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AERONAV ACADEMY (Pty) LTD 79

PPL – BOOK 1

FLIGHT CONTROL SYSTEMS

Aileron and elevator controls

The control wheel controls two of the three axes of motion, roll and pitch. Rolling the control

wheel clockwise rolls the aircraft to the right; rolling the control wheel counter-clockwise rolls

the aircraft to the left. At the same time, the control wheel is moved forward and backward to

change the position of the elevators. The control wheel works the same way for aileron

control regardless of the fore-and-aft displacement of the column to which it is attached.

Pitch control

It has been shown that pitch attitude is

determined to some extent by thrust. The

aerodynamic control for pitch is the

horizontal tail and elevator combination.

The one-piece stabilator works very

similarly to a conventional horizontal

stabilizer-elevator combination; so this

course will use the term elevator in every

discussion of pitch control.

A. The elevator or stabilator is

controlled by fore and aft movement of the

control wheel. When the wheel is pushed

forward, the elevator moves downward,

giving the horizontal tail surface a positive

camber. This produces an upward lift

force over the horizontal tail surface,

raising the tail and lowering the nose

FIG 4 - 7 AILERON AND ELEVATOR CONTROLS

FIG 4 - 8 EFFECTS OF ELEVATOR ON NOSE ATTITUDE


PPL – BOOK 1

FIG 4 - 11 THE THREE AXES

ROLLING PLANE: An aircraft rolls in the

rolling plane about the longitudinal axis

which is an imaginary line running from

the spinner to the tail section through the

centre of gravity. Rolling is controlled by

the ailerons, which are activated by the

sideways movement of the control

column. As the control column is moved

towards the left, the left wingtip will roll

towards the undercarriage and will

continue to roll as long as the control

column is held in that position. Similarly,

as the control column is moved towards

the right, the right hand wingtip will roll

toward the undercarriage.

PITCHING PLANE. An aircraft pitches in

the pitching plane about the lateral axis

which is an imaginary line running from

wingtip to wingtip through the centre of

gravity. Pitching is controlled by the

elevators which are activated by the

forward and backward movement of the

control column. As the control column is

moved forward the nose will pitch

towards the undercarriage and the speed

increases while conversely, as the

control column is moved backwards, the

nose pitches toward the canopy and the

speed decreases. The changes of speed

quoted apply, of course, when the aircraft

is flying normally, if it were inverted the

direction of the speed change would be

reversed.

YAWING PLANE: An aircraft yaws in the

yawing plane about the vertical or normal

axis, which is an imaginary line running

from the roof through the floor and

passes through the centre of gravity.

Yawing is controlled by the rudder and is

activated by application of pressure to the

rudder pedals. If the left rudder pedal is

applied, the nose will yaw towards the

left wingtip, and similarly, if right rudder is

applied, the nose will yaw towards the

right wingtip.


PPL – BOOK 1

The most important of the left-turning tendencies is called P- factor. The thrust line of a

cruising aircraft is almost exactly parallel to the longitudinal axis, but whenever the flight path

is not directly perpendicular to the propeller disc, the disc will produce most of its thrust on

one side, yawing the aircraft (See Fig. 6 - 11).

P-factor is usually considerable at a high angle of attack and high power settings, requiring

strong applications of right rudder pedal pressure. The down going blade on the pilot's right

can produce more thrust than the rising blade on the left under these conditions. This is

called asymmetrical thrust, or P- factor.

FIG 6-12 P- FACTOR

FIG 6 - 11


PPL – BOOK 1

If the approach is high (possibly caused by turning base too early, flying downwind too high,

or beginning the descent too late), it can be corrected by lowering flaps, lengthening the

ground track, reducing power, slipping (to be used with discretion) or a combination of these.

Corrections for a low approach can be made by delaying the use of flaps, by shortening the

ground track, by adding power, or combining these measures.

The last part of the final approach should be a stabilized glide from which it will be easy to

level off just above the runway and touch down at slow speed. Any drift should be corrected,

and both the flight path and longitudinal axis of the aircraft should be aligned with the runway

centreline. If last-minute adjustments must be made during the last part of the final approach,

they will detract from the performance of the flare-out and touchdown. Landing approaches

should be executed without any late drastic changes.

Begin the turn from base leg to final at a point, which allows a roll-out from the turn over the

extended centre line of the runway. To do this visually, extend the centre line of the runway

as an imaginary line onto the approach path. Pick up a ground reference on that line and try

to roll out of the turn over that point.

On final, a reference point on

the windshield (Fig.13 - 6) or

on the engine cowling can

help you to estimate your

glide path. If the intended

touch down point moves

down in relation to the

reference, you will overshoot

the touchdown point unless a

correction is made.

If the intended touchdown point moves up in relation to the reference, you will undershoot the

touchdown point unless a

correction is made.

Another key to glide path

estimation is the apparent shape

and angle of the runway. The

runway shape and the angle

between the aircraft and the

runway should remain constant

throughout the approach.

If the runway appears to shorten

and widen, the glide path is too

flat and will take the aircraft short

of the touch down point. If the

runway appears to lengthen and

become narrower the glide path is

too high and will result in a

landing beyond the touch down

point.

FIG. 13 – 6 DETERMINING THE GLIDE PATH

FIG 13 - 7 RUNWAY SHAPE AND ANGLE


PPL – BOOK 2

CONVERGENCY

Each meridian crosses the Equator at right angles. Meridians on the surface of the Earth

CONVERGE towards the Poles and DIVERGE away from the Poles. Therefore, it will be

seen that at the Equator meridians are parallel to each other – there is therefore no angle

between them. As they leave the Equator and approach the Pole, they converge towards

each other.

The angle of inclination between successive meridians increases with latitude, becoming a

maximum at the Poles. This angle is termed ‘convergency’.

