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

Question 1: An aircraft exhaust system inspection reveals blue discoloration on the exhaust stack. This is significant because it may indicate:

Incomplete combustion from an over-rich mixture
A lean mixture causing excess cylinder head temperature
Normal oxidation from high heat cycles
Engine oil leaking into the exhaust or extreme overheating of the exhaust system (Correct answer)

Correct answer: Engine oil leaking into the exhaust or extreme overheating of the exhaust system

Blue discoloration on exhaust components can indicate oil contamination in the exhaust stream or localized overheating, both of which require investigation for engine health.

Question 2: What is the most important ethical consideration for ACS professionals in hydraulic & pneumatic systems?

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

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 3: Which component in a pneumatic system performs the same function as a hydraulic system relief valve?

Pressure regulator
Check valve
Filter/separator
Pressure relief valve (Correct answer)

Correct answer: Pressure relief valve

A pneumatic pressure relief valve protects the system from overpressure just as a hydraulic relief valve does, opening to vent excess pressure to atmosphere.

Question 4: What documentation best practices should ACS professionals follow?

Documentation is only needed for billing purposes
Maintain thorough, accurate, timely records that support findings, decisions, and compliance requirements (Correct answer)
Brief notes are always sufficient
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 5: When servicing an oleo strut, the correct fluid level is verified by:

Measuring strut extension with a ruler only
Checking the fluid reservoir sight glass
Deflating the strut fully, adding fluid to the specified level, then re-inflating with nitrogen (Correct answer)
Using a pressure gauge on the Schrader valve

Correct answer: Deflating the strut fully, adding fluid to the specified level, then re-inflating with nitrogen

The correct procedure is to fully deflate the strut, fill it with the specified hydraulic fluid to the proper level, then re-inflate with dry nitrogen to the manufacturer's specified pressure.

Question 6: An engine cylinder head temperature (CHT) gauge shows one cylinder consistently 50°F hotter than the others in level cruise. What should be inspected first?

Spark plug gap on that cylinder
Fuel injector flow rate for that cylinder
Cylinder baffling and cooling fins for that cylinder (Correct answer)
Valve timing on that cylinder

Correct answer: Cylinder baffling and cooling fins for that cylinder

Damaged or missing baffling disrupts cooling airflow to individual cylinders and is the most common cause of a single cylinder running consistently hotter.

Question 7: After engine overhaul, a break-in run is performed. What oil type should NOT be used during engine break-in?

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

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 8: What does a hydraulic system pressure relief valve protect against?

Filter bypass due to clogging
Fluid contamination entering the actuator
Pump cavitation during low-fluid conditions
Thermal expansion causing pressure spikes that exceed system design limits (Correct answer)

Correct answer: Thermal expansion causing pressure spikes that exceed system design limits

The pressure relief valve opens to bypass fluid back to the reservoir when system pressure exceeds the maximum design limit, protecting components from overpressure damage.

Question 9: According to 14 CFR Part 39, compliance with an Airworthiness Directive is:

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

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 10: What is the correct tube material for a high-pressure aircraft fuel line (above 1,500 PSI)?

Corrosion-resistant steel (CRES / stainless steel) or titanium (Correct answer)
Copper tubing
Aluminum alloy 5052-O
Rigid PVC tubing

Correct answer: Corrosion-resistant steel (CRES / stainless steel) or titanium

High-pressure fuel lines require CRES (stainless steel) or titanium tubing for the strength and corrosion resistance needed at pressures above 1,500 PSI.

Question 11: An aircraft weighs 3,200 lb with a CG at 95.0 inches. A 50 lb item is removed from a station 120.0 inches aft of datum. What is the new CG?

94.6 inches (Correct answer)
95.4 inches
96.3 inches
93.1 inches

Correct answer: 94.6 inches

New weight = 3,150 lb; Moment removed = 50×120 = 6,000; New moment = (3,200×95) – 6,000 = 298,000; CG = 298,000÷3,150 ≈ 94.6 inches.

Question 12: 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 filter fuel before it enters the engine
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)

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 13: 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 14: When performing a repair to aircraft fabric covering using the brush method, the fabric patches should overlap the damaged area by a minimum of:

2 inches on all sides (Correct answer)
3 inches on all sides
1/2 inch on all sides
1 inch on all sides

Correct answer: 2 inches on all sides

FAA AC 43.13-1B specifies that fabric patches must overlap the undamaged fabric by at least 2 inches on all sides to ensure adequate adhesion and strength.

