RAF Cadets' Handbook

Pilot Elementary Training: RAF Flying Cadets' Manual - Part II

MANOEUVRES - Part I

5 - Taxying

How to Taxy. Taxying is the term given to moving the aircraft on the ground by its own power. You must always keep a very sharp lookout, when taxying, not only for obstructions and aircraft on the ground, but also for other aircraft flying circuits and gliding in to land. Since the speed of the airflow over the control surfaces is small, the controls feel sloppy, and you have to use comparatively coarse movements to get the desired results. You are primarily concerned with the use of the rudder to steer you on the ground and, since this is affected by the slipstream from the propeller, you can increase its effectiveness when you want to turn, by giving a temporary burst of engine, by opening the throttle as you apply the rudder.

Always taxy at a moderate speed, and when taxying get on the edge of the airfield and keep close to it; never taxy across the middle of the landing ground.

To move off, hold the stick back and open the throttle gently, being prepared to throttle back gradually to prevent the speed getting too high; as the aircraft gathers speed, centralize the stick. Since the view forward on the ground in most single-engined aircraft is not good, do not continue forward in a perfectly straight path; follow a 'wavy' track, swinging the nose first to left and then to right so that you can get a good view ahead of the direction in which you wish to go; like this :

You will find that it is always easier to taxy into wind than across or down it ; this is because the pressure of the wind on the keel surfaces tends to make the aircraft head into wind as it moves and therefore keep to a straight path. When taxying down wind an aircraft gathers speed more quickly and is more difficult to control. When taxying down wind, keep the stick well forward to depress the elevators, to prevent the wind getting under the tail and lifting it.

You steer the aircraft on the ground by coarse use of the rudder, giving increased engine when necessary.

Turns should be made at slow speed. If you attempt to turn too fast, the aircraft will tend to heel over on to the wing tip ; you may damage the wing and a gust of wind can easily capsize the aircraft completely in that position.

The brakes should always be used gently and sparingly. They can be used to assist in a turn. The brakes may also be applied to both wheels, gently to bring the aircraft to a stop after the throttle has been closed.

If there is a strong wind, or you are in a confined space, it is advisable to taxy only with men holding the wing tips. In such circumstances don't hesitate to signal for assistance ; it isn't worth risking damage to the aircraft to show your independence.

When the wind is fairly strong, the ailerons may be used to assist turning. When the aircraft is taxying into wind, move the stick to the right, for a left turn. This, by increasing the drag of the left aileron, and reducing that of the right aileron, utilizes the airflow on the wings to help with the turning movement.

When the aircraft is taxying down wind, move the stick to the left for a left turn. This depresses the right aileron and so increases the effective area which that wing offers to the wind blowing from behind, and so helps the aircraft to turn to the left.

Taxying Rules. When two aircraft are meeting head on, each shall alter course to starboard. When one aircraft is overtaking another, the overtaking aircraft shall give way to the other. When two aircraft are on converging courses, the one that has the other on its own starboard side shall give way. An aircraft taxying must always give way to one coming in to land or taking off ; and in the case of an aircraft coming in to land, the taxying aircraft must stop, and remain still, in order that the approaching aircraft can avoid him. Except in extreme circumstances, a pilot, taxying should not try to taxi out of the way of an aircraft coming in to land but should remain where he is.

Taxi close to the perimeter of the airfield, but far enough from the boundary to leave sufficient room in which to manmoeuvre the aircraft in safety.

Note. If the ground is at all soft, the tail skid, if it is connected to the rudder, as is the case in some aircraft, may become slightly embedded in the ground while the aircraft stands still. In such a case you won't be able to move the rudder bar until there is some forward movement on the aircraft following on the throttle being opened.

6 - FLYING STRAIGHT AND LEVEL

What Flying Straight and Level Means. Flying straight and level means keeping level in the rolling plane while maintaining a steady course at a constant altitude.

This involves the use of the ailerons, the rudder and the elevators, and of the trimming devices with which the aircraft is provided. The engine revolutions are normally kept constant at the figure appropriate for cruising speed.

Maintaining a constant altitude means that the lift has to be kept equal to the weight ; and this, when the engine revolutions are also kept constant, means maintaining the wings at a certain angle of attack to the airflow. The principal problem in straight and level flying is therefore to find the appropriate angle of attack, which in the case of level flight at cruising speed you may think of as attitude of the aircraft in relation to the ground. Once you have found the correct attitude and have set the tail trimmer appropriately, the natural stability of the aircraft will do most of the work of keeping straight and level for you.

How to Fly Straight and Level. When, having climbed or descended to the desired height, you wish to fly straight and level, the sequence of operations is as follows:

1. Set the throttle so that the revolution counter records the appropriate revolutions for cruising speed (your instructor will tell you the figure).

2. Looking in the direction in which you wish to fly, select some mark ahead as a guide. This can be some point on the horizon, a cloud, or some distinctive feature on the ground, as far ahead as possible. The best thing is to pick up a point on the horizon in line with the nose, but this is not always easy if the horizon is very hazy or, as in some aircraft, if the view over the nose is not good. In such a case, you will have to select some other point on the horizon, in the sky, or on the earth which you can relate to some part of the aircraft, windscreen frame, a strut, or the instructor's mirror, for example

3. Level the aircraft in the rolling plane, and keep it level throughout.

4. Apply gentle pressure to the stick until you think that the attitude of the aircraft in the pitching plane is that required for level flight.

5. Hold the stick in this position and adjust the tail trimmer so that no pressure is necessary to hold the aircraft in its correct position.

6. WAIT TO SEE WHAT HAPPENS. If the part of the aircraft which you are trying to fix on your mark seems to be rising or falling, it means that you are not maintaining a constant attitude, that is, you are not perfectly trimmed. Hold the aircraft steady on the mark by appropriate pressure on the stick. When the aircraft is quite steady, and has remained steady for about half a minute, look at the airspeed indicator. Your instructor will have told you what your approximate airspeed should be in level flight at the appropriate engine revolutions. If the airspeed indicator shows that your speed is higher than the correct figure, and that it is increasing, you know that you are diving and losing height. If the airspeed indicator shows that your speed is too low, and that it is falling off, you know that you are climbing and gaining height.

7. If you find that you are climbing or diving, you have to guess a new attitude which you hope will give you level flight. This you do by pressing the stick gently forward (if you were climbing) or gently backward (if you were diving), and then holding it at the point you think is right. Then adjust the tail trimmer by moving it in the same direction as you moved the stick until you no longer have to maintain pressure on the stick.

8. Having made your control adjustments you must give the aircraft plenty of time to stabilize itself in the new attitude before, you can decide what result you have obtained. It is no use trying to chase your airspeed hoping to hit on the appropriate attitude.

9. You continue this process of very slight changes in attitude at suitable time intervals until your airspeed remains constant at the correct figure. Then note the reading of the altimeter. Hold the attitude of the aircraft constant by reference to your mark, and to the airspeed indicator, and after say, a minute, look again at the altimeter. It should indicate the same height. If it does not, it means that the aircraft is not flying level and that the approximate airspeed at which you have aimed, and which you have held constant (if you have), is not in fact exactly correct for level flight. You must therefore change the attitude again and experiment with other airspeeds until the altimeter confirms that you are really flying level.

