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100+ Free Part-66 Module 5 Practice Questions

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2026 Statistics

Key Facts: Part-66 Module 5 Exam

72 questions / 90 min

B2 Exam Length

EASA Part-66 (EU 2023/989)

75%

Pass Mark

EASA Part-66

32 bits

ARINC 429 Word Length

ARINC 429 Mark 33 DITS

12.5 / 100 kbit/s

ARINC 429 Speeds

ARINC 429 specification

12 June 2024

EU 2023/989 Applicable

Commission Implementing Regulation (EU) 2023/989

~75 seconds

Time Per Question

EASA Part-66 exam standard

EASA Part-66 Module 5 (Digital Techniques / Electronic Instrument Systems) is a core avionics module for B1 and especially B2 aircraft maintenance licence candidates. The real exam is 3-option multiple choice at about 75 seconds per question, with a 75% pass mark and no essay (essays remain only in Module 7). Category B2 sits 72 questions in 90 minutes, B1 sits 40 in 50 minutes and Category A sits 20 in 25 minutes. The syllabus covers binary/octal/hexadecimal numbering and A-D/D-A conversion; data buses including the 32-bit ARINC 429 word (octal label, SDI, SSM, odd parity, 12.5/100 kbit/s) plus ARINC 629 and AFDX; logic gates, truth tables and flip-flops; CPU/memory and software configuration control; fibre optics; CRT/LED/LCD displays; electrostatic sensitive device handling; EMC, EMI, HIRF and lightning protection; and typical systems such as EFIS, ECAM, EICAS, FMS, GNSS, TCAS and IRS/AHRS. Build to the 2023/989 syllabus, applicable from 12 June 2024.

Sample Part-66 Module 5 Practice Questions

Try these sample questions to test your Part-66 Module 5 exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What is the decimal equivalent of the binary number 1101?
A.11
B.14
C.15
D.13
Explanation: Binary 1101 = (1x8) + (1x4) + (0x2) + (1x1) = 8 + 4 + 0 + 1 = 13. Each bit represents a power of 2 reading right to left (2^0, 2^1, 2^2, 2^3).
2Convert the binary number 011101 to octal.
A.25
B.33
C.35
D.29
Explanation: Group the binary into sets of three bits from the right: 011 101 = 3 and 5, giving octal 35. Each octal digit represents exactly three binary bits.
3What is the decimal number 15 expressed in hexadecimal?
A.E
B.10
C.G
D.F
Explanation: Hexadecimal is base 16, using digits 0 to 9 and letters A to F. Decimal 15 corresponds to the single hex digit F (A=10, B=11, C=12, D=13, E=14, F=15).
4Convert the hexadecimal number 2F to decimal.
A.31
B.37
C.47
D.57
Explanation: Hex 2F = (2 x 16) + (F = 15) = 32 + 15 = 47. The left digit is multiplied by 16^1 and the right digit by 16^0.
5In binary coded decimal (BCD), how is the decimal number 29 represented?
A.0010 1001
B.0001 1101
C.1110 1001
D.0010 1011
Explanation: BCD encodes each decimal digit separately in a 4-bit group. Decimal 2 = 0010 and decimal 9 = 1001, giving 0010 1001. BCD never uses values above 1001 in any group.
6An analogue-to-digital (A-D) converter is required in an avionic system to:
A.Convert a digital computer output into a voltage to drive an indicator
B.Amplify a low-level analogue signal before display
C.Filter electrical noise from a digital data bus
D.Convert a continuously varying sensor voltage into binary data for a computer
Explanation: An A-D converter samples a continuously variable analogue signal (such as a sensor voltage) and represents it as discrete binary numbers that a digital computer can process.
7Increasing the number of bits in an analogue-to-digital converter primarily improves the:
A.Sampling speed of the converter
B.Operating voltage range
C.Immunity to lightning strikes
D.Resolution of the converted signal
Explanation: More bits divide the analogue range into more discrete steps, giving finer resolution (smaller quantisation step) and a more accurate digital representation of the input signal.
8How many bits are contained in a standard ARINC 429 data word?
A.8 bits
B.16 bits
C.32 bits
D.64 bits
Explanation: An ARINC 429 word is exactly 32 bits long, comprising the label (bits 1-8), SDI (9-10), data field (11-29), SSM (30-31) and a parity bit (bit 32).
9Which type of wiring does an ARINC 429 data bus use?
A.A single coaxial cable
B.A fibre optic cable
C.Three unshielded parallel conductors
D.A twisted shielded pair of wires
Explanation: ARINC 429 (Mark 33 DITS) uses a twisted shielded pair carrying a balanced differential signal, which provides good noise rejection in the aircraft electromagnetic environment.
10In an ARINC 429 word, the label is transmitted in which numbering system?
A.Octal
B.Hexadecimal
C.Binary coded decimal
D.Pure decimal
Explanation: The 8-bit ARINC 429 label (bits 1-8) is conventionally expressed in octal to identify the data type or parameter carried by the word.

About the Part-66 Module 5 Exam

EASA Part-66 Module 5 covers Digital Techniques and Electronic Instrument Systems for aircraft maintenance licence candidates. It is one of the avionics-heavy modules and is examined most extensively at Category B2, which sits 72 multiple-choice questions in 90 minutes against a 75% pass mark. The syllabus spans numbering systems and data conversion, aircraft data buses, logic circuits, basic computer structure, fibre optics, electronic displays, electrostatic sensitive devices, software management control, the electromagnetic environment and typical electronic aircraft systems. Content follows Commission Implementing Regulation (EU) 2023/989, applicable from 12 June 2024.

