal is to become proficient at graceful scale-like sport flying, and I have no interest in 3D. So far, I'm able to fly reasonably precise, slow and consistent figure-eights with very few unplanned landings.

I'm currently running my helis with around 20% positive pitch at mid stick. I tried zero pitch for a while, but the Super CP doesn't want to lift off until I've reached around 3/4 of my throttle stick travel (even with 100% head speed) and I find that awkward from an ergonomic standpoint. Perhaps it's a bad habit, but my quads easily lift off at mid stick, so that feels like the sweet spot for me in terms of throttle and rudder control, but I'm concerned that when/if I switch to idle-up, the sudden drop from 20% pitch to zero at mid stick may be too abrupt.

I've assured that I have good blade tracking and zero mechanical pitch at the zero setting on the TX. I'm running 15% negative pitch in normal mode, which seems adequate to fight the wind and get a general feel for it. I still have a ways to go before I trust my throttle-hold reflexes (since I seldom crash, I don't get much practice) but I know what happens if I panic and zero the throttle stick in idle-up.

Which (finally!) brings me to my question: Is there any advantage in switching to idle-up for my preferred flying style or should I just stick with normal mode and forget about large doses of negative pitch?
Uncle Gravity is offline Find More Posts by Uncle Gravity
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 09, 2013, 05:29 PM
Rotor Controller
CaptJac's Avatar
Aachen Germany
Joined Dec 2007
1,941 Posts
The 3D is NOT for everyone thread should help you answer your question.
CaptJac is online now Find More Posts by CaptJac
RCG Plus Member
Reply With Quote
Old Sep 09, 2013, 07:37 PM
Registered User
New Zealand, Canterbury, Christchurch
Joined Jun 2013
130 Posts
If you don't plan to fly inverted then I don't see any reason for a symmetric pitch curve.
tracernz is offline Find More Posts by tracernz
Reply With Quote
Old Sep 10, 2013, 03:08 PM
My other addiction!
norcalheli's Avatar
Marysville, Ca., US
Joined Jan 2007
1,650 Posts
Idle up isn't just for 3D. All full size helicopters spin up to speed, then apply collective as a separate function. You can do the same with idle up. There is nothing that states you have to have a 3D pitch curve in idle up. Set up a gentle 2 or 3 degrees negative up to 8-10 degrees positive, set your zero pitch where you have it in normal, and just enjoy flying. What idle up will give you is the fact that you are only controlling collective pitch, the motor rpm will stay fairly constant. In normal mode you are dealing with changing motor rpm along with changing pitch. Much simpler, and usually smoother, using idle up.

I fly everything in idle up now, and my helis have never been intentionally inverted.
norcalheli is offline Find More Posts by norcalheli
Reply With Quote
Old Sep 10, 2013, 04:55 PM
Registered User
Joined Dec 2012
385 Posts
one thing worth mentioning though. Electric motors have all torque available at 0 rpm. gas engines spin up to speed so they are in their power band when you need the torque its there.
so unless you are doing 3d, or need high head speed to fight major wind, you are just draining your battery faster.
resago is offline Find More Posts by resago
Reply With Quote
Old Sep 10, 2013, 06:42 PM
I can fly 2.5 D
Flying Pitcher's Avatar
United States, FL, North Port
Joined Apr 2013
1,381 Posts
hmm...i don't get all this concept of having those governors and constant RPM for normal flying....
i just made my throttle curve go higher slightly with more pitch on the blades, so because the load increases, RPM pretty much stay the same.

Also, who needs a lot of negative pitch...? the heli will very happily lose altitude even at 0 degree pitch....in fact, because of the weight, it will heftily drop like a heavy size object at 0 degrees.....why go for a full negative pitch band...?

I think it's probably because cool guys say you need negative pitch to fight winds in landing....hehe, must be flying inside a twisteryeep, gotta love 'em diddly gyros.
Flying Pitcher is offline Find More Posts by Flying Pitcher
Reply With Quote
Old Sep 10, 2013, 06:42 PM
My other addiction!
norcalheli's Avatar
Marysville, Ca., US
Joined Jan 2007
1,650 Posts
Quote:
Originally Posted by resago View Post
one thing worth mentioning though. Electric motors have all torque available at 0 rpm. gas engines spin up to speed so they are in their power band when you need the torque its there.
so unless you are doing 3d, or need high head speed to fight major wind, you are just draining your battery faster.
You set the throttle curve, and/or adjust gearing to get the head speed you need. I run 80-90 % throttle curves at 1700 RPM on the Swift 550, 75-80% on the T-Rex 450 with a head speed right around 2100-2200 RPM. Brush-less electric motors are more efficient above 85%, at least that seems to be the consensus in most of the threads I've read. Idle up is nothing more than a fixed throttle position. It could be ten percent if you wanted, though you probably wouldn't get much lift.
norcalheli is offline Find More Posts by norcalheli
Reply With Quote
Old Sep 10, 2013, 06:46 PM
My other addiction!
norcalheli's Avatar
Marysville, Ca., US
Joined Jan 2007
1,650 Posts
Quote:
Originally Posted by Flying Pitcher View Post
hmm...i don't get all this concept of having those governors and constant RPM for normal flying....
i just made my throttle curve go higher slightly with more pitch on the blades, so because the load increases, RPM pretty much stay the same.

