*4F Airplane Systems - Advanced Avionics

Question 0

1. Describe the function of the following avionics equipment acronyms: AHRS, ADC, PFD, MFD, FD, FMS, INS.
   (FAA-H-8083-6, DAT)

Answer 0

AHRS—attitude and heading reference system. Composed of three-axis sensors that provide heading, attitude, and yaw information for aircraft. AHRS are designed to replace traditional mechanical gyroscopic flight instruments and provide superior reliability and accuracy.
ADC—air data computer. An aircraft computer that receives and processes pitot pressure, static pressure, and temperature to calculate precise altitude, indicated airspeed, true airspeed, vertical speed, and air temperature.
PFD—primary flight display. A display that provides increased situational awareness to the pi“lot by replacing the traditional six instruments with an easy-to-scan display that shows the horizon, airspeed, altitude, vertical speed, trend, trim, rate of turn, and more.
MFD—multi-function display. A cockpit display capable of presenting information (navigation data, moving maps, terrain awareness, etc.) to the pilot in configurable ways; often used in concert with the PFD.
FD—flight director. An electronic flight computer that analyzes the navigation selections, signals, and aircraft parameters. It presents steering instructions on the flight display as command bars or crossbars for the pilot to position the nose of the aircraft over or follow.
FMS—flight management system. A computer system containing a database for programming of routes, approaches, and departures that can supply navigation data to the flight director/autopilot from various sources, and can calculate flight data such as fuel consumption, time remaining, possible range, and other values.
INS—inertial navigation system. A computer-based navigation system that tracks the movement of an aircraft via signals produced by onboard accelerometers. The initial location of the aircraft is entered into the computer and all subsequent movement is then sensed and used to keep the aircraft’s position updated.

Question 1

2. What is the function of a magnetometer?

FAA-H-8083-6

Answer 1

A magnetometer is a device that measures the strength of the earth’s magnetic field to determine aircraft heading; it provides this information digitally to the AHRS, which then sends it to the PFD.

Question 2

3. When powering up an aircraft with an FMS/RNAV unit installed, how will you verify the effective dates of the navigation database?
   (FAA-H-8083-6)

Answer 2

The effective dates for the navigation database are typically shown on a start-up screen that is displayed as the system cycles through its startup self-test.

Question 3

4. Does an aircraft have to remain stationary during AHRS system initialization?
   (FAA-H-8083-6)

Answer 3

Some AHRSs must be initialized on the ground prior to departure. The initialization procedure allows the system to establish a reference attitude used as a benchmark for all future attitude changes. Other systems are capable of initialization while taxiing as well as in flight.

Question 4

5. Which standby flight instruments are normally provided in an advanced avionics aircraft?
   (FAA-H-8083-6)

Answer 4

Every aircraft equipped with electronic flight instruments must also contain a minimal set of backup/standby instruments. Usually conventional “round dial instruments,” they typically include an attitude indicator, an airspeed indicator, and an altimeter.

Question 5

6. If one display fails (PFD or MFD), what information will be presented on the remaining display?
   (FAA-H-8083-6)

Answer 5

In the event of a display failure, some systems offer a reversion capability to display the primary flight instruments and engine instruments on the remaining operative display.

Question 6

7. When a display failure occurs, what other system components will be affected? (
   AFM/POH)

Answer 6

In some systems, failure of a display will also result in partial loss of navigation, communication, and GPS capability. Reference your specific AFM/POH.

Question 7

8. What display information will be affected when an ADC failure occurs?
   (FAA-H-8083-6)

Answer 7

Inoperative airspeed, altitude, and vertical speed indicators, shown with red Xs on the PFD, indicate the failure of the air data computer.

Question 8

9. What display information will be lost when an AHRS failure occurs?
   (FAA-H-8083-6)

Answer 8

An inoperative attitude indicator, shown with a red X on the PFD, indicates failure of the AHRS.

Question 9

10. How will loss of a magnetometer affect the AHRS operation?
    (FAA-H-8083-6)

Answer 9

Heading information will be lost.