car 66 b1 lic module 11.5.1 instrument system (ata 31)

Module 11.5.1 Instrument System(ATA 31) and11.18Onboard maintenance System (ATA 45)

CAR 66 Basic Training Manual

MODULE 11.5.1

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PAGEINTENTIONALLY

BLANK

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INSTRUMENT SYSTEMS (ATA 31)

Aircraft instruments can, on initial observation, appear a bewildering mass of dials or 'TV ' type screens. The different types of instrumentation required fall into one of the following types:

Pressure instruments

Gyroscopic instruments

Compasses

Mechanical indicators

Electronic instruments

PRESSURE INSTRUMENTS

AIR DATA INSTRUMENTS

An Air Data system of an aircraft is one which the total pressure created by the forward motion of an aircraft, and the static pressure of the atmosphere surrounding it, are sensed and measured in terms of speed, altitude and rate of change of altitude. The measurement and indication of these three parameters may be achieved by connecting the appropriate sensors, either directly to mechanical-type instruments, or to a remotely-located Air Data Computer (ADC), which then transmits the data in electrical signal format to electro-mechanical or servo-type instruments.

The basic Air Data Instruments display airspeed, altitude, Mach number and vertical speed. All are calculated from air pressure received from a Pitot/Static source.

1. Static air pressure, which is simply the outside air pressure at the instant of measuring.

2. Pitot pressure is the dynamic pressure of the air due to the forward motion of the aircraft and is measured using a tube, which faces the direction of travel.

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Figure 11-5-1-1 shows a Pressure head as fitted to aircraft to allow Pitot and Static pressures to the relevant indicators.

Figure 11-5-1-1 - Aircraft Pressure Head

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Indicated Airspeed (IAS), Mach No, Barometric Height (Height above sea level), and Vertical speed (Rate of climb/dive) are derived from the Pitot/Static inputs.

IAS = Pitot minus Static - (In knots).

Mach No = Pitot - Static divided by Static.

Baro Ht = Static - (In feet).

Vertical Speed = Change in Static pressure - (X 1000ft/min).

Figure 11-5-1.2 shows typical aircraft static vent:

LOCATION OF PROBES AND STATIC VENTS

The choice of probe/vent locations is largely dependent on the type of aircraft, speed range and aerodynamic characteristics, and as result there is no common standard for all aircraft. On larger aircraft it is normal to have standby probes and static vents. These are always located one on each side of the fuselage and are interconnected so as to balance out dynamic pressure effects resulting from any Yawing or side-slip motion of the aircraft. Figure 11.5.1.2 – Aircraft Static Vent

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Figure 11.5.1.3 shows the location of probes and vents on a Boeing 737.

Figure 11.5.1.3 – Boeing 737 Air Data Probe and Vent Location

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Pitot and static pressures are transmitted through seamless and corrosion-resistant metal (light alloy) pipelines. Flexible pipelines are also used when connections to components mounted on anti-vibration mountings is required. In order for an Air Data System to operate effectively under all flight conditions, provision must also be made for the elimination of water that may enter the system as a result of condensation, rain, snow, etc. This will reduce the probability of “Slugs” of water blocking the lines. This provision takes the form of drain holes in the probes, drain taps and valves in the system’s pipelines. The drain holes within the probes are of diameter so as not to introduce errors into the system.Methods of draining the pipelines varies between aircraft types and are designed to have a capacity sufficient to allow for the accumulation of the maximum amount of water that could enter the system between maintenance periods. Figure 11.5.1.4 shows a typical water drain valve.

Figure 11.5.1.4 – Water Drain Valve

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The three primary instruments in the Air Data System are:

Altimeter (Baro Ht).

Indicated Air Speed (IAS) Indicator.

Vertical Speed Indicator.

The IAS is often combined to display Mach No as well as indicated airspeed as is referred to as the “Combined Speed Indicator”.

Figure 11.5.1.5 shows the connection and equations for the primary Air Data instruments.

Figure 11.5.1.5 – Air Data Instrumentation

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ALTIMETER

The operates on the aneroid barometric principle, i.e. responds to changes in atmospheric pressure, and are calibrated to indicate these changes in terms of equivalent altitude values. Figure 11.5.1.6 shows a typical altimeter.

Figure 11.5.1.6 – Altimeter

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The pressure sensing element consists of an aneroid capsule, which transmits deflections in response to pressure changes. They are contained in a sealed container that is evacuated to the static pressure. There is a mechanical linkage to a pointer, which indicates the aircraft’s height above sea level. There is a facility to set the correct pressure of the day in millibars so that the instrument displays the correct height.

Figure 11.5.1.7 shows the simplified operation of the altimeter.

Figure 11.5.1.7 – Simplified Altimeter operation

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“Q” CODE SETTINGS FOR ALTIMETERS

The setting of altimeters to the barometric pressures prevailing at various flight levels and airports is part of the flight operating techniques. It is essential for maintaining adequate separation between aircraft and for terrain clearance during take-off and landing. In order to make the settings, flight crews are dependant on observed meteorological data which is requested and transmitted from ATC and form part of the ICAO “Q” code of communication. There are three code letter groups commonly used in connection with altimeter setting procedures:

QNH.

QFE.

QNE.QNH: Setting the barometric pressure to make the altimeter read airport elevation above-sea level on landing and take-off. When used for landing and take-off, the setting is generally known as “Airport QNH”. Any value set is only valid in the immediate vicinity of the airport concerned.

Since an altimeter with a QNH setting reads altitude above sea level, the setting is also useful in determining terrain clearance when an aircraft is en-route. Fir this purpose, the UK and surrounding seas are divided into fourteen “Altimeter Setting Regions”, each transmitting an hourly “Regional QNH” forecast.

QFE: Setting the barometric pressure prevailing at an airport to make the altimeter read zero on landing at, or taking off from, that airport. The zero reading is regardless of the airport’s elevation above sea level.

QNE: Also known as the “Standard Altimeter Setting (SAS)”. The barometric pressure is set to 1013.25 mb and is used for flights above a prescribed “Transmission Height” and has the advantage that with all aircraft using the same airspace and flying on the same altimeter setting, the requisite separation between aircraft can more readily be maintained. The transition altitude within the UK airspace is usually 3000 - 6000'. Figure 11.5.8 shows QNH, QFE and QNE definitions.

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Figure 11.5.1.8 – QNH, QFE and QNE Definitions

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COMBINED SPEED INDICATOR

This indicator is one, which combines the functions of both a conventional indicator and a Machmeter. Figure 11.5.1.9 shows a typical Combined Speed Indicator (CSI).

Figure 11.5.1.9 – Combined Speed Indicator

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The internal mechanism consists of two elements (pointer and fixed scale for IAS and a digital readout for Mach No). There is also a second pointer on the IAS scale, this is known as the “Velocity Maximum Operating (Vmo)”. It indicates the aircraft’s maximum safe operating speed over its operating altitude range.

To set the desired speed for operation, the flight crew uses the command bug. This speed in turn is the datum speed for the Auto throttle or Fast/Slow speed indicator. The external index bugs are used to set various reference speeds (take-off, flap retract speeds etc.).Figure 11.5.1.10 shows a simplified IAS operation.

Figure 11.5.1.10 – IAS Operation

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VERTICAL SPEED INDICATOR (VSI)

These indicators (also known as Rate-of Speed indicators) are very sensitive differential pressure gauges, designed to indicate the rate of altitude change from variations in static pressure alone. Figure 11.5.1.11 shows a VSI.

Figure 11.5.1.11 – Vertical Speed Indicator (VSI)

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Since the rate at which the static pressure changes is involved in determining vertical speed, a time factor has to be incorporated as a pressure function. This is accomplished by using a special air-metering unit in the sensing system. Its purpose is to create a lag in static pressure across the system and so establish the required pressure difference.Figure 11.5.1.12 shows a simplified VSI operation.

