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Sample SACAA AME Avionics Practice Questions

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1Which digital logic gate produces a HIGH (1) output state ONLY when all of its input signals are in the HIGH (1) state?

A.OR gate

B.AND gate

C.NAND gate

D.NOR gate

Explanation: An AND gate is a fundamental digital logic gate that outputs a logic HIGH (1) if and only if all of its inputs are simultaneously HIGH (1). If any input is LOW (0), the output is LOW (0).

2According to De Morgan's laws, a NOR gate with inputs A and B is logically equivalent to which gate configuration?

A.An AND gate with inverted inputs (NOT A AND NOT B)

B.An OR gate with inverted inputs (NOT A OR NOT B)

C.A NAND gate with non-inverted inputs

D.An XOR gate with inverted inputs

Explanation: De Morgan's first law states that NOT (A OR B) = (NOT A) AND (NOT B). Therefore, a NOR gate is logically equivalent to an AND gate whose inputs have been inverted.

3What is the primary function of a D (Data/Delay) Flip-Flop in avionics digital logic circuits?

A.To multiply binary numbers

B.To store a single bit of digital data and transfer it to the output on an active clock edge

C.To convert analog voltage into a digital pulse train

D.To invert incoming digital signals continuously

Explanation: A D flip-flop captures the logic level present on its D input at the precise moment of an active clock transition (rising or falling edge) and holds that state at its output Q until the next active clock edge, functioning as a 1-bit memory cell.

4What is the standard total bit length of a single ARINC 429 digital data bus word?

A.16 bits

B.24 bits

C.32 bits

D.64 bits

Explanation: An ARINC 429 word consists of exactly 32 bits, divided into functional fields: Label (bits 1-8), SDI (bits 9-10), Data (bits 11-29), SSM (bits 30-31), and Parity (bit 32).

5Which bit position in a standard ARINC 429 word is designated for error detection parity, and what is the standard parity convention used?

A.Bit 1, Even Parity

B.Bit 8, Even Parity

C.Bit 32, Odd Parity

D.Bit 30, Odd Parity

Explanation: Bit 32 is the MSB of the ARINC 429 word and is reserved for Parity. The ARINC 429 standard specifies Odd Parity, meaning bit 32 is set to 0 or 1 such that the total number of logic 1s in the 32-bit word is odd.

6In fiber optic cables used for aircraft data links, what must be the relationship between the refractive index of the core (n1) and the cladding (n2) to achieve total internal reflection?

A.The refractive index of the core (n1) must be greater than the cladding (n2)

B.The refractive index of the cladding (n2) must be greater than the core (n1)

C.The refractive indices n1 and n2 must be exactly equal

D.The core refractive index must be zero

Explanation: Total internal reflection inside an optical fiber occurs only when light propagates from a medium of higher refractive index (n1, the core) toward a medium of lower refractive index (n2, the cladding) at an angle of incidence greater than the critical angle.

7In an ARINC 429 BNR (Binary) word, what information is conveyed by the Sign/Status Matrix (SSM) located at bits 30 and 31?

A.Hardware bus speed and label direction

B.Operating status such as Normal Operation (NO), Failure Warning (FW), No Computed Data (NCD), or Functional Test (FT)

C.Transmitter physical address and receiver pin assignment

D.Checksum count for error correction

Explanation: Bits 30-31 of an ARINC 429 word form the Sign/Status Matrix (SSM). For BNR data, SSM codes indicate status: 00 = Failure Warning, 01 = No Computed Data, 10 = Functional Test, and 11 = Normal Operation (plus sign/direction indications depending on parameter type).

8What are the standard data transmission bit rates defined by the ARINC 429 specification for High-Speed and Low-Speed operation?

A.High-Speed = 1 Mbps, Low-Speed = 100 kbps

B.High-Speed = 100 kbps, Low-Speed = 12.5 to 14.5 kbps

C.High-Speed = 10 Mbps, Low-Speed = 1 Mbps

D.High-Speed = 500 kbps, Low-Speed = 64 kbps

Explanation: ARINC 429 defines two operational speeds: High-Speed at 100 kbps (+/- 1%) and Low-Speed in the range of 12.5 to 14.5 kbps (+/- 1%).

9Which signal modulation format and voltage waveform characteristics are used on an ARINC 429 twisted shielded pair transmission line?