Once you have found the correct attitude for straight and level flight, you have to maintain it. The natural stability of the aircraft once it is correctly trimmed will do most of the work for you, if you will only allow it, but you may have to correct for any violent bump. Glance frequently at your mark and at your airspeed indicator to make sure

that you are keeping to level flight. At the same time also, watch for movement in the yawing plane. If the aircraft swings off to the right of the landmark you must correct this yawing movement by applying left rudder gently, with a little left bank, until you are on the desired course once more. Similarly, if the aircraft moves to the left of the landmark apply a little right rudder, and right bank, until you are straight again. Centralize your controls.

Besides movements in the pitching and yawing planes, which you have to watch for simultaneously, you have also to keep the aircraft level in the rolling plane. If one wing tip seems to move up above the horizon while the other goes down below it, the aircraft is banking, and it must be brought back to the level position.

If the left wing tip has dropped, move the stick smoothly to the right, and at the same time apply a little right rudder When the aircraft is level again, let the stick come back to the central position and take off rudder. Should the right wing go down, the process is just the reverse.

Throughout this manoeuvre, note from time to time the position of the two needles on the turn and sideslip indicator. You will find it interesting to see how the instrument records the fact when you are moving in the yawing plane, and when, if you become banked, you are slipping in towards the lower wing.

Flying straight and level sounds a very complicated business when it is set out like this ; in fact you will quickly get the habit of controlling the aircraft's movements in its three planes, and you will find it easier if you let the aircraft do as much for you as possible through its own stability. Try to avoid a rigid attitude of staring fixedly at your chosen landmark to the neglect of everything else ; relax; keep a lookout for other aircraft; look for signs of the wind. direction, and cast an eye over the instruments from time- to time.

7 - C L I M B I N G

What Climbing Means. In order to change our direction to climb from level flight, we have initially to provide more lift: once this has resulted in a change in. our attitude, the thrust of the propeller is directed, and pulls us, upwards, but at a reduced speed; so the lift is reduced and is in fact somewhat less than that required for level flight. (See pages 21, 22.)

The Best Rate of Climb. The rate at which we gain height depends on the angle of our flight path to the horizontal, and on our forward speed along that path. We can climb slowly at a fairly steep angle, or quickly at a shallow angle. There is one combination of speed and angle which will give the maximum rate of climb, that is, will permit us to increase our altitude by the greatest amount in a given time. Below is a diagram which illustrates the point, the length of the lines representing the distance flown in say, one minute:

You can see that the middle line, although it rises at a less angle than the top line, and although it is not so long as the line beneath it, reaches the highest point, namely 400 feet as compared with 300 feet and 330 feet respectively for the other lines. It therefore represents the best rate of climb of the three, and its angle to the horizontal is the best climbing angle of the three. The speeds in the three cases are reflected in the length of the lines, the speed corresponding to the middle line is the best climbing speed.

The attitude of the aircraft in these three cases is also shown in the diagram. This reveals that the problem of finding the best climbing angle is really that of finding the appro priate attitude of the aircraft which will give the desired angle of attack.

How the Forces on the Aircraft Act in a Climb. As we have seen in pages 21, 22, when the aircraft is climbing, the thrust combines with the lift to permit us to gain altitude. In order to climb at the best rate, the lift must be obtained at the cheapest cost. This means that the angle of attack of the wings to the airflow should be near that giving the maximum lift/drag ratio. Since the wings are bolted to the fuselage so that, in level flight at cruising speed, the angle of attack is rather less than that giving the best lift/drag ratio, it follows that when we climb at the best rate of climb, the direction in which the nose is pointing does not correspond to our flight path. In fact, our attitude and how the forces are arranged in equilibrium are illustrated in the following diagram:

When the throttle is opened to give more thrust for climbing, the best climbing speed in a training aircraft is about 70 per cent. of the normal cruising speed.

The angle of climb in the above sketch is exaggerated. The best angle on a training aircraft being usually about 3½°-4½°.

How to Climb. When you wish to climb from straight and level flight, open the throttle until the revolution counter shows the number of revolutions appropriate to climbing (which your instructor will tell you). Select an appropriate mark ahead as you did when flying straight and level. Your instructor will tell you the best airspeed at which to climb, and you will have to find the correct attitude which corresponds to this speed. Ease the stick back gently until you think the nose is in the right position, or in other words, that your attitude is correct. Then hold this attitude and adjust on the tail trimmer till no pressure is required on the stick ; hold the attitude long enough to let the airspeed settle to the new attitude. Check your airspeed and, if it is still incorrect, make any minor adjustments necessary by altering the attitude, using the same sequence of action as above.

Throughout you will, of course, keep the aircraft from yawing, and also keep it level in the rolling plane by the appropriate use of rudder and ailerons, as was described for straight and level flying.

Once you have attained the attitude which gives the correct climbing speed, and have adjusted the tail trimmer correctly, the stability of the aircraft itself will correct any minor disturbance of attitude. You should, however, keep an eye on your mark and on the airspeed indicator to make sure that you are maintaining the correct attitude and speed.

When you have reached the desired height, ease the stick gently forward, until you think the aircraft is flying level; at the same time ease back th throttle until the revolution counter shows the appropriate cruising revolutions. Then retrim the aircraft, by moving the tail trimmer forward until there is no pressure on the stick, and adjust the aircraft for straight and level flight as before.

8 - G L I D I N G

What Gliding Means. By gliding is meant descending with the throttle closed, or with the engine switched off. In such circumstances we have to rely on gravity to provide us with the means of forward movement, and this necessarily means loss of height. Gliding is the normal method of losing height.

Best Gliding Speed. We can glide at various angles, but there is one at which we can cover the most ground for a given loss of height. It is is known as the optimum gliding angle, and it can be recognized with practice from the aircraft's attitude in relation to the ground. The airspeed indicator also tells us when we are flying at this angle, since there is a correct airspeed for each aircraft which is obtained when our attitude is that corresponding to the optimum gliding angle.

How the Forces on the Aircraft Act in a Glide. The angle of the wings to the airflow which gives the best gliding angle and the best gliding speed is that at which the lift/drag ratio is highest (see graph, page 14). Diagrammatically, the forces involved in gliding can be represented like this (you will remember that the wings are set in the fuselage at an angle rather less than that giving the highest lift/drag ratio) :

The lift is insufficient to counterbalance the weight (if it were sufficient we should be flying level, not gliding), but the total force of lift and drag together, i.e. the total reaction, is equal to the weight. In other words, the aircraft is in equilibrium (see page 19). You can see clearly that to cover the maximum distance in a glide, we want as much lift as possible to keep us from sinking too rapidly, and as little drag as possible so that our forward speed is not unduly retarded. The angle of attack which gives the maximum lift/drag ratio represents the best compromise between the two opposing factors. If we attempt to glide at a greater angle of attack which gives more lift, we also get more drag and therefore less. speed, and this itself reduces the lift. Moreover, the distribution of the forces acting on the aircraft is very different and the aircraft ceases to be in equilibrium. The position is as shown in the first of the two following diagrams, but only momentarily since the aircraft rapidly returns to equilibrium, when the position is as in the second diagram.

Total reaction is now temporarily greater than weight, but the speed. is reduced, and therefore the lift, so that the flight path changes.

Total reaction now equals weight, lift being less and drag greater, than is the case with the best glide path. Note the steeper flight path and increased angle of attack, due to, the direction from which the airflow actually comes.

If, on the other hand, we keep the angle of attack below that giving the highest lift/drag ratio, our path is also steepened, both lift and drag are reduced and our speed is increased until the drag increases and holds it constant. Then, once more, the lift and drag combined equal the weight. The combined effect is that we cover less ground than is the case with the best gliding angle. We can summarize the position in a diagram. Note that when the angle of attack is greater than that giving the best lift/drag ratio, our flight path is by no means in the direction in which the nose is pointing, and that we are in effect sinking through the air.