Figure 11.5.1.12 – VSI Operation

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AIR DATA SYSTEMS

The complexity of an Air Data System depends primarily upon the type and size of the aircraft, the number of locations at which primary air data are to be displayed, the type of instruments installed, and the number of other systems requiring air data inputs.Figure 11.5.1.13 shows a typical air data system for a large aircraft.

Figure 11.5.1.13 – Air Data System

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GYROSCOPIC INSTRUMENTS

A number of instruments depend on the use of gyroscopes for their correct operation. It is useful to know the basic principles of how they work, before describing, in some depth, what they do.

GYROSCOPIC PROPERTIES

As mechanical device a gyroscope may be defined as a system containing a heavy metal wheel (rotor), universally mounted so that it has three degrees of freedom:

Spinning freedom: About an axis perpendicular through its center (axis of spin XX).

Tilting Freedom: About a horizontal axis at right angles to the spin axis (axis of tilt YY).

Veering Freedom: About a vertical axis perpendicular to both the other two axes (axis of veer ZZ).

The three degrees of freedom are obtained by mounting the rotor in two concentrically pivoted rings, called inner and outer rings. The whole assembly is known as the gimbal system of a free or space gyroscope. The gimbal system is mounted in a frame so that in its normal operating position, all the axes are mutually at right angles to one another and intersect at the center of gravity of the rotor.

The system will not exhibit gyroscopic properties unless the rotor is spinning. When the rotor is spinning at high speed the device becomes a true gyroscope possessing two important fundamental properties:

Gyroscopic Inertia (Rigidity).

Precession.

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RIGITITY

The property which resists any force tending to change the plane of rotor rotation. It is dependent on:

1. The mass of the rotor.

2. The speed of rotation.PRECESSION

The angular change in direction of the plane of rotation under the influence of an applied force. The change in direction takes place, not in line with the force, but always at a point 90º away in the direction of rotation. The rate of precession also depends on:

1. The strength and direction of the applied force.

2. The angular velocity of the rotor.

Figure 11.5.14 shows a gyroscope.

Figure 11.5.14 - Gyroscope.

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Figure 11.5.1.15 shows the characteristics of gyro rigidity.

Figure 11-5-1.15 - Gyro Rigidity

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Gyro A has its spin axes parallel with the Earth's spin axes, located at the North Pole. It could hold this position indefinitely.

Gyro B has its spin axes parallel to the Earth's spin axes, but located at the Equator. As the Earth rotates, it would appear to continually point North.

Gyro C is also situated at the Equator. As the Earth rotates, it appears to rotate about its axes, however it is the Earth that is rotating and not the gyro.

This rigidity can be used in a number of gyro instruments including the directional gyro. PRECESSION

If an external force is applied to a spinning gyro, its effect will be felt at 900 from the point of application, in the direction of gyro rotation. This is known as precession. It can be seen in Figure 11.5.1.16, that if a force is applied to the bottom of the rotating wheel, it will rotate about its horizontal axis.

This property is not wanted in some instruments, such as directional gyros. The use of precession is used in turn indicators, which will be covered later.

Figure 11.5.1.16 - Gyro Precession

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VERTICAL GYRO

Figure 11.5.1.17 shows the effects on a free gyro in an aircraft circling the earth. As can be seen, it would only be perpendicular to the earth's surface at two points.

Figure 11.5.1.17 - Behavior of a Vertical Gyro

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In order for the gyro to be used to indicate the aircraft's attitude, it has to be corrected to continually be aligned to the vertical. These corrections are very slow and gentle, since the amount of correction needed, for example, in a ten-minute period is small. Figure 11.5.1.18 shows a vertical gyro corrected to the local vertical.

Figure 11.5.1.18 – Corrected Vertical Gyro

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Instruments that use either the rigidity or the precession of gyros are:

Gyro Horizon Unit.

Attitude Director Indicator.

Standby Horizon Unit.

Direction Indicator.

Turn and Slip Indicator.

Turn Co-ordinator.

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GYRO HORIZON UNIT

The Gyro Horizon Unit gives a representation of the aircraft’s pitch and roll attitudes relative to its vertical axis. For this it uses a displacement gyroscope whose spin axis is vertical. Figure 11.5.1.19 shows a displacement gyro and the two axis of displacement.

Figure 11.5.1.19 – Displacement Gyro

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Indications of attitude are presented by the relative positions of two elements, one symbolizing the aircraft itself, the other in the form of a bar stabilized by the gyroscope and symbolizing the natural horizon. Figure 11.5.1.20 shows a typical Gyro Horizon Unit.

Figure 11.5.1.20 – Gyro Horizon Unit

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The gimbal system is so arranged so that the inner ring forms the rotor casing and is pivoted parallel to an aircraft’s lateral axis (YY1); the outer ring is pivoted at the front and rear ends of the instrument case, parallel to the longitudual axis (ZZ1). The element symbolizing the aircraft may either be rigidily fixed to the case, or it may be externally adjustable for setting a particular pitch trim reference.

Figure 11.5.1.21 shows the construction of the Gyro Horizon unit.

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In operation the gimbal system is stabilized so that in level flight the three axes are mutually at right angles. When there is a change in the aircraft’s attitude, example climbing, the instrument case and outer ring will move about the YY1 of the stabilized inner ring.

The horizon bar is pivoted at the side and to the rear of the outer ring and engages an actuating pin fixed to the inner ring, thus forming a magnifying lever system. The pin passes through a curved slit in the outer ring. In a climb attitude the pivot carries the rear end of the bar upwards so that it pivots about the stabilized actuating pin. The front end of the bar is therefore moved downwards through a greater angle than that of the outer ring, and since the movement is relative to the symbolic aircraft element, the bar will indicate a climb attitude.

Figure 11.5.1.22 shows climb attitude operation.

Figure 11.5.1.22 – Climb Attitude operation.

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Changes in the lateral attitude of an aircraft, i.e. rolling, displaces the instrument case about the axis (ZZ1), and the whole stabilized gimbal system. Hence, lateral attitude changes are indicated by movement of the symbolic aircraft element relative to the horizon bar, and also by relative movement between the roll angle scale and pointer. Figure 11.5.1.23 shows roll attitude operation.

Figure 11.5.1.23 – Roll attitude operation

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Freedom of gimbal system movement is 360º for roll axis and 85º for the and pitch axis. The pitch scale is restricted by means of a resilient stop. This will prevent gimbal lock.ATTITUDE DIRECTOR INDICATOR

This unit performs the same functions as a Gyro Horizon unit; i.e. it establishes a stabilized reference about the pitch and roll axes of an aircraft. Instead, however, of providing attitude displays by direct means, it is designed to be operated via a synchro system, which produces and transmits attitude-related signals to the indicator. The synchro system includes a attitude reference source and a computer linked into the aircraft’s navigational system to produce flight director signals for the flight crew to follow to ensure the aircraft follows the required course. Figure 11.5.1.24 shows a typical Attitude Director Indicator (ADI)

Figure 11.5.1.24 - Attitude Director Indicator (ADI)

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STANDBY HORIZON UNIT

Most aircraft currently in service use Flight Director systems, or more sophisticated electronic flight instrument systems, all of which comprise indicators displaying not only attitude data, but navigational data as well. In such aircraft, the role of the conventional gyro horizon is mainly used as a standby instrument located on the center instrument panel. It is used as a reference in the event of a failure that might occur in the attitude display systems.

Figure 11.5.1.25 shows a Standby Horizon Unit (SHU).

