Electronic Displays in Aviation

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Questions and Answers

What is the primary purpose of an LED in an aircraft?

To provide power to the aircraft's systems

To indicate on/off conditions on panels (correct)

To control the aircraft's temperature

To detect infrared radiation

What is the typical operating voltage of an LED?

1.6 V forward bias (correct)

1.6 V reverse bias

10 V forward bias

20 V reverse bias

What is the function of the arrows in the standard diode symbol for an LED?

Indicate the polarity of the LED

Indicate the operating voltage of the LED

Indicate the direction of current flow

Indicate the direction of light emission (correct)

What is the expected life expectancy of an LED?

Over 100 000 hours of operation Signup and view all the answers

What is the purpose of the flat spot on the red plastic base of an LED?

To indicate the cathode connection Signup and view all the answers

What will happen if an LED is connected to a power supply rated at over 2 V?

The LED will be damaged Signup and view all the answers

What is the typical current required by an LED?

About 10 mA Signup and view all the answers

What type of light can be emitted by an LED?

Visible light, including red, orange, yellow, green, blue, and white, as well as ultraviolet and infrared light Signup and view all the answers

What happens when the second polarizer blocks the passage of light in an LCD?

The segment of the panel appears black. Signup and view all the answers

What is the primary difference between a backlit LCD and a normal-type LCD?

The use of backlighting in the LCD. Signup and view all the answers

What is the function of the white diffusion panel in a backlit LCD?

To redirect and scatter the light evenly. Signup and view all the answers

How many levels of brightness can most modern LCDs display per pixel?

256 levels. Signup and view all the answers

What is required to create a colour pixel in an LCD?

Three sub-pixels with red, green, and blue colour filters. Signup and view all the answers

What determines the intensity of each sub-pixel in a colour LCD?

The voltage applied to the sub-pixel. Signup and view all the answers

What is the result of varying the voltage applied to an LCD segment?

The segment displays a range of brightness levels. Signup and view all the answers

What is the purpose of controlling the voltage applied to an LCD segment?

To create a greyscale display. Signup and view all the answers

What allows the receiving end to perceive an image as a large number of simultaneously produced areas of illumination?

Persistence of vision Signup and view all the answers

What is the method of transmitting photocell signals in rapid succession called?

Sequential scanning Signup and view all the answers

How are the connections to the scanning switch arranged?

Top line first from left to right, then down to the second line from left to right, and so on Signup and view all the answers

What is the function of the common amplifier in the transmitter?

To amplify the signal from each photocell Signup and view all the answers

What is the purpose of the scanning switch in the transmitter?

To pick up signals from individual photocells in sequence Signup and view all the answers

How many photocells are in the transmitter, and how are they arranged?

25 photocells, arranged in a geometric pattern Signup and view all the answers

What is the function of the switch in the receiver?

To connect to the bank of lamps Signup and view all the answers

What happens when the scanning switch reaches photocell 25 in the bottom right corner?

It flies back very rapidly to number 1 and begins the cycle all over again Signup and view all the answers

What happens to the electron beam during the flyback periods?

It is suppressed altogether and produces no trace Signup and view all the answers

What is the movement of the spot or electron beam on a TV screen similar to?

The movement of the eye in reading a printed page Signup and view all the answers

How many sets of line scans per second are notionally performed?

50 sets Signup and view all the answers

What is the effect of varying the CRT modulator grid voltage?

It varies the brightness of the raster Signup and view all the answers

What is the purpose of scanning the screen at no less than 50 times per second?

To avoid flicker of the image Signup and view all the answers

What is the normal state of the raster?

It produces only a series of parallel lines of light Signup and view all the answers

What is the brightest level of the raster called?

Peak White Signup and view all the answers

What is the darkest level of the raster called?

Black Signup and view all the answers

What is the main benefit of interlacing in display systems?

Reducing the flicker in the picture without increasing bandwidth Signup and view all the answers

What controls the picture painted on the screen in an aircraft CRT?

Symbol generators Signup and view all the answers

What is the typical refresh rate of the picture on an aircraft CRT?

50 times a second Signup and view all the answers

What type of displays are used in modern aircraft display systems?

CRTs, LED, or LCD displays Signup and view all the answers

How many main types of electronic instruments make up a full glass cockpit?

Four Signup and view all the answers

What is the purpose of adjusting the brightness of electronic displays and instrument panel lighting?

To prolong life Signup and view all the answers

What is an EADIs?

Electronic Attitude Director Indicators Signup and view all the answers

What is an example of an electronic instrument that provides real-time data to the pilot?

All of the above Signup and view all the answers

Study Notes

Light Emitting Diodes (LEDs) in Aircraft

LEDs are optoelectronic devices used to replace incandescent light bulbs in aircraft.
When forward biased, LEDs produce visible light in various colors (red, orange, yellow, green, blue, white, or ultraviolet) depending on the material used.
LEDs emitting non-visible light in the infrared spectrum are used in detection applications with infrared detector components.
LEDs operate at a low voltage (about 1.6V forward bias) and low current (about 10mA).
LEDs have a long lifespan, exceeding 100,000 hours of operation.
To turn on an LED, the anode and cathode connections must be correctly identified, with the flat spot on the base indicating the cathode connection.

Liquid Crystal Displays (LCDs) in Aircraft

Backlit LCDs function similarly to normal LCDs, but use backlighting to improve visibility.
Backlighting is typically achieved using fluorescent tubes above, beside, or behind the LCD.
A white diffusion panel redirects and scatters the light to ensure a uniform display.
Controlling the voltage applied to an LCD segment in small increments allows for varying light levels, creating greyscale displays (typically 256 levels of brightness per pixel).
Colour LCDs use three sub-pixels with red, green, and blue colour filters to create each colour pixel, with each sub-pixel able to vary in intensity over 256 shades.

Cathode Ray Tubes (CRTs) in Aircraft

CRTs use symbol generators to control the picture painted on the screen, firing electron beams at the appropriate coordinates to paint single-colour pictures.
CRTs are refreshed about 50 times a second.
Aircraft may use one or multiple CRTs, and modern systems may alternatively use LED- or LCD-type displays.

Electronic Instrument Displays in Aircraft

Electronic instrument displays come in four main types: Electronic Attitude Director Indicators (EADIs), Electronic Horizontal Situation Indicators (EHSIs), Engine Indicating and Crew Alerting System (EICAS) or Electronic Centralised Aircraft Monitoring system (ECAM), and Head-Up Display (HUD) or Head-Up Guidance System (HGS).
Electronic displays and instrument panel lighting should be turned down from full brightness whenever possible to prolong life.

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Description

This quiz covers the principles of operation of cathode ray tubes, light emitting diodes, and liquid crystal displays used in modern aircraft. Test your knowledge of electronic instrument systems in aviation.