ppl_02_e2
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CHAPTER 12 THE COCKPIT
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CHAPTER 1 2 : THE COCK PIT
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INTRODUCTION.
Co c k p i t D e s i g n a n d L a y o u t .
In the conception and production of a new aircraft type or model, cockpit design has a profound influence on how effectively and efficiently the pilot will operate in the air.
Cockpit space and comfort, the design and layout of instruments and controls, and the extent of the pilot’s visual field, in terms of his being able to take in the instrument and control layout at the same time as having a satisfactory view of the outside world, are of particular importance.
Over the past 90 years or so, the design and instrument layout of the light aircraft cockpit has evolved steadily, though basic features have remained fairly constant. Until very recently, the main improvements in light aircraft cockpit design have centred around the ergonomics of the cockpit: the comfort of the pilot, the extent of the visual field offered by improved canopy design, and, in the last few years, advances in instrumentation, both in capability and clarity of display.
Figure 12.1 Over the years, cockpit design has evolved steadily while retaining many constant features.
The most revolutionary change in cockpit design in recent years has been the advent of the glass cockpit, where traditional, analogue instrument displays, with their needles and cross-bars, have been replaced by computer-controlled electronic displays that can display various types of flight information, as selected by the pilot.
The capability of the instruments themselves has advanced rapidly, too. Most professional pilots now have the benefit of Electronic Flight
Instrument Systems, which display navigation and attitude information, Flight Management Systems, which help pilots with their flight planning, Traffic Collision Avoidance Systems,
Ground Proximity Warning Systems, and Global Positioning Systems.
By the 1990s, glass cockpits were becoming more and more common in airliners, and, nowadays, glass cockpits are even an option in light training aircraft.
Figure 12.2 The most revolutionary change in recent years has been the advent of the glass cockpit.
It is not, however, the purpose of this chapter to look at these latest developments in the capability and display features of aircraft instruments, but rather to examine how more general cockpit design considerations attempt to take into account the comfort of the pilot and the need for him to operate safely and efficiently.
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CHAPTER 1 2 : THE COCK PIT
An t h r o p o m e t r y .
One of the most important factors in determining the size of an aircraft cockpit is the size of the occupants that the aircraft is designed to carry.
Anthropometry is the name given to the study of the measurement of human beings. From anthropometrical data an enormous amount of information is available to the aircraft designer about the range of sizes of potential pilots, crew and passengers.
Anthropometrical information may be placed into two main groups.
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Static measurements, |
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such as height, ankle-to-knee |
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distance, shoulder width etc. |
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Dynamic measurements, |
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Figure 12.3 Little pilot, big pilot. |
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such as how far a human being |
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can reach or stretch his legs. |
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Having determined the range of different measurements that exist within any population of human beings, the aircraft designer must decide which spread of measurements he will take into consideration in order to determine the size of the cockpit. It is not feasible to allow for all the different sizes of adults. It is not practical, for instance, to design a single cockpit which can be operated by both the very short and the very tall. Consequently, aircraft designers will normally cater for the middle 90% of human beings, in terms of size. Those in the lowest 5% and those in the highest 5% of size range are not considered.
In the United Kingdom, the 5th percentile of height for adult males is 5 feet 4ins (1.625m) (i.e. 5% of adult males are shorter than this) and the 95th percentile is
6 feet 1in (1.855m) (i.e. 5% of adult males are taller than this).
Ask your
instructor to help you
determine the ideal seating position so that you can make the most of your flying instruction.
EYE DATUM.
One of the basic design criteria for cockpits is that the pilot should be able to view all of the important instrument displays within the aircraft while maintaining an adequate forward view through the canopy without the need to make more than the minimum number of head movements. It follows, therefore, that the cockpit space must be designed around a defined position of the pilot’s eye-level.
This position can be called variously the eye datum, the design eye position, or the reference eye point.
Figure 12.4 Adequate forward view.
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CHAPTER 1 2 : THE COCK PIT
The eye datum is sometimes indicated in the cockpit by the provision of an indicator on the central windscreen pillar, which only appears to be aligned when the pilot’s eye is at the designed point.
As the external view is of great importance in piloting the aircraft, the pilot must, without strain, be able to look over the top of the instrument panel and see sufficient of the ground ahead to enable him to fly the aircraft by external references, both in the cruise and on approach to land.
If the pilot is sitting too high in the cockpit, he will have a good downward view, but his view of the flight instruments may be less than optimal.
If, on the other hand, the pilot is sitting too low, he may not be able to see the horizon adequately in the cruise, or have an adequate view of the undershoot on the approach to land.
Oncetheeyedatumhasbeenestablished by the designer, and the anthropometric range of pilots has been determined, the size of the cockpit work space and the amount of adjustment to seat, rudder pedals, etc, can be determined.
From your point of view as a pilot, ensure that you ascertain the correct seat adjustment for yourself, from your very first flying lesson.
Figure 12.5a-c Eye datum positions.
A Sa t i s f a c t o r y V i e w .
From your seating position, with all harnesses tight and locked, you must have a clear view of the instruments and over the nose of the aircraft so that you can correctly judge cruise and approach attitudes.
You must also be able to reach all the controls and manipulate them over their full range of movement. Ask your instructor to help you determine the ideal seat adjustments for you. Effort spent on this detail will help you gain maximum benefit from your flying, whether you are a student or qualified pilot.
Figure 12.6 depicts the type of view you should expect to have in cruising flight.
Figure 12.6 A satisfactory view of the horizon in cruising flight.
The pilot must have a clear view of
the instruments and a good forward view through the canopy, so that he can see the horizon, and the undershoot on approach.
