Tutorial for beginners

This tutorial in intended to be given as a presentation using demonstrations and flight simulators. It is aimed at prospective new members who are beginners to the hobby and would usually be given after the monthly meeting, as the need arises.

John Corkill, November 2010

Purpose of this tutorial

A raw novice can get his first plane into the air quite easily just by placing it on the ground and opening the throttle. What happens after that is largely down to luck, but the chances of an unaided safe return to earth are quite low.

Prior to his first flight the novice will have spent much time thinking about flying his new pride and joy. Logic tells him that the elevator makes the plane go up and down, the ailerons make it bank and the rudder, well it sort of steers it, doesn’t it ?  The throttle, of course, makes it go faster or slower. Reality is a bit more complex than this but an explanation of how the basic controls really work, plus demonstrations on the simulator, will, hopefully, help soften the novice’s undeniably difficult learning curve.

Before discussing control inputs it’s helpful to understand what we’re trying to control, and why, so let’s start by talking about the plane itself.

Natural Stability

It is important to stress that a lot of development work has gone into aircraft design over the last century or so to enable aeroplanes to fly themselves successfully in spite of a pilot’s attempts to persuade them to do otherwise.

One built-in property they have is Natural Stability, which continually attempts to restore the plane to a stable flight path following a disturbance. Flying a model aircraft is a continuous battle between the natural stability of the aeroplane and the pilot’s attempts to overcome this using the controls. It’s no coincidence that there is a mode of stability corresponding to each of the four transmitter stick movements.

The easiest stability to understand is yaw stability, that is the response to a sideways movement of the aircraft tail. This is exactly the same as an arrow, or a dart. The fin is the “flight”. In a similar manner, the tailplane acts as the flight in the pitch direction, controlling the nose up/down attitude of the plane. The fin and tailplane will always try to align themselves with the airflow over them and they have lots of leverage to help them do this.

A little more difficult to grasp is roll stability i.e. what makes a plane try to level its wings if disturbed. Two primary factors influencing roll stability are dihedral and the position of the wing i.e. high or low. We’ll come back to this later.

Finall, there’s speed stability. If a plane, for whatever reason, is travelling too slow to support itself, we don’t want it to stall and fall out of the sky. Rather, it is desirable that it speeds itself up. It does this by dropping its nose as it slows, thus converting energy from height lost into forward speed. One of the important factors here is something you may have heard of : Centre of Gravity position. It really is important in making a model behave in a “friendly” fashion.

All aircraft possess natural stability to a degree. Passenger aircraft and trainer models have high natural stability whilst aerobatic aircraft and full-size fighters have low natural stability. We’ll talk about whether stability is “good” or “bad”, later.

Disturbances may occur for many reasons, including natural inputs such as wind gusts, but we’ll be concentrating here on the most significant, and unpredictable, cause of disturbance known to man: the novice pilot. Many older and experienced modellers will have done their apprenticeships on “Free-flight” models, which have high stability and are capable, when properly trimmed, of take-off, flight and landing all by themselves. The problems only arise when we install radio control, so make sure this is switched off for your first flight ! (only joking !!).

The concept of learning to fly a model being a “battle” is not too far from the truth, as most slightly experienced novices will confirm. The fastest learning novice  pilots are those that recognise the models flight characteristics and make use of, or work with, them. If you fight the model it often wins.   

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So let’s get going with the interesting bit, what do the controls really do.

We’ve talked briefly about the four primary controls, and how they relate to model movement, so let’s look at them in a bit more detail and see exactly how they control the model.

The four primary controls      (using ‘control_demo_1’)

Demo 1        Movements about the plane axes

Demo 2        Movement of control surfaces

Demo 3        Effect of controls on plane

The rudder is relatively straightforward ; it simply moves the tail to the left or right. Note that this, on its own, does not cause the plane to turn, just ‘crab’ sideways. Remember, the fin/rudder assembly always aligns itself with the airflow.

The ailerons are the wiggly bits on the wings; when one goes up the other goes down. When the aileron goes down the effective angle of the wing to the airflow increases so this wing generates more lift and rises, and vice versa. Worth remembering when you’re installing and setting up your servos : aileron down = wing up. Note that the ailerons themselves, do not cause the model to turn.

The next two controls, elevator and throttle, we’ll consider jointly since they tend to work together to make the plane go faster and slower, and up and down, both fairly important in keeping the plane off the ground. However, things are not as straightforward as they appear and this area is one of the main causes of grief to the novice pilot. It’s worth spending a bit of time.