DEFINITION: CONVERGENCY IS DEFINED AS THE ANGLE OF INCLINATION BETWEEN THE

MERIDIANS PASSING THROUGH TWO PLACES AT A GIVEN LATITUDE. IT IS MINIMUM (ZERO) AT

THE EQUATOR AND MAXIMUM AT THE POLES. AT THE POLE, THE VALUE OF CONVERGENCY

BETWEEN EACH SUCCESSIVE MERIDIAN IS 1°. (360 MERIDIANS THEREFORE 1° PER MERIDIAN).

FIG 2-2 RHUMB LINE

FIG 2-3 CONVERGENCY


PPL – BOOK 2

In the lower half of the illustration, E and H have incorrectly selected the 180° radial FROM

the station, although they want to fly TO the station. Again the CDI will cause

misinterpretation and a turn away from the desired radial. F and G have selected the correct

course and can use the CDI to fly TO the station.

PROGRESS CHECKS

Another important use of VOR is for checking the progress of a flight along a planned track.

Two things can be learned, position along a known flight path and groundspeed.

The best way of doing this is to select VOR stations nearly at right angles to your planned

track at the various reporting points and to determine the radial on such stations when you

cross the reporting point on track. Noting the time and using this time to determine the

elapsed time since the last position will enable you to calculate your groundspeed by using

the distance between the last position and your new checkpoint. This is the best method

because the time and distance will be over a reasonably long period.

If there have been insufficient previous positions to use this method it is still possible to

calculate your groundspeed from a knowledge of the one in sixty rule discussed during your

course. The facts we know are: Each radial equals one degree - one degree at sixty miles

from the station equals one nm and pro-rata for shorter distances or greater distances. If you

are crossing close to the VOR station use a radial change of 20° to give a longer time and

FIG 21 - 18

AERONAV ACADEMY (PTY) LTD 206

PPL - BOOK 3

POWER STROKE

Just before the piston reaches TDC on the compression stroke, a spark ignites the gas. As

the flame spreads through the combustion chamber, the intense heat raises the pressure

rapidly to a peak value which is reached when the piston is about 10° past TDC. The gas

continues to burn and its pressure falls as the piston is forced down until, towards the end of

the power stroke, combustion is complete and the pressure on the piston is comparatively

small.

EXHAUST STROKE

With the exhaust valve open, the piston ascends, forcing out the spent gases. Here again it

is important that the flow should be as free as possible. An obstruction would not only exert a

backpressure on the piston, but it would also result in an undesirable amount of burnt gas

remaining in the cylinder. This would contaminate the fresh charge brought in during the next

induction stroke. At the end of the exhaust stroke the exhaust valve closes, the inlet valve

opens, and the cycle begins again.

FIG. 6-5 POWER STROKE

FIG. 6-6 EXHAUST STROKE


PPL - BOOK 3

ROLL

Figure 11-27 shows the indications for an aircraft banking left and right in level flight. Bank

indication is given by an index on the sky plate, which is directly connected to the outer

gimbal. The index reads against a scale printed on the glass face of the instrument.

When the aircraft banks the rotor, inner gimbal and outer gimbal remain rigid in the level

position. The instrument, together with the printed scale and miniature aircraft, moves with

the aircraft. The position of the index on the sky plate indicates the bank angle against the

scale.

FIG 11-27 LEFT & RIGHT (LEVEL) BANK

FIG 11-26 CLIMBING AND DESCENDING


PPL – HUMAN PERFORMANCE AND FLIGHT PLANNING

CHAPTER FOUR

THE SENSES

1. PHYSIOLOGICAL EFFECTS OF FLIGHT AND THE EYE

1.1 The Anatomy Of The Eye

The anatomy of the eye is shown in Figure 4 - 1. Structurally, the eye is like a camera. The pupil is the aperture, the size of which is adjusted by the iris, controlling the amount of light entering the eye. The light then passes through a lens, which, in conjunction with the cornea, focuses it on the retina – the rear wall of the eye, which corresponds to the film in the camera. The refractive power (focus) of the eye is adjusted by the ciliary muscles, which adjust the shape if the lens. The cornea provides the coarse focusing, being responsible for about 70% of the bending of light rays. The lens is responsible for focus adjustment (also known as accommodation) of the eye. The retina is a complex layer of nerve cells connected to the optic nerve, which transmits electrical signals to the brain. These light sensitive cells are made up of two types of receptors, called rods and cones. The central area of the retina, the fovea, is made up entirely of cones with these being progressively replaced by rods towards the peripheral area. The cones are colour sensitive and are used for direct vision in good lighting; the rods are insensitive to colour and are used in poor lighting. The greatest visual accuracy (acuity) occurs at the fovea (up to 2-3 degrees of the fovea), but rapidly decreases away from this point, towards the periphery of vision.

Figure 4 - 1 The Anatomy of the Eye


PPL – HUMAN PERFORMANCE AND FLIGHT PLANNING

2. PHYSIOLOGICAL EFFECTS OF FLIGHT AND THE EAR

2.1. The Anatomy Of The Ear

The anatomy of the ear is shown in Figure 4-10.

Figure 4 – 10 The Anatomy of the Ear

Our ears enable us to hear, but additionally help us to maintain our balance. The external ear is a passage connecting the eardrum to atmosphere. Sounds create pressure variations, which cause the eardrum to vibrate.

This vibration is transferred to the fluid filled cochlea through a series of small bones in the middle ear. Nerves in the cochlea transmit the vibrations as electrical impulses to the brain, where they are interpreted as sounds. The main purpose of the eustachian tube is to allow air pressure to equalise on either side of the eardrum. See Figure 4-11

Figure 4 – 11 The Equalisation of Air Pressure Inside the Ear

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