Free Practice Questions for Iran CAO Part-66 AMT Theory

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Sample Iran CAO Part-66 AMT Theory Practice Questions

Try these sample questions to review concepts for the Iran CAO Part-66 AMT Theory exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A hydraulic hand pump lever has an effort arm of 45 cm and a load arm of 5 cm connected directly to a pump piston with an area of 4 cm². If a technician applies a downward force of 120 N at the end of the effort arm, what total hydraulic pressure is developed in the pump chamber?

A.270 kPa

B.2.7 MPa

C.1.08 MPa

D.10.8 MPa

Explanation: Using the principle of moments for a first-class or second-class lever: Force at piston = Effort Force × (Effort Arm / Load Arm) = 120 N × (45 cm / 5 cm) = 120 N × 9 = 1,080 N. Hydraulic pressure is Force divided by area: P = F / A = 1,080 N / (4 × 10⁻⁴ m²) = 2,700,000 N/m² = 2.7 MPa (or 27 bar).

2Under Pascal's Principle, if a confined hydraulic brake system transmits pressure equally in all directions, what happens to the output force if the master cylinder piston diameter is 2 cm and the slave caliper piston diameter is 6 cm?

A.The slave output force is 3 times the master input force

B.The slave output force is 9 times the master input force

C.The slave output force is equal to the master input force but travels 9 times farther

D.The slave output force is 1/9th of the master input force

Explanation: According to Pascal's principle, pressure P = F₁/A₁ = F₂/A₂. Piston area is proportional to the square of diameter (A ∝ d²). The diameter ratio is 6 cm / 2 cm = 3. Therefore, the area ratio is 3² = 9. The output force at the slave piston is F₂ = F₁ × (A₂ / A₁) = 9 × F₁.

3An aircraft structural member with a cross-sectional area of 25 mm² is subjected to an axial tensile load of 15,000 N. What tensile stress is imposed on the member, and what is its classification if the yield strength is 700 MPa?

A.600 MPa; the stress is within the elastic limit

B.375 MPa; the stress exceeds the yield strength

C.60 MPa; the stress is within the elastic limit

D.600 MPa; the material has undergone permanent plastic deformation

Explanation: Stress (σ) = Force / Area = 15,000 N / 25 mm² = 600 N/mm² = 600 MPa. Since the applied tensile stress of 600 MPa is less than the material's yield strength of 700 MPa, the deformation remains purely elastic, meaning the member will return to its original length when the load is removed.

4A nitrogen charging bottle has an internal volume of 0.05 m³ at a gauge pressure of 200 bar at 20°C. If the ambient temperature in an unconditioned hangar rises to 45°C, what is the new gauge pressure in the bottle, assuming nitrogen behaves as an ideal gas at constant volume?

A.217.1 bar gauge

B.450.0 bar gauge

C.208.5 bar gauge

D.183.9 bar gauge

Explanation: Using Gay-Lussac's Law for an ideal gas at constant volume: P₁/T₁ = P₂/T₂ using absolute temperatures and absolute pressures. Atmospheric pressure ≈ 1 bar, so P₁_abs = 201 bar. T₁ = 20 + 273.15 = 293.15 K; T₂ = 45 + 273.15 = 318.15 K. P₂_abs = 201 × (318.15 / 293.15) = 201 × 1.08528 = 218.14 bar absolute. Converting back to gauge pressure: P₂_gauge = 218.14 - 1 = 217.14 bar gauge (approx. 217.1 bar).

5An aircraft maintenance technician uses a standard torque wrench that is 0.5 m long from the drive center to the handgrip. To reach a recessed nut, a straight extension adapter of 0.1 m is attached directly in line with the wrench handle. If the required torque on the nut is 90 N·m, what torque value must be set on the wrench scale?

A.108 N·m

B.75 N·m

C.90 N·m

D.60 N·m

Explanation: When a straight adapter extends the torque wrench in line, the effective lever arm increases. The formula is: Set Torque = Desired Torque × [L / (L + E)], where L is the torque wrench length (0.5 m) and E is the extension length (0.1 m). Set Torque = 90 N·m × [0.5 / (0.5 + 0.1)] = 90 × (0.5 / 0.6) = 75 N·m.

6Three resistors with values of 20 Ω, 30 Ω, and 60 Ω are connected in parallel across a 24 V DC aircraft avionics emergency bus. What is the total equivalent resistance of the circuit and the total current supplied by the bus?

A.10 Ω and 2.4 A

B.110 Ω and 0.22 A

C.10 Ω and 240 mA

D.6.67 Ω and 3.6 A

Explanation: For parallel resistors: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ = 1/20 + 1/30 + 1/60 = (3 + 2 + 1) / 60 = 6 / 60 = 1 / 10 Ω⁻¹. Thus R_total = 10 Ω. Using Ohm's law, total current I = V / R_total = 24 V / 10 Ω = 2.4 A.

