---
title: "MODULE 12. HELICOPTER AERODYNAMICS, STRUCTURES AND SYSTEMS — Part-66 · Avioverse"
description: "MODULE 12. HELICOPTER AERODYNAMICS, STRUCTURES AND SYSTEMS LEVEL A3 A4 B1.3 B1.4 12.1 Theory of flight — rotary wing aerodynamics 1 2 12.2 Flight control…"
url: "https://avioverse.aero/regulations/easa/continuing-airworthiness/part-66/appendices-to-annex-iii-part-66/module-12-helicopter-aerodynamics-structures-and-systems"
---

# MODULE 12. HELICOPTER AERODYNAMICS, STRUCTURES AND SYSTEMS

Annex III (Part-66) · Regulation (EU) No 1321/2014 · EAR revision 2 Sep 2025

IR Implementing rule

## MODULE 12. HELICOPTER AERODYNAMICS, STRUCTURES AND SYSTEMS

| MODULE 12. [HELICOPTER](https://avioverse.aero/glossary/easa/helicopter) AERODYNAMICS, STRUCTURES AND SYSTEMS |                                                                                                                  |                                                                                                                              | LEVEL |           |
| ------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | ----- | --------- |
|                                                                                                               |                                                                                                                  |                                                                                                                              | A3 A4 | B1.3 B1.4 |
| 12.1 Theory of flight — rotary wing aerodynamics                                                              |                                                                                                                  |                                                                                                                              | 1     | 2         |
| 12.2 Flight control systems (ATA 67)                                                                          |                                                                                                                  |                                                                                                                              | 2     | 3         |
| 12.3 Blade tracking and vibration analysis (ATA 18)                                                           |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.4 Transmission                                                                                             |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.5 Airframe structures (ATA 51)                                                                             |                                                                                                                  |                                                                                                                              |       |           |
|                                                                                                               | (a) General concept;                                                                                             |                                                                                                                              | 2     | 2         |
|                                                                                                               | (b) Construction methods of the principal elements.                                                              |                                                                                                                              | 1     | 2         |
| 12.6 Air conditioning (ATA 21)                                                                                |                                                                                                                  |                                                                                                                              |       |           |
| 12.6.1 Air supply                                                                                             |                                                                                                                  |                                                                                                                              | 1     | 2         |
| 12.6.2 Air conditioning                                                                                       |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.7 Instruments/avionic systems                                                                              |                                                                                                                  |                                                                                                                              |       |           |
| 12.7.1 Instrument systems (ATA 31)                                                                            |                                                                                                                  |                                                                                                                              | 1     | 2         |
| 12.7.2 Avionic systems                                                                                        |                                                                                                                  |                                                                                                                              | 1     | 1         |
|                                                                                                               |                                                                                                                  | Fundamentals of system layouts and operation of: Auto Flight (ATA 22); Communications (ATA 23); Navigation Systems (ATA 34). |       |           |
| 12.8 Electrical Power (ATA 24)                                                                                |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.9 Equipment and furnishings (ATA 25)                                                                       |                                                                                                                  |                                                                                                                              |       |           |
|                                                                                                               | (a) Emergency equipment; Seats, harnesses, and belts; Lifting systems;                                           |                                                                                                                              | 2     | 2         |
|                                                                                                               | (b) Emergency flotation systems; Cabin layout, cargo retention; Equipment layout; Cabin furnishing installation. |                                                                                                                              | 1     | 1         |
| 12.10 Fire Protection (ATA 26)                                                                                |                                                                                                                  |                                                                                                                              |       |           |
|                                                                                                               | (a) Fire and smoke detection systems and Fire-extinguishing systems;                                             |                                                                                                                              | 1     | 3         |
|                                                                                                               | (b) Portable fire extinguishers.                                                                                 |                                                                                                                              | 1     | 1         |
| 12.11 Fuel Systems (ATA 28)                                                                                   |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.12 Hydraulic Power (ATA 29)                                                                                |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.13 Ice and Rain Protection (ATA 30)                                                                        |                                                                                                                  |                                                                                                                              | 1     | 3         |
| 12.14 Landing Gear (ATA 32)                                                                                   |                                                                                                                  |                                                                                                                              | 2     | 3         |
|                                                                                                               | (a) System description and operation;                                                                            |                                                                                                                              |       |           |
|                                                                                                               | (b) Sensors.                                                                                                     |                                                                                                                              | 2     | 3         |
| 12.15 Lights (ATA 33)                                                                                         |                                                                                                                  |                                                                                                                              | 2     | 3         |
| 12.16 (Reserved)                                                                                              |                                                                                                                  |                                                                                                                              | 2     | 3         |
| 12.17 Integrated Modular Avionics (ATA 42)                                                                    |                                                                                                                  |                                                                                                                              | 1     | 2         |
|                                                                                                               | (a) Overall system description and theory                                                                        |                                                                                                                              |       |           |
|                                                                                                               | (b) Typical system layouts                                                                                       |                                                                                                                              | 1     | 2         |
| 12.18 On-board [Maintenance](https://avioverse.aero/glossary/easa/maintenance) Systems (ATA 45)               |                                                                                                                  |                                                                                                                              | 1     | 2         |
|                                                                                                               | Central maintenance computers; Data-loading system; Electronic library system.                                   |                                                                                                                              |       |           |
| 12.19 Information Systems (ATA 46)                                                                            |                                                                                                                  |                                                                                                                              | 1     | 2         |

IR — Regulation (EU) No 1321/2014 · Regulation (EU) 2023/989 · Continuing Airworthiness Easy Access Rules · EAR revision 2 Sep 2025

[All rules in APPENDICES TO ANNEX III (Part-66)](https://avioverse.aero/regulations/easa/continuing-airworthiness/part-66/appendices-to-annex-iii-part-66)

Consolidated from the EASA Easy Access Rules (revision 2 Sep 2025, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.