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

Question 1: Which document is the primary reference for an aircraft's approved weight and balance limits?

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

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 2: According to 14 CFR Part 39, compliance with an Airworthiness Directive is:

Optional if the owner signs a waiver
Mandatory and legally enforceable (Correct answer)
Required only for commercial operations
Advisory for aircraft over 20 years old

Correct answer: Mandatory and legally enforceable

ADs are issued under 14 CFR Part 39 and are mandatory federal regulations; non-compliance renders the aircraft unairworthy.

Question 3: During an annual inspection, you find a crack in an aircraft's aluminum skin near a rivet hole. What is the correct procedure?

Apply a patch and return to service without documentation
Immediately ground the aircraft and replace the entire panel
Report it in the maintenance log and defer repair
Measure the crack, determine if it exceeds limits, and consult manufacturer's structural repair manual (Correct answer)

Correct answer: Measure the crack, determine if it exceeds limits, and consult manufacturer's structural repair manual

The mechanic must measure the defect, compare it against the manufacturer's allowable limits in the SRM, and follow approved repair procedures.

Question 4: The ASRS (Aviation Safety Reporting System) offers reporters immunity from FAA certificate action primarily to:

Reward mechanics financially for reporting
Encourage candid, voluntary disclosure of safety hazards (Correct answer)
Replace mandatory accident reporting requirements
Provide legal immunity in civil lawsuits

Correct answer: Encourage candid, voluntary disclosure of safety hazards

ASRS immunity protects reporters so they will voluntarily disclose safety-relevant incidents without fear of certificate action, improving overall system safety.

Question 5: What career advancement paths exist for ACS certified professionals?

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

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 6: What does a bright fluorescent indication under UV (black) light during fluorescent penetrant inspection (FPI) indicate?

The developer has not yet reacted with the penetrant
Background fluorescence from the developer material only
Penetrant has been drawn out of a surface-opening discontinuity, indicating a crack or porosity (Correct answer)
The part surface was over-cleaned, removing all penetrant

Correct answer: Penetrant has been drawn out of a surface-opening discontinuity, indicating a crack or porosity

A bright fluorescent indication means penetrant trapped in a surface discontinuity has been drawn out by the developer and is fluorescing under UV light, revealing the location and extent of the flaw.

Question 7: An aircraft with a Continental fuel-injected engine experiences engine roughness after takeoff that smooths out as power is reduced. This symptom most closely suggests:

A lean condition caused by a blocked injector nozzle
Magneto timing retarded beyond limits
A cracked cylinder head affecting compression
A rich mixture condition, possibly caused by a malfunctioning fuel control unit (Correct answer)

Correct answer: A rich mixture condition, possibly caused by a malfunctioning fuel control unit

Roughness at high power that smooths at reduced power suggests an over-rich condition, as excess fuel is more problematic at higher power where flow is greatest.

Question 8: A reciprocating engine exhibits detonation during high-power operation. Which of the following will most effectively reduce detonation?

Enriching the fuel-air mixture (Correct answer)
Reducing cooling airflow
Advancing ignition timing
Leaning the mixture further

Correct answer: Enriching the fuel-air mixture

Enriching the mixture reduces cylinder temperatures and lowers the tendency for detonation by decreasing peak combustion temperatures.

Question 9: The concept of 'normalization of deviance' in aviation maintenance describes:

Using unapproved parts in low-risk applications
Applying engineering judgment instead of published data
Accepting small deviations from standards as normal over time until a serious failure occurs (Correct answer)
Documenting non-standard repairs with FAA approval

Correct answer: Accepting small deviations from standards as normal over time until a serious failure occurs

Normalization of deviance occurs when repeated minor violations of standards go uncorrected and become accepted as normal, increasing risk of catastrophic failure.

Question 10: What is the purpose of a pneumatic system bootstrap reservoir?

Pressurize the reservoir above atmospheric pressure to prevent pump cavitation at altitude (Correct answer)
Cool pneumatic fluid before it enters actuators
Store excess bleed air for use during engine failure
Act as an expansion chamber for thermal growth of pneumatic tubing

Correct answer: Pressurize the reservoir above atmospheric pressure to prevent pump cavitation at altitude

A bootstrap reservoir is pressurized above the fluid inlet pressure so the hydraulic or pneumatic pump receives adequate inlet pressure, preventing cavitation at high altitudes.

