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

Question 1: What document governs the minimum bend radii and tube material specifications for aircraft fluid lines?

FAR Part 21
MIL-SPEC-5015 only
AC 43.13-1B Chapter 9 and the applicable aircraft maintenance manual (Correct answer)
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 2: What continuing education is typically required in weight & balance?

Only education obtained before certification matters
Regular training to stay current with industry standards, regulations, and best practices (Correct answer)
No continuing education is ever required
Training is only needed in the first year of certification

Correct answer: Regular training to stay current with industry standards, regulations, and best practices

Professional fields require ongoing education to ensure practitioners stay current with evolving standards, technologies, regulations, and best practices in their specialty.

Question 3: What is the purpose of a fuel heat exchanger on a turbine aircraft?

To use fuel to cool engine oil while also preventing fuel system icing by warming the fuel (Correct answer)
To chill fuel for increased density and greater range
To separate water from fuel using temperature differential
To increase fuel temperature for improved combustion efficiency

Correct answer: To use fuel to cool engine oil while also preventing fuel system icing by warming the fuel

The fuel-oil heat exchanger cools hot engine oil using cooler fuel as the heat sink, simultaneously warming the fuel to prevent ice crystal formation in the fuel system.

Question 4: An engine oil analysis report shows elevated iron and chrome levels. What engine components are most likely experiencing abnormal wear?

Crankshaft main bearings
Piston rings and cylinder walls (Correct answer)
Oil pump gears
Camshaft and lifters

Correct answer: Piston rings and cylinder walls

Chrome (from chrome-plated rings) and iron (from cylinder walls) appearing together in oil analysis are classic indicators of ring and cylinder bore wear.

Question 5: When checking ignition timing using a timing light on a running engine, the light should flash at what point relative to the crankshaft?

At the specified degrees before TDC (Correct answer)
At BDC on the power stroke
At TDC on the compression stroke
At the intake valve opening point

Correct answer: At the specified degrees before TDC

Ignition timing is set to fire the spark plug at a specified number of degrees before TDC to allow the fuel-air mixture to reach peak pressure at the optimal piston position.

Question 6: What does the term 'floating ground' indicate in aircraft wiring troubleshooting?

A wire that is not connected to any circuit
A shielded coaxial cable ground
A ground wire with excessive resistance or an open circuit (Correct answer)
A grounded circuit with proper continuity

Correct answer: A ground wire with excessive resistance or an open circuit

A floating ground refers to a ground connection that has high resistance or is completely open, preventing proper circuit completion.

Question 7: According to FAA AC 43.13-1B, which statement about NDT method selection is correct?

Visual inspection alone is sufficient for all primary structural inspections if performed by a certificated A&P mechanic
The NDT method used must be specified in the manufacturer's maintenance manual or approved equivalent data for that inspection (Correct answer)
NDT is only required on powerplant components, not airframe structures
Any NDT method may be substituted for another without engineering approval if the inspector has been trained in both

Correct answer: The NDT method used must be specified in the manufacturer's maintenance manual or approved equivalent data for that inspection

FAA AC 43.13-1B requires that the NDT method and procedure must be those specified in the manufacturer's approved maintenance data; substituting methods without engineering approval is not acceptable.

Question 8: What type of fuel is used in most turbine-powered aircraft operated in the United States?

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

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 9: When may a certificated mechanic return an aircraft to service after performing a major alteration?

Only if the mechanic holds an Inspection Authorization (Correct answer)
After completing a test flight
After completing the work and making proper maintenance record entries with approved data
Only after FAA Form 337 is approved by the local FSDO

Correct answer: Only if the mechanic holds an Inspection Authorization

Returning an aircraft to service after a major alteration requires an IA or DAR, not just a basic A&P certificate.

Question 10: What is the scope of practice for ACS certification in composite materials & repair?

