Airframe inspection is the ACS area where regulation meets technique. The questions ask what a 100-hour or annual inspection has to cover, where the results are recorded, and, for the larger half, which nondestructive method will actually find a given defect. Every AMTprep question tagged to AM.II.D comes with a rationale and a handbook reference. If you can keep four inspection methods straight and remember that a proper visual inspection is a method in its own right with its own rules, this is one of the more reliable areas to pick up points.
Written by the AMTprep editorial team · Published · Last reviewed
Written against the FAA primary sources cited at the foot of this page.
AM.II.D draws on the inspection material in FAA-H-8083-31 plus the inspection rules in 14 CFR Part 43. On the paperwork side, expect the checklist question: a person performing a 100-hour or annual inspection must use a checklist that covers at least the scope and detail of Appendix D to 14 CFR Part 43, or a manufacturer's equivalent. Expect a second question on where the results go, which is a maintenance record entry stating the type of inspection, the date, the aircraft time in service, and the signature and certificate number of the person approving or disapproving the aircraft for return to service. The technique half starts with the visual inspection, which finds most defects. Questions here reward the mundane answer: clean the area, light it properly, and use a mirror and flashlight to see surfaces you cannot look at directly, with a magnifier for a suspected crack. Then the four methods. Liquid or dye penetrant finds only discontinuities that break the surface and cannot be used on porous material. Magnetic particle finds surface and slightly subsurface discontinuities, but only in ferromagnetic parts such as steel bolts, gear components and engine parts, and the part must be demagnetized afterward. Eddy current works on any conductive material, sees surface and near-surface cracks, and can find cracks in second-layer structure around fasteners with little disassembly. Ultrasonic passes sound through the part to find internal flaws and thickness loss. Symptom questions close the area out: smoking or dark smudges around rivet heads mean working, loose fasteners, and a fine network of surface cracks in an acrylic transparency is crazing.
ACS AM.II.D is tested on the FAA Airframe written test, one of 1,748 ACS-tagged questions in the Airframe bank. Every question tagged to this area carries a worked rationale and its FAA handbook reference, so you can drill the code itself rather than the whole test.
What document serves as the basis for the items checked during a 100-hour or annual inspection of an aircraft?
When performing a visual inspection of an aircraft structure, adequate lighting and the use of a mirror and flashlight are important because they help the technician
A magnetic particle inspection method can be used to detect surface and subsurface discontinuities in
A limitation of the dye penetrant inspection method is that it can only detect defects that
Eddy current inspection of aircraft structure is particularly useful because it can
When inspecting a sheet metal structure, a row of fasteners that shows smoking or a dark smudge pattern around the heads usually indicates
After completing a required 100-hour or annual inspection, the technician must record the results in the
When inspecting a transparent acrylic windshield, fine surface cracks radiating in a network pattern are referred to as
A structural part that must be replaced at a specified number of cycles, flight hours, or calendar time regardless of its apparent physical condition is classified as which type of item?
Under the ATA 100 aircraft zoning system, the 500-series of major zones identifies the:
Using the station system FS 345 and RWS 45, where is this location on the aircraft?
In the ATA 100 zonal numbering system, the 500 series of major zones designates which area of the aircraft?
Under the ATA 100 zonal numbering system, the empennage is identified by which series of major zones?
On a maintenance work card, the approximate location of a component on the aircraft is most commonly indicated by referring to its
Structural survey (sampling) inspections on an aging aircraft are normally called up by the
When performing a symmetry (alignment) check on a large airplane, what method of measurement is normally used?
Which of the following should be accomplished before jacking an aircraft?
An overweight (hard) landing inspection is required because the aircraft has experienced
Airframe symmetry (alignment) checks should normally be carried out
When inspecting stowage (storage) compartment doors, special attention should be given to the
Under 14 CFR Part 43, who is responsible for determining that an aircraft is in condition for safe operation when an annual or 100-hour inspection is required?
When performing a 100-hour inspection, what is a mechanic required to use as the basis for the inspection's scope and detail?
A required inspection reveals an unairworthy condition that the owner declines to have repaired. What must the mechanic provide to the owner?
During an inspection of a fabric-covered control surface, what condition would most directly indicate the fabric covering may no longer be airworthy?
When inspecting a welded steel-tube fuselage structure, what is the most common hidden cause of structural failure that the inspector must look for?
When inspecting an aircraft for compliance with airworthiness directives (ADs), what status must the mechanic confirm to determine if the aircraft is airworthy?
When inspecting riveted aluminum skin, the appearance of black powder or smoking around rivet heads most likely indicates what condition?
Which nondestructive testing (NDT) method is most appropriate for detecting surface and slightly subsurface cracks in ferromagnetic steel landing gear components?