Question 11: When checking valve clearance (tappet clearance) on a reciprocating engine, the piston of the cylinder being checked must be positioned at:

Mid-stroke on the intake stroke
TDC on the compression stroke (Correct answer)
TDC on the exhaust stroke
BDC on the power stroke

Correct answer: TDC on the compression stroke

Valve clearance is checked with the piston at TDC on the compression stroke so that both intake and exhaust valves are fully closed.

Question 12: What type of fuel is used in most turbine-powered aircraft operated in the United States?

MOGAS (automotive gasoline)
Jet-A (kerosene-based turbine fuel) (Correct answer)
100LL AVGAS
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 13: Airworthiness Directives (ADs) issued by the FAA are:

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

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 14: What is the purpose of a firewall shutoff valve (fuel selector/firewall valve) in an aircraft fuel system?

To balance fuel between left and right tanks
To regulate fuel pressure to the engine
To allow the crew to stop fuel flow to the engine compartment in the event of an engine fire or fuel leak (Correct answer)
To filter fuel before it enters the engine

Correct answer: To allow the crew to stop fuel flow to the engine compartment in the event of an engine fire or fuel leak

The firewall shutoff valve allows the flight crew to cut fuel flow to the engine compartment to starve a fire or stop a fuel leak from reaching the engine bay.

Question 15: What standard must aircraft inspections comply with?

Mechanic's experience
FAA and manufacturer standards (Correct answer)
Local weather reports
Pilot's opinion

Correct answer: FAA and manufacturer standards

Inspections must comply with the manufacturer's instructions and FAA regulations.

Question 16: A reciprocating engine's tachometer shows 50 RPM higher than normal at a fixed throttle setting after maintenance. What adjustment was most likely made incorrectly?

Fuel injector nozzles cleaned
Primer system reconnected
Magneto timing advanced beyond specification (Correct answer)
Oil viscosity changed to a lighter grade

Correct answer: Magneto timing advanced beyond specification

Advancing magneto timing beyond specification causes the engine to produce more power at a given throttle setting, resulting in higher RPM.

Question 17: 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)
Annual inspection approval
100-hour inspection on a Part 91 aircraft
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 18: When installing a hydraulic fitting using the B-nut (union nut) method on a flared tube, what is the correct sequence?

Flare the tube first, then thread the B-nut over the flared end
Slide the B-nut onto the tube before flaring, then flare the tube and tighten (Correct answer)
Tighten the B-nut first to seat the flare, then back off and retighten to torque
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 19: What documentation is required when performing weight & balance work?

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

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 20: What condition causes a hydraulic pump to cavitate?

Fluid temperature drops below the pour point, increasing viscosity
System demand exceeds pump output, causing pressure fluctuations
Inlet pressure is too low, causing vapor bubbles to form in the fluid (Correct answer)
Outlet pressure exceeds the system relief valve setting

Correct answer: Inlet pressure is too low, causing vapor bubbles to form in the fluid

Cavitation occurs when fluid pressure at the pump inlet drops below the fluid's vapor pressure, causing vapor bubbles to form and then violently collapse, damaging pump internals.

Question 21: What is the purpose of a diode installed in parallel with a relay coil in an aircraft electrical circuit?

To provide redundant power to the relay coil
To increase the relay switching speed
To reduce current draw during relay operation
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 22: 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 23: During an eddy current inspection of an aluminum wing spar, a large meter deflection is noted at a specific location. This most likely indicates:

A crack, corrosion, or other discontinuity at that location requiring further evaluation (Correct answer)
Normal variation in aluminum alloy composition
The spar material is heat-treated aluminum
Interference from nearby ferromagnetic hardware

Correct answer: A crack, corrosion, or other discontinuity at that location requiring further evaluation

Eddy current meter deflections indicate changes in conductivity or permeability caused by cracks, corrosion, or thickness variations requiring further investigation.

Question 24: A mechanic discovers an Airworthiness Directive applies to a component already installed on an aircraft. The AD has a compliance time of 'next scheduled inspection.' What must the mechanic do?

Comply with the AD at or before the next scheduled inspection (Correct answer)
Contact the FAA for an exemption
Ground the aircraft immediately
Note it in the logbook and defer until owner requests it

Correct answer: Comply with the AD at or before the next scheduled inspection

The compliance time stated in the AD establishes the deadline; the mechanic must accomplish it no later than that time.

Question 25: Which document serves as the authoritative source for an aircraft's certificated weight, engine model, and fuel type?