Defined boundaries of competence and authority established by the certifying body and applicable regulations (Correct answer)
Only the employer defines the scope of practice
The scope is determined individually by each professional
There are no limits on what certified professionals can do

Correct answer: Defined boundaries of competence and authority established by the certifying body and applicable regulations

Scope of practice defines the activities, procedures, and processes that a certified professional is authorized to perform based on their education, training, and certification level.

Question 11: A DME indicator shows distance but the reading fluctuates erratically. Which component is most likely at fault?

The VOR receiver co-located with the DME
The DME transponder reply decoder
The DME antenna (Correct answer)
The aircraft power supply voltage regulator

Correct answer: The DME antenna

An intermittent DME antenna connection causes fluctuating interrogation signal strength, resulting in erratic distance readings.

Question 12: During engine run-up, a pilot reports intermittent engine roughness that disappears when carburetor heat is applied. What does this indicate?

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

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 13: What is the function of a hydraulic power transfer unit (PTU)?

Transfer fluid between two separate hydraulic systems without cross-contaminating the fluids (Correct answer)
Convert hydraulic energy to electrical energy for emergency power
Maintain equal pressure in both main and backup hydraulic systems
Pump fluid when the engine-driven pump fails

Correct answer: Transfer fluid between two separate hydraulic systems without cross-contaminating the fluids

A PTU allows one hydraulic system to power another using a hydraulic motor/pump combination, transferring power but keeping the fluids isolated.

Question 14: What is the most important ethical consideration for ACS professionals in hydraulic & pneumatic systems?

Maintaining objectivity, integrity, and confidentiality in all professional work (Correct answer)
Maximizing personal profit from each engagement
Avoiding all challenging work assignments
Sharing all client information publicly

Correct answer: Maintaining objectivity, integrity, and confidentiality in all professional work

ACS professionals must maintain the highest ethical standards including objectivity, integrity, and confidentiality to protect clients and uphold professional credibility.

Question 15: What is the primary function of an aircraft hydraulic system?

To provide drinking water to passengers
To fuel the aircraft engines
To transmit force for operating flight controls, landing gear, brakes, and other high-load mechanisms (Correct answer)
To cool the engine compartment

Correct answer: To transmit force for operating flight controls, landing gear, brakes, and other high-load mechanisms

Aircraft hydraulic systems use pressurized fluid to operate heavy-duty mechanisms like flight controls, landing gear retraction/extension, brakes, nose wheel steering, and thrust reversers.

Question 16: What does a 'red arc' on an aircraft instrument face represent?

Manufacturer-recommended cruise range
Caution or precautionary range
Normal operating range
Never-exceed or maximum limit (Correct answer)

Correct answer: Never-exceed or maximum limit

A red arc or red radial line on an instrument denotes a never-exceed speed or maximum operating limit that must not be exceeded.

Question 17: What is the correct method for splicing aircraft wiring when a connector is not available?

Use a wire nut connector
Solder the splice without any additional protection
Use a solderless crimp splice with approved heat-shrink tubing (Correct answer)
Twist the wires together and wrap with electrical tape

Correct answer: Use a solderless crimp splice with approved heat-shrink tubing

FAA-approved crimped splices with heat-shrink tubing are the correct method; wire nuts and tape are not approved for aircraft.

Question 18: How should discrepancies be documented during inspection?

Only after repairs
On personal notes
By verbal communication only
In maintenance logbooks (Correct answer)

Correct answer: In maintenance logbooks

All discrepancies should be clearly recorded in the maintenance records/logbooks.

Question 19: Which NDT method is most effective for detecting surface and near-surface cracks in ferromagnetic aircraft components?

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

Correct answer: Magnetic particle inspection

Magnetic particle inspection (MPI) is specifically designed for ferromagnetic materials and can reveal both surface and subsurface discontinuities by applying a magnetic field and iron particles.

