ATA Chapters
The ATA 100 numbering system that organises every aircraft manual.
Open any aircraft maintenance manual — Boeing, Airbus, ATR, business jet — and you will find the same skeleton: numbered chapters where 28 is always Fuel, 32 is always Landing Gear and 34 is always Navigation. That shared skeleton is the ATA numbering system, originally published by the Air Transport Association of America as ATA Spec 100.
The genius of the system is that it is aircraft-agnostic. A mechanic who learned hydraulics on a 737 can pick up an A320 manual and go straight to Chapter 29. Airlines, MROs, parts vendors and software systems all speak the same chapter language, which is why the numbering survives today inside modern standards like ATA iSpec 2200 and S1000D-based publications.
Key areas
Aircraft General (00–12)
Weight and balance, servicing, placards — the general chapters that apply across the aircraft.
Airframe Systems (20–49)
The core systems block: air conditioning, electrics, flight controls, fuel, hydraulics, ice protection, landing gear, navigation and more.
Structures (51–57)
Fuselage, doors, nacelles, stabilisers, windows and wings — the structural repair territory of the SRM.
Powerplant (70–80)
Everything engine: the powerplant, fuel and control, ignition, air, engine indicating, exhaust, oil and starting.
Chapter-Section-Subject
Numbers drill down as 29-10-05: chapter, section, subject — precise addressing for every task and part.
Beyond Maintenance
ATA numbering also organises IPC part listings, defect reporting, reliability data and maintenance IT systems.
How the numbering works
ATA references follow a Chapter-Section-Subject pattern. Take 32-41-11: chapter 32 is Landing Gear, section 41 narrows to wheels and brakes, and the subject pinpoints a specific unit. Task numbering in maintenance manuals extends this further with task and subtask suffixes, so a single lubrication task has a unique, citable address.
This addressing is what makes cross-referencing possible at fleet scale: a task card, the manual procedure it comes from, the parts in the IPC, and the fault reported by the crew can all be tied together through the same chapter reference.
- Chapter 21
- Air Conditioning & Pressurisation
- Chapter 24
- Electrical Power
- Chapter 27
- Flight Controls
- Chapter 28
- Fuel
- Chapter 29
- Hydraulic Power
- Chapter 32
- Landing Gear
- Chapter 34
- Navigation
- Chapter 49
- Airborne Auxiliary Power (APU)
- Chapters 70–80
- Powerplant block — engine, fuel & control, ignition, exhaust, oil, starting
Why a numbering system matters this much
Aviation runs on unambiguous communication. When a pilot logs a defect against chapter 29, maintenance control immediately knows which system, which manuals and often which specialists are involved — before anyone has seen the aircraft. Reliability engineers trend failures by chapter; stores organise parts by chapter; regulators reference chapters in airworthiness directives.
For anyone building a career in maintenance or technical publications, chapter fluency is foundational. Experienced engineers navigate by number the way locals navigate streets — nobody says 'the fuel system manual', they say 'chapter 28'.
From Spec 100 to iSpec 2200 and S1000D
ATA Spec 100 (content and numbering) and Spec 2100 (electronic data) were consolidated into ATA iSpec 2200, which still governs how most commercial air transport manuals are structured and exchanged. Newer programmes — and most defence platforms — use S1000D instead, but even there the ATA chapter concept usually lives on inside the Standard Numbering System used to code data modules.
The practical takeaway: whichever documentation standard an aircraft uses, the chapter numbers you learn once will keep paying off across fleets, employers and decades.
Frequently asked questions
What are ATA chapters?
A standardised numbering system, originating from ATA Spec 100, that divides an aircraft into numbered system chapters — for example 28 Fuel, 29 Hydraulic Power, 32 Landing Gear — so every manufacturer's manuals follow the same structure.
Is the ATA chapter list the same on every aircraft?
The chapter meanings are standard across aircraft types, which is the whole point. Not every aircraft uses every chapter (a piston aircraft has no APU chapter content), but a chapter number never changes meaning between types.
What does a reference like 32-41-11 mean?
It is a Chapter-Section-Subject address: chapter 32 (Landing Gear), section 41 (wheels and brakes area), subject 11 identifying the specific unit or topic. Maintenance tasks extend this with task and subtask numbers.
Do modern S1000D publications still use ATA chapters?
Frequently, yes. S1000D data module codes include a system-breakdown element, and for civil aircraft this is commonly mapped to the familiar ATA chapter numbering.