The aircraft flight manual (AFM)
The Type Certificate Data Sheet (TCDS) (Correct answer)
The aircraft maintenance manual (AMM)
The weight and balance report

Correct answer: The Type Certificate Data Sheet (TCDS)

The TCDS is the FAA's official record of the design specifications and limitations for a certificated aircraft.

Question 26: What is the regulatory requirement for retaining maintenance records after the work is performed?

Records are the owner's property and may be discarded at any time
Records must be kept until the aircraft is scrapped
Records must be kept for 2 years after the work
Records must be kept for 1 year or until the work is repeated (Correct answer)

Correct answer: Records must be kept for 1 year or until the work is repeated

14 CFR 43.9 and 91.417 generally require maintenance records to be retained for 1 year or until superseded by equivalent work.

Question 27: What documentation is required when performing hydraulic & pneumatic systems work?

Only a verbal summary to the supervisor
Detailed records of methods used, findings, conclusions, and supporting evidence (Correct answer)
Documentation is only needed if problems are found
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 28: What is the role of the FAA's Safety Management System (SMS) concept as it relates to maintenance operations?

To replace individual mechanic judgment with automated checklists
To provide a systematic approach for managing safety risks in an organization (Correct answer)
To certify avionics technicians separately from airframe mechanics
To eliminate the need for AD compliance tracking

Correct answer: To provide a systematic approach for managing safety risks in an organization

SMS provides a structured, organization-wide framework to proactively identify and control safety risks in aviation maintenance.

Question 29: When inspecting flexible hydraulic hose for serviceability, which condition requires immediate replacement?

A small area of faded color on the outer jacket from UV exposure
Minor routing deviation of less than 10% from the installed bend radius
Wire braid visible through the outer cover at any point (Correct answer)
Slight surface scuffing on the outer protective jacket without wire braid exposure

Correct answer: Wire braid visible through the outer cover at any point

Exposed wire braid indicates the outer protective cover is compromised, meaning the hose is susceptible to further damage and must be replaced immediately.

Question 30: The correct nitrogen pressure for servicing an aircraft oleo strut is found in the:

FAR Part 91
Aircraft Maintenance Manual for the specific aircraft (Correct answer)
Tire manufacturer's data plate
AC 43.13-1B Table 1

Correct answer: Aircraft Maintenance Manual for the specific aircraft

Nitrogen servicing pressure for an oleo strut is specified in the Aircraft Maintenance Manual and varies by aircraft type, strut position, and aircraft gross weight.

Question 31: When performing a static RPM run-up, the engine reaches maximum RPM but both magneto checks show a greater-than-normal drop. What should the mechanic suspect first?

Retarded ignition timing on both magnetos
Carburetor air leak
Fouled spark plugs (Correct answer)
Enriched mixture setting

Correct answer: Fouled spark plugs

Fouled or carbon-bridged spark plugs are the most common cause of excessive RPM drop on both magneto checks simultaneously.

Question 32: Which type of hydraulic seal is most commonly used between two parts that have relative motion (dynamic application)?

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

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 33: An aircraft has a MAC of 60 inches. The LEMAC is at fuselage station 128. If the CG is at station 146, what is the %MAC?

36.7% MAC
30.0% MAC
30% MAC (Correct answer)
18.0% MAC

Correct answer: 30% MAC

%MAC = ((CG station – LEMAC) ÷ MAC) × 100 = ((146 – 128) ÷ 60) × 100 = 30%.

Question 34: A turbocharged engine's manifold pressure continues to rise after the throttle is advanced to a set position. What component has likely failed?

Wastegate controller (Correct answer)
Intercooler bypass valve
Fuel control unit
Throttle body seal

Correct answer: Wastegate controller

A failed wastegate that sticks closed prevents exhaust from bypassing the turbine, causing uncontrolled manifold pressure rise (overboosting).

Question 35: What is the primary purpose of a fuel strainer (gascolator) in a reciprocating aircraft engine fuel system?

To prevent vapor lock in the fuel lines
To measure fuel flow rate
To regulate fuel pressure to the engine
To remove water and sediment from fuel before it reaches the carburetor or fuel injector (Correct answer)

Correct answer: To remove water and sediment from fuel before it reaches the carburetor or fuel injector

A fuel strainer (gascolator) filters water and particulate contamination from the fuel before it enters the engine fuel metering system.

Question 36: What is the scope of practice for ACS certification in hydraulic & pneumatic systems?

