FAA Aviation Mechanic – ACS Airman Certification Standards Knowledge Test — Questions and Answers

Question 1: Engine oil temperature rises above limits during taxi but returns to normal during climb. What is the most probable explanation?

Defective oil cooler thermostat stuck closed
Insufficient airflow at low taxi speeds with no forward motion cooling (Correct answer)
Incorrect oil viscosity grade
Oil pump cavitation at low RPM

Correct answer: Insufficient airflow at low taxi speeds with no forward motion cooling

Air-cooled engines rely heavily on forward airspeed for cooling; taxiing at low speed reduces airflow over cylinders and oil cooler significantly.

Question 2: Fuel flow is within normal limits but EGT is abnormally high on one cylinder. What is the most likely cause?

Cracked exhaust valve
Clogged fuel injector on that cylinder (Correct answer)
Intake valve sticking open
Incorrect spark plug gap

Correct answer: Clogged fuel injector on that cylinder

A clogged fuel injector delivers insufficient fuel to one cylinder, creating a lean mixture that raises EGT on that cylinder.

Question 3: During a landing gear retraction test, the gear takes longer than the published time to retract. What is the FIRST area to check?

Uplock hook spring tension
Hydraulic system fluid level and accumulator pressure (Correct answer)
Actuator cylinder for internal leakage
Gear door rigging and interference

Correct answer: Hydraulic system fluid level and accumulator pressure

Low hydraulic fluid level or insufficient accumulator pressure is the most common and easily checked cause of slow gear retraction before investigating actuators or rigging.

Question 4: An aircraft owner requests that a mechanic install a non-TSO'd radio as a replacement for a required navigation radio. The mechanic should:

Install it as a temporary fix and document it as a minor repair
Install it and submit a Form 337 to authorize the non-standard equipment
Refuse, because required avionics must meet TSO standards or have FAA approval (Correct answer)
Install it if the owner signs a waiver of liability

Correct answer: Refuse, because required avionics must meet TSO standards or have FAA approval

Required avionics must meet applicable TSO standards or have specific FAA approval; installing non-approved equipment on required systems is not permissible.

Question 5: Under 14 CFR Part 91.409, what is the maximum interval between required annual inspections for a standard category aircraft not operated for hire?

Six calendar months
100 hours time-in-service
Twelve calendar months (Correct answer)
200 hours time-in-service

Correct answer: Twelve calendar months

14 CFR 91.409 requires annual inspections to be performed within the preceding 12 calendar months for aircraft not operated for hire.

Question 6: What is the advantage of a brake-by-wire (electro-hydraulic) braking system compared to a conventional hydraulic brake system?

Reduces aircraft weight by using smaller diameter brake lines
Allows the pilot to apply greater mechanical advantage to brake pedals
Provides faster and more precise brake pressure modulation for anti-skid performance (Correct answer)
Eliminates the need for hydraulic fluid entirely by using electric motors

Correct answer: Provides faster and more precise brake pressure modulation for anti-skid performance

Electro-hydraulic brake systems use electronic control to modulate hydraulic pressure with greater speed and precision than mechanical inputs alone, improving anti-skid performance.

Question 7: Which type of hydraulic seal is most commonly used between two parts that have relative motion (dynamic application)?

Metal crush washer
Anaerobic sealant
O-ring or lip seal in a dynamic groove (Correct answer)
O-ring used as a static seal

Correct answer: O-ring or lip seal in a dynamic groove

Dynamic seals such as O-rings installed in dynamic grooves or lip seals are designed to prevent leakage between moving components.

Question 8: What is the purpose of a desiccant in an aircraft pneumatic system?

Regulate downstream pressure to a constant value
Remove moisture from compressed air before it enters system components (Correct answer)
Filter particulate contamination larger than 10 microns
Lubricate moving components within the pneumatic valves

Correct answer: Remove moisture from compressed air before it enters system components

A desiccant absorbs moisture from compressed air, preventing ice formation at altitude and corrosion within system components.

Question 9: During engine run-up, a pilot reports intermittent engine roughness that disappears when carburetor heat is applied. What does this indicate?

Fouled spark plugs
Cracked intake manifold
Lean fuel-air mixture
Ice formation in the carburetor venturi (Correct answer)

Correct answer: Ice formation in the carburetor venturi

Carburetor ice causes rough running and partial power loss; applying carb heat melts the ice and restores smooth operation.

