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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.
FIG 4 - 7 AILERON AND ELEVATOR CONTROLS
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 - 8 EFFECTS OF ELEVATOR ON NOSE ATTITUDE PPL – BOOK 1
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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.
FIG 4 - 11 THE THREE AXES
PPL – BOOK 1
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FIG 6 - 11
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).
FIG 6-12 P- FACTOR
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.
PPL – BOOK 1
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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 touch- down. 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.
FIG. 13 – 6 DETERMINING THE GLIDE PATH
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 - 7 RUNWAY SHAPE AND ANGLE PPL – BOOK 1
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FIG 2-2 RHUMB LINE
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’.
FIG 2-3 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).
PPL – BOOK 2
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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.
FIG 21 - 18
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
PPL – BOOK 2
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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 10째 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.
FIG. 6-5 POWER STROKE
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. 6-6 EXHAUST STROKE
PPL - BOOK 3
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FIG 11-26 CLIMBING AND DESCENDING
ROLL
FIG 11-27 LEFT & RIGHT (LEVEL) BANK
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.
PPL - BOOK 3
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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
AERONAV ACADEMY (PTY) LTD
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PHYSIOLOGICAL EFFECTS OF FLIGHT AND THE EAR
2.1.
The Anatomy Of The Ear
37
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
PPL – HUMAN PERFORMANCE AND FLIGHT PLANNING