Note. All angles are considerably exaggerated. On training aircraft the best gliding angle is in the neighbourhood of 7½°.

The moral of this is that if, when gliding into land, you think you are not going to reach the point at which you wish to land, it is no use trying to hold the nose up. You will only sink more rapidly and, in fact, cover less ground. You may indeed stall the aircraft if you attempt this procedure, since the relative airflow changes quite quickly as you sink, and increases the angle of attack.

Similarly, a word of warning is necessary about trying to covet less ground by steepening the angle of glide. You can lose height more rapidly, certainly, but only at the expense of gaining speed. When you have lost your height, the problem consequently becomes one of losing speed, which means floating level over the ground for a distance, the length of which you have no means of estimating and which in the end will not be very much shorter than had you glided at the correct speed.

How to Glide. To glide from straight and level flight, close the throttle so that the engine just ticks over ; the nose then drops and you check it when you think your attitude is that corresponding to the best gliding angle. This you do by a slight backward pressure on the stick. Then adjust the tail trimmer by moving it backwards until there is no necessity for you to maintain the pressure on the stick.

Making use of the same mark which you were watching when flying straight and level, prevent the aircraft from yawing or rolling by the appropriate use of the rudder and ailerons. You must now control the attitude of the aircraft so that the best gliding angle and gliding speed can be attained. This you do in the same way as you did for straight and level flight. That is, wait to see at what airspeed the aircraft stabilizes itself ; if it is higher than the correct gliding speed, which your instructor will have told you, you know that the gliding angle is too steep, and that the nose of the aircraft is pointing too much towards the ground. In this case, ease the stick gently back until you think the attitude of the aircraft is that desired; adjust the tail trimmer backwards, and wait to see the result.

If the speed is lower than the correct gliding speed, you know that the nose is too high ; in this case press the stick gently forward until you think the attitude is correct, hold it, and adjust the tail trimmer and await the result on the airspeed indicator.

Remember, you must give the aircraft time to stabilize itself after any alteration of attitude before you can be sure of the result of the change.

As in the case of flying straight and level, repeat the sequence of operations until the airspeed is correct, and remains correct.

When the throttle is closed, the slipstream is very much reduced consequently the effectiveness of the elevator and rudder as compared with normal conditions with the throttle open, is also reduced. Therefore you will notice a difference in the 'feel' of these controls ; they will be less effective.

9 - S T A L L I N G

You will remember that in pages 24-27 we explained the meaning of the term stalling, and explained the circumstances in which stalling occurred ; re-read that part of the manual now.

In normal flying you should not., of-course, stall the aircraft except at the moment of landing. In fact you will only do so as a result of mishandling the controls, by negligent flying, or by failure to understand how and why a stall occurs. This last reason need never arise if you thoroughly grasp the basic principles involved.

How to Detect the Approach of a Stall. Since in some circumstances you may accidentally get into a position when a stall is near, you have to learn to recognize the symptoms, and how to recover from a stall. The symptoms of an approaching stall vary slightly from type to type, but generally the following points apply:

1. The feel of the ailerons changes and they lose their usual control effect.

2. If the aircraft is fitted with slats, the slats begin to open as the stalling point approaches: they can be seen to flutter. When they are open, the stall is, of course, retarded (see page 37), and unless the conditions leading to it continue, it will probably be avoided.

3. Vibration appears, getting more marked as the stall is reached. This vibration is noticed in such parts as stays, and in some types a kind of faint shudder can be felt through the aircraft.

In order to practise recovery from a stall, you have to stall the aircraft deliberately ; take care to do this at a sufficient altitude to give plenty of time for recovery. The recovery time varies for different types, and for different types of stall ; it is quite short with simple training aircraft, but nevertheless you should not deliberately stall unless you are flying at 2,000 feet or higher.

During the stall, there is a considerable loss of effectiveness of the controls, and the aircraft loses height rapidly, since the lift is greatly reduced.

How to Practise Stalls and Recovery from them. To stall the aircraft, first close the throttle and put the aircraft into a glide at the correct speed ; then press the stick gently back. This brings the nose up and increases the angle of attack of the wings: but since you are trying to hold the aircraft on a level course when, in order to maintain speed, it should be gliding downwards, the airspeed falls, until the stalling angle of attack is reached. Then the aircraft stalls. The nose drops, although-you are holding the stick pressed right back, and the aircraft sinks rapidly through the air.

To recover from the stall. Open the throttle fully and move the stick forward. Your forward speed is immediately increased by thrust, and this reduces the angle of attack by changing the direction of the relative airflow. The angle of attack is further reduced by the effect' of the movement of the stick. The aircraft will become unstalled, and full control may be regained by bringing the aircraft out of the dive into which you have put it. It is vital that your first reaction to a stall should be to open the throttle. If you should ever be near the ground* when you stall, you will not, of course, be able to put the stick very far forward; but put it as far as you can without increasing your danger. As the aircraft stalls, note the position of the nose above the horizon.

After you have recovered from the stall, regain height by climbing, and then stall the aircraft once more. This time press the stick back more quickly. You will notice at the stall occurs this time with the nose considerably more above the horizon than the first time.

This will remind you that the angle of attack is the angle made, not by the earth but by the airflow, with the wings. In the first case you were attempting to hold the aircraft on a path horizontal with earth ; when the stall occurred the attitude of the aircraft was rather like this:

In the second case you were attempting to climb when the stall occurred, therefore the attitude of the aircraft was like this:

Note. Both these diagrams are rather exaggerated, but you can see from them. why the nose was more above the horizon in the second case than in the first; and that the attitude of the aircraft to the earth has no positive relation to stalling.

You can, of course, stall the aircraft while the engine is working at normal revolutions. Fly at normal cruising speed, and then press the stick gently right backwards, as in the case of the stall from the glide. It takes considerably longer before the stall occurs, and the nose win be considerably higher above the horizon. Work this out for yourself.

Again you can of course stall at high speeds. This should not be practised and will occur only as a result of coarse and heavy use of controls. In this case, the stall will be too quick for any of the warning symptoms mentioned above to be realized.

In all these forms of stalling you must take care to keep flying straight, checking any tendency to yaw by appropriate use of the rudder.

If a wing drops during the stall, no attempt should be made to pick it up by use of ailerons as this will result in a yawing movement which may lead to a spin. The correct method is to apply sufficient opposite rudder to keep the aircraft straight, throttle fully open and stick forward. The wing then automatically levels itself as flying speed is regained.

Spinning is dealt with later on pages 79-85.

10 - T U R N S

When you wish to alter the course of your aircraft and to fly in another direction, you have to execute a turn. When an aircraft is turning, it is flying on a circular path, and the rate at which it will turn will depend on its speed and on the radius of the circle along which it is flying. If we assume that the speed remains constant, then, if the radius is large, the aircraft will be changing direction slowly ; if the radius is small, it will be changing direction quickly.

Rate of Turn. In order to have a measure of the rate of turn which takes account of the radius of the turning circle and of our speed, we use the number of degrees of arc through which we pass in a second.

(You know that a complete circle is equivalent to 360°'.) The turn indicator is calibrated to show rate of turn in this way. Thus a rate-1 turn means a turn during which we cover 3° per second, a rate-2 turn one in which we cover 6° per second, a rate-3 turn one in which we cover 9° per second.