Questions

72 scored questions

Time Limit

90 minutes (B2); 50 minutes (B1)

Passing Score

75% per module

Exam Fee

Varies by NAA/Part-147 organisation (approximately EUR 50-230 per module sitting) (EASA (examinations conducted by National Aviation Authorities or approved Part-147 maintenance training organisations))

Part-66 Module 5 Exam Content Outline

16%

Numbering Systems & Data Conversion

Binary, octal and hexadecimal conversions, binary coded decimal (BCD), bytes and word lengths, and analogue-to-digital and digital-to-analogue conversion including resolution and sampling

18%

Data Buses

The 32-bit ARINC 429 word (8-bit octal label bits 1-8, SDI bits 9-10, data bits 11-29, SSM bits 30-31, odd parity bit 32), 12.5/100 kbit/s speeds, twisted shielded pair, simplex broadcast to up to 20 receivers, plus ARINC 629 and AFDX/ARINC 664 switched Ethernet

16%

Logic Circuits

AND, OR, NOT, NAND, NOR and XOR gates, truth tables and 2^n combinations, De Morgan equivalents, NAND/NOR universal gates, SR and JK flip-flops, counters and sequential versus combinational logic

14%

Computer Structure & Software

CPU and ALU, volatile RAM versus non-volatile ROM/PROM/EEPROM, address/data/control buses, word length and bus width, multiplexing, clock timing, Integrated Modular Avionics and software configuration/part-number control

16%

Fibre Optics & Electronic Displays

Total internal reflection with higher-index core and lower-index cladding, multimode versus single-mode fibre, EMI immunity, opto-couplers, CRT electron-gun and phosphor operation, LED forward-bias emission, LCD light-valve operation, RGB colour, pixels and display reversion

10%

ESDS, EMC & Electromagnetic Environment

Electrostatic sensitive device damage to CMOS/MOS parts, wrist straps with current-limiting resistors, anti-static packaging and workstations, EMC/EMI, HIRF, lightning protection on composite structures, bonding, static dischargers and cable shielding

10%

Typical Electronic / Digital Aircraft Systems

EFIS PFD and ND, Airbus ECAM and Boeing EICAS with red/amber/green colour coding, FMS and CDU/MCDU, GNSS, TCAS, GPWS/EGPWS, IRS/AHRS, ADIRU, fly-by-wire, BITE and central maintenance computers

How to Pass the Part-66 Module 5 Exam

What You Need to Know

  • Passing score: 75% per module
  • Exam length: 72 questions
  • Time limit: 90 minutes (B2); 50 minutes (B1)
  • Exam fee: Varies by NAA/Part-147 organisation (approximately EUR 50-230 per module sitting)

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

Part-66 Module 5 Study Tips from Top Performers

1Memorise the ARINC 429 32-bit word fields: octal label (bits 1-8), SDI (9-10), data (11-29), SSM (30-31) and odd-parity bit 32, plus the 12.5 and 100 kbit/s speeds and the 20-receiver simplex limit
2Practise conversions in both directions between decimal, binary, octal and hexadecimal, and know BCD (each decimal digit as a 4-bit group, never above 1001)
3Build the gate truth tables from memory and apply De Morgan's theorem: inverting both inputs of an AND gives a NOR, and NAND/NOR are universal gates
4Know the JK flip-flop modes, especially that J=K=1 causes the output to toggle, unlike the forbidden state of an SR flip-flop
5Learn fibre optics fundamentals: light is guided by total internal reflection because the core has a higher refractive index than the cladding, and fibre is immune to EMI
6Lock down ESDS handling: grounded wrist strap with a roughly 1 megohm resistor, anti-static packaging and workstation, and remember CMOS/MOS parts are the most ESD-sensitive

Frequently Asked Questions

How many questions are in EASA Part-66 Module 5 and what is the pass mark?

Category B2 sits 72 multiple-choice questions in 90 minutes, Category B1 sits 40 in 50 minutes and Category A sits 20 in 25 minutes. The pass mark is 75% for the module, with no negative marking and roughly 75 seconds allowed per question.

Does Module 5 include an essay?

No. Module 5 is multiple-choice only. Under Commission Implementing Regulation (EU) 2023/989, essays remain only in Module 7; essays were removed from Modules 9 and 10 in June 2024. The real exam uses 3-option multiple choice.

What topics does Module 5 cover?

Numbering systems and data conversion, data buses (notably ARINC 429), logic circuits, basic computer structure and software control, fibre optics, electronic displays, electrostatic sensitive devices, the electromagnetic environment, and typical electronic aircraft systems such as EFIS, ECAM, EICAS and FMS.

What do I need to know about ARINC 429?

ARINC 429 uses a 32-bit word: an 8-bit octal label (bits 1-8), SDI (bits 9-10), data (bits 11-29), SSM (bits 30-31) and an odd-parity bit (bit 32). It runs at 12.5 or 100 kbit/s over a twisted shielded pair and is simplex, broadcasting from one transmitter to up to 20 receivers.

How do I handle electrostatic sensitive devices (ESDS)?

Wear a grounded wrist strap connected through a current-limiting resistor (about 1 megohm) to an approved ground, work at an anti-static workstation, keep devices in conductive or anti-static packaging until needed, and handle modules by the case rather than the contacts.

Is this practice test current for 2026?

Yes. Questions are written to the syllabus in Commission Implementing Regulation (EU) 2023/989, applicable from 12 June 2024, under which the former sub-module splits were merged. Pre-2024 courses must complete under the old standard by 12 June 2026.