What is phasing

[Dilbeck]

Dont know or have never heard someone talk about in this forum, but heard it mentioned somewhere. Anybody? Anybody?

[BABY HUEY]

A brushless motor has phases (three) but I don't know what you mean about phasing.

[Dilbeck]

Seen on RR, It is set by the washout guide pins, it controls tracking. If its off to much your heli will slide side-ways when you push the cyclic stick forward. I have know idea about this so im asking!!

[BABY HUEY]

Oh, I guess that is what they call the timing of the cyclic pitch inputs as the head rotoates.

[hawkman]

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.

Now:

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 Hiller...is using the flybar...to 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 not...so 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 fly...by 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 high...land 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.

Rob

[hawkman]

If you go to the gallery...look for my pics...the Trex has the blade tips covered in the red/yellow tape...you can see what I mean.

[Dilbeck]

HOLLY COW! Just when you thought you new as much as you didnt know, someone throws a wrench into the mix! Think i will just fuel up and go fly......

[hawkman]

Well no....I didnt know much when I first started out...it was only when I started my current job as a Helicopter mechanic that I really started to realise I knew so little...so I started reading up and pestering the qualified Guys as to how things work.

What happens with real helis applies to our models too.

Rob