AET Navigation Equipment 3 — Questions and Answers
Question 1: What is the primary function of a Distance Measuring Equipment (DME) system?
- Measures magnetic bearing to a station
- Measures slant range distance to a ground transponder (Correct answer)
- Provides vertical guidance during approach
- Measures groundspeed using Doppler shift
Correct answer: Measures slant range distance to a ground transponder
DME measures slant range (line-of-sight distance) between the aircraft and a ground transponder by timing interrogation/reply pulse pairs.
Question 2: In an Inertial Navigation System (INS), what component detects rotational motion?
- Accelerometer
- Gyroscope (Correct answer)
- Magnetometer
- Barometric altimeter
Correct answer: Gyroscope
Gyroscopes detect rotational motion (attitude changes) while accelerometers measure linear acceleration in an INS.
Question 3: A VOR receiver measures the phase difference between which two signals?
- AM reference and FM variable signals
- 30 Hz reference and 30 Hz variable signals (Correct answer)
- 9960 Hz subcarrier and 30 Hz variable signals
- UHF pulse and VHF carrier signals
Correct answer: 30 Hz reference and 30 Hz variable signals
VOR bearing is determined by comparing the phase of the 30 Hz omnidirectional reference signal against the 30 Hz variable phase signal.
Question 4: What does a RAIM (Receiver Autonomous Integrity Monitoring) function do in a GPS receiver?
- Amplifies weak satellite signals
- Detects faulty satellite data using redundant satellites (Correct answer)
- Switches to INS when GPS is unavailable
- Corrects for ionospheric delay errors
Correct answer: Detects faulty satellite data using redundant satellites
RAIM uses extra visible satellites beyond the minimum required to self-check GPS integrity and alert crew if a satellite is providing erroneous data.
Question 5: Which frequency band does a typical radio altimeter operate in?
- VHF (108–118 MHz)
- UHF (329–335 MHz)
- C-band (4.2–4.4 GHz) (Correct answer)
- Ka-band (35 GHz)
Correct answer: C-band (4.2–4.4 GHz)
Radio altimeters operate in the C-band at 4.2–4.4 GHz, transmitting FM continuous-wave signals toward the ground to measure altitude above terrain.
Question 6: What is the maximum theoretical range error caused by Selective Availability (SA) in GPS before it was disabled?
- ±5 meters
- ±15 meters
- ±100 meters (Correct answer)
- ±500 meters
Correct answer: ±100 meters
Selective Availability intentionally degraded civilian GPS accuracy to approximately ±100 meters (95%) until it was disabled by presidential order in May 2000.
Question 7: On a horizontal situation indicator (HSI), what does the course deviation indicator (CDI) needle represent when centered?
- Aircraft is on the selected magnetic heading
- Aircraft is on the selected VOR radial or localizer course (Correct answer)
- Aircraft heading matches the runway bearing
- Aircraft has reached the DME fix distance
Correct answer: Aircraft is on the selected VOR radial or localizer course
A centered CDI needle on the HSI indicates the aircraft is on the selected VOR radial or localizer centerline course.
AET Navigation Equipment 3
What is the primary function of a Distance Measuring Equipment (DME) system?