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E232 – AIRCRAFT INSTRUMENT SYSTEMS
Worksheet for Problem 01: Inside the Cockpit
Aircraft instruments play a critical role during flight. While it is possible to drive a car without any instrumentation, aircraft instruments have been an indispensable part of aircraft since the beginning of flight.
What is the main role of aircraft instruments?
It provide the pilot wih information about the flight situation of that aircraft, such as altitude,airspeed and direction.
Suggest possible reasons why the aircraft cockpit has become progressively more complicated over time.
It was necessary to create some order out of chos, to decide which instruments should have prominence and to achieve some standardisation.
Most instrument systems (including aircraft instruments) comprise four main elements: detecting, measuring, coupling and indicating as shown below.
Explain the function of the each element and how they are related to one another.
An instrument example is the clinical thermometer as shown in Figure Q2a. The 4 elements within the clinical thermometer are:
Detecting element: Bulb detects the temperature
Measuring element: Mercury volume varies according to temperature
Coupling element: Bore amplifies the mercury volume
Indicating element: Glass tube with temperature scale
Figure Q2a. Clinical thermometer
Figure Q2b below shows the schematic of a simple aircraft altimeter. Identify the 4 elements within the altimeter.
Figure Q2b. Altimeter Cut-away
Identify the various aircraft instruments shown in the cockpit of a Cessna 172 aircraft in Figure Q3a below. You may refer to the following videos for an overview of the Cessna 172 cockpit instruments:
Figure Q3a. Cessna 172 Cockpit
One of the ways to classify aircraft instruments is according to the functions that they perform. Based on your knowledge of the various instruments, classify them according to 4 categories as shown in the table below.
Oil pressure indicator
Hydraulic pressure indicator
Cockpit layout generally refers to the arrangement and positioning of the various flying instruments within the cockpit. There are two main types of cockpit layouts: the Basic Six and the Basic T.
Compare and contrast between the Basic Six and Basic T cockpit arrangements.
What is the most common cockpit layout in aircraft today? Provide possible reasons why this layout is so widely used in all different types of aircraft.
In a modern aircraft, it is common to have the following 3 types of instrument displays: analogue dials, multi-functional colour display (MFCD) and LED seven segment display. Referring to the Cessna 172 cockpit in Figure Q3a, identify the 3 types of instrument displays and compare the advantages and disadvantages.
With the introduction of digital signal processing technology into avionics, modern cockpits like the A350 XWB and B787 use various electronic displays to better present the information to pilots.
Find out about the basic principles and typical applications of the following display technologies:
Cathode Ray Tube (CRT)
Active Matrix Liquid Crystal Display (AMLCD)
Light Emitting Diode (LED)
Active Matrix Liquid Crystal Displays (AMLCDs) are gradually replacing the CRT displays in the glass cockpit. Compare the advantages and disadvantages between AMLCD and CRT displays.
Electronic Flight Instrument System (EFIS) replaces conventional, mechanical aircraft instruments with computer-generated, color, digital, electronic displays. EFIS presents aircraft attitude, navigation, weather data and flight data to the flight crew.
It consists of two main displays (Attitude Director Indicator and Horizontal Situation Indicator), a control panel, a symbol generator and a light sensor. Figure Q8a shows in the schematic of a complete (pilot and co-pilot) EFIS in an aircraft.
Figure Q8a. Electronic Flight Instrument System (EFIS)
Explain the function of the 3 symbol generators as shown in Figure Q8a. What is the rationale for using 3 symbol generators compared to only one?
Explain the effect on the whole system when there is a failure of
one of the display units
one of the symbol generators
Light sensors are integrated within EFIS to detect the flight deck ambient light conditions.
Explain the purpose of these light sensors
Briefly discuss the working principle of these light sensors (Figure Q8b)
Figure Q8b. Photo-diode light sensors
The display of symbols, failure annunciators, and messages can come in 6 different colors in EFIS. Write down the uses and significance for each colour scheme
Yellow / Amber
Refer to the cockpits of the passenger airplanes: Airbus A350 XWB and Boeing B737NG in Figure Q9a and Figure Q9b.
Figure Q9a. A350 XWB Cockpit
Figure Q9b. B737NG Cockpit
Refer to the A350 XWB cockpit in Figure Q9a. Are you able to identify the names and functions of the instruments / displays highlighted in yellow? You may refer to the following link:
Refer to the B737NG cockpit in Figure Q9b. Identify the names and functions of the instruments / displays highlighted in yellow.
Distinguish between the functions of the PFD, ND, ECAM and EICAS.
One of the most critical instruments display for pilots is the Primary Flight Display (PFD) as shown in Figure Q9c. Can you interpret what the PFD is telling the pilots? Check out the following video:
Figure Q9c. Airbus Primary Flight Display (PFD)
Does the PFD follow a Basic 6 or Basic T layout? Justify your answer.
In the aviation environment, the instruments are subject to changes in atmospheric conditions, G forces and vibrations. To function properly, the instruments would need to be designed and built to very specific requirements. What are some of the design considerations that are important to aircraft instruments?
To identify cockpit layouts
To familarize with various aircraft instruments
To understand the controls and settings of A320 EFIS Control Panel
To understand the color scheme of display information
Proceed to the AS-76 Cockpit Instrument Trainer and familiarise with the displays of various instruments. Is it a Basic-T or Basic 6 layout? Identify all the instruments and state their respective functions (see Figure L1a below).
Figure L1a. AS-76 Instruments Panel
Refer to the Boeing 737NG cockpit as shown in the problem statement and the A320 cockpit in the Flight Simulator Lab (or refer to Figure L2a). Differentiate between the Boeing 737 NG cockpit and A320 cockpit.
Figure L2a. A320 Cockpit
The A320 has 5 display modes. Select the different ND display modes using the ND mode selector switch on the EFIS Control Panel as shown in Figure L3a. Record your observations for each display mode.
Figure L3a. A320 EFIS Control Panel
The symbols, readouts, annunications, and messages are displayed in PFDs, NDs and Electronic Centralised Aircraft Monitor (ECAM) in different colors. Record and describe your observations of each color.
Page 6 of 12stal Displays (AMLCDs) are gradually replacing the CRT displays in the glass cockpit. Compare the advantages and disadvantages between AMLCD and CRT displays.
Explain the function of the 3 sy