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CHAPTER 1 2 : THE COCK PIT
The forward field of vision you should expect to have on approach is depicted in
Figure 12.7
Figure 12.7 A satisfactory view of the approach.
DESIGN OF COCKPIT SEATS.
You will be working hard during your flying lessons and, once qualified, may hope to do some challenging crosscountry flying. Therefore, it is of the utmost importance that your seating position should be comfortable and adjustable to your height and build.
Cockpit seats should ideally have a lumbar support to maintain the natural spine shape and, thereby, reduce back pain and fatigue. Additionally the seat should, if possible, be isolated from any vibration of the airframe. When adjusting their seats, pilots should attempt to establish a comfortable position that facilitates full control movement, together with a balance between a full instrument scan and outside visibility. This personalised position should be used for all subsequent flights.
Figure 12.8 Five-point harness with negative g strap.
Harness-fit and adjustment is important, too. The pilot must be able to function efficiently with his harness secure and adjusted.
A 5-point harness with a negative g strap. is shown in Figure 12.8.
INSTRUMENT DISPLAYS.
D i s p l a y a n d Pr e s e Re q u i r e m e n t s .
When deciding on the best way to display flight information, the basic choice for an aircraft designer is between a digital or analogue display.
Experiments suggest that for the display of purely quantitative information, the amount of fuel in a tank for example, digital displays might be more effective
(See Figure 12.9).
Figure 12.9 Digital fuel gauge.
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CHAPTER 1 2 : THE COCK PIT
Figure 12.10 Analogue ADF/VOR display.
Figure 12.11 Digital displays can be programmed to simulate analogue instruments.
For displaying qualitative information, and for information which needs to be compared and contrasted, analogue displays provide more easily assessed information. When interpreting navigational information from VOR and ADF equipment, for instance, analogue displays give highly effective situational awareness (See Figure 12.10).
Even when digital displays are used in modern glass cockpits, the digital information is often presented as a simulated analogue display, as depicted in Figure 12.11.
Co n v e n t i o n a l An a l o g u e St a n d a r d ‘ T’ D i s p l a y .
Figure 12.12 The standard ‘T’ instrument panel.
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CHAPTER 1 2 : THE COCK PIT
The basic instrument panel of a conventional instrument display will invariably be of a standard ‘T’ layout with the most important instrument, the artificial horizon or attitude indicator in the upper central position. The other basic flight instruments, the airspeed indicator, the altimeter and the direction indicator are grouped around the artificial horizon to form a T-shape.
It is almost certain that the basic flying training aircraft in which you learn to fly will be equipped with analogue instruments.
An a l o g u e D i s p l a Co m p a s s , D i r e c t Al t i m e t e r .
Many pilots find that an analogue direct-reading compass and direction indicator give a better picture of the aircraft orientation than would a digital readout. (See Figure 12.13). A digital readout for heading makes it more difficult to determine such information as the shortest way to turn onto a new heading.
Figure 12.13 Analogue display of heading information is more intuitive than a digital
display.
Co m b i n a t i o n o f An a l o g u e a n d D i g i t a l D i s p l a y .
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is practicable |
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combine both |
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and analogue information in a single instrument, as seen in the altimeter at Figure 12.14 where the thousands and hundreds of feet are displayed digitally. The hundreds of feet are also shown by a single pointer. While the digital display gives the pilot a clear and unambiguous indication of his altitude or height, the use of a single moving pointer against a fixed scale allows the pilot to judge when the end of the scale is being approached, i.e. when he is approaching the ground.
The single analogue needle is also excellent for showing small changes of altitude such as when levelling off or
departing inadvertently from the selected altitude.
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Th e 3 - Po i n t e r Al t i
The 3-pointer altimeter, depicted in Figure 12.15, has been in use for many years and is still the most commonlyused principal altimeter fitted to light aircraft. Pilots must be aware, though, that the 3-pointer altimeter can easily be misread. The 3-pointer altimeter shown here is indicating 2 720 feet, exactly the same altitude as indicated by the altimeter in Figure 12.14. Notice, however that the the 3-pointer altimeter is not so easy to interpret.
AIRCRAFT CONTROLS.
The instruments pass information from the aircraft and its environs to the pilot. The
aircraft’s controls, on the other hand, pass instructions from the pilot to the aircraft.
There are certain basic considerations which govern the way that aircraft controls should be designed and located in the cockpit. Most importantly, controls should be standardised, in as far as is possible and sensible, from the point of their design, location, and the sense in which they are used, between all aircraft types and models. Controls should also be located so that they are within easy reach of the pilot. Furthermore, controls that are used frequently, or for protracted periods, should be located so that they do not require the pilot to adopt an awkward or tiring posture.
Controls that are normally used in a given order should be laid out so that the sequence of use is represented in that layout. As well as being ergonomically convenient, the order of the layout, itself, will act as a prompt for the pilot to operate the controls in the correct sequence.
Figure 12.16 Controls which are used frequently should not require the pilot to adopt an awkward or tiring posture.
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CHAPTER 1 2 :
Levers, switches and
knobs which control differ-
ent functions must look and feel different from one another.
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THE COCK PIT
Figure 12.17 Important controls must be easy to reach.
Important controls must be located in easily reached and unobstructed positions. Levers, switches and knobs which control different systems or functions should look and feel different from one another (See Figure 12.18). This is an important and fundamental consideration in order to reduce the risk of the pilot mistaking one control for another and making an incorrect, and potentially dangerous, control input.
Those controls that the pilot may need to use simultaneously, or consecutively, such as the throttle and mixture controls, should be located adjacent to each other (See Figure 12.19).
Figure 12.18 Levers, switches and knobs |
Figure 12.19 Throttle and mixture controls. |
which control different functions must look |
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and feel different. |
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