Question 20: According to 14 CFR Part 39, an Airworthiness Directive (AD) that requires compliance within a specific number of hours time-in-service must be complied with:

Within 30 days of the AD's effective date regardless of hours
Before exceeding the specified hours time-in-service (Correct answer)
At the owner's discretion within one year of the effective date
At the next scheduled maintenance interval after the hours are accumulated

Correct answer: Before exceeding the specified hours time-in-service

ADs with hour-based compliance requirements must be accomplished before the aircraft exceeds the specified time-in-service threshold.

Question 21: The FAA's Aviation Safety Hotline (1-800-255-1111) is used to report:

Weather hazards to ATC
Lost or stolen airman certificates
Near-midair collisions only
Alleged violations of aviation regulations or safety concerns (Correct answer)

Correct answer: Alleged violations of aviation regulations or safety concerns

The FAA Safety Hotline allows anyone to anonymously report suspected regulatory violations or safety hazards to the FAA.

Question 22: What must be done before reinstalling a propeller flange nut after engine overhaul?

Apply anti-seize compound to the threads to allow future removal without damaging the crankshaft
Verify the flange mating surfaces are clean, check the nut's thread condition, and torque to the manufacturer's specified value with a calibrated torque wrench (Correct answer)
Safety-wire the nut using 0.020-inch wire regardless of manufacturer specifications
Heat the nut to expand it for easier installation onto the crankshaft flange

Correct answer: Verify the flange mating surfaces are clean, check the nut's thread condition, and torque to the manufacturer's specified value with a calibrated torque wrench

The propeller flange nut must be torqued to manufacturer specification with a calibrated torque wrench after verifying clean mating surfaces; incorrect torque can lead to propeller separation.

Question 23: A suspected unapproved part (SUP) is discovered during maintenance. The correct action is to:

Return it to the supplier for a refund
Test it and install if it passes
Tag it, remove it from service, and report it to the FAA (Correct answer)
Install it if it fits correctly

Correct answer: Tag it, remove it from service, and report it to the FAA

FAA Order 8120.10 directs mechanics to remove SUPs from service, quarantine them, and report to the FAA's Suspected Unapproved Parts Program.

Question 24: Under an SMS framework, a 'just culture' policy primarily aims to:

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

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 25: What documentation is required when performing composite materials & repair work?

Detailed records of methods used, findings, conclusions, and supporting evidence (Correct answer)
No documentation is required for professional work
Only a verbal summary to the supervisor
Documentation is only needed if problems are found

Correct answer: Detailed records of methods used, findings, conclusions, and supporting evidence

Thorough documentation protects both the professional and the client, provides an audit trail, and ensures work can be reviewed, verified, or continued by others.

Question 26: What is the correct procedure if a hydraulic system fluid sample indicates particle contamination above allowable limits?

Continue operation but reduce system pressure by 10% to compensate
Add a chemical dispersant to the fluid to dissolve the particles
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 27: What is the correct procedure when a hydraulic system component is found to have a minor external seepage (not a drip) at a fitting?

Immediately ground the aircraft and replace all seals in the affected component
Apply an external sealant compound to stop the seepage temporarily
Tighten the fitting incrementally until seepage stops, regardless of torque limits
Clean the area and monitor for progression; replace if seepage becomes a drip or increases (Correct answer)

Correct answer: Clean the area and monitor for progression; replace if seepage becomes a drip or increases

Minor seepage that forms no drips is typically acceptable per maintenance manuals — it should be cleaned, identified, monitored, and addressed if it worsens to an active leak.

Question 28: Which document is the primary reference for an aircraft's approved weight and balance limits?

The FAA-approved Airplane Flight Manual (AFM) or Pilot's Operating Handbook (POH) (Correct answer)
The type certificate data sheet only
The repair station's work order
The aircraft maintenance logbook

Correct answer: The FAA-approved Airplane Flight Manual (AFM) or Pilot's Operating Handbook (POH)

The FAA-approved AFM or POH contains the official CG envelope, weight limits, and loading instructions for the aircraft.