Question 10: When the repair data in the Structural Repair Manual (SRM) does not cover the type or size of damage found, the technician must:

Contact the aircraft manufacturer's engineering department for a specific repair disposition (Correct answer)
Use the closest applicable SRM procedure and note any deviations
Ground the aircraft permanently as it is beyond repair
Fabricate a repair based on best engineering judgment and return the aircraft to service

Correct answer: Contact the aircraft manufacturer's engineering department for a specific repair disposition

When damage exceeds SRM limits or the damage type is not covered, FAA regulations require contacting the Type Certificate holder (manufacturer) for engineering approval of the repair.

Question 11: What distinguishes a major repair from a minor repair under 14 CFR Part 43?

Whether FAA-approved tooling was used
The cost of parts used
The potential effect on structural strength, flight characteristics, or other airworthiness qualities (Correct answer)
The amount of time required to complete the work

Correct answer: The potential effect on structural strength, flight characteristics, or other airworthiness qualities

A major repair is one that might appreciably affect structural strength, flight characteristics, or other airworthiness qualities if improperly done.

Question 12: When applying aircraft dope to a fabric-covered surface, runs or sags in the finish are caused by:

Using too little dope per coat and moving the spray gun too fast
Applying dope in cold, dry conditions
Not scuffing the previous coat before applying the next
Using dope that is too thin or applying too heavy a coat in one pass (Correct answer)

Correct answer: Using dope that is too thin or applying too heavy a coat in one pass

Runs and sags in aircraft dope are caused by an over-thinned mixture or applying an excessively thick coat, both of which allow the material to flow before it can flash off.

Question 13: During engine run-up, the prop governor check is performed by increasing RPM and pulling the prop control back. What should happen to RPM?

RPM should fluctuate rapidly
RPM should remain unchanged
RPM should drop and stabilize at a lower value (Correct answer)
RPM should continue increasing

Correct answer: RPM should drop and stabilize at a lower value

Pulling the prop control back commands a lower RPM setting; the governor responds by coarsening the blade pitch, reducing RPM to the selected value.

Question 14: How does technology impact modern hydraulic & pneumatic systems practices?

Technology improves accuracy, efficiency, and capabilities while requiring new skills and knowledge (Correct answer)
Technology has no impact on this field
Technology has made professional expertise unnecessary
Only large organizations benefit from technology in this field

Correct answer: Technology improves accuracy, efficiency, and capabilities while requiring new skills and knowledge

Technological advances have transformed professional practice by improving diagnostic capabilities, data analysis, documentation, and efficiency while requiring practitioners to develop new competencies.

Question 15: An aircraft GPS receiver shows a valid position fix but the CDI needle of the integrated course deviation indicator remains deflected. What is the most likely cause?

Insufficient GPS satellite signal strength
The aircraft is outside of GPS coverage area
A faulty CDI display unit
An incorrectly entered flight plan or destination waypoint in the GPS (Correct answer)

Correct answer: An incorrectly entered flight plan or destination waypoint in the GPS

If the GPS has a valid fix but the CDI is deflected, the most common cause is an incorrect or incomplete flight plan entry causing the unit to navigate to an unintended waypoint.

Question 16: During a structural inspection, a mechanic finds a corrosion pit in an aluminum structural member. Which measurement determines if the component remains airworthy?

The distance of the pit from the nearest fastener
The surface area of the corroded region
The depth of the pit compared to the material thickness and manufacturer's allowable limits (Correct answer)
The color and type of corrosion products present

Correct answer: The depth of the pit compared to the material thickness and manufacturer's allowable limits

Corrosion pit depth relative to material thickness is the critical measurement because excessive pitting reduces structural cross-section below allowable limits.

Question 17: What is the correct torque technique when installing AN/MS flareless tube fittings?

Tighten until resistance is felt, then tighten 1/16 turn more
Thread until metal-to-metal contact, then add 1/4 turn
Use the 'finger-tight plus turns' method specified in the applicable maintenance manual (Correct answer)
Torque to the manufacturer's value using only a calibrated torque wrench

Correct answer: Use the 'finger-tight plus turns' method specified in the applicable maintenance manual

Flareless fitting installation requires presetting the ferrule on the tube first, then during final assembly using the turns method specified in the maintenance manual.

