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

Question 1: The term 'continued airworthiness' under the ACS framework refers to:

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

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

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

Question 2: What is the importance of peer review in aviation mechanics?

Peer review is unnecessary for experienced professionals
Peer review ensures quality, catches errors, provides learning opportunities, and maintains professional standards (Correct answer)
Only management should review professional work
Peer review undermines professional confidence

Correct answer: Peer review ensures quality, catches errors, provides learning opportunities, and maintains professional standards

Peer review is a cornerstone of professional quality assurance, providing independent verification, knowledge sharing, and continuous improvement opportunities.

Question 3: A pitot-static system check reveals the altimeter reads 200 feet higher than field elevation with the static port open on a standard day. This indicates:

The altimeter is functioning correctly within tolerance
The altimeter has an excessive scale error requiring calibration or replacement (Correct answer)
A leak in the static system that must be repaired
The aircraft is at a higher elevation than the airport reference point

Correct answer: The altimeter has an excessive scale error requiring calibration or replacement

An altimeter error of 200 feet at field elevation exceeds the FAA allowable tolerance of ±75 feet and requires calibration or replacement.

Question 4: What is the scope of practice for ACS certification in hydraulic & pneumatic systems?

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
Only the employer defines the scope of practice
The scope is determined individually by each professional

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

Uncontrolled, explosive combustion of the fuel-air charge instead of a controlled flame front (Correct answer)
A normal phase of the combustion process occurring after ignition
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 6: What is the primary purpose of a fuel strainer (gascolator) in a reciprocating aircraft engine fuel system?

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

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

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

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

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

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

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

Question 9: What does a 'red arc' on an aircraft instrument face represent?

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

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

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

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

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

Question 11: Under FAR Part 65, a mechanic certificate with both Airframe and Powerplant ratings is commonly referred to as:

Designated mechanic examiner
Repairman
A&P mechanic (Correct answer)
IA holder

Correct answer: A&P mechanic

A mechanic holding both the Airframe and Powerplant ratings under 14 CFR Part 65 is commonly called an A&P mechanic.

Question 12: Which part of the maintenance manual specifies troubleshooting steps?

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

Correct answer: Troubleshooting section

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

Question 13: What documentation best practices should ACS professionals follow?

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

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 14: Aircraft fuel quantity gauges are required by FAR to be accurate to within what tolerance?

No tolerance is specified — they are advisory only
±5% of total capacity
±10% of indicated reading at all fuel levels
They must only be accurate when reading empty (zero fuel) (Correct answer)

Correct answer: They must only be accurate when reading empty (zero fuel)

FAR 23.1337 requires fuel quantity gauges to be accurate only at the empty (zero) position; at all other quantities, accuracy is advisory and may vary.

Question 15: 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 16: When an Airworthiness Directive is issued as an 'Emergency AD,' what is the typical compliance time frame?

Within the next scheduled inspection interval
Immediately or within a very short specified period such as 24 hours (Correct answer)
At the next annual inspection
90 days from the issue date

Correct answer: Immediately or within a very short specified period such as 24 hours

Emergency ADs require immediate action or compliance within a very short window because the unsafe condition poses an immediate threat to safety.

Question 17: A mechanic notices an aircraft's compass reads 10 degrees off during a compass swing. What is the appropriate corrective action?

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

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

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

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 19: Which tool is commonly used to measure structural alignment in aircraft?

Micrometer
Torque wrench
Caliper
Plumb bob (Correct answer)

Correct answer: Plumb bob

A plumb bob is traditionally used to ensure vertical and horizontal alignment.

Question 20: Which cure condition is typically required for a prepreg composite repair to achieve design strength?

Elevated temperature cure (typically 250°F or 350°F) with applied pressure (Correct answer)
Infrared lamp cure at 150°F for 2 hours
Room temperature cure for 24 hours with no pressure
UV light cure for 30 minutes under sunlight

Correct answer: Elevated temperature cure (typically 250°F or 350°F) with applied pressure

Prepreg systems are formulated to cure at specific elevated temperatures (250°F or 350°F) under pressure to achieve full cross-linking and consolidation.

Question 21: What is the advantage of a brake-by-wire (electro-hydraulic) braking system compared to a conventional hydraulic brake system?

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

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

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

Question 22: When is it mandatory to bond and ground an aircraft during fueling?

Grounding is optional if fueling from a bonded fuel truck
Always, before fueling begins, to prevent static discharge ignition of fuel vapors (Correct answer)
Only when fueling in dry climates with low humidity
Only when fueling turbine aircraft

Correct answer: Always, before fueling begins, to prevent static discharge ignition of fuel vapors

Bonding and grounding are always required before fueling to equalize static electrical charges and prevent sparks that could ignite fuel vapors.

