Definition
The Aircraft Maintenance Manual is the foundational technical reference for maintaining a certificated aircraft type. Its legal status derives from the type-certification process: under 14 CFR §21.50, the type certificate holder is required to make available to owners and operators the Instructions for Continued Airworthiness (ICA), and the AMM is the primary ICA document. Under EASA Certification Specifications (CS-23 for normal-category aircraft, CS-25 for transport-category), Subpart H requires that the applicant for a type certificate provide ICAs meeting the standards of the applicable airworthiness standard. The AMM is prepared to satisfy that requirement and is referenced in the type certificate data sheet.
The AMM is structured using the ATA numbering system — originally ATA Spec 100, now largely superseded by ATA iSpec 2200 (Information Standards for Aviation Maintenance) for large transport aircraft, with many GA manufacturers still using ATA 100 chapter numbering. Each ATA chapter addresses a defined aircraft system: ATA 21 (Air Conditioning), ATA 27 (Flight Controls), ATA 29 (Hydraulic Power), ATA 32 (Landing Gear), ATA 71 (Power Plant), ATA 78 (Engine Exhaust), and so on through 100 numbered chapters. Within each chapter, tasks are structured into sections: Description and Operation (system theory), Maintenance Practices (general maintenance procedures), Servicing (fluids, replenishment), Removal/Installation (step-by-step procedures for removing and installing each LRU), Inspection/Check (inspection criteria, limits, and procedures), and Adjustment/Test (rigging and functional test procedures). This structure means that a maintenance organization and a regulator audit team both know exactly where to find any given procedure, regardless of aircraft type.
Distinctions from related documents are operationally important. The Aircraft Flight Manual (AFM) is a regulatory document for flight crews — performance data, operating limitations, emergency procedures — not a maintenance document. The Illustrated Parts Catalogue (IPC) identifies parts by part number and quantity for procurement; it does not describe how to remove or install them. The Troubleshooting Manual (TSM) provides fault-isolation logic trees to identify the root cause of system failures; it references AMM procedures for the corrective maintenance once the fault is isolated. The Structural Repair Manual (SRM) provides approved repair procedures for structural damage; repairs beyond SRM limits require Engineering Orders with Type Authority involvement. All are cross-referenced through the ATA numbering system.
AMM revisions are the maintenance organization's currency obligation. Manufacturers issue revision service through paper revision pages or electronic AMM databases (Airbus AirbusWorld, Boeing MyBoeingFleet, Cessna/Textron AeroBase). Under EASA Part-145 145.A.45, a maintenance organization must use the current approved revision of the AMM for any maintenance task. Using a superseded revision is a Type A finding in EASA Part-145 audits. Under FAA §43.13(a), maintenance must be performed in accordance with the manufacturer's current instructions or other approved data. The FAA does not always specify "current revision" with the same precision as EASA, but use of outdated data is identified under §43.13 non-compliance findings in FAA oversight.
For aircraft operated under the FAA-EASA Bilateral Aviation Safety Agreement (BASA), AMMs accepted by the original certifying authority are recognized by the bilateral partner. An AMM approved by the FAA as ICA for a 14 CFR Part 23 aircraft is accepted by EASA as the equivalent approved maintenance data for the same type certified in the EASA system — provided the EASA validation of the TC is current.
Why It Matters for Flight Schools
For flight schools maintaining their own fleets under Part-145 approval or under §91.403 owner-performed maintenance, the AMM is the daily working reference document. An A&P mechanic performing a 100-hour inspection, a Part-66 Cat B1 certifying staff member signing off an engine cylinder removal, or an EASA CAO organization conducting a scheduled AMP task all work from AMM task cards. The practical problem in high-utilization training fleets is revision currency: a training aircraft that is flying 800 hours per year accumulates manufacturer-issued AMM revisions across multiple systems, and maintenance organizations that do not have an active AMM revision tracking subscription risk performing maintenance to superseded task standards.
A subtler problem is the interaction between AMM data and Supplemental Type Certificate (STC) modifications. An aircraft modified with an STC for a Garmin G1000 avionics retrofit, for example, is maintained per the AMM for all systems not modified by the STC, and per the STC Instructions for Continued Airworthiness for the STC-modified systems. Where the STC-ICA supersedes an AMM chapter, the AMM task card for that chapter is no longer applicable. Maintenance organizations that fail to manage the AMM/STC boundary correctly may perform maintenance against superseded AMM data for systems that are now governed by the STC-ICA — a finding under both EASA Part-145 145.A.45 and FAA §43.13.
How Aviatize Handles This
Aviatize's maintenance control module maintains an aircraft-level document register that tracks the active AMM revision alongside every STC-ICA that applies to the airframe. When a manufacturer issues an AMM revision, the system flags the aircraft records affected, identifies which AMP task cards reference the revised chapters, and generates a documentation update task for the maintenance control team — ensuring that the organization is aware of revision currency obligations before a maintenance event, not after. For organizations with electronic AMM subscriptions, the platform can accept AMM revision status data via structured import.
In maintenance execution, AMM task cards are attached directly to work orders. The task card reference — including ATA chapter, section, and revision status — is captured in the work order record at the time of task assignment, creating the audit evidence that the correct revision was in use. When a technician opens a work order for a scheduled inspection task, the platform presents the AMM task reference for that task as specified in the Approved Maintenance Programme, with a timestamp confirming the revision status at task assignment. For STC-modified aircraft, the document register clearly flags which systems are governed by STC-ICA rather than AMM, preventing inadvertent application of superseded AMM procedures to STC-modified systems.