Monday, September 14, 2009

Flight School Part 5 - Flips & Rolls

Finally! Some aerobatics! If you have been following this Flight School, Parts 1 to 4 were hardly 3D aerobatics, in fact it feels far from it. But fret no more, now we're gonna get our hands dirty in some beginnings of 3D RC Helicopter aerobatics.

Be warned however, if you haven't got the skills the previous lessons mentioned, it would be kinda risky for your heli. Due to the demands of 3D aerobatic flight, your heli would have to be pretty well setup and maintained, loose/worn-out parts and/or tail not holding when doing aerobatics could spell disaster... However, if you have what it takes you'll find aerobatics on your heli extremely rewarding.

What's the difference between a Flip and a Roll?
OK, to some the answer's obvious, but just to be sure.... Both of them use cyclic controls, just that Flips use the elevator and Rolls use the aileron as the primary cyclic control to accomplish the maneuver. Other than that, the are pretty similar to me, both need good timing and collective management to pull off nicely.

Why do I want to learn Flips and Rolls?
Other than obvious reasons and personal reasons you may or may not have. I believe skills in backward flight and flips and rolls would establish a very good foundation for going into inverted flight/maneuvers. The main reason being, if something good wrong when attempting inverted stuff, you need to quickly roll/flip back to upright flight and when that happens in a hurry/panic, your heli might actually be flying backwards! The the reason why this Flight School teaches hovering in all orientations, backward flight and flips/rolls on that order before teaching anything inverted.

Myth-busters
A common complain is that "My heli drifts whenever it rolls". The drifting here means that it does not roll on axis, somehow it seems that some elevator and/or rudder is mixed into the roll. Here's the myth-buster - most helis, would "drift" a little no matter how good the setup. Some purist would say the drift can extremely little (imperceptible?) if you would mix out the interaction on the swash-plate, adjust phasing and/or mix your throttle with aileron, elevator and rudder inputs. But all this is for another discussion altogether, Google them if you need to satisfy your thirst for knowledge. What I'm tying to say is, you don't need a perfect (or close to perfect) setup to have some fun with 3D flying, you just need a reasonably good setup, the rest is up to your thumbs/fingers - you need to be in control of the heli throughout the maneuver to keep it on track!

The Setup
I like a linear pitch curve on the Collective, have at least 9 degrees for max up collective and at least -9 degrees for your max down collective. I like to have +/-11 to 13 degrees, but you'll need good collective management skills to avoid bogging your head-speed dangerously.

For your Cyclics (Alieron and Elevator) try to make it such that it takes about half a second to one second to roll/flip to inverted from a hover. To adjust the speed of your roll/flip, you'll need to adjust your cyclic pitch and/or paddles and maybe even lighter main blades to speed things up on the cyclics. For paddles, the lighter, the faster your cyclic response will be. Cyclic pitch of +/- 5 degrees to +/- 8 degrees should be fine for most helis.

You'll need a good holding-hold Gyro and Tail Setup for 3D your tail must be able to hold it's heading when punching in Collective and Cyclics, though as mentioned above, don't expect the hold to be perfect, it can wag a little, provided a) the wag does not get worse over time and b) the tail quickly moves back to it's intended position after the little wag.

The Drill
I'll like to think flips are like throwing a stick in the air. You'll give it a boost upwards (from gravity) just as the stick leaves your hand, nudge it so it starts to rotate. The stick should flip in mid-air, as the stick falls back to earth, catch it. If you timed your throw and the stick's rotation nicely, your stick would flip in the air and you'll catch it after it performs a complete flip.

That's essentially what you are trying to do with your heli in a Flip. The Collective gives the heli the initial boost up, then nudge it with your Elevator to perform the Flip. Once Flip has gone one complete round, catch it with your Collective to halt your RC helicopter's fall to earth.

Well, that's an easy way to look at it... unlike the stick in which you have do control once it leaves your hand, as your heli performs the Flip and comes around to inverted (half way point of the complete flip), you'll want to add some negative/down collective to minimize loss of altitude when performing the Flip. Would like to mention at this point, you need to be smooth and gentle with the sticks, especially the Collective, input only what you need and slowly if you're not sure. Just make sure you have enough altitude for mistakes, hesitations and recovery.

You goal when practicing Flips and Rolls should be to maintain your
  1. Altitude (Stay at the same height)
  2. Heading (Point the same direction)
  3. Position (Stay the the same position relative to the ground)
The above takes a combination of good heli setup and good timing on your sticks to perform well.

SIM-ple beats the Hard Ground
Please practice on your Simulator before going ahead with this with your heli. Make sure you and do it without much thinking and you'll do fine with your heli at the field. However, if you have an agenda against Simulators or are Simulator-challenged. Visualize it in your head as you move your transmitter sticks, it's not as accurate as the Sim, but it's better than nothing.

Getting Better Now...
You can learn a Flip or Roll first, that's up to your preference, but you'll need to master both reasonably well before attempting anything more advanced. Always remember to learn both ways, meaning roll right, roll left and flip forward and flip backwards.

Universal Orientation
It's tempting to just master an aerobatic maneuver one way and move on, however, that'll be building on shaky foundations. Do try your Flips (Forwards & Backwards) and Rolls (Left & Right) nose-in/out, nose-left/right. If you really want to be complete, you can also do all that at different altitudes (E.g. Way up high in the sky and too low for comfort) they feel different.

That's all for now, stay tuned for Part 6 - Inverted Flight. Meanwhile, have a flippin' rollin' good time!

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