ATA Codes Every Aviation Mechanic Should Know

Whether you're filling out a work order, referencing a service bulletin, or looking up a chapter in the AMM, ATA chapter codes are the backbone of aviation maintenance documentation. Every aircraft system has one, and knowing them by heart makes you faster and more professional on the job.

This guide explains what ATA codes are, how the numbering system works, and covers the most important chapters that line mechanics and base maintenance technicians encounter daily.

What Are ATA Codes?

ATA codes (also called ATA chapters) are a standardized numbering system for organizing aircraft maintenance documentation. They were originally defined by the Air Transport Association of America in ATA Spec 100, which has since evolved into ATA iSpec 2200.

The system assigns a two-digit chapter number to every major aircraft system — engines, hydraulics, flight controls, avionics, and so on. Every aircraft manufacturer uses the same chapter numbers, which means ATA 32 always means Landing Gear, whether you're working on a Boeing 737, an Airbus A320, or a Cessna 172.

How ATA Reference Numbers Work

A full ATA reference looks like this: ATA 32-10-00

• 32 — Chapter (Landing Gear)
• 10 — Section (Main Gear and Doors)
• 00 — Subject (General / Description)

On work orders and MEL items you'll usually see just the two-digit chapter number. In technical publications you'll see the full three-part reference.

The Most Important ATA Chapters for Line Mechanics

ATA Chapters 71–80: Powerplant Deep Dive

The powerplant chapters (71–80) are among the most referenced in commercial aviation maintenance. Here's how they divide up:

• ATA 71 — Powerplant: Everything between the airframe and engine (mounts, cowls, nacelle)
• ATA 72 — Engine itself: Fan, compressor, combustor, turbine, accessory section
• ATA 73 — Engine Fuel and Control: Fuel metering, FADEC, hydromechanical unit
• ATA 74 — Ignition: Exciters, igniter leads, igniters
• ATA 75 — Air: Engine bleed, cooling, anti-surge bleed valves
• ATA 76 — Engine Controls: Throttle, thrust reverser, ETOPS controls
• ATA 77 — Engine Indicating: EGT, N1, N2, EPR, vibration gauges
• ATA 78 — Exhaust: Exhaust nozzle, thrust reverser, blocker doors
• ATA 79 — Oil: Oil tank, pressure, scavenge, chip detectors
• ATA 80 — Starting: Air turbine starter, start valve, ignition sequence

How ATA Codes Are Used on the Job

• Work orders — Every maintenance task is logged with an ATA chapter number for tracking and billing
• MEL items — Minimum Equipment List deferrals reference ATA chapters to identify the affected system
• AMM navigation — The AMM is organized by ATA chapter — knowing the chapter gets you to the right section fast
• Service bulletins — SBs reference the affected ATA system in their title and header
• Troubleshooting — Fault isolation manuals (FIMs) are organized by ATA chapter
• Parts ordering — Parts catalogs (IPC) use ATA chapters to organize illustrations and part numbers

Tips for New AMTs

• You don't need to memorize every chapter — but know the 15–20 you work on most
• When you get a new work order, identify the ATA chapter first — it tells you exactly where in the AMM to look
• ATA chapters are the same across virtually all commercial aircraft — learning them once means you take the knowledge with you everywhere you work
• Some chapters are aircraft-specific (like APU chapters) while others are universal (landing gear is always 32)