We can carry out a rate-2 turn, for example, by flying along the circumference of a fairly small circle at a moderate speed, or by flying along the tcircumference of a larger circle at a higher speed. In both cases, we cover 6° per second.

The Forces Acting on the Aircraft During a Turn. If we want to change direction and turn, we have to apply some force to the aircraft. You might think that the simplest thing to do would be to make use of the rudder to give us a constant movement in the yawing plane in the direction in which we want to turn ; while it is true that it is possible to turn in this way, it is in fact not easy and is very inefficient. In order to change direction, we have to apply a centripetal force to overcome the tendency of a heavy body like an aircraft to continue on its course. In the case of a turn on a level keel by use of the rudder, the only centripetal force available is that coming from the pressure of the air on the fin and keel surface, as the aircraft skids broadside as it attempts to maintain its former path. This force is naturally not large, and this is why a flat turn, as it is called, is so inefficient.

You will remember that the centripetal force is always proportional to the rate of turn and the airspeed. This is another way of saying that it depends on the radius of the circle on which we are turning, and on the square of our airspeed. (Since, as we have explained, rate of turn takes account of the radius of the circle of turn and the speed.) Consequently, the centripetal force in a turn is not the same in all turns made at the same rate; as was explained above, we can do a rate-2 turn at different forward speeds.

What force have we under our control which we can use to supply the centripetal force ? Lift is the answer: but in order to make use of the lift-or rather of part of it, since we still need the same lift to main tain the weight of the aircraft-we must bank the aircraft so that the direction of the force of the lift is inwards towards the direction in which we want to turn. We can put this position in the diagrams shown on the next page. The sketch on the left represents an aircraft in level flight, with the lift balancing the weight; the sketch on the right represents an aircraft in a turn to the right (in the diagram we are looking at the aircraft's nose). The lift, represented by L, is resolved (by the parallelogram method described on page 19) into two components. One, L1, acts vertically upwards and equals the weight of the aircraft; the other, L2 acts horizontally inwards towards the centre of the circle on which the aircraft is turning, and supplies the necessary centripetal force. L, the total lift, is there-fore a good deal greater in the turn than in level flight, since it has the two functions to perform ; the load factor has therefore obviously increased. In a turn in which the angle of bank is 60°, the load factor is 2; that is to say, the lift is twice that required for level flight.

L, is the same length in all three diagrams, i.e. equal to W; but L is longer in the second diagram than in the first, and becomes longer still

The angle of bank and the amount of lift necessary for the correct execution of a turn depend on the rate of turn and on the airspeed ; for every rate of turn at every speed, there is one angle of bank and one amount of lift which are correct. The importance of the angle of bank lies in the fact that it determines the proportion of the total lift which can be resolved in the horizontal direction, that is, so that it can supply the centripetal force. If we have the right amount of lift, but too great an angle of bank, we shall slip inwards and downwards. The greater the angle of bank necessary, the greater is the lift required. This is shown by the following diagram:

in the third, because L, has to be longer since the centripetal force needed is greater.

The next point to consider is how to provide the additional lift required. It is obtained by increasing the angle of attack of the wings to the airflow. Therefore, although you cannot recognize the difference by eye, the angle of attack to the airflow is not the sa 'me as that for level flight. The airflow is not from the direction in which- the nose is pointing, but can be illustrated thus:

In a gentle turn, the angle of bank and additional lift are not large but as the rate of turn increases, the angle of bank becomes progressively greater, and also the lift required. This means an increase in the drag, and consequently a reduction in speed, which will reduce the lift. Therefore in any turn with the engine, other than a gentle one, we must increase the thrust as we begin to turn, in order to overcome the increased drag and to keep our speed up. Before beginning any turn without the engine, that is while-gliding, we always increase our speed, by putting the nose down, so that we have some spare speed in hand.

If we open the throttle fully and go into a turn at a fairly high speed, making it progressively steeper and steeper, i.e. at a higher and higher rate of turn, we have to go on increasing the angle of attack to increase the lift. The drag also increases, and finally becomes so great that the airspeed cannot be maintained. You can understand from this that the factor which decides the steepest turn an aircraft is capable of carrying out, and how long it can continue in a steep turn, is the amount of thrust available.

Now as the airspeed falls off, so the total lift is reduced; but the centripetal force required is also reduced in the same proportion as the lift, since both vary with the square of the velocity ; this means that the horizontal component of lift is still sufficient, but the vertical component of lift becomes less than the weight of the aircraft. Consequently, the flight path changes and the aircraft begins to lose height.' But the attitude does not change; therefore the change in Right path means a change in the direction of the airflow relative to the wings. This change, as was explained on page 15, produces an increase in the angle of attack. If the angle of attack was near the point of maximum lift, as it would have to be in a steep turn at a fairly high speed, the increase following on the reduction in forward speed explained above may very well put it beyond the critical angle, and the aircraft will stall. If we do not reduce the angle of bank as the airspeed falls off, it will be too steep for the reduced rate of turn, and consequently we shall slip in towards the centre of the turn. The change in the flight path mentioned above is then not only in one direction, downwards, but also sideways.

We have taken a special case to illustrate the point, but the principle applies in all turns : if you attempt to turn without providing sufficient thrust or initial speed for the rate of turn, the final result may easily be a stall. Remember, therefore, that a turn is a manoeuvre when the unintentional stall is likely to arise and, since the aircraft is moving in the yawing plane during a turn, it may well lead to a spin. This is why you must take care to execute your turns correctly so that the risk of an unintentional spin is obviated.

To sum up, what you have to do is

1. Ensure that the angle of bank is appropriate to the rate of turn and airspeed.

2. Ensure that the lift is sufficient to support the aircraft as well as to supply the centripetal force required.

3. Ensure that the thrust is sufficient to provide an airspeed great enough to maintain the increased lift required in a turn-or

4. Ensure that on going into the turn you have spare speed in hand.

The Control Movements in a Turn. We have now to think of the control movements which are necessary to get the aircraft to follow the circular path represented by a turn. What we really have to do is to make the aircraft move so that the horizontal component of lift points always to the centre of the circle which we are following. Now we have seen that to make use of the lift to provide the force necessary to permit us to turn, we must bank the aircraft: throughout the following explanation of the control movements, you should therefore think of the aircraft as banked at a constant angle appropriate for the rate of turn and for the airspeed. For the turn, we need to maintain a movement in the yawing plane and a movement in the pitching plane. You may find this a little difficult to see at first, but if you think of the two extreme cases it becomes clear.

Suppose that the aircraft were to be doing a flat turn with no bank ; it is true that there would be no horizontal component of lift, but the turning movement would be provided by a steady movement in the yawing plane alone. Similarly suppose that an aircraft were turning while banked to 90° (here all the lift would be horizontal), in this case the turning movement would be in the pitching plane alone. Therefore, for angles of bank between 0° and 90°, there must be movement in both yawing and pitching planes. How we regulate the proportions of yawing and pitching is easily understood when we consider the movement of the aircraft in relation to the horizon.

What we have to do, in a turn at a constant height (known as a level turn), is to make the nose move smoothly round the horizon keeping level with it throughout.

Movement in the yawing plane alone, when the nose goes round in the direction of the wing tip, would mean that the nose would not keep moving round the line of the horizon, but would fall below it, like this. (Obviously the yawing movement must be to the left in the case of a left turn.)

You would not be doing a level turn, but a kind of downward spiral.