Question 29: When inspecting control cable tension, you find the elevator cable is at 40 lbs when the maintenance manual specifies 50-70 lbs. What is required?

The cable tension is acceptable as long as it is above 30 lbs
Adjust cable tension to within the specified range using the cable turnbuckles (Correct answer)
Replace the cables as worn cables cause low tension
Document the finding and re-check at the next 100-hour inspection

Correct answer: Adjust cable tension to within the specified range using the cable turnbuckles

Flight control cables must be adjusted to within the manufacturer's specified tension range using the turnbuckles before the aircraft is returned to service.

Question 30: What is the main purpose of a pressurization system in an aircraft?

Provide fresh air
Maintain cabin pressure (Correct answer)
Prevent corrosion
Vent fuel tanks

Correct answer: Maintain cabin pressure

Pressurization systems maintain safe cabin pressure at high altitudes.

Question 31: What documentation is required when performing hydraulic & pneumatic systems work?

Detailed records of methods used, findings, conclusions, and supporting evidence (Correct answer)
Documentation is only needed if problems are found
Only a verbal summary to the supervisor
No documentation is required for professional work

Correct answer: Detailed records of methods used, findings, conclusions, and supporting evidence

Thorough documentation protects both the professional and the client, provides an audit trail, and ensures work can be reviewed, verified, or continued by others.

Question 32: What type of inspection uses sound waves to detect material flaws?

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

Correct answer: Ultrasonic inspection

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

Question 33: What is the primary reason aircraft reciprocating engines use sodium-filled exhaust valves?

Hollow sodium-filled valves weigh less than solid steel valves of the same strength
Sodium expands when heated to maintain a tight seal against the valve seat at operating temperature
Liquid sodium inside the valve transfers heat from the valve head to the stem, cooling the valve (Correct answer)
Sodium reacts with lead in aviation fuel to prevent valve seat recession

Correct answer: Liquid sodium inside the valve transfers heat from the valve head to the stem, cooling the valve

Liquid sodium moves back and forth inside the hollow valve stem as the engine runs, conducting heat from the hot valve head to the cooler stem and valve guide, preventing valve burning.

Question 34: Which agency enforces aviation safety regulations in the U.S.?

NASA
OSHA
FAA (Correct answer)
NTSB

Correct answer: FAA

The Federal Aviation Administration (FAA) regulates all aspects of civil aviation.

Question 35: Which of the following actions requires FAA Form 337 to be submitted to the FAA Aircraft Registration Branch?

Major repair or major alteration (Correct answer)
100-hour inspection on a Part 91 aircraft
Annual inspection approval
Engine oil change with filter replacement

Correct answer: Major repair or major alteration

FAA Form 337 for major repairs and alterations must be submitted to the Aircraft Registration Branch in Oklahoma City within 48 hours of return to service.

Question 36: What is the purpose of a penetrameter (Image Quality Indicator, IQI) in radiographic testing?

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

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 37: What is the maximum period after which a mechanic certificate expires if the holder fails to meet recency-of-experience requirements?

The certificate expires after 12 months of inactivity
The certificate is revoked automatically after 36 months
The certificate expires on the holder's birthday every two years
Mechanic certificates never expire but privileges lapse after 24 months of inactivity (Correct answer)

Correct answer: Mechanic certificates never expire but privileges lapse after 24 months of inactivity

FAA mechanic certificates do not have expiration dates, but privileges cannot be exercised unless recency-of-experience requirements under 14 CFR 65.83 are met.

Question 38: On a radiographic film, a darker area (higher film density) typically indicates what about the inspected material?

Correct exposure with no defects present
Greater material thickness or higher density in that area
A void, crack, or area of reduced material density allowing more radiation to pass through (Correct answer)
A surface contaminant blocking radiation

Correct answer: A void, crack, or area of reduced material density allowing more radiation to pass through

Darker areas on radiographic film indicate that more radiation reached the film in those regions, which occurs where material density is lower — such as at voids, cracks, or inclusions of lower-density material.

