EASA PART 66 : DIGITAL QUESTION 4. EXAM QUESTIONS AND ANSWERS. VERIFIED 2025/2026.

EASA PART 66 : DIGITAL QUESTION 4.
EXAM QUESTIONS AND ANSWERS.
VERIFIED 2025/2026.



Question Number. 1. In arinc 629, LRUs are programmed to transmit.
Option A. one at a time.
Option B. one transmits and one recieves.

Option C. all at the same time. - ANS Correct Answer is. one transmits and one recieves.
Explanation. NIL.


Question Number. 2. In aircraft use, fibre optic cables should comply with.
Option A. ARINC 629 standard.
Option B. ARIND 429 standard.

Option C. ARIND 636 standard. - ANS Correct Answer is. ARIND 636 standard.
Explanation. NIL.


Question Number. 3. ARINC 629 databus is.
Option A. one cable, bi-directional.
Option B. two cables, uni-directional.

Option C. two cables, bi directional. - ANS Correct Answer is. two cables, bi directional.
Explanation. NIL.


Question Number. 4. An ARINC 573 data bus is used.


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,Option A. to input into a Digital Flight Data Recorder.
Option B. to supply digital inputs from a Symbol Generator to the EADI and EHSI.

Option C. to input into a FDR Digital Acquisition Unit. - ANS Correct Answer is. to input into a
Digital Flight Data Recorder.
Explanation. The FDR can have different inputs depending upon the age of the system, modern
systems use ARINC 573. The inputs to FDR DAU are only analogue, discreet and ARINC 429. The
interface between SGUs, EADI and EHSI is only ARINC 429.


Question Number. 5. An ARINC 429 bus uses.
Option A. a twisted shielded pair of wires.
Option B. two bi-directional twin sheathed and earthed wires.

Option C. a single twin wire cable for each transmitter. - ANS Correct Answer is. a twisted
shielded pair of wires.
Explanation. Pallett - Aircraft Instruments Page 157.


Question Number. 6. The ARINC 429 data bus word systems use.
Option A. binary coded decimal.
Option B. decimal numbering.

Option C. hexadecimal numbering. - ANS Correct Answer is. binary coded decimal.
Explanation. Pallett - Aircraft Instruments Page 156.


Question Number. 7. ARINC 573 is related to what system?.
Option A. Weather Radar.
Option B. FDR.

Option C. INS. - ANS Correct Answer is. FDR.
Explanation. Boeing Maintenance Training notes for B757.


Question Number. 8. ARINC 629 current mode couplers are.
Option A. capacitive.
Option B. resistive.
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, Option C. inductive. - ANS Correct Answer is. inductive.
Explanation. NIL.


Question Number. 9. ARINC 629 databus is.
Option A. one bus, bi-directional data flow.
Option B. two buses, unidirectional.

Option C. two buses, bi-directional data flow. - ANS Correct Answer is. one bus, bi-directional
data flow.
Explanation. NIL.


Question Number. 10. Normal transmission order of ARINC 629 LRUs in periodic mode is in
order of.
Option A. shortest to largest TI.
Option B. shortest to largest TG.

Option C. power up. - ANS Correct Answer is. power up.
Explanation. B777 MM 23-91-00 pg 41. Shortest to longest terminal gap is for aperiodic mode
only.


Question Number. 11. In an ARINC 429 wordstring, bits 1 to 8 represent the.
Option A. destination LRU address.
Option B. monitored parameter.

Option C. message. - ANS Correct Answer is. monitored parameter.
Explanation. Aircraft Instruments and Integrated Systems Pallett Page 159 and ARINCs tutorial.


Question Number. 12. ARINC 629 terminal transmit interval is.
Option A. common to each terminal.
Option B. unique to each terminal.

Option C. when all terminals are quiet. - ANS Correct Answer is. common to each terminal.
Explanation. The ARINC 629 TI is common to all LRUs.


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