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10-12-2012 02:18 PM  6 years agoPost 1



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Is there anyone who can explain what phasing is and how it relates to the head of a Heli? How do you set phasing, or is it just making sure you have equal throws in all directions?

10-12-2012 02:47 PM  6 years agoPost 2


Brewerton, New York

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I found this, maybe it will help you:

Re: What is phasing


Phasing is about the cyclic input to the rotor head.

Gyroscopic precession is at work here, this states that where we put an 'input' into a rotating mass the 'reaction' occurs 90 degrees later.


take a small wheel...give it a spin...(small cycle wheel is handy) and try to alter its postion...try tilting it...the reaction takes place where you dont expect it...90 degrees later.

The same thing happens with helicopters, the typical system we use...Bell using the stabilise but also to give a 'power steering' effect whatever input we do to the cyclic...the flybar is altered as it turns, this is then going to influence the rotor blades....turn the head by hand...and observe what happens.

Phasing can only go out if the rotorhead is not quite right...some models are fool proof...others are if something is not lined up right...usually on the main shaft/mast...then the heli will tend to drift in a particular direction...always the same direction...if the direction varies then there is something loose about the mechanics of the heli.

Its important to make sure the flybar paddles are nuetral...or as near as possible...a slight angle can alter the phasing too...usually its an irratating wobble you get.

Tracking is really about the blades and how they using red tape on one tip and yellow on the other...go and hover...and see if there are two tips at the ends of the disc...the colours will tell you which is the highest...if the red is and adjust the pitch link for the blade....make sure to adjust so the red tipped blade rides lower.

DO NOT ADJUST THE MIXING LEVERS...this will only upset the flybar arrangment...some helis might tolerate this...but its not good practice.

Bill Whittaker

10-12-2012 02:52 PM  6 years agoPost 3
John Krebs


Pittsburgh, PA

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With your heli sitting on a table with the blades extended so you can spin them. Move the collective stick to zero pitch. Now move the the cyclic stick in one direct. Say right aileron. Now spin the blades slowly so you can see the blade change pitch as it goes around. The point at which the blade transitions from negative to positive with relation to the airframe, let's say the nose, is the point that is being phased. The releationship between the transition point and the the nose is what you are adjusting. On a heli with a flybar you adjust the position of the mixing base in relation to the feathering shaft. With zero degrees of phasing the arm on the mixing base would be parallel to the feathering shaft. Sometimes the phasing needs to be adjusted to correct thinks like loops that corkscrew.

On a flybarless heli this is an electronic setting in the control unit like the CGY750.

I hope this helps.

Edit to add:
I'm glade Wrongler explained Gyroscopic precession. You may have noticed that while doing the above demonsteation.

10-12-2012 03:53 PM  6 years agoPost 4


42½ N, 83½ W

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Phasing is the same as gyroscopic precession.
You can read more here,

10-12-2012 06:31 PM  6 years agoPost 5


Lafayette, Indiana - US

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Here is a great video on Gyroscopic Precession. He actually has a 4-5 video series on RC helicopters.

Check it out.

Watch at YouTube

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10-12-2012 07:07 PM  6 years agoPost 6


42½ N, 83½ W

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That video is colorful fut not very informative. Sure it tells WHAT happens but not WHY . . . just like 99% of the explanations out there.

My explanation tells why. See the link in my post above.

10-12-2012 07:56 PM  6 years agoPost 7


Cedar Rapids, IA

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Many helicopter kits today do not have adjustable phasing. It's usually fixed by the head block designs that generally have the swash-driver pins pressed into the head block.

If your heli has fixed phasing, you're stuck with it, or you spend $$$ for a new head.


* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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