Question 39: What is the purpose of a hydraulic system case drain line on a variable displacement piston pump?

Return low-pressure fluid that bypasses the internal piston seals back to the reservoir (Correct answer)
Carry pump output to a secondary system during low-demand periods
Vent pressure from the pump housing if the outlet check valve fails
Supply lubrication fluid to the pump shaft bearing from an external source

Correct answer: Return low-pressure fluid that bypasses the internal piston seals back to the reservoir

Case drain lines return internal leakage fluid that bypasses piston seals back to the reservoir, preventing case pressure buildup that could damage pump shaft seals.

Question 40: A repair station technician notices an unapproved part installed on an aircraft during maintenance. The correct regulatory action is to:

Remove the unapproved part, ground the aircraft, and file an Aviation Safety Hotline report
Placard the part as 'unapproved' and allow continued operation
Install an approved replacement part and document the discovery in the maintenance record (Correct answer)
Continue the maintenance and notify the operator verbally

Correct answer: Install an approved replacement part and document the discovery in the maintenance record

The correct action is to replace the unapproved part with an FAA-approved part and document the finding and corrective action in the maintenance records.

Question 41: The 'Swiss Cheese Model' of accident causation, as applied to aviation maintenance, illustrates that accidents occur when:

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

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 42: 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?

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

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

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

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 44: What continuing education is typically required in composite materials & repair?

Only education obtained before certification matters
Training is only needed in the first year of certification
No continuing education is ever required
Regular training to stay current with industry standards, regulations, and best practices (Correct answer)

Correct answer: Regular training to stay current with industry standards, regulations, and best practices

Professional fields require ongoing education to ensure practitioners stay current with evolving standards, technologies, regulations, and best practices in their specialty.

Question 45: What is the main hazard of moisture contamination in a high-pressure pneumatic system?

Moisture reacts with nitrogen to form corrosive compounds
Moisture increases fluid viscosity, reducing flow rates
Moisture can freeze at altitude, blocking orifices and valves (Correct answer)
Moisture causes pump cavitation at sea level

Correct answer: Moisture can freeze at altitude, blocking orifices and valves

Water moisture in pneumatic lines can freeze at altitude temperatures, blocking critical orifices, valves, and lines, causing system failure.

Question 46: What career advancement paths exist for ACS certified professionals?

No advancement is possible beyond initial certification
Only changing careers provides advancement
Leadership roles, specialized consulting, education and training, and executive management positions (Correct answer)
Advancement requires leaving the field entirely

Correct answer: Leadership roles, specialized consulting, education and training, and executive management positions

Certified professionals can advance through specialization, leadership roles, consulting, academic/training positions, and executive management within their field.

Question 47: What is the impact of regulatory changes on ACS professionals?

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

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 48: What parameter is monitored to detect early signs of internal engine bearing failure using oil analysis?

Silicon and chromium levels
Copper and silver levels (Correct answer)
Lead and tin levels
Iron and aluminum levels

Correct answer: Copper and silver levels

Copper and silver are typical bearing overlay and plating materials; elevated levels in oil analysis indicate bearing wear before catastrophic failure occurs.

Question 49: During a preflight fuel check, a pilot/mechanic finds a small amount of water in the fuel sample. The correct action is:

Continue sampling and draining until no water is found, verifying the sample is clear (Correct answer)
Add fuel system icing inhibitor and return to service
Drain only the affected sump and continue
Ground the aircraft indefinitely until the tank is removed

Correct answer: Continue sampling and draining until no water is found, verifying the sample is clear

When water is found in a fuel sample, continue draining and sampling from all sumps until all samples are consistently clear and free of water, then verify the quantity before flight.

Question 50: What is the purpose of a diode installed in parallel with a relay coil in an aircraft electrical circuit?