Liquid penetrant inspection is limited to detecting which kind of defects?
When using eddy current inspection on aircraft structure, what is one principal advantage over other NDT methods?
During inspection of control cables, fraying or broken wires are most critical when found at which location?
When inspecting transparent acrylic (Plexiglas) windshields and windows, which defect is most likely to be cause for concern regarding structural integrity?
What is the principal reason an inspector taps a coin or uses a tap-test on a honeycomb composite control surface?
When inspecting a bonded honeycomb structure, the presence of water intrusion in the core is a concern primarily because it can cause what?
When inspecting magnesium aircraft components, what condition makes corrosion of magnesium especially serious compared to aluminum?
During inspection, which area of an aircraft is identified as a corrosion-prone region requiring special attention?
While inspecting an aircraft structure, an inspector finds a small crack at the edge of an inspection access cutout. Why are such cutouts and openings common locations for cracks?
ACS code: AM.II.D
Correct answer: The scope and detail listed in 14 CFR Part 43, Appendix D
Rationale: Annual and 100-hour inspections must cover the scope and detail of items listed in 14 CFR Part 43, Appendix D, unless an approved inspection program is used. The Airframe Handbook stresses that this appendix defines the minimum checklist content for a complete airframe inspection.
ACS code: AM.II.D
Correct answer: detect defects in areas that are not directly visible
Rationale: Visual inspection is the most widely used method, and the handbook notes that mirrors, flashlights, and magnifiers extend the inspector's reach into hidden or shadowed areas. These aids reveal cracks and damage that would otherwise be missed, but they do not measure depth or alloy.
ACS code: AM.II.D
Correct answer: ferromagnetic materials such as steel
Rationale: Magnetic particle inspection relies on magnetizing the part, so it only works on ferromagnetic materials like iron and steel. The handbook notes nonmagnetic materials such as aluminum, magnesium, and composites cannot be inspected by this method.
ACS code: AM.II.D
Correct answer: are open to the surface of the part
Rationale: Penetrant inspection works by capillary action drawing fluid into a defect that breaks the surface; if a crack is not open to the surface, the penetrant cannot enter it. The handbook therefore limits this method to detecting surface discontinuities only.
ACS code: AM.II.D
Correct answer: detect cracks without removing surface coatings
Rationale: Eddy current testing induces circulating currents in conductive material; a crack disrupts those currents and changes the probe reading. The handbook notes it can find surface and near-surface cracks, including around fastener holes, often without removing paint.
ACS code: AM.II.D
Correct answer: working or loose rivets in the joint
Rationale: A dark 'smoking rivet' trail of aluminum oxide powder around a rivet head is caused by the rivet working in its hole, abrading metal as the joint flexes. The handbook identifies this as a sign of loose or working rivets requiring further inspection and repair.
ACS code: AM.II.D
Correct answer: aircraft maintenance records
Rationale: Upon completing an inspection, the person must make an entry in the aircraft maintenance records describing the inspection and its findings, as required by Part 43. The handbook reinforces that proper recordkeeping is part of completing the inspection.
ACS code: AM.II.D
Correct answer: crazing
Rationale: Crazing is the fine network of hairline surface cracks that forms in acrylic transparencies from age, solvent exposure, or stress. The handbook identifies crazing during transparency inspection; delamination applies to laminated glass and exfoliation is a form of corrosion in metal.
ACS code: AM.II.D
Correct answer: Safe-life item.
Rationale: A safe-life item is assigned a fixed retirement life in cycles, hours, or calendar time and must be replaced when that life is reached because fatigue damage accumulates unseen. A fail-safe design instead relies on multiple load paths to tolerate a failure, and a condition-monitored (on-condition) item is retained as long as inspection shows it serviceable. (FAA-H-8083-31, Airframe Inspection — fatigue and life-limited parts.)
ACS code: AM.II.D
Correct answer: Left wing
Rationale: Under the ATA 100 zoning system the 500 series of major zones identifies the left wing, while the 600 series covers the right wing. Standard zoning lets maintenance documentation reference a location independent of aircraft type (FAA-H-8083-31, Airframe Inspection — ATA zoning and documentation).
ACS code: AM.II.D
Correct answer: 345 inches aft of the reference datum and 45 inches outboard along the right wing
Rationale: Per FAA-H-8083-31, fuselage station (FS) is measured rearward in inches from the reference datum, and right wing station (RWS) is measured outboard along the right wing. FS 345 / RWS 45 is therefore 345 inches aft of the datum and 45 inches outboard along the right wing. This station system locates structure and equipment for maintenance and weight-and-balance work.