Also, who needs a lot of negative pitch...? the heli will very happily lose altitude even at 0 degree pitch....in fact, because of the weight, it will heftily drop like a heavy size object at 0 degrees.....why go for a full negative pitch band...?

I think it's probably because cool guys say you need negative pitch to fight winds in landing....hehe, must be flying inside a twisteryeep, gotta love 'em diddly gyros.
Re-read my post. I don't have more than two or three degrees of negative even in idle up. And that two or three degrees isn't in effect until low stick, so I don't dip below zero much at all. The only reason I have any negative is when I land, I apply negative just before killing the motor. Kind of glues the heli down as I slowly lose control authority. All of my flying is geared toward scale, so even in idle up I'm running a scale pitch curve. I just find it smoother to run a fixed RPM and only control collective for flying around. It's all up to you and what, and how, you want to fly.
norcalheli is offline Find More Posts by norcalheli
Reply With Quote
Old Sep 10, 2013, 07:19 PM
I can fly 2.5 D
Flying Pitcher's Avatar
United States, FL, North Port
Joined Apr 2013
1,381 Posts
norcalheli...i didn't mean to say it only at you. We all know you're the best:P I've seen many guys who say straight pitch curve -max to +max is the way to go because it's easier to land, and I am always thinking...why ?(don't worry, i love everyone here....umm, guy hug, nothing slurry)

original poster also wrote.....
Quote:
..... I'm running 15% negative pitch in normal mode, which seems adequate to fight the wind and get a general feel for it.........
Flying Pitcher is offline Find More Posts by Flying Pitcher
Reply With Quote
Old Sep 11, 2013, 01:30 AM
Registered User
New Zealand, Canterbury, Christchurch
Joined Jun 2013
130 Posts
A symmetric pitch curve doesn't make landing easier, it does make inverted flying and 3D flying possible. 15% negative pitch at bottom stick is about -2 degrees if you've got your heli setup for 12-13 degrees of collective travel, that's a scale type pitch curve and certainly does help with landing.

As for governed RPM, the heli responds in a very linear fashion if you only change pitch while RPM remains constant. My brain handles linear behaviour far better, non-linear behaviour is what I use fancy maths and computers for.
tracernz is offline Find More Posts by tracernz
Reply With Quote
Old Sep 11, 2013, 03:42 PM
Rocket Programmer
jasmine2501's Avatar
United States, AZ, Mesa
Joined Jul 2007
25,354 Posts
Cyclic response is mainly a function of RPM - that's why constant rpm feels a little better. A governor or constant-rpm throttle curve reduces pilot workload.

Quote:
Some helicopters do not have correlators or governors and
require coordination of all collective and throttle movements.
When the collective is raised, the throttle must be increased;
when the collective is lowered, the throttle must be decreased.
As with any aircraft control, large adjustments of either
collective pitch or throttle should be avoided. All corrections
should be made through the use of smooth pressure.
http://www.faa.gov/regulations_polic...a/hfh_ch03.pdf

Our pitch and throttle curves work together to form an electronic correlator.
jasmine2501 is offline Find More Posts by jasmine2501
Reply With Quote
Old Sep 11, 2013, 05:16 PM
Auntie Gravity left me hangin'
Uncle Gravity's Avatar
United States, CA, Los Angeles
Joined Nov 2007
640 Posts
Thanks, guys - some excellent info here. I'm slowly working through your various suggestions in idle-up, trying to find a good balance between solid handling characteristics and decent flight times. The brushless V120D02S makes this kind experimentation easy because it has plenty of power, and especially torque (comparatively speaking), but I find that the Super CP's coreless motor is a torque-less little thing that tends bog down pretty easily as the pitch increases, so I'm trying to compensate with higher RPMs to keep it in my preferred mid-stick hovering range.