The gyro is powered by 115V; three phase ac supplied from a static inverter, which in turn is supplied by 28V from the battery busbar. In place of the stabilized horizon bar a stabilized attitude sphere is used as the reference. The upper element is coloured blue to display climb attitudes, and black/brown for descending attitudes.

A pitch trim adjustment and fast erection facility is provided, both being controlled by a knob on the lower right-hand corner of the indictor. When the knob is rotated the aircraft symbol can be positioned through 5º, thereby establishing a variable pitch trim reference. Pulling the knob out and holding it actuates the fast-erection circuit.

Figure 11.5.1.25 – Standby Horizon Unit

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DIRECTION INDICATORS

This indicator was the first gyroscopic instrument to be introduced as aheading indicator, and although for most aircraft currently in service it has been superseded by remote-indicating compass systems (see later). The instrument uses a horizontal axis gyroscope and, being non-magnetic, is used in conjunction with a magnetic compass.

In its basic form, the outer ring of the gyro carries a circular card, graduated in degrees, and referenced against a lubber line fixed to the gyro frame. When the rotor is spinning, the gimbal system and card are stabilized so that, by turning the frame, the number of degrees through which it is turning may be read on the card.

Figure 11.5.1.26 shows a Directional Indicator

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In the directional gyro, the rotor is enclosed in a case, or shroud, and supported in an inner gimbal which is mounted in an outer gimbal, the bearings of which are located top and bottom on the indicator case. The front of the case contains a cut-out through which the card is visible, and also a lubber line reference.

The caging/setting knob is provided at the front of the case to set the indicator onto the correct heading (magnetic). When the setting the heading, the inner gimbal has to be caged to prevent it from precessing as the outer gimbal is rotated. Figure 11.5.27 shows the construction of a directional gyro.

Figure 11.5.1.27 – Directional Gyro

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TURN & SLIP INDICATOR

This indicator contains two independent mechanisms:

1. A gyroscopically controlled pointer mechanism for the detection and indication of the rate at which an aircraft turns.

2. A mechanism for the detection and indication of slip/slide.

A gimbal ring and magnifying system, which moves the pointer in the correct sense over a scale calibrated in what is termed “Standard Rates”, actuate the rate of turn pointer. Although they are not always marked on a scale, they are classified as follows:

Rate 1 - Turn Rate 180º per minute.




Figure 11.5.1.28 shows a typical Turn & Slip indicator.

Figure 11.5.1.28 – Turn & Slip Indicator

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For the detection of rates of turn, a rate gyroscope is used and is arranged in the manner shown in figure 11.5.1.29.It differs in two respects from the displacement gyro as it only has one gimbal ring and a calibrated spring restraining in the longitudinal axis YY1. When the indicator is in its normal operating position the rotor spin axis, due to the spring restraint, will always be horizontal and the turn pointer at the zero datum. With the rotor spinning, its rigidity will further ensure that the zero position is maintained.

Figure 11.5.1.29 – Rate Gyro Turn Indicator

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When the aircraft turns to the left about the vertical input axis the rigidity of the rotor will resist the turning movement, which it detects as an equivalent force being applied to its rim at point F. The gimbal ring and rotor will therefore be tilted about the longitudinal axis as a result of precession at point P.

As the gimbal ring tilts, it stretches the calibrated spring until the force it exerts prevents further deflection of the gimbal ring. Since precession of a rate gyro is equal to its angular momentum and the rate of turn, then the spring force is a measure of the rate of turn.

Actual movement of the gimbal ring from its zero position can, therefore, be taken as the required measure of turn rate.

BANK INDICATION

In addition to the primary indication of turn rate, it is also necessary to have an indication that an aircraft is correctly banked for the particular turn. A secondary indicating mechanism is therefore provided, which, depends for its operation on the effect of gravitational and centrifugal forces. A method commonly used for bank indication is one utilizing a ball in a curved liquid-filled glass tube as shown in Figure 11.5.1.26.

In the normal level flight the ball is held at the center of the tube by the force of gravity. Let us assume the aircraft turns left at a certain airspeed and bank angle. The indicator case and the tube move with the aircraft and centrifugal force (CF) in addition to that of gravity acts upon the ball and tends to displace it outwards from the center of the tube. However, when the turn is executed at the correct bank angle and matched with airspeed, then there is a balanced condition between the two forces and so the resultant force (R) hold the ball in the center of the tube.

If the airspeed were to be increased during the turn, then the bank angle and centrifugal force would also be increased. As long as the bank angle is correct for the appropriate conditions, the new resultant force will still hold the ball central.

If the bank angle for a particular rate of turn is not correct (under-banked/over-banked), then the aircraft will tend to either skid or slip. In the skid condition the centrifugal force will be the greatest, whereas in the slip condition the force of gravity is greatest.

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Figure 11.5.1.30 shows bank indication for various aircraft bank conditions.

Figure 11.5.1.30 – bank Indications

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TURN COORDINATOR

The final instrument in this group is the turn co-ordinator. Basically, its mechanism is changed slightly from the turn and slip indicator, so that it senses rotation about the longitudinal axis, (bank) as well as the vertical axis, (turn). This gives a more accurate indication to the pilot, of the turning of the aircraft.

Figure 11.5.1.31 shows a Turn coordinator indicator.

Figure 11.5.1.31 - Turn coordinator Indicator

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HORIZONTAL SITUATION INDICATOR

This indicator derives its name from the fact that its display presents a pictorial plan of the aircraft’s situation in the horizontal plane in the form of its heading, VOR/LOC deviation and other data relating to navigation.

Figure 11.5.1.32 shows a typical HSI.

The aircraft symbol is fixed at the center of the instrument and displays the heading of the aircraft in relation to a rotating compass card and the VOR/LOC deviation bar (lateral bar). The selector knobs at the bottom corners of the instrument permit the setting of desired magnetic heading and VOR course.

Figure 11.5.1.32 – Horizontal Situation Indicator

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COMPASS SYSTEMS

The compass has, since the earliest times, given information to travelers with regards to the direction to go. Mounting a compass on a moving object, whether it was a vehicle, a ship or an aircraft poses certain problems. This includes how to mount the compass without the, motion (maybe violent), upsetting the device.

Another problem that besets compasses is the fact that they usually point to magnetic north, which slowly moves, and not true north, the difference between the two is something like 1,300-miles/2,000 km. This is of little concern if we are moving slowly, on a boat, in the vicinity of the equator, but vital in an aircraft flying what is known as a 'Trans-polar route' from say, New York to Tokyo. The effect this has on navigational charts is referred to as 'variation'.

Figure 11.5.1.33 shows the difference between True North and Magnetic North.

Figure 11.5.1.33 - True North & Magnetic North

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DIRECT READING COMPASS

Direct-reading compasses have the following common principal features:

Magnet system housed in a bowl.

Liquid damping and liquid expansion compensation.

Figure 11.5.1.34 shows a direct reading compass used as a standby compass in most aircraft.

Figure 11.5.1.34 – Standby Compass

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The magnet system comprises an annular cobalt-steel magnet to which is attached a light-alloy card. The card is graduated in increments of 10º, and referenced against a lubber line fixed to the interior of the bowl. The system is pendulously suspended by an iridium-tipped pivot resting in a sapphire cup supported in a holder or stem.

The bowl is of a plastic (diakon) and so moulded that it has a magnifying effect on the card and its graduations. It is filled with a silicone fluid to prevent the card oscillating or overshooting after changes of heading. The fluid also provides the system with a certain buoyancy, thereby reducing the weight on the pivot and so diminishing the effects of friction and wear.

Changes in the volume of the fluid due to temperature changes, and their resulting effects on damping efficiency, are compensated by a bellows type of expansion device secured to the rear of the bowl.