Question 18: What does a hydraulic system ground test unit (GTU) allow a technician to do?

Test hydraulic systems with engines running at high power settings safely on the ground
Measure hydraulic fluid contamination levels during system operation
Operate aircraft hydraulic systems using external ground power without running the engines (Correct answer)
Pressurize only the brake system independently from the main hydraulic system

Correct answer: Operate aircraft hydraulic systems using external ground power without running the engines

A ground test unit provides external hydraulic pressure and flow, allowing full system operation and testing without starting the aircraft engines.

Question 19: What is the function of a hydraulic system priority valve?

Regulate pump output pressure to a constant predetermined value
Ensure flight-critical systems receive hydraulic pressure before non-critical systems during low-pressure conditions (Correct answer)
Prevent two hydraulic systems from operating at the same time
Switch automatically from one hydraulic system to another if pressure drops

Correct answer: Ensure flight-critical systems receive hydraulic pressure before non-critical systems during low-pressure conditions

A priority valve ensures that flight-critical hydraulic consumers (such as flight controls) are served first, with non-essential systems receiving flow only when adequate pressure exists.

Question 20: What is the correct procedure when an engine fire occurs during start on a reciprocating aircraft engine?

Continue cranking with mixture at idle cutoff and throttle full open to draw fire into engine (Correct answer)
Immediately shut off fuel and use fire extinguisher on the engine
Apply carburetor heat and reduce throttle to idle
Continue cranking to draw the fire into the engine while keeping the mixture rich

Correct answer: Continue cranking with mixture at idle cutoff and throttle full open to draw fire into engine

Continuing to crank with mixture cut off and throttle full open creates airflow that can draw burning fuel back into the induction system and extinguish the fire.

Question 21: Which type of damage to a composite structure is MOST difficult to detect visually?

Frayed edges at fastener holes
Impact craters that dent the outer ply
Surface scratches and paint chips
Delamination beneath an intact surface skin (Correct answer)

Correct answer: Delamination beneath an intact surface skin

Delamination (separation of plies) can exist beneath an undamaged-looking outer skin and requires tap testing or NDI methods to detect.

Question 22: Which part of the maintenance manual specifies troubleshooting steps?

Parts Catalog section
Troubleshooting section (Correct answer)
Schematics section
General Information section

Correct answer: Troubleshooting section

The Troubleshooting section of the manual provides step-by-step diagnostic guidance.

Question 23: Under an SMS framework, a 'just culture' policy primarily aims to:

Eliminate punishment for all maintenance errors
Differentiate between honest mistakes and reckless behavior to encourage reporting (Correct answer)
Standardize disciplinary procedures across all maintenance stations
Transfer liability for errors to the operator rather than the mechanic

Correct answer: Differentiate between honest mistakes and reckless behavior to encourage reporting

Just culture distinguishes between unintentional errors and willful violations so that honest mistakes are treated with support and coaching, encouraging open reporting of safety concerns.

Question 24: A mechanic who suspects a fellow technician is working while impaired by alcohol should FIRST:

Immediately report it to the supervisor or safety officer (Correct answer)
Confront the technician privately and warn them
Ignore it unless the aircraft is about to fly
Annotate the maintenance log and continue working

Correct answer: Immediately report it to the supervisor or safety officer

Safety culture requires immediate escalation to a supervisor or safety officer when impairment is suspected, preventing unsafe maintenance from reaching an aircraft.

Question 25: Why must aircraft fuel tanks be vented to atmosphere?

To enable fuel cross-feed between tanks
To allow fuel vapors to escape for fire prevention
To prevent tank collapse or pressure differential as fuel is consumed and altitude changes (Correct answer)
To equalize pressure between wing tanks

Correct answer: To prevent tank collapse or pressure differential as fuel is consumed and altitude changes

Tank venting prevents vacuum buildup as fuel is consumed and compensates for atmospheric pressure changes with altitude, preventing tank deformation and fuel flow interruption.

Question 26: An A&P mechanic with an Inspection Authorization (IA) may perform which of the following that a basic A&P may not?

Approve major repairs and alterations for return to service (Correct answer)
Perform sheet metal repairs
Replace aircraft engines
Sign off 100-hour inspections

Correct answer: Approve major repairs and alterations for return to service

An IA holder can approve major repairs and major alterations for return to service on certificated aircraft.