Similarly, movement in the pitching plane alone will not give the required result. You can see that you would have to press the stick backward, so that the nose goes up towards the fin, and, in the case of a left turn, A result would be I ike this:

In other words you would be doing a kind of climbing spiral.

It is clear therefore, that you must combine movement in the yawing plane with movement in the pitching. plane, in order to make the aircraft follow the level course required. You will see, too, that the relative amounts of movement in the two planes will depend on the degree of bank of the aircraft, which depends on the rate of turn and speed. Thinking always of the effect of the controls and of the attitude of the aircraft, work out for yourself how, when the bank is steep, you will need less yawing and more pitching movement. Do this now.

You will find it much easier to make correct turns if you have correctly grasped what you are really trying to make the aircraft do.

Keeping the Bank Constant. There is yet another point which you must understand. It is that in a turn, the outer wing is moving at a greater speed than the inner wing. This is because it- is farther from the centre round which the aircraft is turning, and accordingly has to cover a slightly greater distance in the same time. Since it is moving faster, it gets more lift. (Remember the formula which shows that lift is affected by the velocity of the airflow.) You will appreciate that the steeper the angle of bank, the less the difference in speed between the two wings. It follows that in a turn, this greater lift of the outer wing would make the angle of bank get steeper and steeper unless it were counteracted. In the level and climbing turns, after you have applied the desired angle of bank, you do not merely centralize the stick, you press it slightly in the opposite direction to the bank. This is known as 'holding off bank'. In gliding turns, however, there is another factor -operating which gives the inner wing greater lift than the outer wing. This is rather difficult to grasp, and the explanation is therefore postponed till a later chapter of this manual. The effect is that in a gliding turn you do not 'hold off 'bank, but rather 'hold on' bank. As a matter of fact, you need not and should not consciously think of holding the' bank off or on ; your job is to use the stick in such a way that the angle of bank remains correct throughout the turn.

One last point: In turns, we do not talk of applying left or right rudder, but of top or bottom rudder. Top rudder is always that which would give a movement of the nose in the yawing plane away from the direction of the turn. Bottom rudder is that which would give a movement of the nose towards the direction of a turn. It is very simple to. remember, because top rudder is just the side of the rudder bar which is on the upper side of the aircraft as it lies banked in the rolling plane.

The Actual Manoeuvres

In the preceding sections the principles involved in turns have been described. Here we now set out the actual sequence of movements carried out in what may be called the three parts of a turn, namely going in, staying in, and coming out.

The first point to remember is never start to go into a turn without looking all round to make sure there is no aircraft whose path you might cross. It is not sufficient to look merely in the direction into which you wish to turn; there may be an aircraft coming up behind you at a higher speed, or there may be an aircraft cutting across your path, either below or above, in such a manner, i.e. climbing or gliding, that your path might coincide with his if you turn.

Gentle Level Turns. Going In. First look all round; then, to go into a left turn, move the stick to the left until you have applied a moderate degree of bank which you think will be appropriate for the gentle turn you propose to make. When the bank has reached the desired angle, centralize the stick and hold that bank at a constant angle throughout the turn. To do this, you may have to press the stick slightly to the right, i.e. to 'hold off' bank; but don't think consciously of this-just use the stick to hold the bank constant. At the same time as you apply the bank in the first case, apply a little left rudder, i.e. in the same direction. As the bank goes on, and as the nose starts to go down, press the stick gently back towards you.

This pressure on the stick, by raising the nose in relation to the airflow, gives the increased angle of attack necessary to supply the additional lift required in the turn. It also provides, in conjunction with the rudder, the actual turning movement of the aircraft, and with the rudder, it keeps the nose on the horizon throughout the turn.

Although we have had to describe the stick movements controlling the ailerons and the elevators separately, the sideway and backward movements are, in fact, combined into one smooth continuous movement. Starting from the central position, the stick is moved over to the left, then towards you, and, still kept pressed towards you, back to the central position and then back a little past it.

,Staying In. To stay in the turn, keep the angle of bank constant by use of the ailerons, and keep the nose moving round the horizon in a level path by use of the elevators and rudder. If the nose drops below or rises above the horizon, it means that you have not the proper co-ordination of elevators and rudder. If it drops, press the stick very slightly backwards and ease off the bottom rudder slightly ; if the nose rises, ease the stick slightly forward and apply a little more bottom rudder.

Coming Out. To come out of the turn, press the stick in the direction opposite to that of the bank of the aircraft, until the aircraft once more resumes the level position; then centralize it. At the same time as you apply the opposite bank, press the stick slightly forward and apply a little top rudder. Top rudder provides movement in the yawing plane, and the elevators movement in the pitching plane, to permit the aircraft to take up a straight course once more. The forward pressure on the stick will keep the nose on the horizon. Don't forget, you have moved the stick back to keep the aircraft turning. When the aircraft reaches the straight and level attitude on the new course, centralize the rudder and the stick.

Note. When applying pressure to the stick to level the aircraft in the rolling plane on coming out of the level turn, merely increase the pressure you are already applying in 'holding off' bank. Remember the point, as at first you may feel a natural impulse to alter the direction of the pressure you are applying, when keeping in the turn, in order to come out of it.

Important Footnote. As we have said, movement in both pitching and yawing planes is necessary during a turn. Movement in the pitching plane is provided by the use of the elevators. Movement in the yawing plane in the case of a modern aircraft of clean design is largely provided by the further effect of the ailerons which, as was described on page 33, leads to a movement in yaw in the direction of the lower wing when the aircraft is banked. You will therefore find that very little pressure on the rudder bar is necessary.

Gentle Gliding Turns. First look all round, then press the stick slightly forward to gain a little more speed. Then go into the turn as in the case of a level turn, except that, in order to keep the angle of bank constant, you will not have to hold off bank, but in fact hold on bank (see page 62).

The nose of the aircraft will then be below the horizon, and you must keep it moving round the horizon, at a constant distance below it, by the use of elevators and rudder as described for a level turn.

Coming out of a gliding turn is achieved in the same way as in the case of a level turn, except that a rather heavier forward pressure on the stick is necessary to ensure that adequate gliding speed is maintained.

Note. Since in a gliding turn you are holding on bank, instead of holding off bank, as in a level turn, you must in levelling the aircraft in the rolling plane on coming out of the turn, quite definitely alter the direction of the pressure you are applying to the stick.

Faults in a Turn

The main faults which are liable to be made in a turn arise from incorrect combinations of the degree of use of the three controls, ailerons, elevators and rudder. Consequently they can be looked at from two points of view: for example, either that you have too much bank for the amount of elevator and rudder movement applied; or that you have too little elevator and rudder movement for the amount of bank applied. In practice, however, carry out turns by keeping the angle of bank constant once it has reached the desired angle, and by adjusting the rate of turn to suit the bank, by the use of elevators and rudder. You are taught to turn by keeping the angle of bank constant, because it is something you can always see, either from the real horizon or from the gyro horizon instrument at night or in cloud.

Therefore, the faults in a turn, other than failure to keep the angle of bank constant, mean incorrect use of the elevators and rudder.

Variation in the Relation of the Nose to the Horizon. If the nose is seen to be climbing and moving higher above the horizon, it means that you have either too heavy backward pressure on the stick or insufficient bottom rudder, or both. Therefore, to bring the nose back to the appropriate point, ease the stick slightly forward, and give a little more bottom rudder.