Compensation of the effects of deviation due to longitudinal and lateral components of aircraft magnetism is provided by permanent magnet coefficient “B” and “C” corrector assemblies secured to the compass mounting plate. A small lamp is also provided for illuminating the card.

Figure 11.5.1.35 shows a complete standby compass indicator.

Figure 11.5.1.35 – Standby Compass

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REMOTE READING COMPASS

A remote reading compass, is basically one in which an element detects an aircraft’s heading with respect to the horizontal component of the earth’s magnetic field in terms of flux and induced changes in voltage. It then transmits these changes via a synchronous/servo system to a heading indicator. There are two types of remote reading compass systems:

The detector element monitors a directional gyro unit linked with a heading indicator.

The detector element operates in conjunction with the platform of an inertial navigation system (INS).

DETECTOR UNIT (FLUX VALVE)

The detector unit detects the effect of the earth’s magnetic field as an electromagnetically induced voltage and controls the heading indicator by means of a variable secondary output voltage signal. The construction of the element takes the form of a three-spoked wheel, slit through the rim between the spokes so that they, and their section of rim, act as three individual flux collectors. Figure 11.5.36 shows the construction of a flux valve.

Figure 11.5.1.36 – Flux Valve Construction

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The paths taken by the earth’s magnetic field through the spokes for differnet headings is shown at Figure 11.5.1.37.

The detector unit on its own is not very accurate by virtue of its limited pendulous suspension arrangement. Errors will occur as a result of its tilting under the influence of acceleration forces, e.g. during speed changes on a constant heading and during turns. It is necessary to incorporate within the system a means of monitoring the detector’s output. The horizontal directional gyro is used to give the system short-term accuracy with the detector unit providing long-term accuracy.

Figure 11.5.1.37 – Earth’s Flux path

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Figure 11.5.1.38 shows the arrangement of a remote reading gyro compass system.

Figure 11.5.1.38 – Gyro Magnetic Compass System

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Figure 11.5.1.39 shows a schematic of a Gyro Magnetic Compass system.

Figure 11.5.1.39 - Gyro Magnetic Compass System Schematic

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ANGLE OF ATTACK (AOA)

Apart from the main flight instruments, one item of information that the pilot needs to know at various stages of flight is the angle of attack. Earlier aircraft had a range of devices that gave the pilot indication of an approaching stall, which was an essential indicator but knowing the angle of attack has become an essential part of flying modern, larger aircraft.

The simplest forms of angle of attack indicators are the AOA probe and the stall vane. The probe contains slots on the leading edge of the probe itself and, depending on the angle of attack; the air flowing through the different slots move a 'paddle' which indicates the AOA electrically in the cockpit.

The stall vane is rather like a small weather vane mounted on the side of the aircraft. The vane follows the airflow, much like the weather vane, but indicating, not pitch angle, but the angle of the airflow relative to the aircraft centerline. i.e. the angle of attack.

Figure 11.5.1.40 shows a vane type Angle of Attack transducer.

Figure 11./5.1.40 - Angle of Attack Transducer

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STALL WARNING INDICATION

To maintain lift at low airspeed, the angle of attack is increased. When this angle is above a critical angle, the aircraft wings will not produce enough lift to support the aircraft, which will begin to stall. Before this situation occurs, the aircraft will shake heavily, this being a natural alert to the pilot.

If, however, the aircraft is configured for an approach (Wheels & Flaps down), the airspeed difference between the natural warning and the actual stall is very small, so an alert must be generated before the stall occurs.

Modern performance aircraft use the output from an Angle of Attack probe, connected to a Stall Warning system. The stall warning system also has other sensor inputs (Flap, Slat positions). Once the critical angle prior to actual stall is reached, the stall warning system initiates a "Audio warning" and operates a "Stick Shaker", which actually shakes the control column. Figure 11.5.2.40 shows simple stall warning system.

Figure 11.5.1.40 - Stall Warning System

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ELECTRONIC INSTRUMENT SYSTEMS

Modern technology has enabled some significant changes in the layout of flight instrumentation on most aircraft currently in service. The biggest change has been the introduction of Electronic Instrument systems. These systems have meant that many complex Electro-mechanical instruments have now been replaced by TV type colour displays. These systems also allow the exchange of images between display units in the case of display failures.

There are many different Electronic Instrument Systems, including:

1. Electronic Flight Instrument System (EFIS).

2. Engine Instrumentation & Crew Alerting System (EICAS).

3. Electronic Centralised Aircraft Monitoring (ECAM).

Figure 11.5.1.41 shows a typical flight deck layout of an Airbus A320.

Figure 11.5.1.41 - Flight Deck Electronic Instrumentation Layout

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The Electronic Instrument System (EIS) also allows the flight crew to configure the instrument layout by allowing manual transfer of the Primary Flight Display (PFD) with the Navigation Display (ND) and the secondary Electronic Centralized Aircraft Monitoring (ECAM) display with the ND. Figure 11.5.1.42 shows the switching panel from Airbus A320.

Figure 11.5.1.42 – A320 EIS Switching Panel

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As well as a manual transfer, the system will automatically transfer displays when either the PFD or the primary ECAM display fails. The PFD is automatically transferred onto the corresponding ND, with the ECAM secondary display used for the primary ECAM display.

The system will also automatically transfer the primary ECAM information onto the ND if a double failure of the ECAM display system occurs. Figure 11.5.1.43 shows a block schematic of the EIS for the Airbus 320.

Figure 11.5.1.43 – Electronic Instrument System (EIS)

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ELECTRONIC FLIGHT INSTRUMENT STSTEM

As in the case of conventional flight instrument systems, a complete EFIS installation is made up of left (Captain) and right (First Officer) systems. Each system comprises:

1. Electronic Attitude Director Indicator (EADI).

2. Electronic Horizontal Situation Indicator (EHSI).

3. Display Control Panel.

4. Symbol Generator.

The EADI and EHSI can either be positioned side by side or vertically top and bottom. Normally the EADI is positioned on the top or on the onside position.

ELECTRONIC ATTITUDE DIRECTOR INDICATOR (EADI)

GENERAL

The EADI displays traditional attitude information (Pitch & Roll) against a two-colour sphere representing the horizon (Ground/Sky) with an aircraft symbol as a reference. Attitude information is normally supplied from an Attitude Reference System (ARS).

The EADI will also display further flight information, Flight Director commands right/left to capture the flight path to Waypoints, airports and NAVAIDS and up/down to fly to set altitudes. Information related to the aircraft’s position w.r.t. Localizer (LOC) and Glideslope (GS) beams transmitted by an ILS. Auto Flight Control System (AFCS) deviations and Autothrottle mode, selected airspeed (Indicated or Mach No) Groundspeed, Radio Altitude and Decision Height information.

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Figure 11.5.1.44 shows a typical EADI display

Figure 11.5.1.44 - Electronic Attitude Director Indicator (EADI) Display

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The EADI has two display formats:

1. Full Time EADI Display (Data which is always present).

2. Part Time EADI Display (Data which is only present when active).

FULL TIME EADI DISPLAY DATA

Attitude Sphere: Moves with respect to the aircraft symbol to display actual pitch and roll attitude.

Pitch Attitude: The pitch attitude display has white scale reference marks at 5, 10, 15, 20, 30, 40, 60 and 80 on the sphere.

Roll Attitude: Displays actual roll attitude through a moveable index and fixed scale reference marks at 0, 10, 20, 30, 45, 60 and 90.

Aircraft Symbol: Serves as a stationary symbol of the aircraft. Aircraft pitch and roll attitudes are displayed by the relationship between the fixed miniature aircraft and the moveable sphere.

Flight Director Cue: Displays computed commands to capture and maintain a desired flight path. Flying the aircraft symbol to the command cue satisfies the commands.