Question 27: According to the Dirty Dozen human factors in aviation maintenance, 'complacency' is best described as:

Overconfidence combined with reduced vigilance on familiar tasks (Correct answer)
Working beyond approved data
Physical fatigue causing missed inspection steps
Failure to communicate a discrepancy to the next shift

Correct answer: Overconfidence combined with reduced vigilance on familiar tasks

Complacency in the Dirty Dozen refers to overconfidence and reduced vigilance—often on routine, familiar tasks where errors are most likely to be overlooked.

Question 28: When inspecting a riveted skin joint, you find a rivet with a shop head that is too small. What is the correct corrective action?

Drill out and replace with the same diameter rivet driven correctly (Correct answer)
Apply epoxy adhesive to fill the gap around the rivet
Drill out and replace the rivet with the next larger diameter
Leave in place if the shop head diameter is at least 1.2 times the rivet diameter

Correct answer: Drill out and replace with the same diameter rivet driven correctly

An undersized shop head indicates improper driving; the rivet must be drilled out and replaced using correct driving technique with the same specification rivet.

Question 29: An aircraft maintenance record entry for a 100-hour inspection must include all of the following EXCEPT:

Total time in service
Date of inspection
Fuel quantity at time of inspection (Correct answer)
Signature and certificate number of the person approving return to service

Correct answer: Fuel quantity at time of inspection

14 CFR 43.11 specifies required logbook entries for inspections; fuel quantity is not among the required items.

Question 30: A landing gear retraction test reveals the gear takes 12 seconds to retract, while the maintenance manual specifies 6-8 seconds maximum. What is the most likely cause?

The gear is properly functioning within actual operational tolerances
A faulty gear position indicator causing incorrect timing
Excessive aerodynamic drag on the gear doors
Low hydraulic fluid level or reduced hydraulic pump output (Correct answer)

Correct answer: Low hydraulic fluid level or reduced hydraulic pump output

Slow gear retraction is typically caused by low hydraulic fluid, a worn pump with insufficient flow, or a restriction in the hydraulic circuit.

Question 31: What is the primary purpose of Advisory Circular AC 43.13-1B?

To provide acceptable methods and techniques for aircraft inspection and repair (Correct answer)
To establish Part 145 repair station requirements
To define ACS testing standards for mechanics
To outline pilot operating procedures

Correct answer: To provide acceptable methods and techniques for aircraft inspection and repair

AC 43.13-1B provides FAA-accepted methods, techniques, and practices for aircraft inspection and repair.

Question 32: Airworthiness Directives (ADs) issued by the FAA are:

Recommended practices that operators may choose to follow
Manufacturer service bulletins incorporated by reference
Legally mandatory corrective actions for identified unsafe conditions (Correct answer)
Advisory-only notices for aging aircraft

Correct answer: Legally mandatory corrective actions for identified unsafe conditions

ADs are legally mandatory regulations issued under 14 CFR Part 39 that require specific corrective actions to address unsafe conditions in aircraft or components.

Question 33: How should an aircraft mechanic test a repaired fuel system for leaks before returning the aircraft to service?

Pressure test or operational test per the AMM with fuel system pressurized and all connections checked for leaks (Correct answer)
Visual inspection alone with the fuel caps open
Run the engine to operating temperature and inspect
Dye penetrant test on all fittings

Correct answer: Pressure test or operational test per the AMM with fuel system pressurized and all connections checked for leaks

After repair, the fuel system must be leak-tested per the AMM procedure, typically by pressurizing the system and inspecting all connections, fittings, and repaired areas for any leakage.

Question 34: An aircraft uses a power-boost hydraulic flight control system. How does it differ from a full-power hydraulic system?

Power-boost allows the pilot to feel aerodynamic loads through the control surface; full-power does not (Correct answer)
Power-boost uses electrical actuators as a backup, while full-power is purely hydraulic
Power-boost uses mechanical cables only, while full-power uses hydraulic lines
Power-boost requires higher hydraulic pressure than full-power systems

Correct answer: Power-boost allows the pilot to feel aerodynamic loads through the control surface; full-power does not

In a power-boost system, hydraulic pressure assists but does not completely replace pilot effort, allowing aerodynamic feedback; in a full-power system, the pilot has no direct aerodynamic feel.