I'm still trying to wrap my head around the proportionate relationship between normal and Idle-up settings. Using the Super CP as an example, if I'm running a 0 - 80 - 100 throttle curve, and a -15% - +25% - +60% pitch curve in normal mode, which idle-up settings would be appropriate for improved scale-like flying performance? Keeping the suggestions in percentages would be helpful, as I don't have a pitch gauge (I've read that accurate readings are problematic with micro helis).
Uncle Gravity is offline Find More Posts by Uncle Gravity
Last edited by Uncle Gravity; Sep 11, 2013 at 09:27 PM. Reason: Clarified pitch curve numbers
Reply With Quote
Old Sep 11, 2013, 05:36 PM
Rocket Programmer
jasmine2501's Avatar
United States, AZ, Mesa
Joined Jul 2007
25,354 Posts
Quote:
Originally Posted by Uncle Gravity View Post
Thanks, guys - some excellent info here. I'm slowly working through your various suggestions in idle-up, trying to find a good balance between solid handling characteristics and decent flight times. The brushless V120D02S makes this kind experimentation easy because it has plenty of power, and especially torque (comparatively speaking), but I find that the Super CP's coreless motor is a torque-less little thing that tends bog down pretty easily as the pitch increases, so I'm trying to compensate with higher RPMs to keep it in my preferred mid-stick hovering range.

I'm still trying to wrap my head around the proportionate relationship between normal and Idle-up settings. Using the Super CP as an example, if I'm running a 0 - 80 - 100 throttle curve, and a -15% - 25% - 60% pitch curve in normal mode, which idle-up settings would be appropriate for improved scale-like flying performance? Keeping the suggestions in percentages would be helpful, as I don't have a pitch gauge (I've read that accurate readings are problematic with micro helis).
That's why I wanted you to read the FAA handbook... it explains how the pitch/throttle correlation works. That is what we are setting up with pitch and throttle curves. You do understand what the settings mean, right? If we put them next to each other in a table, does it make more sense? See how a given stick position causes a specific pitch and throttle to be used. This is the same thing as pulling on the collective bar in a full scale helicopter, if a correlator is being used.

Code:
stick pitch throttle
----- ----- --------
LOW    -15%       0%
25%   *-20%     *40%
MID    -25%      80%
75%    *17%     *90%
HIGH    60%     100%
* - interpolated values

Do you see why you're not getting any lift until high stick? (Your zero pitch point is way above mid-stick.)
jasmine2501 is offline Find More Posts by jasmine2501
Reply With Quote
Old Sep 11, 2013, 05:59 PM
Auntie Gravity left me hangin'
Uncle Gravity's Avatar
United States, CA, Los Angeles
Joined Nov 2007
640 Posts
I'm sorry Jasmine - my fault. I should have written -15% - +25% - +60%. My hyphens look too much like minus signs . The 15% is the only negative pitch I'm using. I'm hitting zero pitch at -63% on the throttle stick and +25% pitch at mid-stick.
Uncle Gravity is offline Find More Posts by Uncle Gravity
Last edited by Uncle Gravity; Sep 11, 2013 at 06:16 PM.
Reply With Quote
Old Sep 11, 2013, 06:29 PM
Rocket Programmer
jasmine2501's Avatar
United States, AZ, Mesa
Joined Jul 2007
25,354 Posts
Quote:
Originally Posted by Uncle Gravity View Post
I'm sorry Jasmine - my fault. I should have written -15% - +25% - +60%. My hyphens look too much like minus signs . The 15% is the only negative pitch I'm using. I'm hitting zero pitch at -63% on the throttle stick and +25% pitch at mid-stick.
Ok that makes more sense. So, what do you not like about this flying style and what changes would you like to see? Can you describe the things you don't like and what you think might make it better?

My personal opinion is - I don't fly like that. However, I suspect the problem, if there is one, is your throttle changing too much in the hovering area. This can cause tail control problems and makes the helicopter feel punchy. All you need to do to fix that is level out the throttle curve in that area. For example use a curve of 0-60-80-80-80.

Without getting into why, because you can read it elsewhere, I'm against setups with zero pitch anywhere but mid-stick, so I don't have a ton of experience flying the way you're trying to do it, but I have enough general experience to know that it's probably the jumpy throttle that's bothering you if anything.
jasmine2501 is offline Find More Posts by jasmine2501
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Any Advantage To Not Using Aileron "Y" Cable? itsme2 Electric Plane Talk 5 Jan 06, 2013 02:53 PM
Question Scale Flying in Idle Up Mode radarman Mini Helis 22 Sep 15, 2010 02:23 PM
Discussion Any advantage to a pumped engine for sport flying? Bart4 Engines 2 Sep 23, 2007 03:35 AM
Discussion Using CP2 and "audio cable" for sim. Always in Idle Up mode! nickbuol Micro Helis 4 Apr 02, 2007 03:11 PM