Question 15: Which instrument uses a Wheatstone bridge circuit to measure fuel quantity?

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

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 16: What is the purpose of a flow control valve in a hydraulic system?

Prevent reverse fluid flow through a hydraulic line
Block fluid flow completely when a system is not in use
Control the rate of actuator movement by limiting fluid flow regardless of pressure differential (Correct answer)
Reduce system pressure to a lower value for downstream components

Correct answer: Control the rate of actuator movement by limiting fluid flow regardless of pressure differential

A flow control valve meters fluid flow rate to an actuator, controlling movement speed independently of the pressure differential across the valve.

Question 17: When using a Structural Repair Manual (SRM) for composite repairs, a mechanic must ensure the manual revision used is:

The latest revision that is current and applicable to the specific aircraft serial number (Correct answer)
The revision the operator's maintenance director approves
Any revision published after the aircraft was manufactured
The original issue regardless of subsequent revisions

Correct answer: The latest revision that is current and applicable to the specific aircraft serial number

Technicians must use the current, applicable revision of the SRM for the specific aircraft's serial number to ensure the repair meets the type design requirements.

Question 18: When inspecting a hydraulic actuator for internal leakage, what is the most reliable method?

Measure the time it takes the actuator rod to drift under a known load with ports blocked (Correct answer)
Pressurize the extend port and check for fluid weeping at the retract port with both ports open
Visually inspect the cylinder bore for scoring using a borescope
Check the fluid level drop in the reservoir over a 24-hour period

Correct answer: Measure the time it takes the actuator rod to drift under a known load with ports blocked

Applying a load and timing rod drift with ports blocked reveals internal seal bypass, which is the definitive test for internal actuator leakage.

Question 19: 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 20: 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
200 hours time-in-service
100 hours time-in-service
Twelve calendar months (Correct answer)

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 21: When is a Form 337 (Major Repair and Alteration) required to be submitted to the FAA?

When performing any repair listed in AC 43.13
Only when the repair involves powerplant components
Upon completion of a major repair or major alteration (Correct answer)
For every scheduled maintenance inspection

Correct answer: Upon completion of a major repair or major alteration

FAA Form 337 must be completed and submitted to the FAA Flight Standards District Office within 48 hours after a major repair or major alteration is completed.

Question 22: What is the impact of regulatory changes on ACS professionals?

Regulatory changes require updating practices, procedures, and documentation to maintain compliance (Correct answer)
Only government employees need to follow regulatory changes
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 23: What does a hydraulic snubber do in a pressure gauge line?

Dampens pressure surges to protect the gauge and provide a steady reading (Correct answer)
Filters contamination out of the fluid sample going to the gauge
Prevents fluid from flowing backward through the gauge during pressure drops
Amplifies small pressure changes to improve gauge sensitivity

Correct answer: Dampens pressure surges to protect the gauge and provide a steady reading

A snubber is a small orifice or restriction that dampens rapid pressure pulsations, protecting the gauge bourdon tube from fatigue damage and providing a readable steady indication.

Question 24: 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
Clean the area and monitor for progression; replace if seepage becomes a drip or increases (Correct answer)
Tighten the fitting incrementally until seepage stops, regardless of torque limits
Apply an external sealant compound to stop the seepage temporarily

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

It authorizes the next scheduled maintenance
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 satisfies all AD requirements automatically

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 26: Which human factors concept describes a mechanic's tendency to complete a task as originally planned despite new information suggesting a change is needed?

Confirmation bias
Complacency
Plan continuation error (Correct answer)
Normalization of deviance

Correct answer: Plan continuation error

Plan continuation error (get-there-itis equivalent for maintenance) occurs when a technician proceeds with an original plan even after cues indicate it should change.

Question 27: What is the purpose of a pneumatic system bootstrap reservoir?

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

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 28: What is the purpose of performing a porosity check (resin content test) on a wet layup repair sample panel?

To verify the fiber orientation matches the parent laminate
To confirm the repair resin is fully cured before service return
To ensure the fiber-to-resin ratio meets structural requirements and voids are minimal (Correct answer)
To measure electrical conductivity for lightning strike compliance

Correct answer: To ensure the fiber-to-resin ratio meets structural requirements and voids are minimal

A porosity or resin content check verifies that the repair has the correct fiber volume fraction and void content to meet the structural properties assumed in repair design.

Question 29: When must a mechanic make an entry in the aircraft maintenance records after completing an inspection?

