Learning to fly

Last time I wrote about my new hobby - RC Planes. After returning from Christmas holidays, with my new Electrafun plane in hand, I set about trying to learn to fly it properly.

I decided it might be a good idea to get some practice in using a simulator. There are a number of commercial RC flight simulators available, but after a bit of googling I found two pretty good free ones: FMS and CRRCSim. Both can theoretically be controlled with a mouse or the keyboard, but to learn properly you need a controller.

I found this USB RC controller at R2 Hobbies for the ridiculous price of only AUD$12.98 (the postage was actually more than the controller). It looks and feels like a real RC transmitter, with the same control layout, but instead of transmitting the position of the sticks, it sends them down the USB cable.

These controllers (and for that matter real RC Transmitters) come in 2 flavours: Mode 1 and Mode 2. The difference is related to which of the two little joysticks is used for what: Mode 1 has the throttle and ailerons on the right, with elevator and rudder on the right. Mode 2 is the other way around. If ordering a simulator controller you should order one with the same configuration as the real one you will use, otherwise it would get really confusing!

Another thing worth noting - if you read my previous post you would have seen that the Electrafun has no ailerons, so the only way to turn is via the rudder. It comes with a Mode 1 RC Transmitter, however, the rudder is bound to the right stick. This is actually a good thing because you learn to control the left/right direction using the same stick as you would in a plane that does have ailerons.
I was initially more impressed with CRRCSim, as it seemed to have a better flight model, taking into account wind gusts etc. I also liked the fact that it I'd an open source project. On the other hand FMS seems to have a much larger and more active user base, with more user contributed models and landscapes.

Then I tried the 2.0 beta 8 version of FMS. I am not sure why this version is marked as unstable/testing on their website - I did not have any problems with it. But it includes a much more advanced flight model, on a par with CRRCSim in my opinion.

I also found a huge collection of models, at Gunnerson's FMS Models site. Of special interest to me was the Toytronix THawk model, which appears to be very similar to the Electrafun. Having a stimulator model with similar characteristics to the plane you are trying to learn to fly makes obvious sense. I found that the THawk model handles quite similar to the EF.

Next Time: How to lose your plan on top of some building .....


My New Hobby

For the last few years or so, my brother Ben has been getting into radio controlled models. It started with model cars, about the size of a shoebox but with large tyres like some kind of miniature monster trucks, and equipped with nitro powered engines. In the last year he seems to have gotten bored with these and moved onto RC boats and planes.

Anyway, for Christmas he decided to get me a small RC plane, the ElectraFun 2.4 Actually it was more of a combined Birthday and Christmas pressie. This plane is a relatively simple one designed for newbies like myself. It is equipped with a small brushed electric motor, a small 900mAH 8.4V NiMH rechargeable battery, and a 2.4GHz remote control system.

It uses three channels to control the plane - one for elevator, one for rudder and one for throttle. It does not have any ailerons. This didn't mean much to me to start with, so I will explain for any other neophytes out there. Most aircraft have ailerons - control surfaces on the trailing edge of the wings - which can be used to turn the aircraft. When you want to go left, for instance, the aileron on the right wing will go down and the left one will go up, causing the plane to bank. This is used most of the time to steer the plane. Such planes will also have a rudder (a control surface on the vertical stabilizer, or fin, at the back of the plane) which can also be used to turn the plane. But the rudder is normally only used to turn the plane without banking, ie. when coming down for a landing.

So why does the Electrafun have no ailerons? Well for one thing, the less controls to operate, the easier it is to master. But doesn't this mean it can't bank when it is turning? No, because it has another feature - wings that sweep up at the ends (so called dihedral or polyhedral wings). These wings will introduce a roll (or bank) when the plane starts to turn. Another consequence of this effect, probably a more important one, is that it tends to stabilize the plane - it will tend to go back to a state where the wings are level.