A.NRZ (Non-Return-to-Zero) with 0V and +5V TTL logic levels

B.Bipolar RZ (Return-to-Zero) with differential +10V (HI), 0V (NULL), and -10V (LO) nominal levels

C.Manchester II biphase encoding with 0V to +3.3V differential swing

D.PWM (Pulse Width Modulation) with +28V DC pulses

Explanation: ARINC 429 uses Bipolar Return-to-Zero (RZ) signaling over a twisted shielded pair. Line A relative to Line B swings +10V +/- 1V for a logic HIGH ('1'), -10V +/- 1V for a logic LOW ('0'), and 0V +/- 0.5V for a NULL state between bits.

10How is the 8-bit Label field (bits 1 through 8) transmitted on the wire in an ARINC 429 data word?

A.Bit 1 first (MSB first)

B.Bit 8 first (LSB of the label transmitted first)

C.Bits 1 through 8 simultaneously on 8 parallel lines

D.Bit 32 first, followed by Label bits in reverse order

Explanation: ARINC 429 transmits the Label field (bits 1-8) in reverse bit order compared to the rest of the word: bit 8 is transmitted first on the wire, followed by bit 7, bit 6 down to bit 1. The remaining bits 9-32 are transmitted LSB to MSB in numerical order.

About the SACAA AME Avionics Exam

The SACAA AME Avionics examination is a mandatory theoretical knowledge paper covering digital logic, avionics buses (ARINC 429), communication radios (VHF/HF/SATCOM), navigation systems (VOR/ILS/DME/GPS), pulse systems (Radar/Transponder/TCAS), and EFIS/FMS integration for aircraft maintenance engineers.

Exam sponsor: South African Civil Aviation Authority (SACAA). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Question count not published by the exam provider

Time Limit

75 minutes

Passing Score

75%

Exam / Certification Fees

~R425–R450 per subject (confirm current SACAA Part 187 fee)

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

25%

Digital Electronics & Data Buses

Logic gates, flip-flops, microprocessors, ARINC 429, ARINC 629, MIL-STD-1553, and optical fiber data bus fundamentals.

20%

Communication Systems

VHF transceivers, HF communications, SATCOM, SELCAL, audio integrating systems, and emergency locator transmitters (ELTs).

20%

Navigation Systems

VOR, ILS (Localizer & Glide Path), Marker Beacons, DME, ADF/NDB, GNSS/GPS receivers, and Inertial Reference Systems (IRS).

20%

Radar, Transponder & Surveillance

Airborne Weather Radar, Mode A/C/S Transponders, ADS-B Out/In, Traffic Collision Avoidance System (TCAS II), and TAWS/EGPWS.

15%

EFIS, FMS & Auto-Flight Systems

Electronic Flight Instrument System (EFIS), Flight Management System (FMS), Autopilot, Flight Director, and Auto-throttle systems.

Preparing for the SACAA AME Avionics Exam

What You Need to Know

Passing score: 75%
Assessment: Question count not published by the exam provider
Time limit: 75 minutes
Exam / certification fees: ~R425–R450 per subject (confirm current SACAA Part 187 fee) Official sources

Using Our Practice Resources

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SACAA AME Avionics: Suggested Study Strategy

1Memorise radio frequency bands: VHF Comms (118.0–136.975 MHz), VOR (108.0–117.95 MHz), ILS Localizer (108.1–111.95 MHz odd tenths).

2Understand ARINC 429 word format: 32 bits (Label 8 bits, SDI 2 bits, Data 19 bits, SSM 2 bits, Parity 1 bit).

3Review TCAS warning levels: Traffic Advisory (TA) vs Resolution Advisory (RA) and antenna positioning.

4Understand ELT transmission frequencies (406 MHz digital satellite alert and 121.5 MHz homing).

Frequently Asked Questions

What is the pass mark for SACAA AME Avionics?

The pass mark is 75%, tested centrally via SACAA PEXO multiple-choice computer exam.

Does this exam include ARINC 429 data bus specifications?

Yes, ARINC 429 word structure, parity bits, bit rate (high 100 kbps / low 12.5 kbps), and shielded twisted pair cabling are standard topics.

What pulse systems are covered?

Weather radar (X-band ~9.3–9.5 GHz), DME (960–1215 MHz), Mode S transponders (1030/1090 MHz), TCAS II resolution advisories, and EGPWS.

Free Practice Questions for SACAA AME Avionics

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