Introduction
This guide is aimed primarily at beginners to FBL setup. The approach is takes is not supposed to be any kind of “super correct 100% you must do it this way” - but more of a guide based on my own experience.
The guide tries to present each step with a reason. That’s the “why”. Why do this step? This is followed by the moves (or a set to choose from depending on pilot ability) that tend to show negative behaviour for that step. The guide then gives suggestions for tuning out that negative behaviour for that step. The moves presented try to be as simple as possible to show up negative flight characteristics… this is both because I want the guide to be as useful as possible, and also because I’m not a world class 3D champ.
this is a work in progress. I'm always happy to write up more, or change things. I plan to add more as I tune the Spirit more myself (i.e: it has to stop raining here first!). I have plans to post up a glossary / advanced guide later, which I think at this stage will be taking Thomas's tuning post and turning that into 'Neil Speak'. I want to play with those CFF/FS values and describe what I see on the Warp, and then take that to the X4/N7 as well.
If Thomas decides this is irrevevant, or he makes it obsolete by adding to his posts / PDF manual, this post can and should disappear.
Note: It’s important to follow this in order. If you skip a step and that part of the flight dynamic isn’t good/perfect, then you can find that negative tendencies appear in later steps but not necessarily because that part of the setup that’s being discussed is wrong. You may be seeing a negative behaviour based on skipping some previous step. A classic examine is not disabling (or at the least turning down the aggressiveness of) governors while testing tail holding. An aggressive governor in this case can make it look like the FBL isn’t set right, when in fact it’s over aggressive governor gain that is the culprit.
About the author:
I fly a Synergy N7 (OS105 with BD3SX), Gaui X4II (BD3SX) and Warp360 (Spirit) . If my experiment with Spirit goes well, I don’t see why I’ll be hanging onto my BD units
Anyway; previous to these heli's I have owned a Gaui X2 and various micros. I’ve been flying for about three years total.The Guide
Cyclic Gain (aka: Head Gain)
The first thing we want to do is make sure the heli feels “reasonable” to fly. By “reasonable” I mean:
- Able to be flown comfortably.
- Not too fast (i.e: it doesn’t react too fast) and not sluggish (i.e: you the pilot have sufficient control and feel OK flying it).
We want this setup right so that the remainder of this tuning guide is possible, and so the heli doesn’t fall out of the sky
We are going to set the gain at the Spirit recommended default, and check that it’s OK. The guide will not increase the gain at this stage. Right now we’re looking to see that it flies OK without any oscillation in the head.
Steps:
- As per manual set main gain to 55%.
- Fly
- General flying
- Aileron stabs
- Elevator stabs
- Oscillation: if the heli “wobbles” when you stop one of these moves, the gain may be too high. If you see this ‘wobble’ lower cyclic gain by 10% and try again.
“Wobble”: Watch the blades when you perform a stop move during flying. It doesn’t at this stage need to be a super fast hard stop, but do take notice of what the blades do during this initial flight. If there is any back-and-forth motion before they settle down within a hover; this is oscillation / a “wobble”. It can happen either in the aileron or the elevator axis, but it’s easier to observe in the aileron (left/right stick movements).
TODO: Provide pointers on what to change here if the flight is completely sluggish and slow. This step comes primarily from my BD tuning days. I don’t known if it’s strictly necessary for the Spirit, but it doesn’t hurt to check cyclics are sane before moving on to other tuning.
Rudder Gain (aka: tail gain)
Now the heli is generally flying OK from an aileron / elevator perspective, we want to ensure the tail responds well. This is defined as:
- When you ask the heli to rotate (via rudder), it does so in a timely manner. It doesn’t “lag” or feel like it is slow to respond.
- When you return the stick to centre, the heli stops crisply without “sliding” to the stop, and without bouncing at the stop.
- When stopping the tail, no oscillation (like a vibration) is observed.
We’re going to split this into two parts. First we will set overall gain, then second we’ll tune the heading hold response.
Before you begin:
- Set Rudder Common Gain to 1.0x
- Set Rudder Gain to 50%
- Ensure Rudder Gain can be changed via Gyro Channel (set under “General” tab of the Spirit software) or if you have no Gyro Channel assigned, setup bank switching with 50, 60 and 70% gains on banks 1/2/3, or finally just land and set the gain manually via Spirit software.
Here we are setting up the rudder gain so that it the FBL unit responds well to rudder control. We're in effect matching the FBL unit to the mechanics of your heli, making sure that when it attempts to stop the tail from rotating, it does so quickly and without bounce or vibrations.
The first part to this is making sure the gain is about in the right place. There's no point trying to tune the heading hold / responsiveness of a tail if the general overall tail gain isn't near-right.
Steps:
- Get into the air, and into a hover, tail in.
- Perform both left right piro 360 deg stops. You rotate the heli 360 degrees around, and finish with the tail facing you again just like you started.
- or; fast forward flight
- or; aileron rolls (these ask a lot of the tail)
- or; fast backwards inverted flight
- “Oscillation on tail”: What we’re aiming for is to up the gain a little bit at a time, until we get a tail vibration. I have mine on a dial I can change mid flight. I generally perform quick tail stops rather than fast flight, because if it goes crazy on me I want to retain control. If you don’t want to take your hands away from the sticks, ask a friend to slowly turn it up (being ready to back it off!) for you, little by little. When vibration occurs, you want to back off by about 10%.
Part 2 - Stopping Performance / Heading Hold Control
Assuming we've the tail gain in the right range, we're now going to tune the tail so that it both stops quickly, and without bouncing at the stop point. This gives a nice 'connected' feeling during flight, one where you no longer have to worry about what the tail is doing. It should "just work".
Steps:
- Get into the air, and into a hover, tail in.
- Perform both left right piro 360 deg stops. You rotate the heli 360 degrees around, and the up with the tail facing you again just like you started. Note: When stopping a rudder movement, do so with control. Don’t let the rudder “bounce” back to neutral, you’ll see false ‘bounce’ behaviour on the tail if you do that.
When you quickly return to the rudder neutral position:
- “Slide on stop”: the tail sort of slowly comes to a stop. It slides into place. As though it were moving through a dense liquid. In this case Piro Consistency needs to be increased. Do so in increments of 5 (up to a limit of 190 - at which point stop). If you need > 190 you probably have a mechanical issue that needs sorting out first.
- “Bounce”: the tail bounces before coming to a stop. <help needed here, I haven’t had this happen on Spirit for me yet>
- "Different behaviour on left/right stops": If you see different a response between a left/right stop, it's often a mechanical problem. This can be caused by:
- any tightness on any component of the tail mechanism, from control arm right through to tail blades.
- Incorrect mechanical setup / not neutral in rate mode. (See below)
Rate mode setup
Often it can be useful to first spool up the heli carefully in rate mode. When I do this I do nothing other that very carefully spooling up and lifting into a hover, all the time keeping a very careful eye on rudder movement. I then tune the length of the tail control rod so that I need the least amount of input on the rudder to keep the tail still in the hover. It's not always possible to get it perfect, because you have to use 1/2 (or full if you're being 'proper') turns on the tail link.
When you have the heli hovering well in rate mode with minimal rudder input, you have effectively balanced it's tail [i]mechanically[i/]. If you re-do the tail holding left/right piro moves above, you may now find that they are a lot more consistent on both sides.