Throttle demo :

Fly straight and level at part throttle, note speed.

Open throttle a bit, note speed. Note altitude.

Close throttlea bit, note speed. Note altitude.

Conclusion : stable condition is throttle controls rate of climb, not speed.

Sounds odd, but actually, this is quite logical. As mentioned previously, if the plane is flying too slowly its natural stability causes the nose to drop and the plane to lose height to maintain flying speed. Here, we’re seeing the opposite effect : if we try to force the plane to fly faster, the nose lifts and the plane climbs to prevent speed rising.

Elevator demo :

Repeat above, having trimmed to a higher speed in level flight.

Same happens in response to throttle, but speeds are higher in all cases.

Conclusion : overall, elevator controls speed, not rate of climb.

Again, although not obvious this is logical. Lift generated is related to both wing “angle of attack” and airspeed. Elevator, like the rudder, behaves like an arrow flight and alters the pitch angle of the whole plane relative to the airflow. Reducing the wing angle of attack by means of down elevator means it must fly faster to maintain lift. Conversely, if we increase the angle of attack using up elevator it need not fly so fast.

Summary

So, we’ve discovered so far that, in the main, the throttle does not make it go faster or slower, the elevator does not make it go up or down, and the rudder and ailerons do not make the plane turn. Thank heavens birds aren’t as clever as us.

In order to execute even the most basic manoeuvres, the control inputs required are a combination of the above primary inputs. Let’s move on to look at these.

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The level turn

Probably the most important manoeuvre since it needs to be carried out every few seconds and it is probably the first manoeuvre the novice will encounter (assuming the tutor has taken off. It actually involves three main control inputs.

i)   The plane needs to be banked using the ailerons to a suitable angle.

ii)  This is followed by some up elevator and the plane will then start the turn

iii)  Finally, the elevator input is removed and some opposite aileron is applied to

       level the wings and complete the turn

Demo 4   The level turn

What is a “suitable” bank angle is determined solely by how tight the turn needs to be and this is entirely at the pilots discretion. When banked, the elevator is now acting partly as elevator, to raise or lower the nose, and partly as rudder to turn the plane into the turn. There is only one correct elevator input for any model particular speed; too much and the plane will climb as it turns, too little and the nose will drop. Don’t worry if you don’t get this right, it’s not a problem. It just looks untidy. Practice will soon sort this out.

Novices often initially run into trouble by holding on aileron for too long on entering the turn The plane banks very steeply and loses height, and the natural (i.e. panic) reaction is to give “up” which simply tightens the turn into a spiral dive, or worse, which could be terminal.

Once banked into the turn, a small amount of aileron may still be needed to maintain the bank. This is actually required to counteract the planes natural stability which is trying to right itself, as it should. How much sustained aileron is required is dependant on the individual plane’s design. 

At this stage, the use of rudder and throttle in the turn can be ignored completely. The novice will have quite enough to concentrate on with just aileron and elevator controls. In fact, virtually all early flying can be done using these two controls plus a little throttle input. 

Just  remember the three main inputs :  i) bank  ii) apply up elevator  iii)  “unbank”

Take off

Demo 5   The take off

Probably the second inportant manoeuvre encountered. Fortunately, planes are quite good at taking off. If full throttle is applied, and the plane stays straight, then the natural state of the plane is a steep climb – the pilot needs only to make sure the plane does not climb too steeply by using the elevator.

Note : Ailerons do little when the plane is on the ground (since it can’t bank) and the main steering input is rudder or steerable nosewheel. At least one of these is desirable.

Important tip :  do not try to gently “ease” the plane off the ground using small throttle openings. As it lifts off it is at its most vulnerable to stalling and safe flying speed must be attained as quickly as possible. In this condition “power is good”.

Landing

Demo 6  Landing

The only compulsory manoeuvre. It’s difficult because there are so many model control inputs to get right, in addition to assessing both the height off the ground and the position of the model in the air with respect to the runway. Likely to be the most unnerving manoeuvre for the novice; fortunately the tutor and his buddy box is available for initial attempts.

Landings are always carried out into wind or as close to this as possible. If your tutor is unhappy with wind strength or direction, i.e. is it across the runway, then this does probably mean that conditions are not right for tuition.

