AET Instrument Systems 2 — Questions and Answers
Question 1: What type of gyroscope is used in modern Inertial Reference Systems instead of mechanical gyros?
- Mechanical spinning gyro
- Ring Laser Gyro (RLG) or Fiber Optic Gyro (FOG) (Correct answer)
- Vibrating beam gyro
- Pneumatic gyro
Correct answer: Ring Laser Gyro (RLG) or Fiber Optic Gyro (FOG)
Modern IRS units use Ring Laser Gyros (RLGs) or Fiber Optic Gyros (FOGs), which have no moving parts and measure rotation via the Sagnac effect.
Question 2: What does EICAS stand for and what is its primary function?
- Electronic Instrument Control and Alert System
- Engine Indication and Crew Alerting System (Correct answer)
- Electronic Integrated CAS
- Engine Instrument and Checklist Advisory System
Correct answer: Engine Indication and Crew Alerting System
EICAS (Engine Indication and Crew Alerting System) displays engine parameters and generates crew alert messages for abnormal aircraft system conditions.
Question 3: What is the function of a Flux Valve (flux detector) in an aircraft compass system?
- Generate aircraft heading from engine data
- Sense the direction of the Earth's magnetic field to provide a slaved magnetic heading (Correct answer)
- Measure atmospheric pressure
- Detect lightning strikes
Correct answer: Sense the direction of the Earth's magnetic field to provide a slaved magnetic heading
A flux valve (also called a flux gate) detects the horizontal component of the Earth's magnetic field to provide an accurate magnetic heading signal to the heading indicator or AHRS.
Question 4: What does AHRS stand for and what sensors does it use?
- Altitude and Heading Reference System — altimeters only
- Attitude and Heading Reference System — gyros, accelerometers, and magnetometers (Correct answer)
- Aircraft Horizontal Reference System — GPS only
- Avionics Hub Relay System — databus
Correct answer: Attitude and Heading Reference System — gyros, accelerometers, and magnetometers
AHRS (Attitude and Heading Reference System) uses solid-state gyroscopes, accelerometers, and magnetometers to compute aircraft attitude and magnetic heading.
Question 5: What causes a static port blockage to affect aircraft instruments?
- Affects only the fuel gauge
- Freezes airspeed, altimeter, and VSI at the values present when blockage occurred (Correct answer)
- Causes engine instruments to fail
- Disables the autopilot only
Correct answer: Freezes airspeed, altimeter, and VSI at the values present when blockage occurred
A blocked static port traps static pressure at the level when blocked, causing the altimeter, airspeed indicator, and VSI to freeze or show erroneous values.
Question 6: Which component converts a synchro signal to a DC voltage for use in digital avionics?
- Flux valve
- Synchro-to-digital converter (SDC) (Correct answer)
- Resolver
- Comparator circuit
Correct answer: Synchro-to-digital converter (SDC)
A Synchro-to-Digital Converter (SDC) translates the three-wire AC synchro signal from angular position sensors into a digital word for avionics computers.
AET Instrument Systems 2
What type of gyroscope is used in modern Inertial Reference Systems instead of mechanical gyros?