ACS code: AM.II.D
Correct answer: The left wing
Rationale: The ATA 100 zonal system divides the airframe into numbered major zones: 100 lower fuselage, 200 upper fuselage, 300 empennage, 400 powerplants and nacelles, 500 left wing, and 600 right wing. The 500 series therefore identifies the left wing. Technicians use these zone numbers on work cards and inspection documents to locate the general area of a component.
ACS code: AM.II.D
Correct answer: The 300 series
Rationale: In the ATA 100 zonal system the 300 series of major zones designates the empennage. Within that series, the tens and units digits further identify individual tail surfaces such as the horizontal and vertical stabilizers. The lower and upper fuselage carry the 100 and 200 series respectively.
ACS code: AM.II.D
Correct answer: zone number
Rationale: The ATA zonal numbering system divides the airframe into numbered zones that work cards and inspection documents use to direct the technician to the general area where a component is located. Station numbers and the reference datum give precise dimensional positions, whereas zones give the broad location used for access planning and task assignment.
ACS code: AM.II.D
Correct answer: manufacturer
Rationale: Structural survey inspections are part of the continued-airworthiness program defined by the type-design holder, so they are normally called up by the manufacturer through the maintenance manual and service documents. The operator and the mechanic carry them out but do not originate the requirement.
ACS code: AM.II.D
Correct answer: A steel tape tensioned with a spring scale.
Rationale: A symmetry check compares dimensions between symmetrically located reference points (wingtips, fuselage, and tail). On a large airplane a steel tape is stretched between the points and tensioned with a spring scale to a constant load so the tape sag is repeatable and the side-to-side measurements are accurate and comparable, per the manufacturer's maintenance manual.
ACS code: AM.II.D
Correct answer: Install critical stress panels or plates.
Rationale: Before jacking, any stress panels, access plates, or doors designated as critical to structural integrity must be installed so the airframe can react the jacking loads through the proper paths without distortion. Emptying fuel tanks or stripping optional equipment is not a general jacking prerequisite and would not protect the structure during the lift.
ACS code: AM.II.D
Correct answer: too much kinetic energy at touchdown.
Rationale: An overweight or hard landing is one in which the aircraft touches down above its maximum landing weight or at an excessive sink rate, so the landing gear and structure absorb more kinetic energy than they are designed for, triggering a special inspection. It is defined by the energy dissipated at touchdown, not by a takeoff fuel load or a center-of-gravity position.
ACS code: AM.II.D
Correct answer: in a hangar with the aircraft leveled on jacks.
Rationale: Symmetry checks are performed indoors in a hangar with the aircraft leveled on jacks so it is out of the wind, in a stable temperature, and set to the correct datum attitude. On its wheels or out on the ramp the aircraft would not be properly leveled and external conditions could distort the measurements.
ACS code: AM.II.D
Correct answer: catches.
Rationale: Stowage doors are held shut by their catches, and a worn or failed catch lets the door fly open in turbulence and become a hazard, so the catches receive special inspection attention. Trim is cosmetic, and these doors are not pressure-sealed by microswitches.
ACS code: AM.II.D
Correct answer: The person performing the inspection
Rationale: Per 14 CFR 43.15 and the inspection requirements of Part 91, the person performing the inspection must determine whether the aircraft, or portion inspected, meets all applicable airworthiness requirements and is in condition for safe operation. The certificated mechanic or repair facility performing the inspection makes this determination.
ACS code: AM.II.D
Correct answer: A checklist containing the scope and detail of items in Appendix D to Part 43, or an equivalent
Rationale: Per 14 CFR 43.15(c) and Appendix D to Part 43, a person performing a 100-hour or annual inspection shall use a checklist that includes the scope and detail of the items in Appendix D (or a manufacturer's equivalent inspection program). The checklist ensures all required items are covered.
ACS code: AM.II.D
Correct answer: A signed and dated list of the discrepancies and unairworthy items
Rationale: Per 14 CFR 43.11(b), if the inspection results in a disapproval, the person performing the inspection must give the owner or lessee a signed and dated list of the discrepancies and unairworthy items. This list documents the items that must be corrected before the aircraft can be returned to service.
ACS code: AM.II.D
Correct answer: Fabric tested below the minimum acceptable breaking strength
Rationale: FAA-H-8083-31 states that fabric condition is judged largely by its strength. Deterioration of the fabric to below the minimum acceptable breaking strength (commonly tested with a punch tester) renders the covering unairworthy, regardless of surface appearance.
ACS code: AM.II.D
Correct answer: Internal corrosion within the steel tubing
Rationale: FAA-H-8083-31 notes that corrosion inside welded steel tubing is a primary hidden hazard. Moisture trapped inside tubes corrodes from the inside out, and the inspector should look for evidence of internal corrosion, often detected by tapping, weight changes, or drilling small test holes per the manufacturer's procedure.