To increase the relay switching speed
To reduce current draw during relay operation
To provide redundant power to the relay coil
To suppress the voltage spike (back-EMF) generated when the relay de-energizes (Correct answer)

Correct answer: To suppress the voltage spike (back-EMF) generated when the relay de-energizes

A flyback (snubber) diode connected across a relay coil absorbs the inductive voltage spike that occurs when coil current is interrupted, protecting other circuit components.

Question 51: What is the purpose of a fuel crossfeed system on a multi-engine aircraft?

To dump fuel overboard in an emergency
To preheat fuel in cold weather
To feed both engines from either tank to manage fuel load or feed a live engine from any tank after an engine failure (Correct answer)
To transfer fuel only to the landing gear hydraulic reservoir

Correct answer: To feed both engines from either tank to manage fuel load or feed a live engine from any tank after an engine failure

A crossfeed system allows either engine to draw from any tank, balancing fuel loads and enabling a surviving engine to draw from the opposite side's tank after an engine failure.

Question 52: What is the correct torque technique when installing AN/MS flareless tube fittings?

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

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 53: Airworthiness Directives (ADs) issued by the FAA are:

Manufacturer service bulletins incorporated by reference
Recommended practices that operators may choose to follow
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 54: A mechanic who makes a maintenance error that goes undetected and results in an accident may face all of the following EXCEPT:

Civil lawsuit from affected parties
FAA certificate action
Automatic loss of all future FAA employment eligibility (Correct answer)
Criminal prosecution

Correct answer: Automatic loss of all future FAA employment eligibility

While mechanics can face certificate action, criminal charges, and civil liability, there is no automatic statutory bar from all FAA employment eligibility following an accident.

Question 55: After engine overhaul, a break-in run is performed. What oil type should NOT be used during engine break-in?

Straight mineral oil
Multi-viscosity mineral oil
Ashless dispersant oil
Synthetic oil (Correct answer)

Correct answer: Synthetic oil

Synthetic oil is too slippery during break-in and prevents cylinder walls from seating properly; mineral oil is required for new or overhauled engines.

Question 56: Which 14 CFR Part governs the certification of aviation mechanics?

Part 43
Part 147
Part 65 (Correct answer)
Part 91

Correct answer: Part 65

14 CFR Part 65 covers airmen other than flight crewmembers, including the certification requirements and privileges of aviation mechanics.

Question 57: Engine oil temperature rises above limits during taxi but returns to normal during climb. What is the most probable explanation?

Insufficient airflow at low taxi speeds with no forward motion cooling (Correct answer)
Incorrect oil viscosity grade
Defective oil cooler thermostat stuck closed
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 58: Which inspection method is best suited for detecting fatigue cracks in thick aluminum wing spars where cracks may be below the surface?

Surface eddy current inspection
Visual inspection with magnification
Ultrasonic inspection (Correct answer)
Dye penetrant inspection

Correct answer: Ultrasonic inspection

Ultrasonic inspection can penetrate thick aluminum to detect subsurface fatigue cracks, whereas surface methods like dye penetrant and eddy current only detect surface or near-surface defects.

Question 59: During maintenance, a mechanic finds corrosion on a primary structural member exceeding limits in the SRM. This is classified as a:

Minor repair
Preventive maintenance item
Major repair (Correct answer)
Cosmetic issue requiring no documentation

Correct answer: Major repair

Damage to primary structure exceeding manufacturer limits is a major repair requiring FAA-approved data and Form 337.

Question 60: Which formula correctly expresses the relationship used to find CG from weight and moment data?

CG = Total Moment ÷ Total Weight (Correct answer)
CG = Total Weight ÷ Total Moment
CG = Total Moment × Total Weight
CG = Weight × Moment

Correct answer: CG = Total Moment ÷ Total Weight

CG arm = Total Moment divided by Total Weight, giving the CG location in inches from the datum.

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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Exam Rules

You can skip questions and return to them later
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No feedback shown until you submit the entire exam
Unanswered questions count as wrong — answer everything
10 pretest questions are mixed in and don't affect your score
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