450 Flybar's Real Function.

[Rob Lancaster]

Hi all,
Hey, I've had my little 450 with a flybar for years and even flew in a chopper with a flybar, (Bell 47), many years ago, but I'm still trying to understand the flybar's job.

I figure the FBL system controls all the movements of the swashplate. Left, right, forward, back and up and down. Of course, at a limited level; right? (electrically controlled stability) And the tail too as well.

But with a flybar, I don't understand how the flybar assists with stability??

It seems like something that would lag out the cyclic response control; or something like that, I don't know , I'm still confused at all those linkage functions.

I also noticed that only 2 bladed helicopters have or had a flybar; why?
Please save my sanity on this one folks! <<<< Hawaiian Apple Banana>>>>HA!.....

 

[Tony]

It is for stability. You know when on a flybarless helicopter, you tilt the heli to the right, the swash goes left? Well when those blades are spinning, the flybar does the exact same thing. So if wind hits the helicopter and tilts it left, it will apply left cyclic to level the heli back out. But, it is Rate Mode only so it will never correct to perfectly level.

It has nothing to do with the swash or tail though.

As for no flybar on multi-bladed heads, I'm not sure, but think it is because 1, there is not much room for one, 2, it would be a nightmare to connect 3 or more blades to the swash cage and most importantly, I think timing would be a nightmare.

 

[Admiral]

The second set of blades on a four blade head appear to do the same as a fly bar, I heard that you could fly a four blade head without a flight controller so I tried it just with a tail gyro. It worked OK but no where near as stable as with an FC, I have been advised since was that was because I had a fixed head and that a floating head is a lot more stable.

 

[Rob Lancaster]

Very interesting Tony, I'm playing around with my 450 and studying this here Bell/Hiller rotor head. I think your right about all three. I'm starting to see what you mean about the flybar's roll when it comes to mechanical stabilization. I'm take'n her out tomorrow in the back yard and pay close attention to how the flybar moves under certain light maneuvers. For some strange reason, I understand how the FBL system works but this mechanical setup is a mind bender... I guess it's the mechanic/technician in me that's gots to know....

Oh hey, about the timing, can you explain more about that? What is timed?

Also, hi Admiral, how's your winter going down under, and what's the difference between a fixed head and a floating head? Interesting indeed...……
Thanks guys!!

 

[Admiral]

I’ve never used a floating head but I understand that they are based on the flapping hinge system used on full size helicopters, if a blade needs to it can move up or down without effecting all the other blades which makes the flight characteristics more stable.

Winter is going well, I’m on the island of Phuket in Thailand at the moment at about 35 degrees Celsius and high humidity.

 

[murankar]

I think the fly bar has a natural tenancy to stay level. So if the fly bar stays level during a tilt, then the swash will be pulled to correct for the tilt.

That's my view of the world.

 

[Rob Lancaster]

I’ve never used a floating head but I understand that they are based on the flapping hinge system used on full size helicopters, if a blade needs to it can move up or down without effecting all the other blades which makes the flight characteristics more stable.

Winter is going well, I’m on the island of Phuket in Thailand at the moment at about 35 degrees Celsius and high humidity.

Wow Thailand! They make bottle rockets the size of telephone poles over there... I'm a huge fire working fan to be sure..
With the high humidity and high temperature; ha, welcome to my world....
Hey your right, a floating head has hinged blade holders. 5 blade floating rotor head - Google Search

I believe the head on my 450 is considered a semi-ridged rotor head. The blades only swing back and forth and not up and down too.

Thanks buddy, have fun...

 

[Rob Lancaster]

I think the fly bar has a natural tenancy to stay level. So if the fly bar stays level during a tilt, then the swash will be pulled to correct for the tilt.

That's my view of the world.

Yes, yes!! That's the key to it all. It's sure starting to sink in now.
Thanks thanks....

 

[Tony]

Timing is just how the flybar acts with the helicopter. If you notice when you give forward cyclic that the helicopter is actually going forward but drifting to the left or right, then it may need to be adjusted. You can adjust it on some, but not all. Not really that big of a deal on most of the newer flybar units out there. They are pretty close to where they need to be.

If you want to see the flybar in action, take all of your blades off but leave the flybar paddles on (this includes tail blades, take those off as well) and spool it up to about 25%. With it sitting on the desk, you can move the cyclic and see the helicopter moving the flybar. Also, you can pick it up (keep your hand and face away from the flybar...) and move it around in space and watch how the flybar acts. I still find it fun to watch sometimes.

 

[Rob Lancaster]

Remove the blades "A",,, hummmm, why didn't I think of that...
Now that'll be fun!
Defiantly learning a lot here..

 

[Rob Lancaster]

Hey Tony; if timing was adjustable, how would it be done?
Are we having fun yet...………..

 

[Tony]

Well, I have never done it, but from what I understand, you would just adjust the head or even the swash driver slightly to tune it in. This is for a flybarless head of course. To adjust a flybar, more is involved since you have mixing and washout arms. But the principal is the same, you just adjust the head to the swash so that you either advance or retard (not used in a derogatory way) when it actuates the movement the helicopter is requiring.

 

[Rob Lancaster]

what's the swash driver?

 

[Tony]

The swash driver is only on FBL heads that are Non DFC. It is the mixing (or is it washout...) arms that have the radius arms that connect to the swash. Since the base of the swash stays stationary for the servo connection, but you still need rotational adjustment, you need a way to spin the center part of the swash while the outer part of the swash stays stationary. This is where the swash driver comes into play.

The swash driver will connect to the center swash balls with Radius Arms and keeps the helicopter under control. If you have a DFC head, then the made blade grip arms ARE the swash driver, but DFC has a reputation of destroying servos in the event of a crash. This is why companies like Goblin still use a swash driver type head rather than DFC. And FYI, DFC came from Compass however Align adopted it and people started calling it Direct From Compass.

 

[Rob Lancaster]

Ok whew!,,, I need some time to go over all this sh__ I mean stuff... HA!
I found a really great animated video of the Bell/Hiller head in action. It's slowed for us slow guys and sub-titled.


Study continues...
I'm love'n it! Yes, yes; have'n fun!!
Rster...

 

[murankar]

Actually SAB had dfc under the hps name. Then the non dfc head is under the hps2 head style and the hps3 head is the tri blade format.

Yes dfc will kill a set of servo gears due to the direct force of the blade grip links. Those links are designed to not pop off in a crash. So in the end you kill your servos which are the weakest link in the system.

 

[Rob Lancaster]

I always knew a helicopter's rotor head was a complex mechanism.
I just didn't know how complex until now...
Interesting stuff for sure.

 

[Kentucky Fly Boy]

Nice one, I am new and here is What I have learned fly bar is similar to gyro provides stability I have co axial`s and single blades with them. For fixed pitch they help with stabilization after a while with some aggressive flying I find them to be detrimental they strike blades now that I have a V-955 collective pitch I do miss the stability of the fly bar helicopters however I am getting the hang of it. With the collective pitches it is like laws of motion every action does need a slight counter action.

 

[Rob Lancaster]

Welcome aboard!
What kind of coaxial do you have and what's a V-955? Pictures??

 

[Kentucky Fly Boy]

Syma 107, Syma 800g Are coaxial`s and the V-955 and I have

Welcome aboard!
What kind of coaxial do you have and what's a V-955? Pictures??

V-955 pix exact same mine are to big for an up load