Brain: Cyclic behaviour before takeoff

I read somewhere that when spooling up a heli that uses a fbl controller, if you give any, even small cyclic inputs it might bury it's self into the ground before takeoff.
I understand that the fbl unit is effected by ground vibration and that it doesn't function properly until it's in the air, however I'm not sure how or what would cos the heli to tip over before taking off.
I am setting up my Raptor 50 with the brain fbl controller and would be grateful if you would give some advice on this.


Many thanks :-)

[coolice]

Hey Buddy.

The problem here comes from the fact that the gyros are rate demand, eg. they will throw in the required amount of cyclic to effect an attitude change based on the pilots stick input.
With the skids still in contact with the ground, the fuselage of the model will be reluctant to move if the pilot asks it to, the FBL gyro then deems it needs to throw in more cyclic deflection which is then too much and can cause a tip over.

Having said this I have found you can use small cyclic inputs to make corrections while on the ground, but all the time be aware not to over do it. For me it is the smaller models that suffer more than the larger ones, which is to be expected, your Raptor 50 should be ok with small cyclic corrections.
With time on the setup you'll soon learn the feel for the model and be able to make adjustments just before lift off without any worry.
.

[simon_s]

Newer flybarless units cope with inputs on the ground better than the older ones. The swash will self level, so if you add stick movement and/or carry it to the flight line after powering it up it should lift off nice and flat.

[dbull46]

Coolice. What you have said makes good sense and gives reassurance that if I see a small correction is needed, then it can be done with care. I have a Trex 450 plus which is fbl and it can be corrected but like you say, is lighter. I never used one on a bigger heli and want to be prepared when the time comes so thank you.

Simon. I can see I am going to have to learn to watch the swash very closely. After turning the unit on, I might try moving the heli around and see how the swash reacts, and when I spool it up without the blades and observe the swash movement. Now you've mentioned it, when going through the set up I did see that the swash self levels itself.

Thanks guys :-)

[PaulJC]

I tend to describe it as flying it from the beginning of spool up as opposed to the flybar models which you can spool up without corrections, FBL requires corrections while you spool up, not a big deal just something to be mindful of

[dbull46]

Thank for the advice Paul good tip. I think I might need to take an extra pair of pants with me for the maiden flight..........

Cheers

[David Drew]

I found the whole exercise a bit daunting for the first few flights with the Brain.

After putting the heli down on the flightline I let the swash level off and I switch the gyro to rate and back to HH to centre the tail.

Works for me.

[dbull46]

I found the whole exercise a bit daunting for the first few flights with the Brain.

After putting the heli down on the flightline I let the swash level off and I switch the gyro to rate and back to HH to centre the tail.

Works for me.

I like the idea of flicking it into rate mode to centre the tail and back to HH as I find that always needs a correction before take off with all the other heli's I've flown, in less it's just normal behaviour anyway.

Cheers Dave