Within 72 hours of completing the work
Before the aircraft is returned to service (Correct answer)
Within 30 days of the inspection
At the end of the business day the work was completed

Correct answer: Before the aircraft is returned to service

Per 14 CFR Part 43.9 and 43.11, maintenance record entries must be made before the aircraft is approved for return to service.

Question 30: 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 reacts with lead in aviation fuel to prevent valve seat recession
Liquid sodium inside the valve transfers heat from the valve head to the stem, cooling the valve (Correct answer)
Sodium expands when heated to maintain a tight seal against the valve seat at operating temperature

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

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

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

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

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 33: Before applying a chemical film treatment (Alodine/Iridite) to an aluminum repair part, the surface must be:

Heated to 250°F to remove all moisture
Primed with zinc chromate and allowed to dry completely
Roughened with 120-grit sandpaper to improve adhesion
Thoroughly cleaned and deoxidized to bare, active metal (Correct answer)

Correct answer: Thoroughly cleaned and deoxidized to bare, active metal

Chemical film treatments react with bare aluminum oxide; the surface must be completely clean and freshly deoxidized so the conversion coating bonds directly with the base metal.

Question 34: Quality escape prevention in aviation maintenance requires mechanics to prioritize:

Minimizing downtime regardless of procedure compliance
Verification that every step was completed using approved data before signing off (Correct answer)
Cost-effective parts substitutions
Speed of repair over documentation

Correct answer: Verification that every step was completed using approved data before signing off

Aviation quality systems require procedural compliance verification at each step; documentation confirms that approved data was followed before return to service.

Question 35: What type of fitting is typically used on high-pressure aircraft hydraulic lines (3,000 psi and above) where vibration is a concern?

Flared AN fitting with double flare
Compression fitting with soft copper ferrule
NPT pipe thread fitting with Teflon tape
Flareless MS fitting with bite-type ferrule (Correct answer)

Correct answer: Flareless MS fitting with bite-type ferrule

MS flareless (bite-type) fittings are preferred for high-pressure, high-vibration applications because the ferrule bites into the tube and provides excellent resistance to loosening.

Question 36: An engine oil analysis report shows elevated iron and chrome levels. What engine components are most likely experiencing abnormal wear?

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

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

Magnetic particle inspection (Correct answer)
Dye penetrant inspection
Eddy current testing
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 38: What is the primary purpose of ballast in an aircraft weight and balance context?

To reduce fuel consumption
To shift the CG to within approved limits (Correct answer)
To increase structural load capacity
To increase gross weight capacity

Correct answer: To shift the CG to within approved limits

Ballast is temporary or permanent weight added to move the aircraft CG into the approved operating range.

Question 39: Which inspection method is best suited for detecting fatigue cracks in thick aluminum wing spars where cracks may be below the surface?

Visual inspection with magnification
Dye penetrant inspection
Ultrasonic inspection (Correct answer)
Surface eddy current 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 40: To exercise Inspection Authorization (IA) privileges, a mechanic must hold an IA for at least how long before it must be renewed?

12 months (Correct answer)
24 months
6 months
It never expires

Correct answer: 12 months

An Inspection Authorization must be renewed annually (every 12 calendar months) by meeting one of the renewal activity requirements in 14 CFR 65.93.

Question 41: Which NDT method is most appropriate for detecting internal voids and delaminations in composite aircraft structures?

Ultrasonic inspection or tap testing (Correct answer)
Dye penetrant inspection
Magnetic particle inspection
Eddy current 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 42: An aircraft landing gear extends normally but the green 'gear down and locked' light does not illuminate. The FIRST troubleshooting step should be:

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
Assume the gear is down and locked since it extended normally

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 43: Which of the following best describes 'detonation' in an aircraft reciprocating engine?

A normal phase of the combustion process occurring after ignition
Uncontrolled, explosive combustion of the fuel-air charge instead of a controlled flame front (Correct answer)
Pre-ignition caused by a hot spot in the cylinder firing before the spark plug
Backfiring through the induction system due to a late ignition timing

Correct answer: Uncontrolled, explosive combustion of the fuel-air charge instead of a controlled flame front

Detonation is the spontaneous, explosive auto-ignition of the end-gas portion of the fuel-air charge ahead of the flame front, producing damaging pressure spikes and characteristic knocking.

Question 44: Which type of damage to a composite structure is MOST difficult to detect visually?

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

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 45: What continuing education is typically required in hydraulic & pneumatic systems?