If, on the contrary, the nose is seen to be sinking steadily below the horizon, it means that you have not sufficient backward pressure on the stick, or too much bottom rudder, or both. Therefore, ease the stick slightly backward, and give a little top rudder.

Slipping In. if an aircraft is correctly banked for a certain rate. of turn at a certain speed, and that rate of turn is allowed to become less, the aircraft will slip inwards in the direction towards which the inner wing is pointing. You can detect 'slipping in' in various ways. The top needle of the turn-and-sideslip indicator will move towards the direction in which you are turning. You will feel a tendency to slide inwards on the seat, in the direction of the turn ; in an open cockpit" aircraft you will feel a draught on that side of your face which is towards the direction into which you are turning.

To stop slipping in, adjust the elevator and rudder controls so as to increase the rate of turn. This you do by pressing the stick a little further back towards you and applying a little more bottom rudder, until the slipping stops.

Skidding Out. During a skid the aircraft is moving in a crabwise fashion, with the fuselage turned broadside in the direction in which the aircraft is moving. 'Skidding out' can be detected in various ways. The top needle of the turn-and-sideslip indicator will swing outwards, away from the direction in which the aircraft is turning. You will feel a tendency to slide outwards in your seat in the same direction ; in an open-cockpit aircraft you will feel a draught on the side of your face opposite to the direction in which you are turning.

To stop skidding out, adjust the elevator and rudder controls so as to decrease the rate of turn. This you do by easing the stick slightly forward and at the same time applying a little top rudder until the skidding stops.

Failure to Keep the Angle of Bank Constant. If you fail to keep the angle of bank constant, although you maintain a constant rate of turn, you will either slip in, if you allow the bank to increase, or skid out, if you allow the bank to decrease. Consequently, before correcting for slipping in or skidding out, as described in the previous sections, look at the angle of bank, and make sure that it has not varied. If it has become steeper, take off a little bank by pressing the stick in the direction opposite to the turn ; if it has become less steep, apply a little more bank by pressing the stick towards the direction of the turn. In each case, once you have found the correct angle once more, use the stick to hold it constant.

11 - TAKING OFF INTO WIND

Normally we take-off into wind, never down wind. We take-off out of wind only if we are in some awkwardly shaped area which does not allow sufficient room for a take-off into wind, or on a runway with the wind blowing at an angle to it, or where there are obstructions to windward. Instructions for this form of take-off will be found in chapter 20.

The reason why we take-off into wind is quite simple: before the wings can obtain sufficient lift to support the aircraft, they have to be encountering an airflow of a certain speed. In the take-off, this airflow is made up partly by the aircraft's speed in relation to the ground, and partly by the speed of the air movement which is wind. Now suppose that the speed of the airflow necessary for the wings to take the weight of an aircraft is 60 miles per hour and that the wind velocity is 15 miles per hour : if we take-off into wind, our speed over the ground has to be raised to only 45 miles per hour before the necessary 60 miles per hour airflow is obtained. (45 m.p.h. plus 15 m.p.h. wind.) If we were to take-off down wind, our speed over the ground would have to be 75 miles per hour before the speed of the airflow would be 60 miles per hour. (75 m.p.h. minus 15 m.p.h. wind.) This naturally means a much longer take-off run, with the wheels still on the ground at high speed. At such speed, unevenness in the ground imposes shocks and strain on the undercarriage.

To take-off , first ascertain the direction of the wind, and taxy out to a position which gives a clear path and sufficient room for the necessary run. On reaching a suitable position, stop the aircraft across the wind in this position:

Then carefully make the correct cockpit check. Next look down wind to make sure that no aircraft is about to land, and into wind to see that no aircraft has taxied across your take-off path. If all is clear, turn into wind, fix upon a spot well ahead at which to keep the aircraft pointed and take-off without delay.

The actual take-off is done like this : hold the stick slightly back and open the throttle smoothly until it is full open. As the aircraft gathers speed, keep straight on your selected spot with the rudder and move the stick forward: this raises the tail and makes the aircraft adopt the flying position. Keep the aircraft in this attitude by moving the stick gently back as speed increases and, finally, when flying speed has been reached, a further slight backward pressure will take the aircraft off the ground. Do not attempt to climb quickly as soon as you are airborne: fly level to gain speed, and, when you have attained a speed rather above correct climbing speed press the stick further back to put the aircraft in a climbing attitude. Gain height as quickly as possible ; this means by keeping the aircraft at the best climbing speed, which, of course, varies for different types, but which your instructor will tell you. Don't try to climb too steeply, thus letting the aircraft's speed fall below the best climbing speed.

If the aircraft is fitted with flaps which are partially lowered for the take-off (this is covered by the cockpit-check instructions), raise them when you have reached about 400 feet. Flaps must on no account be raised before reaching 300 feet.

Keep your hand on the throttle as you open it, and hold it full open there can then be no chance that the throttle may slip back because the friction plate has not been tightened enough.

At first you may find some difficulty in keeping the aircraft straight on the ground and, as it leaves the ground; be ready to apply rudder as necessary to keep it straight.

If the engine should fail as, or just after, you take-off, or before you have gained at least 700 feet, press forward the stick to pick up speed, and set the aircraft in the correct gliding attitude. KEEP STRAIGHT ON: in no circumstances attempt to turn back to land on the airfield. You won't get there, at least not with an intact aircraft ; go on and land as nearly as possible into wind, only turning slightly if it is necessary to avoid large obstacles. Don't worry about small things like bushes or low hedges; it won't damage the aircraft very greatly to run into this kind of thing.

The discussion on stalling at pages 24-27 and on turns at pages 56-65 will explain why the procedure set out above must be followed. You are close to the ground and have only the speed obtained from the effect of gravity ; if you try to turn round to return to the airfield you will lose a lot of height on your gliding turn, for you must put the nose down to get the increased speed required. This would probably mean flying into the ground. In fact the temptation would be to try to keep height by not increasing the speed sufficiently to make the turn..

Then you would stall on the turn without enough height to permit you to recover from the stall. Even if you had sufficient height to make your first turn successfully, you could not repeat this process in order to land into wind, and would have to land down wind. This would probably result in more damage to the aircraft than would be incurred in making your forced landing in a field straight ahead, even if this did mean running into a hedge.

Remember the golden rule, therefore: If your engine fails an the take-off, carry on straight ahead. Never turn back to the airfield.

12 - LANDING

The Prinziples involved

The Circuit. Before coming down to land, we always make a circuit of the airfield, flying at about 1,000 feet, at least half a mile from the edge and at a moderate speed. This allows us to look over the landing ground and note other aircraft and any obstructions, such as waterlogged ground, to check the direction and strength of the wind, and to observe any signals displayed. It also allows those on the ground to observe us.

You must never glide straight into the airfield into wind and land without making a preliminary circuit. Should you ever do this despite this warning, you will find yourself very unpopular when you have landed !

When bringing an aircraft down to the ground, it is clearly desirable that, at the actual moment of contact of the wheels with the surface of the ground, the ground speed of the aircraft shall be as low -as possible. Consequently, we always seek to land into wind, never down wind, for the reason discussed on page 66 on the take-off.

We therefore arrange our circuit so that the last leg will be across wind on the side of the airfield towards which the wind is blowing, as shown in the diagram on the next page.

We turn in across wind on to this last leg, and soon close the throttle, starting to lose height. We note the amount of drift, which we use to judge the strength of the wind ; we select a clear landing path, into which we shall turn when we come opposite it, and if necessary we turn slightly towards or away from the airfield so that when we come to turn in we are about 500 feet high and at the right distance from the point on which we propose to touch down. The distance varies, of course, according to the strength of the wind, our height, and the type of aircraft.