7In an aircraft DC circuit, a 50 μF capacitor is connected in series with a 40 kΩ resistor across a 28 V DC source. How long does it take for the capacitor to charge to approximately 63.2% of the applied voltage, and after how many time constants is it considered fully charged?

A.2.0 seconds; 5 time constants (10 seconds)

B.0.2 seconds; 3 time constants (0.6 seconds)

C.200 milliseconds; 5 time constants (1.0 second)

D.2.0 seconds; 1 time constant (2 seconds)

Explanation: The time constant of an RC circuit is τ = R × C = (40 × 10³ Ω) × (50 × 10⁻⁶ F) = 2.0 seconds. By definition, a capacitor reaches 63.2% of supply voltage after 1 time constant (2.0 s). In standard aviation electrical engineering, a capacitor is considered fully charged (99.3%) after 5 time constants: 5 × 2.0 s = 10.0 seconds.

8What primary hazard distinguishes Nickel-Cadmium (Ni-Cad) aircraft batteries from Lead-Acid batteries during high-rate charging or elevated ambient temperatures?

A.Sulphation of the positive plates leading to sudden open-circuit failure

B.Thermal runaway caused by a negative temperature coefficient of internal resistance

C.Spontaneous generation of pure chlorine gas inside the sealed cell matrix

D.Immediate polarity reversal whenever the state of charge drops below 50%

Explanation: Ni-Cad batteries possess a negative temperature coefficient of resistance: as temperature increases, internal resistance decreases. Under constant-voltage charging, this causes the charging current to rise, further heating the battery and creating a vicious cycle known as 'thermal runaway', which can result in battery boiling, fire, or explosion. Aircraft Ni-Cad systems incorporate temperature sensors and chargers that isolate the battery if temperature exceeds limits.

9In a 400 Hz AC aircraft electrical generation system, what is the inductive reactance (X_L) of a 15 mH relay coil?

A.37.7 Ω

B.6.0 Ω

C.377 Ω

D.0.038 Ω

Explanation: Inductive reactance is calculated as X_L = 2πfL. With f = 400 Hz and L = 15 mH = 15 × 10⁻³ H: X_L = 2 × 3.14159 × 400 × 0.015 = 2513.27 × 0.015 ≈ 37.7 Ω.

10What is the primary function of a Zener diode in an aircraft solid-state electronic power supply circuit?

A.To rectify high-frequency alternating current into pure direct current

B.To provide voltage regulation by operating in reverse breakdown mode

C.To act as a variable capacitor when subjected to forward bias

D.To amplify weak radio frequency signals received from antenna couplers

Explanation: A Zener diode is heavily doped so that it exhibits a sharp, stable reverse-breakdown voltage (Zener voltage). When reverse-biased beyond this threshold, it conducts reverse current while maintaining a nearly constant voltage across its terminals, making it ideal as a voltage reference or regulator in aircraft electronic power supplies.

About the Iran CAO Part-66 AMT Theory Exam

The Civil Aviation Organization of Iran (CAO.IRI) Part-66 Aircraft Maintenance Engineer (AME/AMT) theoretical examination validates the technical competency of personnel seeking certification privileges on civil aircraft. Structured in compliance with ICAO Annex 1 and international Part-66 requirements, the modular syllabus tests mechanical and avionics fundamentals, workshop maintenance practices, regulatory compliance under Part-145/Part-M, and aviation human factors. This free practice bank provides 100 comprehensive technical questions with full explanations.

Exam sponsor: Civil Aviation Organization of the Islamic Republic of Iran (CAO.IRI). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Modular closed-book examinations administered by the Civil Aviation Organization of Iran across the Part-66 basic knowledge modules, including Mathematics, Physics, Electrical Fundamentals, Electronics, Digital Techniques, Materials and Hardware, Maintenance Practices, Aerodynamics, Human Factors, Aviation Legislation and Aircraft/Engine Systems. Each module is examined by three-option multiple-choice questions, and the Maintenance Practices, Human Factors and Aviation Legislation modules also require written essay answers. A minimum of 75% is required on each module.

Time Limit

Timed per module at a nominal average of 75 seconds per multiple-choice question, plus 20 minutes for each essay question, under the Part-66 basic examination standard.

Passing Score

75% on the multiple-choice part of each module. Penalty marking is not used to decide whether a candidate has passed. Where a module also carries essay questions, the written answer must separately reach the required standard, assessed on the proportion of the examiner's key points covered and the absence of significant error.

Exam / Certification Fees

Modular examination fees are regulated by CAO.IRI and payable upon registration through Part-147 Approved Maintenance Training Organizations or direct CAO examination sittings.

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.