A landing actually starts very early, with the model travelling into wind at about 100ft right above the landing strip. It executes a large circuit, left r right as appropriate, in front of the pilot and finishes up once again in line with the runway at a lower altitude. Such a circuit allows the plane to settle into a smooth descent with the wings level and at a steady speed. It also allows the pilot time to gather his thoughts and, if he, or the tutor, is not happy with the circuit, they can abort it at any point. If the model is not stable, or in the correct position, during this circuit don’t try and recover, just start again.

The main control of rate of descent is throttle. If the plane seems too high, or is not descending fast enough, close the throttle a bit. The circuit describe above should bring the model to within approximately 5m off the ground, lined up with the centre of the runway about 50m or so away on the approach side, and with the wings level.

Even at this point the pilot, or tutor, can still abort the landing by opening the throttle.

On the final approach the throttle should be almost closed and the model slowed down as it approaches the ground by application of up elevator (remember throttle = climb/descend, elevator = speed). The pilot should aim to touch down in right front of himself.

Common problems with initial unassisted landings include

i)   Plane not lined up with runway. Finishes up in field.

ii)    Plane veers off to side when approaching ground. Pilot tries to correct with aileron,. Plane stalls and cartwheels in. Often caused by landing too slowly. Landing a bit too fast is more preferable than landing too slowly.

iii)   Pilot “landing” several feet above ground level. Everything has gone perfectly and the model flares out right in front of the pilot, but at a height of several feet (or more), stalls and falls to the ground.

iv)  Similar to the above but misjudging the ground position and flying “into” the ground at a relatively high speed. Usually followed by an equally high rebound.

v)   Forgetting that throttle = height and elevator = speed. Pilot approaches runway and attempts to lose height by just giving down elevator on the approach. Plane absolutely refuses to descend, accelerates and passes pilot at a high rate of knots 

The experienced tutor should pick up and correct any of the above before they happen. The likelihood of any of them happening to a novice should be very small.

Plenty of practice is required here; one good landing does not make you an expert !

Trainer types     3 or 4 channel

Demo 7  3-channel trainer  (‘control_demo_2’)

The above discussion has concentrated on the 4-channel trainer (aileron, elevator, rudder and throttle). Some models, particularly vintage and powered gliders, do not have ailerons. How do these manage to turn ?

Three-channel, or “rudder” models all have one feature not strictly required by aileron equipped models (although most have some to a degree) and that is dihedral. That is the angle each wing is tilted above the horizontal.

As demonstrated before the rudder simply slews the tail of the plane left or right. Viewing the model from the front it’s clear how slewing the tail sideways increases the angle of attack of one wing and reduces that of the other, forcing the wings to behave just as if they had ailerons. Here, rudder input is equivalent to aileron.

So which is better as a first model, 3- or 4-channel ? Dihedral is a very effective stabiliser, making the model right itself quickly, and the models with rudder only, and dihedral, tend by their nature to be very stable and forgiving aircraft. On the other hand, rudder only as a means of turn is not as precise or responsive as aileron. Overall, if you stay out of trouble the 3-channel model is very relaxing, but if you get into trouble then the response given by ailerons may get you out of it better. On the other hand, ailerons, themselves, can get you into trouble if over-applied at low speeds, i.e. when landing. Yes, you’ve guess it, there’s no straight answer. However, both will do the job if you’ve got a good tutor, (and both will can you into trouble). 

Final points

You’re possibly trying to reconcile my previous advice that elevator controls speed when you may have seen the club experts carrying out repeated loops or bunts using elevator – where elevator’s definitely making the model go up or down (or round).

Well, I have said that flying is always a “battle” between stability and disturbance which, in this case is the pilot’s control input. A trainer will have high stability (lots of dihedral, high wing position) and control input will be low (small surfaces, small movement). In this case gravity is a significant input, pilot input is relatively mild and stability tends to dominate, with the model flying mainly according to its inbuilt features. For obvious reasons I have concentrated on describing this type of model in these notes.

An aerobatic model, on the other hand, has low, or zero, built-in stability and large control inputs, and relatively high power, enough to make gravity relatively unimportant. Here, power and disturbance, or pilot input, dominate. This is an obvious design feature, since the pilot does not want the plane fighting, or resisting, him when he is trying to carry out precision manoeuvres. These types of planes do behave differently to trainers.

Final point to novices : Spitfires tend be towards the latter category. 

John Corkill