Our object is to make our final approach to the ground so that we comfortably clear the near boundary of the airfield but actually touch the ground sufficiently far from the far boundary to enable the aircraft finally to come to rest without any risk of running into that boundary. Thus, besides choosing a landing path, we also choose a spot on that path at which we intend to touch the ground. This is the problem of the approach.

The Approach. Touching down on our selected spot is not a question of luck. The problem is one of keeping the aircraft to the flight path which will permit us to touch down where we intended. An additional requirement is that we should glide down that flight path at a constant speed ; this rules out any idea of trying to keep to the flight path merely by putting the nose up or down.

In other words, there are two things to be done:

1. to control our rate of descent ; that is, the rate at which we lose height ; and

2. to keep our forward airspeed constant.

We must maintain a constant speed, and for the moment assume that we are gliding without engine power. It is clear then that it is drag which controls our angle of descent. No drag would mean gliding horizontally and losing no height, and a parachute attached to the tail would mean enormous drag and vertical descent. Drag, therefore, controls the angle at which we must glide to maintain fixed speed.

Now consider the effect of power. Power is used to overcome drag, and we can, therefore, quite logically look upon any increase in power as merely cancelling drag. The first and easiest way to control the rate of descent is to choose a flight path which is somewhat shallower than the best angle of glide, which means using some engine power to maintain this path. If we do this, it is easy to vary our flight path by opening or closing the throttle ; if we open the throttle our rate of descent is reduced, and if we close the throttle our rate of descent is increased. We use the elevators to hold the nose in such a position that, no matter what alterations we make to the throttle, our forward speed remains the same. This diagram illustrates the effect of the throttle on the rate of descent:

There is, however, another way of altering the drag and that is by flaps. This method has several great advantages.

When the flaps are down the lift and drag co-efficients of the wings are increased. The increased lift co-efficient means that we can fly more slowly, the total lift at the slower speed still being sufficient. This reduced approach speed is an advantage, since it allows us more time to make the necessary judgments involved.

Here again, the steepness of the path down which we glide to achieve this speed is governed by the drag. The greater the drag the steeper must be our path. The extra drag of lowering the flaps forces us to glide more steeply for the same speed, and thus overcomes the difficulty of the long approach which the use of the engine otherwise makes flatter and longer. Furthermore, when the flaps are down the trim of the aircraft is altered, the nose going down. This means that our visibility is improved.

It seems, therefore, that we can solve our problem of varying our rate of descent by using the flaps as a brake in precisely the same way as a driver of a car would use his brakes. This would be a definite possibility if the flaps were pure brakes and were in no way related to lift. Unfortunately, this is not so, and any alteration in the angle of flap used not only varies the brake power, but also the lift.

Now the increase of lift caused by lowering the flaps will seldom, if ever, be an embarrassment to a pilot ; while, on the other hand, raising the flaps and so reducing the drag has the unfortunate effect of decreasing the lift suddenly, which may be of considerable embarrassment. The best technique, therefore, for the use of flaps as a variable drag, is to apply full flap permanently during the approach, and overcome this drag at will by the use of throttle ; in other words, drive the aircraft against the brakes.

But if our engine has failed we cannot use this form of approach, which is known as the engine-assisted approach ; we must make a glide approach. This means that the judgment called for in choosing and maintaining our flight path has to be much more accurate. We can increase our rate of descent, but we cannot decrease it. There are two ways of increasing the rate of descent on a glide approach-one by the use of flaps, and another by sideslipping.

On a glide approach we want to have the advantage of slower forward speed which we get from the use of flaps, but we also want to have something in hand to correct for any error of judgment. We therefore lower the flaps only partially to begin with, and aim rather to overshoot our selected spot. Then, as we get nearer the ground, we can increase our rate of descent, if we are still overshooting, by lowering the flaps a little more. In any case we lower the flaps fully when we are certain that we shall land on our selected spot, so as to have their full braking advantage during the hold off.

Sideslipping, the other method of increasing the rate of descent, is described in a later chapter.

We cannot reduce our rate of descent by raising the flaps, even partly, for the reason explained above.

Nor can we reduce our rate of descent by holding the nose up and trying to 'stretch the glide'. This only means increasing the rate of descent, as we explained on page 52.

Basic Principles of the Touch Down. Now we cannot just let an aircraft drop to the ground from any height ; we must glide it as close to the ground as possible, and we must see that it is gliding at the lowest speed possible before we let the wheels touch the ground. The lowest speed at which an aircraft can fly is that just above the stalling speed. Accordingly when we are landing, we reduce the speed steadily until the aircraft does stall, when it ceases to be airborne, and consequently drops on to the ground on its wheels.

You can see, therefore, that besides flying at the lowest possible speed just before the wheels touch the ground, we must also glide as close as possible to the ground so that, when the stall occurs, we have the least possible distance to drop.

Flattening Out. The correct touchdown is therefore carried out like this. We glide down towards the spot on which we propose to land, approaching it at a moderate angle to the horizontal: when we are close to the ground, the exact height depending on our angle of approach and speed, we gradually alter that angle until we are floating level with the ground. This is called flattening out. While this change in angle of approach is going on, we are still sinking towards the ground, and accordingly, by the time we are floating level, we are very close to the ground. In fact, we aim at floating with our wheels about one to two feet above the ground. Our path, therefore, is like this :

We make this first part of the approach to the ground in a glide without the engine, or with the throttle partly open. In the latter case, once we have begun to float level, just above the ground, we close the throttle smoothly. Now since we have no power from the engine, our speed through the air from now on will steadily decrease, and consequently the lift of the wings will also decrease. To avoid touching the ground very soon, we must therefore increase the lift ; this we do by increasing the angle of attack of the wings to the airflow. We must do this very gradually, so that the increased lift obtained from this increased angle of attack just balances the loss of lift due to reduction in airspeed.

If we increase the angle of attack too rapidly, the aircraft will begin to climb, and our object will be defeated. If we do not increase the angle of attack sufficiently, we shall 'fly in' and hit the ground too early.

Holding Off. We go on increasing the angle of attack very gradually so that we continue to float, with our wheels just above the ground, at a steadily decreasing speed. If we are to increase the angle of attack of the wings while the wheels remain at the same distance from the ground, we can only do it by changing the attitude of the aircraft to the ground, so that the tail gets nearer and nearer to the ground. The tail goes on dropping until the attitude of the aircraft is that which it takes up when standing on the ground. The aircraft is so constructed that, at this attitude, the wings are at about the stalling angle to the horizontal ; consequently once this attitude has been reached as a result of our gradual increase of the angle of attack of the wings, the air-craft stalls and drops to the ground, the wheels and the tail skid or wheel all touching the ground simultaneously. Since we started our float parallel to the ground about one or two feet above it, and since we have taken great care not to climb, we have achieved our object of dropping the aircraft on to the ground at the lowest possible speed, from a very small height. The attitude of the aircraft throughout the last part of the landing which is called the 'hold off,' is like this :

Circuits and Landings: the Manoeuvres Summarized

When you practise landings you will do this by making a number of circuits, approaches and touch-downs. The whole exercise can be summarized as follows:

The Circuit. Take off as described in chapter 11 and climb on a straight course until you have reached 1,000 feet. Then make a gentle turn through 90° in the direction of the circuit. (Most airfields make use of a left-hand circuit ; that is, you fly round the landing ground by making turns to the left. Your instructor will tell you the correct direction for your airfield. In some cases the circuit direction varies according to the wind ; with these airfields you must always take care to check which circuit is in operation before joining it ; signals on the ground give you the necessary information.)

