Aircraft Electronic Instruments

Aircraft Electronic

Instruments

Brief description of aircraft instrument categories and their history. Overview of analogue and digital signals and their usage in aviation industry.

Site: e-Õppe Arenduskeskuse Moodle (ver 1.9.9+)Course: Aircraft Digital Electronics and Instrument Systems Book: Aircraft Electronic InstrumentsPrinted by: Jaanus JakimenkoDate: Monday, 20 December 2010, 11:13 AM

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20.12.2010https://moodle.e-ope.ee/mod/book/print.php?id=126733

Table of Contents

Introduction

ICAO rules for instrumentation

Flight and Navigation Instruments

Engine Instruments

Basic principles

Glass cockpit EFIS - PFD EFIS - ND Control Panel

EFIS VIDEO

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Introduction

Aircraft intruments may be categorised by their use as:

1. Flight progress monitoring instruments

2. Aids for aircraft position/location monitoring

3. Instruments to monitor functions of all the aircraft parts and systems .

Commercial passenger aircraft require at least a two pilot crew, some require flight engineer to monitor and control all the air craft systems from information placed on separate panels.

Pilots need to monitor, process different signals and indications . This can o nl y be achieved safely when all aircraft instrument layouts conform to internationally agr ee d standards.

To fullfill needed safety requirements standards are laid down by the International Civil Aviation Organisation (ICAO) and set the minimum requirements for aircraft certification.

These standards do not replace the national regulations of countries, but are the minimum for international recognition.

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ICAO rules for instrumentation

ICAO rules for instruments require following conditions:

1. All instruments must be mounted so they can be easily read by the appropriate flight crewmember

2. Instrument lighting must be sufficient to provide adequate lighting during darkness and adverse conditions and any installed lighting must not shine directly at the flight crew or reflect in an obtrusive manner

3. Flight, navigation and engine instruments must be mounted so they are always plainly visible to the flight crew

4. Instruments should also be mounted so there is a natural movement of the flight crew's vision from the instrument panels to the outside of the aircraft, along its flight path

5. All main flight instruments must be grouped on the instrument panel so they may be readily seen by the appropriate flight crewmember and must also be mounted in a standard format

6. All engine instruments must be grouped on instrument panels so they may be readily seen by the appropriate flight crewmember

7. In a multi-engined aircraft, the identical engine instruments must be mounted so not to confuse the engine to which they relate. For example, on a four-engine aircraft that numbers the engines from one to four (1-4), left to right, the englne instruments must be mounted in the panel in the same way.

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Flight and Navigation Instruments

Most common aircraft instruments are:

1. Altimeter - displays pressure altitude.

2. Airspeed Indicatosr (ASI) - displays aircraft movement speed against surrounding air mass

3. Vertical Speed Indicator (VSI) -displays descent or climb rate Ft/min.

4. Attitude Indicator - artifical horizon which shows aircraft attitude related to earth surfice.

5. Rate of Turn Indicator - Displays how fast the aircraft is turning.

6. Gyroscopic Dir ection In dicat or - Shows aircraft direction usually related to magnetic north which is set as reference during flight preparation.

7. Magnetic Compass - Shows aircraft magnetig heading related to earth magnetic north.

8. Outside Air Temperature Indic ator (OAT) - Shows outside temperature in C or F degrees.

9. Clock - Shows time and allows different time measurements.

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Engine Instruments

Most common Engine Instruments are:

1. Tachometer to measure the rotation speed of a crankshaft or compressor shaft (N1 or N2)

2. Cylinder Head Temperature Indicator to indicate the temperature of the hottest cylinder

3. Carburettor-intake air temperature indicator for piston engine only

4. Oil temperature indicator

5. Turbine exhaust gas temperature indicator

6. Fuel pressure indicator with an additional warning to indicate when the pressure is low

7. Oil pressure indicator

8. Manifold pressure indicator for piston engined only

9. Fuel quantity indicator

10. Fuel fl ow indicator

11. Thrust indicator for turbojet engines

12 . Torque indicator for a turbo propeller engine

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Basic principles

Since the first days of aviation pilots needed basic instruments for monitoring most

important parameters during flight. These parameters are:

1) Airspeed

2) Attitude

3) Altitude

4) Heading

Instruments to show this information are always arranged in same way and this

arrangement is called "Basic T"

Early instruments were designed very simple and reliable. Later when flying became

more popular and commercial there raised higher need for instrumentation because of

safety and navigation requirements.

If we describe instruments by looking at the technology we can divide them:

1. Analogue mechanical and pneumatic instruments like this simple altimeter

2. Analogue electrical or electromechanical instruments have two subcategories:

a) direct reading instruments

b) remote instruments

Remote instruments have sensor part located in suitable place at the aircraft fuselage.

Sensor is connected with cockpit indicator in series with amplifier. These instruments are

more accurate then mechanical instruments but require precise calibration and

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adjustment.

For example the remote compass system has instrument, sensor, amplifier and control

panel.

3. Digital remote instruments are the newest generation of instruments. These

instruments have following parts:

a) Analogue or digital sensors

b) Digital computer

c) Display system and control panel in cockpit

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Glass cockpit

Modern digital instruments have usually CRT or LCD displays which are used display most important flight, navigation and system parameters.

When we compare this glass cockpit with older type electromechanical instrument system we can see many benefits.

1. Information is much easily readable for pilots.

2. Instruments are software based and image can be transfered from one display pane to another during flight.

3. Maintenance is cheaper because of one display type and less calibration.

When design organisations looked these advantages they created following instruments and systems:

EFIS - Electronic Flight Instrument Systems

ECAM/EICAS - Electronic Centralised Aircraft Monitoring

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EFIS - PFD

EFIS - means Electronic Filght Infromation System.

In EFIS system there are following main components:

PFD - Primary Flight Display

ND - Navigation Display

CP - Control Panel for source and mode selecting functions

Primary Flight Display shows to pilots all the information which was eraslier available through Basic T intruments.

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EFIS - ND

EFIS Navigation Display shows to pilots navigation information. Following sources and options are usually available:

a) VOR

b) ILS

c) ADF

d) Weather radar infromation

e) Flight plan and track through FMS

Basic Infromation which is always present:

a) Heading

b) True Air Speed (TAS)

c) Ground Speed (GS)

d) Aircraft Symbol as reference

e) Next waypoint

d) Wind direction and speed

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Control Panel

Control Panel allows to adjust settings and functions for ND and for PFD:

PFD barometric pressure can be set as pressure or standard pressure (STD, 1013 hPa)

For ND pilot can select different navigation sources with rotaty source knobs and range for navigation display image. With pushbuttons pilot can select additional functions.

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EFIS VIDEO

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Aircraft Electronic Instruments

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