The scope is determined individually by each professional
Only the employer defines the scope of practice
Defined boundaries of competence and authority established by the certifying body and applicable regulations (Correct answer)
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 37: When must a maintenance log entry be made?

Only after inspections
Only after engine overhauls
Every time maintenance is performed (Correct answer)
At the end of the year

Correct answer: Every time maintenance is performed

A maintenance log entry must be made anytime maintenance, preventive maintenance, or alteration is performed.

Question 38: A fuselage frame made of 4130 steel tubing has a crack in a non-primary member. Which welding rod is most appropriate for repair?

ER4043
E308L
E6013
ER70S-2 (Correct answer)

Correct answer: ER70S-2

ER70S-2 is the correct TIG welding rod for 4130 chromoly steel airframe tubing repairs, providing compatible strength and weld characteristics.

Question 39: Which formula correctly expresses the relationship used to find CG from weight and moment data?

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

Question 40: What is the purpose of a fuel crossfeed system on a multi-engine aircraft?

To transfer fuel only to the landing gear hydraulic reservoir
To preheat fuel in cold weather
To dump fuel overboard in an emergency
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)

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

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

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 42: When replacing an aircraft battery, what information must be recorded in the aircraft maintenance records?

Date, battery part number, serial number, battery type, and a description of the work performed (Correct answer)
Date and next scheduled replacement interval only
Only the date of replacement and technician's name
Only the battery voltage and capacity rating

Correct answer: Date, battery part number, serial number, battery type, and a description of the work performed

Per 14 CFR Part 43.9, maintenance records must describe the work, include a reference to data used, date, and the certificate number of the person performing the work, including battery traceability data.

Question 43: An aircraft's ELT activates inadvertently on the ground. What is the required action?

Deactivate it immediately and report the inadvertent activation to the nearest FAA FSDO
Notify ATC immediately and deactivate the ELT as quickly as possible (Correct answer)
Replace the ELT before the next flight regardless of the reason for activation
Allow it to transmit for no more than 10 minutes, then deactivate

Correct answer: Notify ATC immediately and deactivate the ELT as quickly as possible

An inadvertent ELT activation must be silenced immediately, and ATC must be notified to prevent unnecessary search and rescue operations.

Question 44: After an alteration that changes aircraft weight or balance, the mechanic must:

Only update the logbook entry
Ground the aircraft until a new type certificate is issued
Reweigh the aircraft and update the weight and balance record (Correct answer)
Notify the FAA within 30 days

Correct answer: Reweigh the aircraft and update the weight and balance record

Any alteration affecting weight or CG requires reweighing and updating the official weight and balance data in the aircraft records.

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

Regulations never change once established
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

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: What is the minimum dwell time typically specified for dye penetrant inspection of standard discontinuities in aluminum alloy parts?

1 to 2 hours
30 seconds
5 to 30 minutes (Correct answer)
1 minute

Correct answer: 5 to 30 minutes

For most aluminum alloy parts, penetrant dwell times typically range from 5 to 30 minutes to allow adequate capillary action into discontinuities, as specified by the applicable process specification.

Question 47: What is the significance of 'oil consumption trend monitoring' in turbine engine health management?

Monitoring trends determines the oil viscosity grade for the next service
A sudden increase in oil consumption can indicate bearing failure or internal seal deterioration (Correct answer)
Oil consumption trends are used to calculate fuel burn efficiency
Oil consumption trend predicts when the next oil change should be performed

Correct answer: A sudden increase in oil consumption can indicate bearing failure or internal seal deterioration

Sudden increases in oil consumption are an early warning of bearing wear, internal seal failure, or other internal engine degradation before catastrophic failure occurs.

Question 48: Under the ACS standards, a mechanic must demonstrate knowledge of quality assurance by understanding that an Inspection Authorization (IA) is required to:

Sign off on 100-hour inspection records
Install PMA parts
Approve an aircraft for return to service after an annual inspection (Correct answer)
Perform routine oil changes on turbine engines

Correct answer: Approve an aircraft for return to service after an annual inspection

Annual inspections can only be approved for return to service by a mechanic holding an IA, per 14 CFR 65.95.

Question 49: A mechanic completes a 100-hour inspection and finds several discrepancies. The aircraft owner declines repairs. What must the mechanic do?

Return the aircraft to service anyway
Ground the aircraft permanently
Refuse to sign off the inspection and note discrepancies in writing to the owner (Correct answer)
Contact the FAA immediately

Correct answer: Refuse to sign off the inspection and note discrepancies in writing to the owner

The mechanic must not approve an unairworthy aircraft for return to service and must advise the owner in writing of discrepancies found.