Fast/Slow Display: The pointer indicates fast or slow error provided by an angle-of-attack, airspeed or alternative reference system.

Inclinometer: The EADI uses conventional inclinometer, which provides the pilot with a display of aircraft slip or skid, and is used as an aid for coordinated maneuvers.

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Attitude SourceAnnunciation: The selected attitude source is not annunciated if it is the normal source for that indicator. As other attitude sources

are selected, they are annunciated in white at the top left-hand side of the EADI. When the pilot and co-pilot sources are the same, then the annunciation is amber.

PART TIME EADI DISPLAYS

Several displays are in view only when being used. When not in use, these displays are automatically removed from the EADI.

Radio Altitude: Displayed by a four-digit display from –20 to 2500 feet. Display resolution between 200 and 2500 feet is in 10 foot increments. The display resolution below 200 is 5 feet. The display disappears for altitudes above 2500 feet (Radio Altitude max altitude is 2,500 feet).

Decision Height: Decision Height is displayed by a three-digit display. The set range is from 0 to 990 feet in 10 foot increments. The DH display may be removed by rotating fully counterclockwise the DH set knob.

Note; when the Radio Altimeter height is 100 feet above the DH, a white boxappears adjacent to the radio altimeter display. When at or below the DH, anAmber DH will appear inside the white box.

Flight DirectorMode Annunciators: Flight director vertical and lateral modes are annunciated along the top of the EADI. Armed vertical and lateral modes

are annunciated in white to the left of the captured vertical and lateral mode annunciators. Capture mode annunciators are displayed in green and are located on the top center for lateral modes and in the top right corner for vertical modes. As the mode's transition from armed to capture, a white box is drawn around the capture mode annunciator for 5 seconds.

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Marker Beacon: Displayed above the Radio Altimeter height information. The markers are of a specified colour of:

Blue - Outer Marker.

Amber - Middle Marker.

White - Inner Marker.

Rising Runway: a miniature rising runway displays Absolute altitude reference above the terrain. It appears at 200 feet, and contacts the aircraft symbol at touchdown (0 feet).

Rate-of-Turn: Pointer and scale at the bottom of the display indicates rate or turn. Used with the inclinometer, will enable coordinated turns to be achieved.

Glide Slope: By tuning to an ILS frequency, the Glide Slope information will be displayed. Aircraft displacement from the Glide Slope beam centerline is then indicated by the relationship of the aircraft to the Glide Slope pointer. The letter “G” inside the vertical scale pointer identifies the information as Glide Slope deviation. When tuning to other than an ILS frequency, the Glide Slope display is removed.

Expanded Localizer: By tuning to an ILS frequency, the Rate-of-Turn display is replaced by the expanded Localizer display. When tuning to other than an ILS frequency, the expanded localizer display is replaced by the Rate-of-Turn display.

Vertical NavigationDisplay: The deviation pointer indicates the VNAV’s computed path center to which the aircraft is to be flown. In this mode,

the letter “V” inside the vertical scale pointer identifies the information as VNAV deviation.

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ELECTRONIC HORIZONTAL SITUATION INDICATOR

The EHSI presents a selectable, dynamic colour display of flight progress and plan view orientation. The EHSI has a number of different modes of operation, these are selectable by the flight crew and the

number will be dependant on the

system fitted.

Figure 11.5.1.45 shows an EHSI display.

Figure 11.5.1.45 - Electronic Horizontal Situation Indicator (EHSI) Display

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The EHSI has two display formats:

1. Full Time EADI Display (Data which is always present).

2. Part Time EADI Display (Data which are only present when active).

FULL TIME EHSI DISPLAYS

Aircraft Symbol: The aircraft symbol provides a quick visual cue as to the aircraft’s position in relation to the selected course and heading, or actual heading.

Heading Dial: Displays the heading information on a rotating heading dial graduated in 5 increments. Fixed heading indexes are located at each 45 position.

Heading “Bug” &Heading Readout: The notched heading bug is positioned around the rotating heading dial by the remote heading select knob on the

Display Controller. A digital heading select readout is also provided for convenience in setting the heading bug. Heading select error information from the heading bug is used to fly to the bug.

Course DeviationIndicator: The course deviation bar represents the centerline of the selected navigation or localizer course. The aircraft symbol

pictorially shows the aircraft position in relation to the displayed deviation.

Select Course Pointer& Course Readout: Course pointer is positioned inside the heading dial by the remote select knob on the Display Controller. Course error

information from the course select pointer is used to fly the selected navigation path. A digital course select readout is provided for convenience in setting the select course pointer.

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Distance Display: The distance display indicates the nautical miles to the selected DME station or LRN Waypoint. Depending on the equipment, the distance will be displayed in a 0 to 399.9 NM or a 0 to 3999 NM format. An Amber “H” adjacent to the distance readout indicates DME Hold. This will indicate to the crew that DME information is from the previous VOR/DME beacon, and not the one providing VOR bearing.

Navigation SourceAnnunciators: Annunciation of the navigation source is displayed in the upper right hand corner. Long range navigation sources

such as INS, VLF, RNAV and FMS are displayed in blue to distinguish them from short-range sources, which are annunciated in white.

Time-to-Go/GroundSpeed: Either Time-to-Go or Groundspeed can be displayed, selected via the Display Controller. Ground Speed is calculated

using the LRN, if fitted. If no LRN, then the EFIS uses the DME distance to calculate Ground Speed.

Drift Angle Bug: The drift angle bug w.r.t. the lubber line represents drift angle left or right of the desired track. The drift angle bug w.r.t. the compass card represents actual aircraft track. The bug is displayed as a magenta triangle that moves around the outside of the compass card.

Desired Track: When LRN is selected, the Course Pointer now becomes the Desired Track Pointer. The position of the desired Track Pointer is controlled by the LRN. A digital display of desired track (DRAK) is displayed in the upper left-hand corner.

TO-FROM Annunciator: An Arrowhead in the center of the EHSI indicates whether the selected course will take the aircraft TO or FROM the station or Waypoint. The TO-FROM annunciator is not in view during ILS operation.

Heading SourceAnnunciation: At the top center of the EHSI is the heading source annunciator.

Heading SYNC

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Annunciator: The heading SYNC annunciator is located next to the upper left corner and indicates the state of the compass system in the slaved mode. The bar represents commands to the compass gyro to slew to the indicated direction (+ for increased heading and 0 for decreased heading). Heading SYNC is removed during compass FREE mode and for LRN derived heading displays.

PART TIME EHSI DISPLAYS

Vertical NavigationDisplay: The vertical navigation display comes into view when the VNAV mode on the flight director is selected. The deviation

pointer then indicates the VNAV’s computed path center to which the aircraft is to be flown. In this mode the letter “V” inside the scale pointer identifies the deviation display.

Glide Slope Deviation: The Glide Slope display comes into view when a VHF NAV source is selected and the NAV source is tuned to an ILS frequency. The deviation pointer then indicates the Glide Slope beam center to which the aircraft is to be flown. The letter “G” inside the scale pointer identifies the deviation display.

Bearing PointerSource Annunciators: The bearing pointers indicate relative bearing to the selected NAVAID. Two bearing pointers are available and can be

tuned to either VOR or ADF NAVAIDs. If no NAVAIDs are selected then the pointers and annunciators are removed. The bearing source annunciators are colour and symbol coded with the bearing pointers.

Elapsed TimeAnnunciation: When in the Elapsed Time (ET) mode, the ET display can read minutes and seconds or hours and minutes. The

hour/minute mode will be distinguishable from the minute/second mode by an “H” on the left of the digital display.

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PARTIAL COMPASS FORMAT

The partial compass mode displays a 90 ARC of compass coordinates. The Partial mode allows other features such as MAP and Weather Radar displays to Be selected. Figure 11.5.1.46 shows a Partial EHSI display (Compass Mode).