The 2.4GHz radio system is another bonus. The Electrafun has been around for a while, previous incarnations came with a FM radio system. These systems work well enough but it is a real problem if anyone nearby uses one on the same channel as yours. The 2.4GHz systems tend to use some form of spread spectrum modulation technique, where the transmitter and reciever share a common code - other transmitters can transmit on the same frequency as yours, but because they do not use the same code, they don't interfere with each other.

The system provided with the Electrafun is a FHSS (Frequency Hopping Spread Spectrum) system, meaning that it constantly cycles through a set of channels while it transmits in a particular sequence. The reciever listens for the same pattern of channel hops to decode the signal. (This explanation is a gross oversimplification ... maybe another time I will go into more detail.) Anyway, the gist of it is such systems are relatively immune to noise, interference and other nasties and thus more reliable.

Another key feature is that the propeller faces backwards in a so-called 'pusher prop' configuration. This is important in a beginners plane for a number of reasons. For one thing, if you crash the plane into the ground, it is going to go down nose first - if the propeller and motor are both at the nose of the plane, and you hit the ground hard, then one or both will get wrecked. On the other hand, if they are behind the wing, then it is nearly impossible to crash the prop into the ground (well not totally - one time I crashed it upside down and the prop did break... luckily they supply a spare). But there is an even more important reason why it is better to  have a pusher prop - if you are unlucky enough to crash the plane into a person (or even a pet) then a prop on the front could seriously injure them, but a pusher won't get near them.

Some other features:
  • The wing is easily attachable / detachable, making it easy to transport. The modest wing span (1041mm) also helps with that
  • The wings are secured with rubber bands. At first glance this may seem crazy, but actually it is a good idea - in a heavy crash the wing is likely to slip around or off (or the bands break) rather than snap. There is a down side which I will come to later ...
  • The wings and stabilizers are made of foam. Easy to repair and cheap to replace.
  • It is capable of quite slow flight and can be flown at a football / cricket oval. I have found that finding good places to fly when you live in a city is not as easy as it may seem. It can also glide pretty well (ie. with the power cut).
  • It has landing gear (although primitive). From what I hear most pilots prefer to throw it (hand launch is the term they use) and land it on it's belly, but I have actually found that quite hard, particularly when I have to do it on my own, because after throwing it you have a fraction of a second to get your hands onto the controls before it crashes. On the other hand I have found taking off from the ground using the landing gear is really easy - and fun! Landing on the wheels is a little harder but also gives you a great buzz.

First Flights

We had Christmas at my parent's place, the Brindabella Hills Winery. We went to a paddock nearby to the vineyard, which had very high grass - handy to land the plane in without damaging it. At the first attempt I threw the plane with Ben at the controls, once he had it up at a safe height he handed the controls to me. I found it very hard to control - I couldn't get it to go the direction I wanted and kept losing control and having to hand back to Ben. Most flights ended with me crashing it.

Ben had a couple of crashes with it also, one of which damaged the wing. Although it is good that the wing can come away in a crash, one of the down sides is that if the wing skews around, the prop digs into the trailing end of the wing and chops a nice big hole in it. Also, the rubber bands slip off the plastic strengthener in the middle of the wing edge and cut right through the foam wing. Later, I read on various forums that it is good practice to tape up the trailing edges with gaff tape to strengthen them against this kind of accident.

Another problem that can occur is that after a crash the wing can become weakened such that it will fold up during a flight (esp. when under high acceleration). Ben taped a piece of balsa on the wing to strengthen it. However we later found that this was adding too much weight, which had shifted the centre of gravity and made the plane more unstable, so we removed it.

In the end, the time available during the Christmas break, when I had Ben available to help me, was not enough to learn how to fly well. I only managed one hand launch successfully (ie. where I was able to get the plane into the air unaided) and no landings - I crash landed every time. Luckily because of the long grass in the paddock we were using the damage was limited though.

Next time:  Practicing with a simulator, some disasters, and some successes