Question 35: An aircraft landing gear extends normally but the green 'gear down and locked' light does not illuminate. The FIRST troubleshooting step should be:

Assume the gear is down and locked since it extended normally
Perform an emergency landing immediately
Manually verify gear position via the viewing port and check the indicator light bulb (Correct answer)
Check the position switch and wiring circuit associated with the indicator light

Correct answer: Manually verify gear position via the viewing port and check the indicator light bulb

The safest first step is to visually verify gear position via mirror or viewing port, then check if the indicator bulb is burned out before assuming a more serious fault.

Question 36: The 'Swiss Cheese Model' of accident causation, as applied to aviation maintenance, illustrates that accidents occur when:

A single catastrophic component failure overwhelms all safety systems
Multiple layers of defenses each have gaps that align to allow a hazard to reach an outcome (Correct answer)
Maintenance errors are not caught by quality assurance inspection
An individual mechanic ignores established procedures

Correct answer: Multiple layers of defenses each have gaps that align to allow a hazard to reach an outcome

James Reason's Swiss Cheese Model shows that accidents result from multiple aligned failures across defensive layers (procedures, inspections, design), not a single cause.

Question 37: Which type of inspection checks for internal engine cracks?

Magnetic particle inspection (Correct answer)
Dye penetrant inspection
Visual inspection
Ultrasonic inspection

Correct answer: Magnetic particle inspection

Magnetic particle inspection detects surface and subsurface cracks in ferrous materials.

Question 38: What is the impact of regulatory changes on ACS professionals?

Only government employees need to follow regulatory changes
Regulatory changes require updating practices, procedures, and documentation to maintain compliance (Correct answer)
Regulatory changes only affect large organizations
Regulations never change once established

Correct answer: Regulatory changes require updating practices, procedures, and documentation to maintain compliance

Professionals must monitor and adapt to regulatory changes that affect their practice, ensuring continued compliance and effective service delivery.

Question 39: What is the MAIN reason that cure pressure is applied during composite repair?

To prevent thermal expansion of the honeycomb core during cure
To increase the cure temperature uniformly across the repair
To hold the repair patch in position until the adhesive sets
To consolidate plies, remove voids, and ensure intimate fiber-to-matrix contact (Correct answer)

Correct answer: To consolidate plies, remove voids, and ensure intimate fiber-to-matrix contact

Applied pressure (via vacuum bag or autoclave) compacts the fiber layers, expels entrapped air and excess resin, and ensures full consolidation for maximum structural properties.

Question 40: FAA Form 337 is used to document which of the following?

Annual inspection results
Engine time between overhauls
Major repairs and major alterations (Correct answer)
Routine scheduled maintenance

Correct answer: Major repairs and major alterations

FAA Form 337 is the Major Repair and Alteration form required to document and approve major repairs and alterations under 14 CFR Part 43.

Question 41: Which FAR part primarily governs the maintenance, preventive maintenance, rebuilding, and alteration of aircraft?

14 CFR Part 65
14 CFR Part 39
14 CFR Part 21
14 CFR Part 43 (Correct answer)

Correct answer: 14 CFR Part 43

14 CFR Part 43 specifically regulates the performance of maintenance, preventive maintenance, rebuilding, and alteration of aircraft.

Question 42: What is 'nitriding' as applied to aircraft engine crankshafts?

A surface hardening process using nitrogen gas to increase wear resistance (Correct answer)
A cadmium plating process applied to crankshaft journals
A chemical cleaning process to remove carbon deposits from journal surfaces
A heat treatment to relieve internal stress after grinding

Correct answer: A surface hardening process using nitrogen gas to increase wear resistance

Nitriding is a surface hardening process in which the crankshaft is exposed to ammonia gas at elevated temperature, infusing nitrogen into the steel to create a hard wear-resistant surface layer.

Question 43: The term 'continued airworthiness' under the ACS framework refers to:

An optional manufacturer maintenance program
Maintaining an aircraft to its type certificate standards throughout its operational life (Correct answer)
Flying until an aircraft breaks down
Issuing a new airworthiness certificate annually

Correct answer: Maintaining an aircraft to its type certificate standards throughout its operational life

Continued airworthiness means sustaining compliance with the aircraft's type design through ongoing maintenance and inspections throughout its life.

