12.1 Aircraft Inspection Programs & Inspection Concepts

12.1 Aircraft Inspection Programs & Inspection Concepts

Inspection Concepts and Techniques (AM.I.K) is a full ACS subject in its own right, and it is the one most often missing from commercial AMG question banks — it did not exist as a separate block in the retired Part 147 appendices, so older material simply does not cover it. This section handles inspection programs and concepts (AM.I.K.K4 and K5, with skill elements S4 perform a visual inspection and S6 inspect an aircraft for compliance with an Airworthiness Directive). Section 12.2 handles the measuring tools and calibration elements.

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1. The Vocabulary the Examiner Will Use

FAA-S-ACS-1 Appendix 1 defines six maintenance verbs, and the Designated Mechanic Examiner is instructed to review them with you. Confusing them on the written test costs points; confusing them on the job costs money.

Note that inspect does not require a tool, and check is about operation, not condition.

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2. Part 91 Inspection Programs (AM.I.K.K4)

14 CFR § 91.409 is the controlling rule, and its structure is the exam's favourite target.

Annual inspection — § 91.409(a)

No person may operate an aircraft unless, within the preceding 12 calendar months, it has had an annual inspection under Part 43 and been approved for return to service by a person authorized by § 43.7. "12 calendar months" means the inspection is good through the last day of the twelfth month — an annual signed off on 14 March 2026 is good until 31 March 2027. An annual may substitute for a 100-hour inspection; a 100-hour may not substitute for an annual unless it is performed by a person authorized to do annuals and is entered as an "annual" in the records.

100-hour inspection — § 91.409(b)

Required when the aircraft carries any person other than a crewmember for hire, or when flight instruction for hire is given in an aircraft the instructor provides. Two details are heavily tested:

• The 100-hour limit may be exceeded by not more than 10 hours — and only while en route to reach a place where the inspection can be done. It is not a 110-hour inspection interval.
• Any excess time used must be included in computing the next 100 hours of time in service. Fly 6 hours over, and the next inspection is due at 94 hours.

Who may approve what

An A&P mechanic may perform and approve a 100-hour inspection. Only a mechanic holding an Inspection Authorization, an appropriately rated repair station, or the manufacturer may approve an annual. Section § 65.95(a)(2) also gives the IA the authority to perform an annual, or perform or supervise a progressive inspection.

Progressive inspection — § 91.409(d)

An owner or operator who wants to break the annual into smaller recurring events must:

1. Submit a written request to the responsible Flight Standards office;
2. Provide a certificated mechanic holding an Inspection Authorization, a certificated airframe repair station, or the aircraft manufacturer to supervise or conduct the inspection;
3. Provide a current inspection procedures manual available and readily understandable to pilot and maintenance personnel;
4. Ensure the frequency and detail provide for a complete inspection of the aircraft within each 12 calendar months;
5. Provide appropriate housing and adequate equipment for necessary disassembly and proper inspection.

If a progressive program is discontinued, the owner must immediately notify the responsible Flight Standards office, and the next annual is due within 12 calendar months of the last complete inspection.

Exceptions and alternative programs — § 91.409(c), (e), (f)

Annual and 100-hour requirements do not apply to an aircraft carrying a special flight permit, a current experimental airworthiness certificate, a special airworthiness certificate in the light-sport category, or a provisional airworthiness certificate; nor to an aircraft inspected under an approved aircraft inspection program under Part 125 or 135 and identified by registration number in the operator's operations specifications; nor to aircraft covered by paragraphs (d) or (e). Large airplanes, turbojets, and turbopropeller-powered multiengine airplanes select from the § 91.409(f) menu: a continuous airworthiness program under Part 121, an approved aircraft inspection program under § 135.419, the current manufacturer-recommended inspection program, or any other FAA-approved program.

The other recurring clocks a mechanic must track

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3. Scope and Detail: Part 43 Appendix D and the Checklist Rule

14 CFR § 43.15(c) requires that each person performing a 100-hour or annual inspection use a checklist that includes at least the scope and detail items of Part 43 Appendix D — the mechanic's own checklist, the manufacturer's, or one designed by the person doing the work. Section 43.15(c)(1) also requires that before the inspection the aircraft be thoroughly cleaned, and § 43.15(c)(2) requires a run-up and operational check of the engine covering power output, magnetos, fuel and oil pressure, and cylinder and oil temperature.

Appendix D drives the sequence: open every inspection plate and access panel, clean the aircraft and engine, then inspect the fuselage and hull, cabin and cockpit, engine and nacelle, landing gear, wing and center section, empennage, propeller, radio and electrical, and finally each installed miscellaneous item.

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4. Inspection Methods and Tools (AM.I.K.K5)

Visual inspection does the overwhelming majority of the work and it is a skill element (AM.I.K.S4). Do it methodically:

• Adequate, correct lighting — a bright flashlight held at a low grazing angle reveals surface irregularities that flood lighting hides.
• A mirror and a 10x magnifier for hidden and fine detail; a borescope for internal spaces such as cylinders, ducts, and wing box interiors.
• Clean first. Dirt, oil, and old sealant hide cracks; but note the reverse clue — a clean streak on a dirty surface or a dye-like oil weep often marks a working crack or a leak path.
• Work a consistent pattern and inspect for the specific list: cracks, corrosion, distortion, nicks and gouges, chafing, security, wear, elongated holes, missing or loose fasteners, and smoking rivets (a dark halo of fretting oxide around a rivet head, indicating a working joint).

Special inspections are triggered by events rather than the calendar: hard or overweight landing, severe turbulence or high-G maneuvering, lightning strike, fire, propeller strike or sudden engine stoppage, and flood or salt-water immersion. Each has a manufacturer-published procedure — the general lesson is that hidden damage propagates away from the visible contact point along the load path.

AD compliance inspection (AM.I.K.S6) is a distinct skill. Determine applicability from the AD's Applicability paragraph by model and serial number, read whether the AD is one-time or recurring, note the compliance time (calendar, hours, cycles, or "before further flight"), perform the required action or verify prior compliance, and make the maintenance record entry including AD number, revision date, method of compliance, date, total time in service, and the next due point.

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5. Where the Other Inspection Techniques Sit

AM.I.K.K3 covers nondestructive testing procedures and methods, and AM.I.K.R1 the requirement to demagnetize a component after a magnetic particle inspection. Those are taught in depth in Section 4.3, Nondestructive Testing (NDT/NDI) Inspection Methods — the ACS places NDT inside this subject, so review 4.3 as part of Subject K rather than as a materials topic. Likewise AM.I.K.R5, damage prevention when using an ohmmeter, is covered in Section 3.1: never apply an ohmmeter to an energized circuit, and isolate at least one lead of the component to eliminate parallel sneak paths.