How To Loop Your Heli
Bored with hovering, circuits and stall turns? take the path to more advanced flying by following our new series. John Parker starts us off with a loop
Some of you remember, and some of you have yet to remember, your first real aerobatic manoeuvre. Personally, I recall getting bored with just flying about, not knowing how to advance to the next level of getting my helicopter through inverted safely. What does that mean? I’m talking about your very first loop.
For you to be thinking about performing a loop, you must have an understanding of what lies ahead, and realise that you will be caught out if the helicopter strays from your intended path of travel. You need a safe platform to fall back on in the event of your manoeuvre faltering.
Knowing The Basics
Where do you begin? Well, before even contemplating a loop, you really ought to be competent in performing fast forward flight moving left to right, in a straight and level fashion with, perhaps, nice high vertical stall turns at either end. Also, figure eights with the turns looking towards you rather than away are a must. This way, I feel reckon you’ll be confident in your perception of the helicopter’s orientation, and fully aware of exactly what is required for controlled flight.
Preparation is the key to most things, and such is the case for you and your helicopter before performing our imminent loop. First of all, we must ask, is your helicopter aerobatic? Yes, I know that most pod-and-boom examples are these days, but when I started, some weren’t so if you have an old model it’s worth thinking about.
Second, do you have idle-up 1 set on your transmitter? If so, have you dedicated your idle-up 1 (sometimes called the ‘stunt mode 1′ programme) to an aerobatic pitch and throttle curve? In order to perform short periods of inverted flight, you will need to set and activate this programme in your transmitter. When done, this can be activated by the flick of a switch in those pre-hovering moments or during the hover itself; and, you can switch it on during the flight to sustain a constant rotor speed as the collective is reduced and increased throughout your manoeuvre.
Check your normal fly around set-up, and make sure you have the following settings in place.
Getting Set Up
Bottom stick has no relevance at this stage, so we’ll ignore that and look at the other positions. Let’s say most of you have 5-6° at mid stick for the hover, and 10° plus e.g. if your machine will pull at top stick. You will now need to copy this to you stunt or idle-up mode, along with the throttle curves. Now, we have all your normal settings copied into this new idle-up programme.
Next, grab the pitch gauge out of your toolbox and set the low stick pitch position. Yes, bottom stick has now become relevant, because having set the other positions, you will now need to achieve -6˚ at the low end.
So, now you have -6° at bottom stick, +5 to +6° at middle stick, and +10˚ or more at top stick… but that’s not ‘job done’, because you’ll need enough throttle in the lower stick positions to keep those rotors from stopping when we go inverted. We know we can leave all the settings alone from mid to top stick, because you have tested these in your normal circuit flying; but, you must copy the throttle percentage setting needed for hovering between +5 to +6° and set this to the -6° bottom stick setting too. What I’m trying to say is that if you can hover with, say, 60% throttle at +6°, you can then hover inverted with 60% throttle at -6°. It’s as simple as that in layman’s terms.
Right, back on with the pitch gauge, and find your zero degrees position on the collective stick. Throttle in this area will need to be reduced; for starters, try 15% below your hovering settings. All we are looking for at zero degrees is enough power from your engine to keep those rotors turning at a constant speed.
You should now have a form of ‘V’ curve set up in your stunt / idle-up 1 mode, meaning you’re ready to fly.
I can remember getting to this very stage in my flying career. I’d read all the books, and had performed dozens of stall turns, often wondering whether they were high enough, whether they were vertical, and whether I was reducing collective in the vertical section. If you look at a perfect stall turn, it does in fact contain two parts of a loop: the entry and exit quarters.
Okay, so you can fly fast, straight and level in front of yourself, and are able to perform a nice high stall-turn at either end. But are you aware of your collective control throughout the turn? Are you reducing pitch to zero in the vertical climb, and is the entry and exit of the stall turn a smooth arc back into, or out of, straight and level flight? If you are answering ‘yes’ to these questions and are confident in your ability to deal with a new manoeuvre, then all I can say is, here we go!
Like most people, I have a preferred side of approach; I come in from the right, and exit to the left. This means that the ideal day for my first loop, weather wise, would have had a bright clear sky and the wind to my left. Why? Well, a nice gentle breeze helps many manoeuvres on their way, and the loop is one of these. Go and perform a stall turn into wind and just watch how much height is gained on the climb; now try the same down wind… your helicopter will not go so high this time.
I’ve talked about two quarters of the loop manoeuvre being in the stall turn, i.e. entry and exit. The rotation from your vertical climb to inverted, and inverted to vertical decent, both rely on the entry speed you have achieved at the start of the loop. I would suggest you go out and practice making some nice straight-and-level flights around 50 metres out and 50 metres up, because this will give you enough height to buy you time in the event of disorientation, or indeed anything else that can go wrong.
Think about the loop – it is a back cyclic manoeuvre with the correction only for pitch. As you approach into wind, remember the stall turn; a gentle easing of the stick, with a small amount of back-cyclic, is all that’s required – too much and it will kill your speed, along with your height. As you’ve eased in some back cyclic, keep the pitch on, to power your helicopter up to the near vertical part of the first quarter of the loop; now, you need to be thinking of reducing that collective as the helicopter goes past the vertical.
Finishing The Job
You can still abort the loop at this point fairly simply, by turning it into the now familiar stall turn. Is it still looking good? Have you got most of the speed you started with? If you’re losing speed and are now approaching the inverted top section, just apply a little more rear cyclic because a tighter loop can be achieved with less speed. Remember, the perfect loop takes a lot of practice. Pitch at the inverted top section will vary according to speed, and the size of the loop. A big, slow loop requires more negative at the top than, say, a large fast loop, which can be flown with positive pitch all the way around.
So, lets say your helicopter is now approaching the third quarter of its loop. All that’s required is the same, small amount of rear cyclic, with the reduced amount of pitch and forward speed. But what if you have lost a lot of height? All you can do is apply more rear cyclic to pull out level, and all things being well – and if you hold your nerve – you can resort to that familiar exit portion of the downwind stall-turn, before returning to straight and level flight.
When attempting this manoeuvre for the first time, most people end up performing figure ‘9’ loops. By this I mean that all goes well running into the vertical climb, but then a lot of speed is lost, due to the unintentional application of more back cyclic, and very little pitch correction. Exits will vary from very fast to a hover, the latter taking you backwards if the back-cyclic is not checked.
Generally, if you have enough height and a good, modern light machine / engine combination, a loop, flop or flip will be the outcome when attempting this manoeuvre. Try to have an understanding in your head of exactly what you’re going to attempt, and pick your days regarding wind and visibility. Height is your friend, but don’t overdo it because you’ll need to see exactly what’s going on with your model. Think about the safety aspect too when you want to try a new trick – let others on the field know what your intentions are. Finally, remember to have fun!