Question 44: If an aircraft hydraulic system uses MIL-PRF-5606 fluid and is inadvertently serviced with MIL-PRF-83282 fluid, what action is required?

No action; the fluids are completely interchangeable
Replace only the hydraulic pump since it is most susceptible to damage
Simply add the correct fluid to dilute the contamination
Flush the system and replace all seals, as the fluids have different seal compatibility (Correct answer)

Correct answer: Flush the system and replace all seals, as the fluids have different seal compatibility

MIL-PRF-5606 and MIL-PRF-83282 have different base oils and different seal material requirements, requiring a full system flush and seal replacement if mixed.

Question 45: What is the impact of regulatory changes on ACS professionals?

Regulatory changes only affect large organizations
Only government employees need to follow regulatory changes
Regulations never change once established
Regulatory changes require updating practices, procedures, and documentation to maintain compliance (Correct answer)

Correct answer: Regulatory changes require updating practices, procedures, and documentation to maintain compliance

Professionals must monitor and adapt to regulatory changes that affect their practice, ensuring continued compliance and effective service delivery.

Question 46: A 10-lb item is added at a station 50 inches aft of the CG. What is the moment change?

500 in-lb aft (Correct answer)
50 in-lb aft
500 in-lb forward
100 in-lb aft

Correct answer: 500 in-lb aft

Moment change = Weight × Arm from CG = 10 × 50 = 500 in-lb acting aft, tending to move the CG aft.

Question 47: What is the purpose of a penetrameter (Image Quality Indicator, IQI) in radiographic testing?

To verify that the radiograph has sufficient sensitivity and quality to detect a defined minimum flaw size (Correct answer)
To measure the total radiation dose received by the technician
To remove scattered radiation artifacts from the film
To calibrate the X-ray machine voltage and current settings

Correct answer: To verify that the radiograph has sufficient sensitivity and quality to detect a defined minimum flaw size

An IQI/penetrameter is placed on the part during exposure; its visibility on the finished radiograph confirms that the technique has adequate sensitivity to detect the minimum required discontinuity size.

Question 48: What document governs the minimum bend radii and tube material specifications for aircraft fluid lines?

AC 43.13-1B Chapter 9 and the applicable aircraft maintenance manual (Correct answer)
FAR Part 21
MIL-SPEC-5015 only
NFPA 407

Correct answer: AC 43.13-1B Chapter 9 and the applicable aircraft maintenance manual

AC 43.13-1B Chapter 9 provides the FAA-accepted data for aircraft plumbing including bend radii, materials, flare types, and installation standards, supplemented by the AMM.

Question 49: Which NDT method is most appropriate for detecting internal voids and delaminations in composite aircraft structures?

Eddy current inspection
Magnetic particle inspection
Ultrasonic inspection or tap testing (Correct answer)
Dye penetrant inspection

Correct answer: Ultrasonic inspection or tap testing

Ultrasonic testing and tap testing are the primary methods for detecting internal defects such as voids and delaminations in composite structures.

Question 50: What documentation best practices should ACS professionals follow?

Maintain thorough, accurate, timely records that support findings, decisions, and compliance requirements (Correct answer)
Brief notes are always sufficient
Documentation is only needed for billing purposes
Documentation can be completed months after the work

Correct answer: Maintain thorough, accurate, timely records that support findings, decisions, and compliance requirements

Comprehensive documentation provides an audit trail, supports decision-making, facilitates knowledge transfer, and demonstrates compliance with professional standards.

Question 51: Which document provides type-specific limitations, required equipment, and approved data sources for a certificated aircraft?

Aircraft logbook
FAA Form 337
Pilot's Operating Handbook
Type Certificate Data Sheet (TCDS) (Correct answer)

Correct answer: Type Certificate Data Sheet (TCDS)

The TCDS is the official FAA document that defines certification basis, approved configurations, required equipment, and limitations for a specific aircraft type.

Question 52: What type of fuel is used in most turbine-powered aircraft operated in the United States?

100LL AVGAS
Jet-A (kerosene-based turbine fuel) (Correct answer)
MOGAS (automotive gasoline)
Jet-B wide-cut turbine fuel

Correct answer: Jet-A (kerosene-based turbine fuel)

Jet-A is the standard turbine fuel used in most US turbine aircraft, with a flash point above 100°F and freeze point around -40°C.

