Digital Avionics and Instruments Flashcards

A pilot reports an intermittent 'red X' over the airspeed tape on their Primary Flight Display (PFD). From a maintenance perspective, which system is the most likely source of this failure?

Answer: The Air Data Computer (ADC)

A 'red X' over a specific parameter like airspeed on an EFIS display indicates that the data is invalid or not being received. The Air Data Computer (ADC) is responsible for calculating airspeed, altitude, and vertical speed from pitot and static pressure inputs. A failure or data corruption from the ADC would cause the PFD to flag the related parameters as invalid.

Which of the following digital data bus standards is characterized by a unidirectional, twisted-pair wire connection that transmits 32-bit words at either a low speed (12.5 kbps) or a high speed (100 kbps)?

Answer: ARINC 429

ARINC 429 is the predominant avionics data bus for commercial and transport aircraft. Its key characteristics include using a unidirectional (one transmitter, up to 20 receivers), twisted-pair wire, and transmitting 32-bit data words at either a low speed (12.5-14.5 kbps) or high speed (100 kbps).

Which of the following best describes the primary function of an Attitude and Heading Reference System (AHRS)?

Answer: To provide aircraft attitude (pitch, roll) and heading information to the flight displays.

An Attitude and Heading Reference System (AHRS) is designed to replace traditional mechanical gyroscopic instruments. It uses solid-state sensors like accelerometers, gyroscopes, and magnetometers to compute and output the aircraft's pitch, roll, and yaw, which is then sent to the EFIS displays, autopilot, and other systems.

On an aircraft equipped with an Engine Indicating and Crew Alerting System (EICAS), a 'HYD QTY LOW' message appears in amber. What does this color typically signify?

Answer: A caution requiring immediate crew awareness and possible future action.

EICAS uses a standardized color scheme to denote the urgency of a message. Red is used for warnings (immediate action required), while amber (or yellow) is used for cautions, which require immediate crew awareness but may not require immediate action.

In a modern Flight Management System (FMS), what is the primary source of real-time, high-accuracy position information used to continuously update and correct the aircraft's calculated position?

Answer: Global Positioning System (GPS)

While the FMS uses a blend of sensors for position determination, the Global Positioning System (GPS) is the primary source for accurate, continuous, and global position updating. The Inertial Reference System (IRS) calculates position but is subject to drift over time and relies on updates from GPS to maintain its accuracy.

An AME is performing a functional test of a TCAS II system. The test set simulates a conflict that generates a 'Climb, Climb' aural alert and a corresponding visual command on the PFD. What type of advisory has been generated?

Answer: Resolution Advisory (RA)

TCAS II provides two levels of alerts. A Traffic Advisory (TA) simply alerts the crew to the presence of nearby traffic. A Resolution Advisory (RA) is a command that instructs the pilot to perform a specific vertical maneuver, such as 'Climb' or 'Descend', to avoid a collision.