Absent extraordinary piloting skills, helicopters require gyros on all three axes. These are pitch-and-roll gyros for the main rotor head, plus a yaw-gyro for the tail rotor system. Gyros for model helicopters may be either all-electronic (3-axis, aka an FBL-gyro), or a hybrid-gyro setup.
Pitch, Roll, and Yaw axes
Note: the hybrid setup is the combination of a mechanical gyro (known as a flybar system) plus a single-axis gyro for the tail rotor. This briefing is in regard to hybrid-gyros.
Terms
There are two common terms using 'pitch' when it comes to helicopters; cyclic pitch and collective pitch. They are vastly different.
Cyclic-pitch is the equivalent of aileron and elevator for rolling and pitching about the CG. And when one blade has +8° (positive pitch), the other blade has -8° (or negative pitch).
Collective-pitch refers to using the throttle/collective stick position both blades in either +/- pitch equally. So you're changing the pitch of both blades. This, for the purpose of maneuvering a model helicopter vertically instead of about its CG (center of gravity). In the above graphic, collective pitch is along the blue axis.
Moreover, when you hear the term collective-management, this is principally used in reference to what in the hobby is referred to as 3D-flight (though technically, all flight consists of maneuvers within 3D-space). This principally applies to maintaining main rotor RPM. E.g. when a pilot consistently bogs the main rotor (applies so much pitch the main rotor RPM slow down) then they are said to have poor collective-management skills.
Note; terrain following (collective pitch-motion along the blue axis) is available with appropriate equipment, but out of the scope of hobby applications.
Mechanical pitch and roll gyroscope
We supply the Pantera P6 Classic with a 2-axis mechanical gyro, which is attached to the main rotor head (the mechanism is referred to as a flybar). When combined with a single-axis (or 1-axis) gyroscope, the two mechanical gyros and the one electronic gyro together form the basis of the hybrid-gyro setup (2+1 gyros). Many find this a really fine option for their Pantera P6.
Note; the flybar combines both Bell and Hiller mixing on the main rotor head to achieve stabilization. These can be adjusted to modify handling and is the subject of a separate article.
Anyway, if you’re unfamiliar with flybar-gyros (and admitting they look much like a Mickey Mouse complication due to the added parts), what matters is this . . . these things are so highly developed they just work. No muss, no fuss straight out of the box!
By the way, not only does a flybar (mechanical pitch and roll gyros) offer excellent trouble-free performance whilst stabilizing pitch and roll axes of your helicopter, it's the sole instance in our experience where mechanically complicating something (by added the flybar components) actually makes something better. Models with flybars are simply easier to live with because you go fly instead of fiddle with the FBL-gyroscope. The strange but true reason for this is entirely due to how over the years the mechanism of the mechanical gyro has been perfected. Honestly, unless you delight in the process of adjusting parameters, more flying due to less fiddling is a winning formula with those who desire to reduce life's complications.
Brings up the most important question; how well do hybrid-gyros function? Judge for yourself; watch Kyle Stacy – as a 9 year old – put his Pantera through its paces.
Note; while this video predates the greater agility of present-day 2300RPM setups (he was flying at 2000RPM), it nevertheless shows a few things. 1st, a Pantera flies exactly the same with or without a flybar (and yes, a slight-edge horsepower-wise to FBL due to less aerodynamic drag after ditching the mechanical gyros). 2nd, it's not enough difference (performance-wise) to be a deal breaker. Especially amongst mere mortals. And 3rd, while that 9 y/o is now a grown man, for our part, we're bursting with pride for our early association.
Honestly? Being a stepping stone on his path to the top was an honor (and in truth, we knew the instant we saw him fly he was destined for bigger things than us). Anyway, we remain delighted for his success whilst relishing our small role in his pilot-development.
The major benefit of a flybar head is it's a set-it and forget-it setup. After the first flight or two setting high and low gain on the tail rotor gyro, you're largely done and you just fly your model week-in and week-out.
Changing your mind?
What if you subsequently decide you'd rather go FBL, or flybarless? Honestly? There's nothing wrong with geeking out on gyro-settings (after all, flying model helicopters is a hobby and who is to say what aspect is more worthy than another? This, even though at the extreme, some guys drag a laptop to the field to fiddle with gyro settings.
The purpose of this next photo is to show how-to convert is virtually free because you simply repurposes existing control-arms and bearings into pitch-arms.
Mechanical adjustments
Adjusting the mechanical gyro is beyond the scope of this briefing. But since tuning the flybar is an analog process, it means instead of a computer, all you need are a screwdriver and ball link pliers! This link is to the flybar tuning how-to article.
Summary:
Considered old school, the really nice thing about flybar setups is they work straight out of the box. That, and because single-axis gyros can be had on the cheap (and cheaper still 2nd hand off eBay), then being able to put a 600-build in the air without a money tree is a 'huge' P6 advantage.
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Anyway, view all this in the reflection of the Frost poem we first read in high school about two roads diverging in a yellow wood. With the Classic you get the optional hybrid gyro, which gives you the opportunity to take the path less traveled on. Ideal 'if' you find the idea of the old-school flybar-gyro approach, intriguing. |
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Closing thoughts
If you happen to have an FBL-gyro laying around, connecting just the tail rotor servo sees it functions 'perfectly' as a single-axis gyro! Sure the other 2-gyros are doing their thing but because they're not connected to servos, then it doesn't matter!
proTIP: take a few minutes and visit – National Air & Space - axes of flight