Figure 11.5.1.46 - EHSI Partial Compass Mode Display

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Wind Vector Display: Wind information is displayed in any partial format. The wind information can be shown as magnitude and direction or as head/tail component and cross wind component, type used is determined on installation of EFIS. In both cases, the arrow shows the direction and the number indicates the velocity of the wind (in knots). Wind information is calculated from the LRN.

Range Rings: Range rings are displayed to aid in the determining the position of radar returns and NAVAIDs. The range ring is the compass card boundary and represents the selected range on the Radar.

NAVAID Position: NAVAID position can be selected during MAP mode. The source of the NAVAID position marker is selected and annunciated in conjunction with the associated bearing source and is colour coded.

Weather Information: Weather information from the Radar can be displayed in partial compass mode. Weather Radar data is presented in the following colours:

1. Black - No storm.

2. Green - Moderate storm.

3. Yellow- Less severe storm.

4. Red - Severe storm.

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Figure 11.5.1.47 shows an EHSI partial format with Weather Radar information.

Figure 11.5.1.47 - EHSI Weather Radar Display

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MAP MODE

The MAP mode will allow the display of more navigational information in the partial compass mode. Information on the location of Waypoints, airports, NAVAIDs and the planned route can be overlaid on the compass mode. Weather information can also be displayed in the MAP mode to give a very comprehensive display.

Figure 11.5.1.48 shows an EHSI MAP mode display.

Figure 11.5.1.48 - EHSI MAP Mode Display.

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COMPOSITE DISPLAY

In the event of a display unit failure, the remaininggood display can display a “Composite Display”. This display is selected via the Display Controller and is basically a display consisting elements from an EADI and EHSI display.

Figure 11.5.1.49 shows a typical composite display.

Figure 11.5.1.49 - EFIS Composite Display

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DISPLAY CONTROLLER

Allows the crew to select the required display configuration and what informationis to be displayed. Both Captain and Co-Pilot have their own display Controller’s. The controllers have two main functions:

Display Controller: Selects the display format for EHSI as either FULL, ARC, WX or MAP.

Source Select: Selects the system that will provide information required for display. The source information will be VOR, ADF, INS, FMS, VHF and NAV.

EFIS Display Controllers are shown at Figure 11.5.1.50.

Figure 11.5.1.50 - EFIS Display and Source Controllers

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DISPLAY CONTROLLER

FULL/ARC: The FULL/ARC button is used to change the EHSI display from full compass rose display to a partial compass display format. Successive pushes of the button change the display format back and forth between FULL and ARC.

WX (Weather): The WX button is used to call up weather radar returns on the partial compass display. If the EHSI is in the FULL display format, selecting the WX display will automatically select the ARC format. A second push of the WX button will remove the weather information but the ARC format will remain.

GS/TTG: By pressing the GS/TTG button, Groundspeed or the Time-to-GO will alternately be displayed in the lower right corner of the EHSI.

ET: By pressing the ET button, Elapsed time is displayed. If the ET button is pressed again, it will zero the displayed time. The sequence is:

1. Zero.

2. Start.

3. Stop.

MAP: By pressing the MAP button, the full compass display is changed to the partial compass display, with active Waypoints displayed. Also VOR/DME ground station positions will be displayed.

SC/CP: By pressing the SC/CP button, the flight director command cues are toggled back and forth from single cue (SC) configuration to cross pointer (CP) configuration.

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REV: In the event of an EADI/EHSI display failure, the REV button may also be used to display a composite format on the remaining good display. The first push of the button will blank the EHSI and put the composite display onto the EADI. The second push blanks the EADI and puts the composite display onto the EHSI. A third push will return EHSI/EADI to normal.

CRS Select Knob: Rotation of the Course select knob allows the course pointer on the EHSI to be rotated to the desired course.

DIM: Rotation of the outer concentric DIM knob allows the overall brightness of the EADI, EHSI to be adjusted. After the reference levels are set, photoelectric sensors maintain the brightness level over various lighting conditions.

DH: Rotation of the inner concentric DH knob allows the Decision Height, displayed on the EADI, to be adjusted. If the knob is rotated fully counterclockwise, the DH display is removed.

TEST: By pressing the TEST button, the displays will enter the test mode. In the test mode, flags and cautions are presented along with a check of the flight director mode annunciations. If the test is successful a “PASS” is displayed. If the test is unsuccessful then an “FD FAIL” is annunciated.

RASTER DIM TOP/BOT: Rotation of the outer (Bottom display) and inner (Top display) concentric knobs adjusts the raster scan display (Weather Radar and Attitude Sphere).

HDG: Rotation of the heading select knob allows the heading select bug to be rotated to the desired heading.

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SOURCE CONTROLLER

Used to select the available sources of heading, attitude, bearing and navigational information for display. Since each aircraft is different, the source controller is normally tailored to fit each need.

NAV: This button is used to control the source of VHF NAV display information. Each push of the button will toggle the source between pilot and copilot’s NAV information. VHF systems include DME, ILS and VOR.

LRN: Long Range Navigation selections depend on the systems available. These include INS, VLF and FMS systems.

ATT: Attitude button selects the source of attitude information. Each push of the button will select a different source for display. Not available to all aircraft.

BRG: This knob allows the selection of VOR and ADF bearings to be displayed. The selected source is annunciated on the left-hand side of the display and the bearing to the selected beacon via two bearing pointers.

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The EFIS comprises the following units:

1. Symbol Generator (SG).

2. Display units X 2 (EADI & EHSI).

3. Control Panel.

4. Remote Light Sensor.

Figure 11.5.1.51 shows the EFIS units and signal interface in block schematic form.

Figure 11.5.1.51 - EFIS Block Schematic

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OTHER SYSTEM INDICATIONS

There are endless different instrument displays, which show the pilot's or flight engineer, the condition of the aircraft's many systems, the range of instruments depending on the size of the aircraft. On earlier airliners there could have been dozens of instruments on the panels to pass on information regarding, for example, oil temperature & pressure, cabin altitude, hydraulic oil quantity, electrical power being used, etc.

POWERPLANT INSTRUMENTATION

Information required by the flight crew to enable them to monitor the engines include:

1. Fuel Contents.

2. Fuel Flow.

3. Engine RPM.

4. Engine Temperature.

5. Engine pressure.

FUEL CONTENTS GAUGE

Most modern aircraft have a number of fuel tanks within the wing structure and each individual tank's contents must be known. There are two main methods of indicating fuel contents:

Resistance Gauges.

Capacitance Quantity Indicators.

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RESISTANCE GAUGES

This type of gauge tends to found on smaller aircraft. It has a float in the fuel tank that is connected to a variable resistor. As the fuel level changes, the float will move, thus changing the resistance, which in turn will alter the current flow through a DC circuit, which in turn will operate a meter indicating fuel contents.

Figure 11.5.1.52 shows a simplified resistance gauge.

Figure 11.5.1.52 - Resistance Gauge

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CAPACITANCE QUANTITY INDICATORS

This has the advantage over other quantity systems in that it can give accurate readings in very large or unusually shaped tanks. The probes within the fuel tank are actually capacitors. The two plates of the capacitor will be separated by fuel on the lower end and air on the upper end. Since fuel and air have different dielectric constant values, the amount of capacitance will change as the fuel level rises and falls. The probes will then send signals to the flight deck gauges to indicate fuel contents. This system usually includes a totalizer, which will give a reading of the total fuel on board. Some fuel systems will also include indications of fuel used since take-off.

Figure 11.5.1.53 shows a circuit of a capacitance quantity system.

