How To Perform Rolling Autos
John Parker offers some help and handy tips designed to help intermediate 3D pilots improve their rolling autorotations.
Spring is coming and with all the winter flying that you’ve done just to keep your hand in, have you made any real progress? Of course you have, and you know that really. In these articles I will be explaining a few basic aerobatic manoeuvres such as loops and flips right through to pirouettes and more precision manoeuvres. Being able to complete these is a very important skill to have and a fundamental part of medium to advanced 3D. This time around, however, I want you to start feeling confident about rolling auto-rotations. This is not an easy manoeuvre and is aimed at intermediate 3D pilots and is something beginners can aspire to and try once they’ve mastered more basic aerobatics. Don’t worry, you’ll get there in the end and we’ll have something for you to try in the next issue.
Don’t think for one minute that the auto came more naturally for me than most; in truth, I’ve had some hard contact with mother earth on many occasions. No, they’re not easy, and just as happens with the pirouetting stuff, aerobatic autos often come into the category of “I really MUST learn to do them some time.” As with any advanced manoeuvre, things can go wrong very quickly, and often this happens with no time to recover before the ground comes up to consume your pride and joy.
A few years ago, I was fortunate enough to have Mr Auto himself, Bob Johnston, give me some handy tips on these manoeuvres. Bob managed to point out a few areas where I was going wrong. Naturally I’m happy to pass on this wisdom to Rotorworld readers.
Preparing Your Kit
Let’s begin by having a look at your machine’s set-up. For the beginner to this type of manoeuvre, I recommend a 50-size helicopter and 600mm main blades as a minimum requirement; the larger 90-size model will have an advantage, but 50s are just fine for all aerobatic autos. Don’t worry if your tail is a non-driven type – it is still just as capable for this exercise.
How is your hold pitch curve set? It will need to be zero at centre, with mirror curve top and bottom. You may be running 9 – 12˚, depending on what your machine can pull at the extremes, and this is the same as your 3D idle-up curves. The only adjustment that’s essential here is a tightening of the main blades in their grips; don’t make them absolutely solid, but they should be quite tight (I will explain why later).
There are several ways that you can lead into this type of manoeuvre, but I think we’ll stick to a couple of the least terrifying ones! For the standard auto approach, with hold engaged, we are trying to use the air in our descent to power the rotors. With a descent at, say, -4˚, we need to flair slightly before landing, and bring the pitch up to (e.g.) -2˚. Thanks to the forward speed your helicopter is carrying, and a pitch reduction in the flair, you should find the rotor disc will spool up with only a small loss in forward speed.
I hope you can understand this concept, because I found it to be a key-learning feature when Bob Johnston explained the manoeuvre – basically, you trade forward speed for rotor speed.
With all this 3D that we do, and mirror set-ups, we should find that, if our machine does it the right way up, it will do it inverted too. To believe in this, go out and try some quick auto approaches, flaring at the bottom; remember to keep -2˚ pitch in the flair, until most of the forward speed has bled off. You should hear the rotor disc spool up dramatically. When I first attempted rolling autos, I started from an inverted position, and at a good height of around 300 feet.
My second tip, which also works with the standard approach, is to raise the throttle in the hold function. Now, your model will not quite hover, but it has the ability the keep those rotors turning in an emergency situation… it’s starting to sound much easier, don’t you think?
So, we are at 300 feet, with the model inverted into wind and looking at you, with an approach line of 60˚ from the horizontal. As soon as the hold function is flicked, move the pitch to about +4˚, and try to feel and look for a smooth descent path. With an increased throttle in the hold, we should have no fear of those blades stopping on the way down. Trying not to panic, you now need to start thinking about rolling the helicopter over; at this point, priority number one is rotor speed preservation during the auto. Okay, you need lots blade pitch, to rob the rotors of their speed. Any cyclic input needs to be gentle – half amounts are normal in the auto.
With our inverted descent in full swing, we need to build some reserve rotor speed up; we do this much the same way as we would in the flair. With a steady descent at +4˚, slightly push the nose of the helicopter up, and reduce the pitch to +2˚. This will kill some forward speed, whilst building up the rotor speed. Be careful not to lose too much forward momentum though – about half is okay, but no more. As soon as you have flared, start to roll upright, in a nice and steady fashion. If you introduce a nose-high attitude with a small flair in the inverted section, once rolled over, the helicopter will be in the correct position for a standard auto approach. At this point, your collective pitch needs reducing to -4˚, whereupon a standard auto is executed.
A full roll uses much the same technique. Go a little higher this time, to a position around 400 feet up, with the helicopter’s nose towards you and into wind. Chop the throttle, and settle into the descent. Time is in short supply, so raise the nose to that familiar flair position, and adjust your pitch to -2˚; now, start making a gentle roll to the inverted, and push in collective to the upper position of +4˚. Establish a good descent line, then once again bring the nose up slightly. Reduce the collective to 2˚, and roll over again to the upright. Finish with a straight-in auto.
For starters, I recommend that the beginner pauses between sections, to give himself time to set-up each half roll. In an emergency, switch-out of hold and go into level flight.
Oh yes, I was going to tell you the reason why your blades must be tight in those grips. Well, this is a good safety net should any unforeseen circumstances cause the rotor speed to drop dangerously low; the sudden application of throttle stops the main blades from folding back, and damaging your helicopter beyond recovery.
The more proficient you get, the more flexible and varied the descent will become – roll-outs can become spectacularly low with enough rotor speed.
Enjoy the experience…