Free CAAS SAR-66 M05 Digital Techniques / Electronic Instrument Systems (Category B2) Practice Questions

Sample Practice Questions

Try these 10 sample questions from the CAAS SAR-66 M05 Digital Techniques / Electronic Instrument Systems (Category B2) practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1In a conventional EFIS installation, which pair of presentations replaces the attitude indicator and directional gyro?

   1. A.EADI and EHSICorrect answer: A
   2. B.ECAM and EICAS
   3. C.FMS and ACARS
   4. D.TCAS and GPS

   Explanation: The FAA handbook states, "The attitude indicator and directional gyro are replaced by cathode ray tubes (CRT) used to display EADI and EHSI presentations." The two EFIS presentations replace attitude and heading instruments; the other pairs name monitoring, management or navigation systems.

   Reference: FAA Aviation Maintenance Technician Handbook—Airframe, Volume2 — Aircraft Instrument Systems, Electronic Flight Instrument System (EFIS), opening paragraph

2. 2What distinguishes an analogue representation from a digital representation of a measured quantity?

   1. A.Analogue varies continuously; digital uses discrete valuesCorrect answer: A
   2. B.Analogue uses discrete values; digital varies continuously
   3. C.Both are continuous, but digital changes only its units
   4. D.Both are discrete, but analogue has a longer word length

   Explanation: The handbook states, "Analog representations are continuous." It also states, "A digital electronic representation of a real-world event is discontinuous." Analogue varies continuously whereas digital uses discrete increments. Reversing the relation is incorrect; changing units does not define digital data, and word length does not define analogue representation.

   Reference: FAA Aviation Maintenance Technician Handbook—Airframe, Volume2 — Communication and Navigation, Analog Versus Digital Electronics

3. 3Why can a digital data bus reduce instrument-system wiring weight?

   1. A.It shares message-carrying wires among digitally encoded signalsCorrect answer: A
   2. B.It assigns a permanent independent wire to each instrument value
   3. C.It combines all readings into one unencoded analogue voltage
   4. D.It requires a separate parallel wire for each transmitted bit

   Explanation: The source states, "these are wires that share message carrying for many instruments by digitally encoding the signal for each.". The data bus shares an encoded communications path. Dedicated wires, an unencoded analogue sum and separate parallel bit lines do not describe this sharing.

   Reference: FAA Aviation Maintenance Technician Handbook—Airframe, Volume2 — Chapter10, Classification of Instruments

4. 4Which memory is used as working read/write storage that can be overwritten when its data is no longer needed?

   1. A.ROM
   2. B.PROM
   3. C.RAMCorrect answer: C
   4. D.EPROM

   Explanation: The Navy handbook states, "In the computer, RAM is the working memory." RAM supports routine read/write use. ROM and PROM retain fixed programming; EPROM requires a separate erase/program operation.

   Reference: US Navy NEETS Module22—Introduction to Digital Computers — Chapter2, Random-Access Memory

5. 5Which description defines the function and construction of a microprocessor?

   1. A.A memory chip providing read-only program storage
   2. B.A semiconductor chip implementing the central processing unitCorrect answer: B
   3. C.An interface chip transferring data to peripheral devices
   4. D.A logic chip implementing a single basic gate

   Explanation: The source states, "MICROPROCESSOR—The semiconductor central processing unit (cpu) of a microcomputer that fits on a small silicon chip.". The microprocessor implements the CPU. A memory, interface device and single gate chip perform narrower or different functions.

   Reference: US Navy NEETS Module22—Introduction to Digital Computers — Glossary, Microprocessor

6. 6What is the normal signal-routing function of an eight-input, one-output multiplexer?

   1. A.Route one input to one of eight selectable outputs
   2. B.Select one of eight input sources for the outputCorrect answer: B
   3. C.Encode eight simultaneous inputs into three output bits
   4. D.Store eight samples and average them into one result

   Explanation: The datasheet identifies "one of eight data sources". A multiplexer selects a source, unlike a demultiplexer, encoder or averaging memory.

   Reference: Texas Instruments SNx4HC151 Data Selectors/Multiplexers — 7.1 Overview

7. 7How is information carried through a fibre-optic link?

   1. A.As modulated light detected at the receiving endCorrect answer: A
   2. B.As a signal current conducted through the glass core
   3. C.As an electrical resistance change along the cladding
   4. D.As a variable electrical potential on the protective coating

   Explanation: The source states, "Digital or analog signals are transmitted by modulating an opto-electronic source". The link modulates and detects light. The alternative descriptions incorrectly make the optical core, cladding or coating an electrical signal-transmission element.

   Reference: FAA Airport Fiber Optic Design Guidelines — Chapter2, paragraph20

8. 8Which situation illustrates the latent failure mode of ESD damage?

   1. A.A device passes initial checks but hidden damage shortens its lifeCorrect answer: A
   2. B.A device stops operating immediately after a discharge
   3. C.A device already operates outside a specified performance limit
   4. D.A device fails immediately because its supply polarity is reversed

   Explanation: The source states, "A latent failure occurs when a device has been damaged so slightly that it does not fail but performs within its parametric tolerance limits.". Latent damage initially remains within functional tolerances. Immediate loss after ESD is catastrophic; already out-of-tolerance performance is parametric; reversed-polarity damage is a different cause.

   Reference: NASA Workmanship Manual for Electrostatic Discharge Control — 5.2, ESD damage failure modes, latent failure

9. 9Why is installing the newest available LRU software not, by itself, enough to establish the correct aircraft software configuration?

   1. A.The approved revision can differ with aircraft modification statusCorrect answer: A
   2. B.The LRU label alone establishes the aircraft's approved configuration
   3. C.The highest revision number automatically establishes applicability
   4. D.The file's download date alone establishes installation suitability

   Explanation: The source states, "The approved software configuration may vary from aircraft to aircraft due to system modification levels and operating environment.". Approved configurations are aircraft-specific. A component label, highest revision number or download date alone does not establish applicability.

   Reference: FAA Software Management During Aircraft Maintenance — 8.2.5 Configuration Control

10. 10What does an EICAS principally monitor and present to the crew?

    1. A.Heading and navigation-course deviation
    2. B.Present position based on satellite ranging
    3. C.Engine and airframe parameters with crew alertsCorrect answer: C
    4. D.Selected routes from stored flight plans

    Explanation: The FAA handbook states, "All EICAS display engine, as well as airframe, parameters." EICAS combines engine/airframe monitoring and alerting. Heading, satellite position and stored flight plans are different primary functions.

    Reference: FAA Aviation Maintenance Technician Handbook—Airframe, Volume2 — Aircraft Instrument Systems, Engine Indicating and Crew Alerting System (EICAS)