Figure 11.5.1.53 - Capacitance Quantity Indicating System

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FUEL FLOW INDICATOR

As the name suggests, these indicators show the amount of fuel flowing into the engines. Fuel flow information can be represented as either LBS/HR, Gallons/HR or PSI. Some indicators will show both PSI and either LBS/HR or Gallons/HR. Figure 11.5.1.54 shows a fuel flow indicator.

Figure 11.5.1.54 - Fuel Flow Indicator

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FUEL PRESSURE INDICATOR

Some engines have a fuel pressure gauge that displays the pressure of the fuel supplied to the fuel control unit. Most display the pressure in pounds per square inch (psi) and provide indications to the pilot that the engine is receiving the fuel required for a given power setting. Figure 11.5.1.55 shows a fuel pressure gauge.

Figure 11.5.1.55 – Fuel Pressure Gauge

There are two types of pressure gauge:

Bourbon Tube type.

Pressure Capsule type.

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BOURBON TUBE FUEL PRESSURE INDICATOR

Is made with a metal tube that is formed in a circular shape with a flattened cross-section. One end is open while the other is sealed. The open end of the bourbon tube is connected to a capillary tube containing pressurized fuel. As the pressurized fuel enters the bourbon tube, the tube tends to straighten. Through a series of gears, this movement is used to move the indicating pointer on the instrument face. Figure 11.5.1.56 shows a Bourbon type fuel pressure gauge and its operation.

Figure 11.5.1.56 – Bourbon Tube Fuel Pressure Gauge

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PRESSURE CAPSULE FUEL PRESSURE INDICATOR

This type of indicator utilizes a “pressure capsule” or “diaphragm”. Like the bourbon tube, a diaphragm type pressure indictor is attached to a capillary tube, which attaches to the fuel system and carries pressurized fuel to the diaphragm. As the diaphragm becomes pressurized it expands, causing an indicator pointer to rotate. Figure 11.5.1.57 shows a pressure capsule type fuel pressure indicator.

Figure 11.5.1.57 – Pressure Capsule Fuel Pressure Gauge

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ENGINE RPM INDICATORS

These instruments indicate the rotational speed of the engine. Low Pressure Compressor (N1), Intermediate Pressure Compressor (N2) and High Pressure Compressor (N3). Figure 11.5.1.58 a RPM gauge for N1 measurement.

Figure 115.1.58 - N1 RPM Gauge

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The indicator use electromagnetic sensors (which contains a coil of wire that generates a magnetic field) to measure the RPM of the respective compressor blades. The sensor is mounted in the shroud around the fan so, when each fan blade passes the sensor, the magnetic field is interrupted. The frequency at which the fan blades cut across the field is measured by an electronic circuit and then transmitted to a RPM gauge in the cockpit. Figure 11.5.1.59 shows the operation of a N1 & N2 gauges.

Figure 11.5.1.59 – N1 & N2 Pressure Gauges Operation

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Engine Temperature Gauges

Because turbine engines can be severely damaged by high temperature in the turbine sections, a means of measuring the temperature is required. Because of the high temperatures involved, this is carried out using thermocouples.

There are a number of different terms and abbreviations used for the gas temperature in turbine engines, these are:

Turbine Inlet Temperature (TIT).

Inter Turbine Temperature (ITT).

Turbine Outlet Temperature (TOT).

Engine Gas Temperature (EGT).

Measured Gas Temperature (MGT).

Jet Pipe Temperature (JPT).

Figure 11.5.1.60 shows a typical EGT indicator

Figure 11.5.1.60 - EGT Indicator

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Each type of EGT system consists of several thermocouples spaced at intervals around the circumference of the engine exhaust section casing. The EGT indicator in the cockpit displays the average temperature measured by the individual thermocouples. Figure 11.5.1.61 shows EGT indicator operation.

Figure 11.5.1.61 – EGT Indicator Operation

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ENGINE PRESSURE INDICATORS

Engine pressure indicators provide indications of the thrust being produced by a turbojet or turbofan engine. Figure 11.5.1.62 shows an EPR indicator.

Figure 11.5.1.62 - EPR Indication System

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The EPR is the ratio of turbine discharge pressure to compressor inlet pressure. Pressure measurements are recorded by total pressure pickups, or EPR probes, installed in the engine inlet Pt2 section and at the exhaust Pt7 section. Once collected, the data is sent to a differential pressure transducer, which drives a cockpit EPR gauge. Figure 11.5.1.63 shows the operation of an EPR indicator.

Figure 11.5.1.63 – EPR Indicator Operation

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Figure 11.5.1.64 shows the engine instrument grouping for a twin engine aircraft.

Figure 11.5.1.64 - Power plant instrument grouping

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ELECTRONIC INSTRUMENTS (ENGINE & AIRFRAME SYSTEMS)

With the introduction of the "Glass Cockpits", most traditional gauges, instruments and warning lights have been replaced by fully electronic display systems. There are different types of display systems available, the two main ones being:

1. Engine Instrument and Crew Alerting System (EICAS).

2. Electronic Centralized Aircraft Monitoring (ECAM).

ENGINE INDICATING & CREW ALERTING SYSTEM (EICAS)

The basic system comprises two display units, a control panel and two computers supplied with analog and digital signals from the engine and system sensors. The computers are designated “Left” and “Right” and only one is in control of the system at any one time, the other is held in standby. In the event of a failure, it may be switched in either manually or automatically.

Operating in conjunction with the system are discrete caution and warning lights, standby engine indicators and a remotely-located panel for selecting maintenance data display. The system provides the flight crew with information on primary engine parameters (Full-time), with secondary engine parameters and advisory/caution/warning alert messages displayed as required.DISPLAY UNITS

These units provide a wide variety of information relevant to engine operation, and operation of other automated system. The operation of these displays is the same as those in the EFIS as previously described.

The upper unit displays primary engine parameters, i.e. N1 speed, EGT, and warning and caution messages. The lower unit displays secondary parameters, i.e. N2 speed, fuel flow, oil quantity, pressure and temperature. In addition, the status of non-engine systems e.g. flight control surface position, hydraulic system, APU, etc., can be displayed.

On the upper unit, a row of Vs will appear when secondary information is being displayed on the lower unit. Seven colours are produced by the CRTs for displaying information. Table 11.5.1.1 shows the colours and description of there uses.

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Colour DescriptionWhite All scales, normal operating range of pointers, digital readouts.Red Warning messages, maximum operating limit marks on scales,

and digital readouts.Green Thrust mode readout and selected EPR/N1 speed marks or

target cursors.Blue Testing of system only.

Yellow Caution and advisory messages, caution limit marks on scale, digital readouts

Magenta During in-flight engine starting, and for cross bleed messages.Cyan Names of all parameters being measured (e.g. N1, oil pressure,

TAT, etc.) and status marks or cues.

Table 11.5.1.1

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Figure 11.5.1.65 shows layout of the EICAS Displays.

Figure 11.5.1.65 - EICAS Primary and Secondary

Display Formats

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Figure 11.5.1.66 and 67 show display formats for primary and secondary displays.

Figure 11.5.1.66 – Primary EICAS Display

89



Figure 11.5.1.67 – Secondary EICAS Display

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DISPLAY MODES

EICAS is designed to categorize displays and alerts according to the functionand usage. For this purpose there are three modes of displaying information:

1. Operational (selected by the flight crew).

2. Status (selected by the flight crew).

3. Maintenance (ground use only and selected via the maintenance panel).

OPERATIONAL MODE

This mode displays the engine operating information and any alerts required to be actioned by the crew in flight. Normally only the upper display unit presents information: the lower one remains blank and can be selected to display secondary information as and when required.