Question 23: Which tool is essential for checking the torque of aircraft fasteners?

Rivet gun
Micrometer
Torque wrench (Correct answer)
Caliper

Correct answer: Torque wrench

A torque wrench ensures that fasteners are tightened to the correct specifications.

Question 24: What is the function of a boost pump in an aircraft fuel system?

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

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 25: What is the primary radiation safety concern for technicians performing X-ray radiographic inspection?

Ultraviolet skin burns from the X-ray tube housing
Hearing damage from high-frequency radiation noise
Cumulative exposure to ionizing radiation increasing the risk of biological harm (Correct answer)
Chemical burns from radiographic film developer solutions

Correct answer: Cumulative exposure to ionizing radiation increasing the risk of biological harm

Ionizing radiation (X-rays and gamma rays) can damage living tissue and DNA; cumulative occupational exposure is regulated by the NRC/OSHA, and technicians must use dosimetry badges and stay within annual dose limits.

Question 26: When an aircraft is sold, what maintenance records must be transferred to the new owner per 14 CFR 91.419?

Only the engine and propeller logbooks
All maintenance records required to be kept under 14 CFR 91.417 (Correct answer)
Only the records from the last annual inspection
Records from the last five years of operation only

Correct answer: All maintenance records required to be kept under 14 CFR 91.417

14 CFR 91.419 requires that all maintenance records required under 91.417 be transferred with the aircraft at the time of sale.

Question 27: A landing gear retraction test reveals the gear takes 12 seconds to retract, while the maintenance manual specifies 6-8 seconds maximum. What is the most likely cause?

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

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

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

Question 28: 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?

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
Contact the FAA for an exemption

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 29: A mechanic's certificate, once issued, is:

Valid for life unless surrendered, suspended, or revoked (Correct answer)
Valid only while employed by a certificated repair station
Valid as long as annual recurrency training is completed
Valid for two years and must be renewed

Correct answer: Valid for life unless surrendered, suspended, or revoked

An FAA mechanic certificate is issued for life and does not expire; however, privileges can only be exercised if the currency requirements of 14 CFR 65.83 are met.

Question 30: Under 14 CFR 65.83, a certificated mechanic must have performed or supervised work in the aviation maintenance field within the preceding how many months to exercise certificate privileges?

12 months
36 months
24 months (Correct answer)
6 months

Correct answer: 24 months

14 CFR 65.83 requires mechanics to have performed or supervised at least 6 months of work within the preceding 24 months to exercise certificate privileges.

Question 31: What is the minimum record retention period for maintenance records on life-limited parts under 14 CFR Part 91?

Five years from the date of installation
One year from the date of maintenance
Until the work is repeated or superseded
The life of the part (Correct answer)

Correct answer: The life of the part

Records for life-limited parts must be retained for the life of the part, as required by 14 CFR Part 91.417.

Question 32: When the repair data in the Structural Repair Manual (SRM) does not cover the type or size of damage found, the technician must:

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

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

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

Question 33: 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
Anaerobic sealant
O-ring used as a static seal

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

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

Question 34: A mechanic discovers that a repair was incorrectly performed by a previous technician. Under professional and regulatory standards, the mechanic should:

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

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 35: In ultrasonic testing, what is 'back-wall echo loss' an indication of?

Surface roughness causing signal scatter at the entry point only
Calibration error in the time base
A large internal discontinuity or severe attenuation blocking the return of the back-wall reflection (Correct answer)
Insufficient couplant application

Correct answer: A large internal discontinuity or severe attenuation blocking the return of the back-wall reflection

Loss of the back-wall echo indicates that a large internal flaw or severe attenuation is preventing the ultrasonic pulse from reaching and reflecting off the far wall of the test piece.

Question 36: How do ACS professionals contribute to organizational success?

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

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

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

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

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

Correct answer: Major repairs and major alterations

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

Question 39: 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 verify that the radiograph has sufficient sensitivity and quality to detect a defined minimum flaw size (Correct answer)
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 40: What is the function of a hydraulic power transfer unit (PTU)?

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

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

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

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

Report it in the maintenance log and defer repair
Immediately ground the aircraft and replace the entire panel
Apply a patch and return to service without documentation
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 43: Fuel flow is within normal limits but EGT is abnormally high on one cylinder. What is the most likely cause?