10%

Mathematics and Physics (Modules 1 & 2)

Algebra, trigonometry, mechanics, static equilibrium, fluid dynamics, thermodynamics, wave motion, and sound applicable to aircraft maintenance engineering.

14%

Electrical Fundamentals and Electronics (Modules 3 & 4)

DC/AC circuit theory, Ohm's law, Kirchhoff's laws, capacitive and inductive reactance, semiconductors, diodes, transistors, and rectification circuits.

10%

Digital Techniques & Electronic Instrument Systems (Module 5)

Binary and hexadecimal systems, logic gates, microprocessors, ARINC 429 and 629 data buses, fiber optics, and electronic flight instrument architectures.

14%

Materials and Hardware (Module 6)

Ferrous and non-ferrous aircraft alloys, composite materials, corrosion types and treatment, standard AN/MS/NAS fasteners, rivets, bearings, and control cables.

16%

Maintenance Practices & Standard Procedures (Module 7)

Safety precautions, precision measuring tools, fits and clearances, torque loading, safety wiring, non-destructive testing (NDT), EWIS, and sheet metal repairs.

Basic Aerodynamics (Module 8)

Atmospheric physics, airflow over aerofoils, lift, drag, boundary layer control, flight control surfaces, high-speed compressible airflow, and stability.

Human Factors in Aviation Maintenance (Module 9)

Human performance and limitations, situational awareness, fatigue management, communication protocols, shift work, and error management models (PEAR and SHELL).

10%

Aviation Legislation & Regulatory Framework (Module 10)

CAO.IRI Part-66, Part-145, Part-147, and Part-M regulations, Certificate of Release to Service (CRS), Airworthiness Directives, Service Bulletins, and logbook entries.

10%

Turbine Engines & Aircraft Systems (Modules 11 & 15)

Gas turbine engine operating principles, compressor stall prevention, fuel metering, hydraulic power distribution, pneumatic de-icing, and flight control actuation.

Preparing for the Iran CAO Part-66 AMT Theory Exam

What You Need to Know

Passing score: 75% on the multiple-choice part of each module. Penalty marking is not used to decide whether a candidate has passed. Where a module also carries essay questions, the written answer must separately reach the required standard, assessed on the proportion of the examiner's key points covered and the absence of significant error.
Assessment: Modular closed-book examinations administered by the Civil Aviation Organization of Iran across the Part-66 basic knowledge modules, including Mathematics, Physics, Electrical Fundamentals, Electronics, Digital Techniques, Materials and Hardware, Maintenance Practices, Aerodynamics, Human Factors, Aviation Legislation and Aircraft/Engine Systems. Each module is examined by three-option multiple-choice questions, and the Maintenance Practices, Human Factors and Aviation Legislation modules also require written essay answers. A minimum of 75% is required on each module.
Time limit: Timed per module at a nominal average of 75 seconds per multiple-choice question, plus 20 minutes for each essay question, under the Part-66 basic examination standard.
Exam / certification fees: Modular examination fees are regulated by CAO.IRI and payable upon registration through Part-147 Approved Maintenance Training Organizations or direct CAO examination sittings. Official sources

Using Our Practice Resources

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Frequently Asked Questions

What is the passing standard for CAO Iran Part-66 examinations?

Candidates must achieve at least 75% on the multiple-choice part of each module, and penalty marking is not used to decide a pass. Where a module also carries essay questions, the written answer has to reach the required standard in its own right.

What licence categories are covered under CAO.IRI Part-66?

CAO.IRI Part-66 establishes Category A (Line Maintenance Certifying Mechanic), Category B1 (Mechanical Certifying Technician covering airframes, engines, and mechanical/electrical systems), Category B2 (Avionics Certifying Technician covering avionics and electrical systems), and Category C (Base Maintenance Certifying Engineer).

What language is used for the CAO Iran AME examinations?

The theoretical examinations are administered in English, aligning with international civil aviation technical documentation, aircraft maintenance manuals (AMM), and ICAO standards.

What is the Certificate of Release to Service (CRS)?

A CRS is an official regulatory document issued under CAO.IRI Part-145 by authorized certifying staff certifying that maintenance work has been properly carried out in accordance with approved data.

Is this practice question bank affiliated with the Civil Aviation Organization of Iran?

No. This question bank is an independent educational prep resource developed by OpenExamPrep to help maintenance engineers and technicians master Part-66 technical and regulatory subjects.

Does this practice bank match the official CAO.IRI Part-66 question format?

Not exactly, and that is deliberate. OpenExamPrep presents four answer options, while official Part-66 multiple-choice questions offer three. The official basic examinations also include written essay questions in some modules, which no multiple-choice bank can rehearse. Treat this as an independent English-language study aid for the underlying Part-66 knowledge rather than a simulation of the official paper.