Explainer
The Aircraft Manual Family: AMM, IPC, CMM, SRM, and WDM
The Core Five
One Aircraft, Five Manuals
- AMM — Aircraft Maintenance Manual
- The working core of the library: system descriptions and the maintenance procedures performed on the aircraft — servicing, removal and installation, tests and checks — organized by the ATA chapter numbering, so air conditioning is chapter 21 and landing gear is chapter 32 on any type. Published by the airframe manufacturer, revised continuously, and the document a line or base maintenance technician lives in.
- IPC — Illustrated Parts Catalog
- The parts side of the same aircraft: exploded-view illustrations with numbered items tying every part position to a part number and its effectivity. The IPC is how a physical part on an aircraft becomes an orderable item — used by stores, planning, and technicians confirming the right part for the right serial. Its accuracy is decided upstream, in the provisioning data it is generated from.
- CMM — Component Maintenance Manual
- Where the AMM stops at removal and installation, the CMM begins: shop-level disassembly, inspection, repair, and test of an individual component — a pump, an actuator, an avionics unit — off the aircraft, on the bench. Published by the component's own manufacturer rather than the airframer, which is why an operator's CMM library has dozens of sources and why keeping it current is a discipline of its own.
- SRM — Structural Repair Manual
- The structure specialist's authority: allowable damage limits, inspection requirements, and approved repair schemes for the airframe itself — skins, frames, stringers, composites. The SRM is what determines whether a dent is documented and flown, repaired per an existing scheme, or escalated to the manufacturer for engineering disposition. Working beyond its limits is not a repair; it is an unapproved modification.
- WDM — Wiring Diagram Manual
- The electrical map: wiring diagrams, harness routing, connector and pin data, and equipment lists for the aircraft's electrical systems. Troubleshooting an intermittent fault without a current WDM is guesswork with a multimeter — and because wiring differs by serial and modification state, effectivity matters more here than almost anywhere else in the library.
The family is larger than five — fault isolation and troubleshooting manuals sit beside the AMM, and the flight operations shelf (flight crew operating manuals, the minimum equipment list) runs as a parallel stream governed by ATA Spec 2300 rather than the maintenance specs. But these five are the load-bearing ones, and they share one spine: the ATA chapter numbering defined through ATA iSpec 2200, which puts the same system in the same chapter across every manual and every aircraft type.
The Connective Tissue
What Keeps the Family Honest
None of these manuals is a book; each is a revision stream. Between scheduled revisions, service bulletins carry specific changes from the manufacturer — a modified part, a new inspection — and each incorporated bulletin ripples through the family: a procedure changes in the AMM, part effectivity shifts in the IPC, sometimes a wiring run moves in the WDM. Airworthiness directivesare the regulator's overlay, making certain of those changes mandatory. The library is only as good as the operation's ability to prove all of it: which revision was current, which bulletins were incorporated, and what a technician was reading on a given date.
That proof problem — not authorship — is what most operators actually struggle with, and it is a delivery problem: revisions arriving from many publishers, in mixed formats spanning iSpec 2200 and S1000D, reaching hangar floors that may be offline. We wrote a field guide to the systems that solve it — and the manual family above is the content those systems exist to carry.
FAQ
Questions We Hear
What is the difference between an AMM and an IPC?
The AMM tells you how to do the work — procedures, servicing, removal and installation — while the IPC tells you what the aircraft is made of: illustrated part positions tied to orderable part numbers with effectivity. A technician works from the AMM and orders from the IPC, and the two are revised in step because a procedure that references a part the catalog no longer lists is a defect in both.
What is a CMM in aviation?
A Component Maintenance Manual: the shop-level manual for overhauling, repairing, and testing an individual component off the aircraft, published by that component's manufacturer. Aircraft-level manuals stop at removing and installing the unit; the CMM covers everything that happens to it on the bench in between.
Who publishes aircraft manuals — the airline or the manufacturer?
Manufacturers publish; operators customize and maintain their copies. The airframer publishes the AMM, IPC, SRM, and WDM for its aircraft; component OEMs publish CMMs for their units. Operators then hold their libraries current against manufacturer revisions and, where approved, incorporate their own operational content — which is why proving which revision a technician worked from on a given date is an operator obligation, not a manufacturer one.
How do the manuals stay current?
Through the revision stream: manufacturers issue scheduled revisions, and between them, service bulletins describe specific changes — which, once incorporated, change the AMM, IPC, and effectivity data. Airworthiness directives are the regulator's layer on top, mandating action. An operation's real challenge is rarely a missing manual; it is proving that every copy in use reflects the current revision and every incorporated bulletin.
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Wrangling the Library?
Whether you produce these manuals or consume them, keeping the family current and provable is the actual job. Tell us where yours stands.