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

Correct answer: Clogged fuel injector on that cylinder

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

Question 44: When making a flared tube fitting for an aircraft fuel line, the correct flare angle for AN (Army-Navy) fittings is:

60 degrees
90 degrees
45 degrees
37 degrees (double flare equivalent per AN standard) (Correct answer)

Correct answer: 37 degrees (double flare equivalent per AN standard)

AN (Army-Navy) standard fittings use a 37-degree flare angle, which is different from the 45-degree flare used in automotive applications.

Question 45: Under the ACS standards, a mechanic must demonstrate knowledge of quality assurance by understanding that an Inspection Authorization (IA) is required to:

Approve an aircraft for return to service after an annual inspection (Correct answer)
Install PMA parts
Sign off on 100-hour inspection records
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 46: What is the significance of a 'return to service' signature by a certificated mechanic?

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

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

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

Question 47: How often should fire extinguishers be inspected on aircraft?

Every 24 months
Only after discharge
Every 6 months
Every 12 months (Correct answer)

Correct answer: Every 12 months

Fire extinguishers must be inspected at regular intervals, typically annually.

Question 48: A mechanic discovers a discrepancy that is beyond the scope of their certificate. What is the correct action?

Defer the work to an appropriately rated mechanic or repair station (Correct answer)
Placard the item inoperative and release the aircraft
Request a Special Airworthiness Certificate
Attempt the repair using available tools

Correct answer: Defer the work to an appropriately rated mechanic or repair station

FAA regulations require that work outside a mechanic's rating must be performed by someone who holds the proper authority.

Question 49: A 10-lb item is added at a station 50 inches aft of the CG. What is the moment change?

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

Correct answer: 500 in-lb aft

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

Question 50: Under 14 CFR Part 65.92, a mechanic with both Airframe and Powerplant ratings may supervise and approve the return to service of aircraft maintained by:

Student pilots performing owner-authorized maintenance
Certificated mechanics holding the appropriate ratings under their supervision
Only certificated repair stations
Any person performing maintenance under their direct supervision per applicable regulations (Correct answer)

Correct answer: Any person performing maintenance under their direct supervision per applicable regulations

An A&P mechanic may supervise and approve work performed by others when the mechanic directly supervises the work and it is performed within applicable regulatory authority.

Question 51: Which adhesive film storage requirement is MOST critical to maintaining its properties?

Store in a dry cabinet at low humidity only
Store at elevated temperature to keep it pliable
Store at room temperature away from UV light
Store refrigerated or frozen and track out-time carefully (Correct answer)

Correct answer: Store refrigerated or frozen and track out-time carefully

Adhesive films and prepregs must be stored frozen (typically at 0°F or below) to arrest curing, and out-time at room temperature must be logged and not exceeded.

Question 52: 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)
Centrifugal pump
Gear pump
Vane 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 53: What part regulates the speed of a propeller?

Throttle
Mixture control
Tachometer
Governor (Correct answer)

Correct answer: Governor

A governor adjusts the propeller blade angle to control RPM.

Question 54: A suspected unapproved part (SUP) is discovered during maintenance. The correct action is to:

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

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

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

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

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

Question 56: When using a dial indicator to check crankshaft runout, the total indicated reading (TIR) is 0.006 inches. If the maximum allowable runout is 0.004 inches, what action is required?

The crankshaft can be re-indexed to reduce runout
The crankshaft must be replaced or sent to an overhaul facility for evaluation (Correct answer)
Polish the crankshaft journals to correct the runout
The crankshaft is within limits and may be returned to service

Correct answer: The crankshaft must be replaced or sent to an overhaul facility for evaluation

When TIR exceeds the manufacturer's maximum allowable limit, the crankshaft must be replaced or sent for overhaul evaluation—it cannot be returned to service as-is.

Question 57: During a preflight fuel check, a pilot/mechanic finds a small amount of water in the fuel sample. The correct action is:

Drain only the affected sump and continue
Add fuel system icing inhibitor and return to service
Ground the aircraft indefinitely until the tank is removed
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 58: According to 14 CFR Part 43.13, maintenance must be performed using methods, techniques, and practices that are acceptable to the FAA and:

Documented in the mechanic's personal logbook
Listed only in AC 43.13-1B regardless of the manufacturer's data
Described in the current manufacturer's maintenance manual or an equivalent accepted by the FAA (Correct answer)
Approved by the aircraft owner in writing

Correct answer: Described in the current manufacturer's maintenance manual or an equivalent accepted by the FAA

14 CFR 43.13 requires maintenance to be performed per the current manufacturer's maintenance manual or other methods, techniques, and practices acceptable to the FAA.

Question 59: 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 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 dump fuel overboard in an emergency
To preheat fuel in cold weather

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

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 regulate fuel pressure to the engine
To balance fuel between left and right tanks
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.

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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