ACS code: AM.II.D
Correct answer: That all applicable airworthiness directives have been complied with
Rationale: Per 14 CFR 39 and 43.13, all applicable airworthiness directives must be complied with for the aircraft to be airworthy. During inspection the mechanic reviews the maintenance records to confirm that every applicable AD has been complied with, including the method, date, and recurring intervals.
ACS code: AM.II.D
Correct answer: Working or loose rivets that may have lost clamping force
Rationale: FAA-H-8083-31 notes that a dark, smoky stain or black powder around rivet heads (often called 'smoking rivets') indicates the rivets are working loose, allowing fretting and corrosion. This is evidence of a loose or failed riveted joint and requires further investigation and repair.
ACS code: AM.II.D
Correct answer: Magnetic particle inspection
Rationale: FAA-H-8083-31 describes magnetic particle inspection as the method for detecting surface and near-surface (slightly subsurface) discontinuities in ferromagnetic materials such as steel landing gear parts. The part is magnetized and ferrous particles concentrate at flux leakage points caused by cracks.
ACS code: AM.II.D
Correct answer: Defects that are open to the surface
Rationale: FAA-H-8083-31 explains that liquid (dye) penetrant inspection can only detect defects that are open to the surface, because the penetrant must enter the discontinuity and then be drawn back out by developer. It cannot find subsurface flaws, which is why it works on nonporous metals and nonmetals alike for surface-breaking defects.
ACS code: AM.II.D
Correct answer: It can detect cracks around fastener holes and through coatings without disassembly
Rationale: FAA-H-8083-31 notes that eddy current inspection can detect surface and subsurface cracks in conductive materials and is particularly valuable because it can inspect for cracks around fastener holes and through layers of structure or paint without removing the part or coating, making it efficient for in-place inspections.
ACS code: AM.II.D
Correct answer: Where the cable passes over pulleys and through fairleads
Rationale: FAA-H-8083-31 indicates that control cables should be inspected for broken wires, especially where the cable passes over pulleys, through fairleads, and at terminal ends, because these high-wear and flexing points are where broken strands most commonly occur and most affect cable strength.
ACS code: AM.II.D
Correct answer: Crazing and cracks, particularly at edges and mounting holes
Rationale: FAA-H-8083-31 explains that crazing — a network of fine surface cracks in transparent plastics — and deeper cracks are inspected because they reduce strength and visibility. Cracks that progress, especially around mounting holes or edges, are structural concerns; the inspector evaluates crazing and cracks against the manufacturer's limits.
ACS code: AM.II.D
Correct answer: To detect disbonds or delaminations between the skin and core
Rationale: FAA-H-8083-31 describes the tap test (coin tap) as a quick method to detect disbonds or delaminations in bonded honeycomb and composite structures. A dull or dead sound, compared to a sharp ring over a sound area, indicates a separation between the skin and core or between plies.
ACS code: AM.II.D
Correct answer: Disbonding and core corrosion, often worsened by freeze-thaw cycles
Rationale: FAA-H-8083-31 notes that water trapped in honeycomb core adds weight, promotes corrosion of metal core/skins, and—through freeze/thaw cycling—can cause disbonding and core damage. Detecting and removing trapped water is an important part of inspecting bonded composite and honeycomb panels.
ACS code: AM.II.D
Correct answer: Magnesium is highly chemically active and corrodes rapidly once unprotected
Rationale: FAA-H-8083-31 notes that magnesium is the most chemically active of the common structural metals and corrodes rapidly, producing a voluminous white corrosion product. Because it deteriorates quickly and severely once protective coatings are breached, magnesium corrosion demands prompt detection and treatment during inspection.
ACS code: AM.II.D
Correct answer: Battery compartments and adjacent vent areas
Rationale: FAA-H-8083-31 identifies battery compartments and vent openings as classic corrosion-prone areas because electrolyte fumes and spillage attack adjacent structure. Other listed areas include lavatories, bilges, wheel wells, exhaust trail areas, and any place water can collect; battery areas are a well-known example.
ACS code: AM.II.D
Correct answer: They act as stress concentrations where fatigue cracks tend to originate
Rationale: FAA-H-8083-31 explains that holes, cutouts, and abrupt changes in section act as stress concentrations (stress raisers). Because stress flow is interrupted and concentrated at edges of openings, fatigue cracks frequently originate there, making cutouts, fastener holes, and corners high-priority inspection points.
Enter the ACS codes from your FAA fail report and get a targeted study plan — the exact areas the examiner must re-test you on, with the handbook references for each.
Build my remediation planAdaptive engine, timed exam simulator, ACS-code remediation, and oral prep — everything you need to pass.