STATUS MODE

When selected this mode displays data to determine the dispatch readiness of an aircraft, and is closely associated with details contained in the aircraft’s Minimum Equipment List. The display shows the positions of the flight control surfaces in the form of pointers registered against vertical scales, selected sub-system parameters, and equipment status messages on the lower display unit. Selection is normally done on the ground, either as part of the pre-flight checks of dispatch items, or prior to shutdown of electrical power to aid the flight crew in making entries in the aircraft’s Technical log. Figure 11.5.1.68 shows an example of a status page.

MAINTENANCE MODE

This mode provides maintenance engineers with information in five different display formats to aid them in fault finding and verification testing of major sub-systems.

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Figure 11.5.1.68 – EICAS Status Page

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DISPLAY SELECT PANEL

To control the operation of the EICAS, a control panel is situated on the center pedestal. Figure 11.5.1.69 shows a typical EICAS control panel.

Figure 11.5.1.69 - EICAS Control Panel

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DISPLAY SELECT PANEL OPERATION

Engine Display Switch: This is a push type switch for removing or presenting the display of secondary information on the, lower display. Status Display Switch: This is a push type switch for removing or presenting the status page on the lower display.

Event Record Switch: Normally, there is an auto event function, this will automatically record any malfunctions as they occur. The push switch enables manual event marking so that the crew can record a suspect malfunction for storage in a non-volatile memory. This data can be retrieved from the memory and displayed by ground engineers by operating the ground maintenance panel. This manual switch can also be used for activating the recording of fault data, either in the air or on the ground, on the Environmental Control system, Electrical Power system, Hydraulic system and APU.

Computer Select Switch: In the “AUTO” position it selects the left or primary computer and automatically switches to the other in the event of a failure. The other positions are for manually selecting either the right or left computers.

Display Brightness: Controlled by the inner knob for the display intensity, the outer for display brightness.

Thrust Reference SetSwitch: Pulling and rotating the inner knob positions the reference cursor on the thrust indicator display (either EPR or N1) for

the engines, which are selected by the outer knob.

Max Indicator Reset: If any of the measured parameters e.g. Oil Pressure, EGT etc. and if they exceed normal operating limits, this will be automatically alerted on the display units. The purpose of the reset button is to clear the alerts from the display when the excess limits no longer exist.

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ALERT MESSAGES

The system will continually monitor a large number of inputs (400+) from engine and airframe systems. If a malfunction is detected then the appropriate alert message is annunciated on the upper display. Up to 11 messages can be displayed and are at the following levels:

LEVEL A - Warning: Requiring immediate corrective action and are displayed in “RED”. Master warning lights are also activated and aural warnings from the Central Warning System are given.

LEVEL B - Caution: Requiring immediate crew awareness and possible action. They are displayed in “AMBER”. An aural tone is also repeated twice.

LEVEL C - Advisory: Requiring crew awareness, displayed in “AMBER”. There are no caution lights or aural tones associated with this level.

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Figure 11.5.1.70 shows a display with the three different types of alert messages Displayed.

Figure 11.5.1.70 - Upper EICAS Display – Alert Messages

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MAINTENANCE CONTROL PANEL

This panel is used by maintenance engineers for the purpose of displaying maintenance data stored within the system’s computer memories. Figure 11.5.1.71 shows a typical maintenance control panel.

Figure 11.5.1.71 - Maintenance Control Panel

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ELECTRONIC CENTRALIZED AIRCRAFT MONITORING (ECAM)

ECAM differs from EICAS in that the data displayed relate essentially to the primary systems of the aircraft and are displayed in checklist and pictorial or synoptic format.

DISPLAY UNITS

These can be mounted either side-by-side or top/bottom. The left-hand/top unit is dedicated to information on the status of the system; warnings and corrective action in a sequenced checklist format, while the right-hand/bottom unit is dedicated to associated information in pictorial or synoptic format. Figure 11.5.1.72 shows the layout of ECAM displays.

Figure 11.5.1.72 – ECAM Display Layout

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ECAM DISPLAY MODES

There are four display modes, three of which are automatically selected and referred to as phase-related, advisory (mode and status), and failure-related modes. The forth mode is manual and permits the selection of diagrams related to any one of 12 of the aircraft’s systems for routine checking, and also the selection of status messages provided no warnings have been triggered for display. Selection of the displays is by means of a system control panel. See Figure 11.5.1.80.

FLIGHT PHASE RELATED MODE

In normal operation the automatic flight phase-related mode is used, and the displays will be appropriate to the current phase of aircraft operation, i.e. Pre-flight, Take-off, Climb, Cruise, Decent, Approach, and post landing. Figure 11.5.1.73 shows display modes. The upper display shows the display for pre-take off, the lower is that displayed for the cruise.

Figure 11.5.1.73 – ECAM Upper and Lower Display (Cruise Mode)

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ADVISORY MODE

This mode provides the flight crew with a summary of the aircraft’s condition following a failure and the possible downgrading of systems. Figure 11.5.1.74 shows an advisory message following a Blue Hydraulic failure.

Figure 11.5.1.74 – ECAM Advisory Mode

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ECAM FAILURE MODE

The failure-related mode takes precedence over the other modes. Failures are classified in 3 levels

LEVEL 3: WARNING

This corresponds to an emergency configuration. This requires the flight crew to carry out corrective action immediately. This warning has an associated aural warning (fire bell type) and a visual warning (Master Warning), on the glare shield panel.

LEVEL 2: CAUTION

This corresponds to an abnormal configuration of the aircraft, where the flight crew must be made aware of the caution immediately but does not require immediate corrective action. This gives the flight crew the decision on when action should be carried. These cautions are associated to an aural caution (single chime) and a steady (Master Caution), on the glare shield panel.

LEVEL 1: ADVISORY

This gives the flight crew information on aircraft configuration that requires the monitoring, mainly failures leading to a loss of redundancy or degradation of a system, e.g. Loss of 1 FUEL TANK PUMP LH or RH but not both.

The advisory mode will not trigger any aural warning or attention getters but a message appears on the primary ECAM display.

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Figure 11.5.1.75 – 11.5.1.79 shows the 12-system pages and status page available.

Figure 11.5.1.75 - ECAM System Displays

Note; These pages are displayed:Automatically due to an advisory or failure related to the system.Whenever called manually.

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Note; These pages are displayed:Automatically due to an advisory or failure related to the system.Whenever called manually.

103




Note; These pages are displayed:

Automatically due to an advisory or failure related to the system.Whenever called manually.

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The Gear/Wheel page is displayed at the related flight phase.

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Related flight phase.

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CONTROL PANEL

The layout of the control panel is shown in Figure 11.5.1.80.

Figure 11.5.1.80 - ECAM Control Panel

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ECAM CONTROL PANEL

SGU Selector Switches: Controls the respective symbol generator units. Lights are off in normal operation of the system. The “FAULT” caption is illuminated amber if the SGU’s internal self-test circuit detects a failure. Releasing the switch isolates the corresponding SGU and causes the “FAULT” caption to extinguish, and the “OFF” caption to illuminate white.

System Synoptic Display Switches: Permit individual selection of synoptic diagrams corresponding to each of the 12 systems, and illuminate white when pressed. A display is automatically cancelled whenever a warning or advisory occurs.

CLR Switch: Light illuminates white whenever a warning or status message is displayed on the left-hand display unit. Press to clear messages.

STS Switch: Permits manual selection of an aircraft’s status message if no warning is displayed. Illuminates white when pressed also illuminates the CLR switch. Status messages are suppressed if a warning occurs or if the CLR switch is pressed.

RCL Switch: Enables previously cleared warning messages to be recalled provided the failure conditions which initiated the warnings still exists. Pressing this switch also illuminates the CLR switch. If a failure no longer exists the message “NO WARNING PRESENT” is displayed on the left-hand display

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car 66 b1 lic module 11.5.1 instrument system (ata 31)

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