Question 53: Which instrument uses a Wheatstone bridge circuit to measure fuel quantity?

The float-type fuel quantity system
The pressure-differential fuel system
The resistor-type fuel quantity system
The capacitance-type fuel quantity system (Correct answer)

Correct answer: The capacitance-type fuel quantity system

Capacitance-type fuel quantity systems use a Wheatstone bridge to compare capacitance values and determine fuel quantity accurately.

Question 54: What is the importance of professional networking in aviation maintenance?

Building relationships with peers enables knowledge sharing, professional development, and career advancement (Correct answer)
Networking is a waste of time for established professionals
Only online networking has value
Networking only benefits entry-level professionals

Correct answer: Building relationships with peers enables knowledge sharing, professional development, and career advancement

Professional networks provide opportunities for knowledge exchange, mentorship, collaboration, and staying informed about industry trends and opportunities.

Question 55: In a pneumatic de-icing system, what is the function of a distributor valve?

Control the flow rate of bleed air to maintain boot inflation time
Filter moisture from bleed air before it reaches the de-ice boots
Sequence the inflation and deflation of individual de-ice boot sections (Correct answer)
Regulate bleed air pressure to the de-ice boots to a safe working pressure

Correct answer: Sequence the inflation and deflation of individual de-ice boot sections

The distributor valve sequences inflation of leading-edge boot sections in the correct order to most effectively shed ice while minimizing bleed air consumption.

Question 56: What is the significance of a 'return to service' signature by a certificated mechanic?

It satisfies all AD requirements automatically
It certifies that the work was performed per approved data and the aircraft is airworthy (Correct answer)
It transfers liability to the aircraft owner
It authorizes the next scheduled maintenance

Correct answer: It certifies that the work was performed per approved data and the aircraft is airworthy

The return to service signature is the mechanic's professional certification that work was accomplished per approved standards and the aircraft is airworthy.

Question 57: What is the correct procedure if a hydraulic system fluid sample indicates particle contamination above allowable limits?

Add a chemical dispersant to the fluid to dissolve the particles
Continue operation but reduce system pressure by 10% to compensate
Filter the system fluid through progressively finer portable filters
Replace the hydraulic fluid and clean or replace contaminated components per maintenance manual (Correct answer)

Correct answer: Replace the hydraulic fluid and clean or replace contaminated components per maintenance manual

Contamination above allowable limits requires fluid replacement and inspection/cleaning of components because dispersants are not approved and portable filtering may not address the contamination source.

Question 58: When installing a hydraulic fitting using the B-nut (union nut) method on a flared tube, what is the correct sequence?

Tighten the B-nut first to seat the flare, then back off and retighten to torque
Slide the B-nut onto the tube before flaring, then flare the tube and tighten (Correct answer)
Flare the tube first, then thread the B-nut over the flared end
Install B-nut, then flare the tube, then tighten

Correct answer: Slide the B-nut onto the tube before flaring, then flare the tube and tighten

The B-nut must be slid onto the tube before flaring because the nut cannot pass over a completed flare, making pre-positioning mandatory.

Question 59: When troubleshooting an intermittent avionics failure, what is the recommended first approach?

Replace the suspected unit immediately
Duplicate the failure condition, inspect connectors and wiring for corrosion or loose connections (Correct answer)
Send the unit for bench testing even if the fault cannot be duplicated
Monitor the system over several flights before taking action

Correct answer: Duplicate the failure condition, inspect connectors and wiring for corrosion or loose connections

Intermittent avionics faults are most commonly caused by poor connections; inspecting connectors and wiring while attempting to duplicate the failure is the systematic first step.

Question 60: What type of inspection uses sound waves to detect material flaws?

Visual inspection
Dye penetrant inspection
Ultrasonic inspection (Correct answer)
Magnetic particle inspection

Correct answer: Ultrasonic inspection

Ultrasonic inspection uses high-frequency sound waves to detect flaws inside materials.

FAA Aviation Mechanic – ACS Airman Certification Standards Knowledge Test

The FAA Aviation Mechanic knowledge test evaluates candidates on general aviation maintenance principles, airframe systems, fuel/hydraulic systems, and NDT inspection skills required to earn an FAA Mechanic Certificate under the Airman Certification Standards (ACS) framework.

Questions

150 min

Time Limit

70%

To Pass

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