Aug 11, 2013

Phasing – The free performance upgrade

So you might have heard the term swash plate phasing or maybe even seen it in your FBL system software but what exactly is it?  Well swash plate phasing is the angle of relationship between the swash plate and the head. Why is it important.  Swash plate phasing directly affects how the helicopter reacts when you give it a command.  If you give a strictly aileron command and the phasing is off  the mechanics of the swash plate will apply a slight elevator command automatically and cause your perfect aileron roll to wobble.  Ever done an elevator flip tail-in and noticed that 1/2 way through it your tail is off heading?  That could be because your phasing is off and despite you giving strictly an elevator command it’s causing an aileron interaction at the same time.


First lets go over how to check it and then I think you’ll start to understand a little more about why it’s so important.  First step is to align the feathering shaft/head perfectly parallel and in line with the tail boom.  It might be easiest to take your blades off so you can help sight down the head.  Now depending on the type of swash plate and anti-rotation setup you have you might be able to see the phasing without touching your TX.  If your swash plate has 4 balls on the inner ring you’ll notice that one of them will be in line (or close) with the outer swash ring elevator ball.  If they are not perfectly aligned then that’s a great indication that you have a phasing issue.


So at this point you see that the inner ball is slightly off center from the outer elevator ball but now it’s time to find out exactly how far off it is precisely and compensate for it.  First lets turn your radio on and get into the setup portion of your FBL system software.  What this generally does is de-activate the gyros and allow you to see this interaction. With the head still perfectly aligned with the tail boom if you give an elevator command (front or back doesn’t matter) in a perfect world you should not see the grip arms on the main blade grips move at all. Please be very cautious that you’re ONLY giving elevator and not accidentally moving over into the aileron command at all. If you see the grip arms move even the slightest amount you’re actually witnessing that interaction and need to compensate for that phasing issue electronically. Adjust the phasing one degree at a time in your FBL system software until that interaction goes away or minimizes as much as it can.  Most FBL systems have adjustments for both positive and negative phasing so you’ll just have to experiment which direction yours needs to go.  It will be very obvious if you’re going in the wrong direction because you’ll see the interaction increase dramatically.


Taking the time to properly check and adjust your swash plate phasing is one of the best “free” upgrades you can do to your heli to help it track better and be more locked during flight.  Out of all the helis I’ve owned about 8 out of 10 have needed some level of adjustment ranging from 1*-5* to get in there, check that phasing, and watch those rolls and flips smooth out like the pros – Nick