Question 50: 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)
NFPA 407
MIL-SPEC-5015 only
FAR Part 21

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 51: What qualifications are needed for advanced aviation mechanics practice?

Only a college degree in any subject
Advanced practice requires no formal credentials
Advanced certifications, specialized training, demonstrated experience, and ongoing professional development (Correct answer)
No additional qualifications beyond initial certification

Correct answer: Advanced certifications, specialized training, demonstrated experience, and ongoing professional development

Advanced practice requires building upon foundational knowledge through specialized certifications, targeted training, and demonstrated competence in specific areas.

Question 52: How do ACS professionals contribute to organizational success?

Only executives contribute to organizational success
Professional expertise has minimal organizational value
They only perform routine tasks with no strategic impact
By applying specialized knowledge to solve problems, reduce risks, improve processes, and drive strategic outcomes (Correct answer)

Correct answer: By applying specialized knowledge to solve problems, reduce risks, improve processes, and drive strategic outcomes

Certified professionals bring specialized expertise that directly contributes to organizational goals through problem-solving, risk reduction, process improvement, and strategic decision support.

Question 53: What reading on a differential compression tester indicates a cylinder is in acceptable condition?

Equal pressure on both gauges only at TDC
Less than 25 psi differential between reference and cylinder pressure (Correct answer)
Differential pressure greater than 80/80
Greater than 50% pressure drop

Correct answer: Less than 25 psi differential between reference and cylinder pressure

FAA guidance generally accepts cylinders with no more than a 25% (about 20 psi on an 80 psi tester) differential pressure drop as serviceable.

Question 54: What causes brake fade on aircraft disc brakes during repeated hard stops?

Excessive heat buildup reducing friction between pads and disc (Correct answer)
Low hydraulic fluid viscosity
Air in the brake lines
Worn brake pressure seals

Correct answer: Excessive heat buildup reducing friction between pads and disc

Brake fade occurs when excessive heat reduces the coefficient of friction between the brake pads and disc, decreasing stopping effectiveness.

Question 55: What is the main hazard of moisture contamination in a high-pressure pneumatic system?

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

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 56: Honeycomb core damage repair typically requires restoring core density primarily to:

Provide an attachment point for skin repair plies
Restore the electrical conductivity of the panel
Prevent moisture ingress into the honeycomb cells
Maintain the compressive and shear strength the core provides to the sandwich panel (Correct answer)

Correct answer: Maintain the compressive and shear strength the core provides to the sandwich panel

Honeycomb core transfers shear loads between face sheets and provides compressive stability; restoring equivalent density/cell size is essential for structural integrity.

Question 57: What type of hydraulic pump is most commonly used in high-performance aircraft as an engine-driven pump due to its variable output capability?

Variable displacement piston pump (Correct answer)
Vane pump
Gear pump
Centrifugal pump

Correct answer: Variable displacement piston pump

Variable displacement piston pumps can adjust their output flow based on system demand, maintaining constant pressure while reducing heat generation and power consumption when demand is low.

Question 58: Which type of visual inspection tool is used to inspect the interior of an engine cylinder without disassembly?

Borescope (Correct answer)
Dial indicator
Feeler gauge
Micrometer

Correct answer: Borescope

A borescope is an optical instrument with a rigid or flexible tube used to inspect the interior of inaccessible areas such as engine cylinders without requiring disassembly.

Question 59: The glass transition temperature (Tg) of a cured composite resin is important because:

It specifies the lowest operational temperature for the composite
It defines the temperature at which the fibers begin to melt
It determines the maximum cure temperature allowed during manufacturing
Above Tg, the resin softens significantly and loses stiffness and strength (Correct answer)

Correct answer: Above Tg, the resin softens significantly and loses stiffness and strength

The glass transition temperature is the point above which an amorphous polymer transitions from a rigid glassy state to a rubbery state, causing a dramatic drop in structural properties.

Question 60: Which eddy current probe orientation is most effective for detecting cracks perpendicular to the surface on a flat plate?

Encircling probe
Bobbin probe
Surface (pancake) probe (Correct answer)
Reflection probe

Correct answer: Surface (pancake) probe

A surface (pancake) probe placed flat against the test surface is most effective for detecting surface cracks in flat materials because its coil orientation maximizes sensitivity to surface discontinuities.

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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