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

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 46: 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 47: 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
Mechanic certificates never expire but privileges lapse after 24 months of inactivity (Correct answer)
The certificate is revoked automatically after 36 months
The certificate expires on the holder's birthday every two years

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

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

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 49: A TSO authorization granted to a manufacturer signifies that the article:

Has been certified for 10,000 flight hours
Meets the minimum performance standards of the TSO (Correct answer)
Is exempt from AD compliance
Has been approved for installation on any aircraft

Correct answer: Meets the minimum performance standards of the TSO

A TSO authorization means the article was produced to meet FAA minimum performance standards, but installation approval is still required.

Question 50: Airworthiness Directives (ADs) issued by the FAA are:

Advisory-only notices for aging aircraft
Legally mandatory corrective actions for identified unsafe conditions (Correct answer)
Recommended practices that operators may choose to follow
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 51: What is the most common material used for aircraft skin?

Steel
Copper
Aluminum alloy (Correct answer)
Titanium

Correct answer: Aluminum alloy

Aluminum alloys are lightweight and corrosion-resistant, making them ideal for aircraft skins.

Question 52: A mechanic notices an aircraft's compass reads 10 degrees off during a compass swing. What is the appropriate corrective action?

Adjust the compensation screws and update the compass correction card (Correct answer)
Replace the compass immediately
File a maintenance discrepancy and allow the pilot to compensate mentally
Declare the compass unserviceable if error exceeds 5 degrees

Correct answer: Adjust the compensation screws and update the compass correction card

Compass deviation within allowable limits can be corrected by adjusting the compensating magnets and must be documented on an updated compass correction card.

Question 53: What is the function of a boost pump in an aircraft fuel system?

It provides positive fuel pressure for starting, backup fuel pressure, and transfer between tanks (Correct answer)
It filters fuel before delivery to the engine
It controls the fuel-air mixture ratio
It replaces the engine-driven fuel pump as the primary pump

Correct answer: It provides positive fuel pressure for starting, backup fuel pressure, and transfer between tanks

Electric boost pumps provide fuel pressure for engine starting, serve as backup if the engine-driven pump fails, and assist in fuel transfer between tanks.

Question 54: Which regulation requires that aircraft ELTs be inspected and the battery replaced or recharged at specific intervals?

14 CFR Part 43.9
14 CFR Part 91.413
14 CFR Part 43.15
14 CFR Part 91.207 (Correct answer)

Correct answer: 14 CFR Part 91.207

14 CFR Part 91.207 specifies ELT inspection, battery replacement, and operational requirements including the 50% cumulative use or expiration date rule.

Question 55: During engine run-up, a pilot reports intermittent engine roughness that disappears when carburetor heat is applied. What does this indicate?

Lean fuel-air mixture
Fouled spark plugs
Ice formation in the carburetor venturi (Correct answer)
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 56: What is the function of an engine 'breather' or crankcase vent in a reciprocating aircraft engine?

Supply fresh air to the oil sump to oxidize and break down combustion byproducts
Provide a vacuum source for flight instruments
Vent crankcase pressure and blow-by gases overboard to prevent pressure buildup and oil leaks (Correct answer)
Equalize pressure between the crankcase and the induction manifold

Correct answer: Vent crankcase pressure and blow-by gases overboard to prevent pressure buildup and oil leaks

The crankcase breather vents combustion blow-by gases that pass the piston rings into the crankcase, preventing pressure buildup that would force oil out of seals and gaskets.

Question 57: 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?

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

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 58: An aircraft engine exhibits low oil pressure during ground run-up but normal pressure in flight. What is the most likely cause?

Diluted oil from fuel contamination
Worn main bearings
Clogged oil suction screen
Faulty oil pressure relief valve (Correct answer)

Correct answer: Faulty oil pressure relief valve

A stuck-open oil pressure relief valve can allow excess oil to bypass at low RPM, causing low pressure at idle that normalizes at higher power settings.

Question 59: A mechanic discovers that a repair was incorrectly performed by a previous technician. Under professional and regulatory standards, the mechanic should:

Perform a risk assessment and decide independently
Document the discrepancy and refuse to approve the aircraft until it is corrected (Correct answer)
Sign off the work since it is not their error
Notify the owner only if the aircraft is about to fly

Correct answer: Document the discrepancy and refuse to approve the aircraft until it is corrected

A mechanic has a professional and regulatory obligation to document discrepancies and withhold approval for return to service until all known airworthiness issues are resolved.

Question 60: 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.

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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