Fly on your new course, across wind, until you have just passed the airfield boundary, and then make another gentle turn through 90° in the circuit direction. You will then be flying down wind. Continue until you are just past the lee boundary of the airfield, when you turn through 90° once more on to the last leg of the circuit and then the approach proper begins. Throughout the circuit keep a sharp lookout for other aircraft.

Engine-Assisted Approach. This form of approach employs a descent across wind on the last leg of the circuit from about 1,000 feet to about 500 feet, at a moderate angle. This is followed by a turn into wind and a straight descent at the same angle. Soon after turning on to the last leg of the circuit, partly close the throttle (your instructor will tell you the appropriate engine revolutions required for the particular type of aircraft), and assume the correct approach speed. On throttling back, you must, of course, adjust the tail trimmer. Keep the aircraft flying straight by the appropriate use of the rudder and ailerons. If flaps are fitted, you must lower them at this stage.

Continue to keep a watch on the movements of other aircraft, both in the air and on the ground, and select a clear path on which to land. Decide at what point on the path you want to land. When you are almost opposite your selected landing path, turn gently into wind (having taken a good look round flrst) and continue to glide down at the same angle. You should arrange your approach so that the turn is made when you are about 500 feet high. Keep on steadily, keeping the aircraft well trimmed, and avoiding movement in the yawing plane. Keep the airspeed constant at the correct figure by use of the elevators. If the airspeed is rising, ease the stick slightly backwards ; if it is falling, case the stick forward.

Watch the spot on which you propose to touch down, and if you think you are going to undershoot (that is, not sufficiently clear the near boundary of the airfield) open the throttle slightly ; this, when you are keeping the airspeed constant, means that you reduce your rate of descent towards the ground. If you think you are overshooting, (that is, that you will clear the near boundary at too great height to let you land on your. selected point on the landing path), close the throttle as you estimate necessary. This will increase your rate of descent when you are holding the airspeed constant with the elevators. As you come down, look well ahead and to one side. If you notice any drift it means that you are slightly out of wind. Correct this with the rudder and just a little bank at the same time.

When the appropriate moment comes, ease the stick backwards, so as to flatten out, until the aircraft is floating just above the ground. Gradually close the throttle and keep a steadily increasing backward pressure on the stick ; continue to look well ahead and to one side.

This steady pressure on the stick must be such that the wheels of the aircraft continue just clear of the ground, while the tail drops lower and lower. When the stick is pressed right back the aircraft stalls, and the perfect three-point landing is made-but not finished ; the aircraft continues to run forward and you must take care to keep it straight by coarse use of the rudder until you come to rest. Then raise the flaps if fitted, look round, and if all is clear turn the aircraft across wind, at an angle of about 45°' and taxy the shortest way to the nearest boundary.

Glide Approach. A glide approach is similar to an engine-assisted approach, but it involves more accurate judgment since the engine is not used to vary the angle of approach and the rate of descent. The flaps can be used to some extent to steepen the angle of approach and to increase the rate of descent, but since they must not be lifted even partially during the approach, they cannot be used to reduce the angle of approach and to decrease the rate of descent. It is very important that you should become thoroughly skilled in making the glide approach, since if you have to make a forced landing through engine failure it is naturally the only method open to you.

You begin your approach in the same way as for an engine-assisted approach ; when you are about half-way along the last leg, close the throttle till the engine ticks over. Trim the aircraft to glide at the correct speed and partly lower the flaps if fitted. Watch your drift over the ground and judge from it the strength of the wind. If you are drifting a good deal, turn slightly towards the airfield ; if there is very little drift, which means that the wind is very light, you may have to turn slightly away from the airfield. The reason for these slight changes from the original course is that you want to be at the right distance from your landing spot when you are turning in at 500 feet. This distance is not fixed ; it depends on the strength of the wind, which will affect your angle of descent. (In the engine-assisted approach the engine lets you deal with this point ; in the glide approach you have to judge the position much more accurately.)

After you have turned on to your selected landing path, keep the aircraft well trimmed and flying straight at the appropriate speed. Watch the spot on which you propose to touch down ; if you are overshooting you must not attempt to land, but must open the throttle and make another circuit. If you appear to be undershooting, open the throttle somewhat without delay, closing it again when you think you are correctly placed to touch down on your selected spot. If you undershoot, always open the throttle promptly; do not leave it till the last minute. Look out well ahead and to one side as you come down ; watch for drift and correct for it as necessary. When the appropriate moment comes, ease the stick backwards so as to flatten out, and hold off the aircraft by a steady backward pressure on the stick until she stalls and touches down. After landing, keep the aircraft straight while it is running on the ground, by coarse use of the rudder. When the aircraft has come to a standstill, raise the flaps if fitted and look round. If all is clear, turn across wind and taxy the shortest way to the nearest boundary.

Hints for Practising Landing

Many cadets find that learning to land an aircraft calls for more practice than the other manoeuvres ; so the following amplification of the preceding summary is given.

The landing really begins when you come on to the first leg of your circuit. While flying round the airfield, try and take in, as much as possible of the situation below ; note which aircraft have just landed, which are preparing to take-off, and so forth. Keep a watch for other aircraft in the air and estimate their probable behaviour in relation to your own course.

If you are landing at an airfield other than that to which you are attached, always fly over it at a minimum height of from 1500 to 2,000 feet. Examine the surface for areas on which landing is prohibited and look for signals in the signal area. Note the direction of the wind and make a tentative choice of a landing path; then come down to 1,000 feet to make your circuit.

The better you have the general position in mind, the easier it will be for you to make up your mind quickly about the landing path you will finally choose.

Note the direction of the wind and whether it is inclined to veer , try to determine its strength from your drift.

When you close the throttle to glide, or partly close it for an engineassisted approach, make sure you trim the aircraft correctly, and see that you maintain the appropriate speed ; choose a point at which you will try to touch down. Watch a spot about 50 yards nearer to you ; the distance -varies somewhat according to the type of aircraft and the strength of the wind, but the spot is in fact that at which you will have flattened out and have begun to float level with the ground if you are to touch down where you wish. If your flight path is correct, that is, if you are going to achieve your object of touching down at your selected point, this spot will remain relatively stationary on the plane of the earth. If you are undershooting, the spot will seem to move away from you ; if you are overshooting, it will move towards you, and ultimately of course beneath you. In a forced-gliding approach, when the engine has failed, it is best to aim rather at overshooting, since it is possible to lose surplus height, and even if you cannot lose all of it, it is better to run into the far boundary after you have touched down than. to hit the near boundary while you are airborne.

Undershooting and Overshooting. If you think you are going to undershoot your selected landing spot, it is no use merely trying to hold the nose up ; this will mean that you will undershoot still more ; you must open the throttle so that the engine can provide the power to carry you forward for the necessary distance. If you think there is a possibility of undershooting, always open the throttle early in the proceedings-don't leave it till the last moment when you will have other things to think about.

In your early landing practices using the glide approach, you will not be sufficiently skilled to vary the flap angle to increase your rate of descent, and you will not have been taught how to sideslip. Consequently if you think you are going to overshoot you must not attempt to land, but must open the throttle and do another circuit (or go round again as it is popularly called). If you try to land too near the far boundary you will probably run into it.