Aircraft General Knowledge (subject 021) is the EASA ATPL theory exam that explains the aircraft itself — how the airframe carries load, and how the systems that keep it flying are built and operated, from hydraulics and landing gear to fuel, electrics, engines and emergency equipment. This guide breaks the syllabus into its 13 official topic areas, shows how the systems connect, and sets out a study plan to pass the exam at the 75% mark.
Aircraft General Knowledge — often abbreviated to AGK, and sometimes titled “Airframe, Systems, Power Plant and Emergency Equipment” — is the subject that explains the aircraft itself. It starts with how the airframe is designed to carry load, then works through the systems that keep it flying: hydraulics, landing gear, flight controls, pressurisation, ice protection, fuel, electrics, the engines that power it, and the fire and oxygen systems that protect it. It rewards understanding how each system works and how it can fail rather than heavy calculation.
EASA structures the 021 syllabus into thirteen topic areas, progressing from structural design and the airframe, through the aircraft’s mechanical and electrical systems, to the piston and turbine power plants and the emergency equipment. The sections below walk through each one.
These are the official EASA topic areas for subject 021, in syllabus order. They broadly move from how the airframe is built to the systems and power plants that operate it, so working them roughly in sequence keeps the subject manageable.
Every EASA ATPL theory subject is passed at a minimum of 75%, and each subject is passed independently. For a broad, systems-heavy subject like Aircraft General Knowledge, the most reliable route to that mark is understand-then-drill:
Note: Exam rules — the pass mark, sittings and attempt limits — are set by EASA Part-FCL and applied by your national authority (NAA). Always confirm the current figures with your ATO/NAA before you plan, as they are periodically updated.
ATPL Training is an all-in-one platform for the theory phase: an ECQB-aligned question bank with worked explanations, structured lessons, built-in spaced-repetition review, and an AI tutor that explains the reasoning behind every answer — at around half the price of the established providers. For a broad, systems-led subject like Aircraft General Knowledge, that combination turns the theory into exam marks.
Aircraft General Knowledge, EASA learning-objective subject code 021, is the ATPL theory exam covering the aircraft itself — its airframe and structures and the systems that operate it: hydraulics, landing gear, flight controls, air conditioning and pressurisation, ice and rain protection, fuel, electrics, piston and turbine engines, and fire and oxygen systems. It is examined as one of the 13 EASA ATPL theory subjects and is sometimes labelled "Airframe, Systems, Power Plant and Emergency Equipment".
The 021 syllabus is built around 13 topic areas: System Design, Loads and Stresses; Airframe and Structures; Hydraulics; Landing Gear, Wheels, Brakes and Tyres; Flight Controls; Air Conditioning and Pressurisation; Ice and Rain Protection; Fuel Systems; Electrics; Piston Engines; Turbine Engines; Fire and Smoke Protection; and Oxygen Systems.
Like every EASA ATPL theory subject, Aircraft General Knowledge is passed at a minimum of 75%. Each subject is passed independently, so you only re-sit the exams you do not pass. Exam rules are applied by your national authority (NAA), so confirm the current figures with your ATO/NAA.
Many students find 021 demanding because it is broad rather than deep — it asks you to understand how a large number of unrelated systems work, from structures and hydraulics to two very different engine types. It is more memory- and understanding-led than calculation-heavy, so working a large bank of exam-style questions with worked explanations, system by system, is the most reliable way to turn the theory into exam marks.
Take it one system at a time: understand what each system does, its main components and how it fails, then drill ECQB-aligned questions on that system and read every explanation. Because 021 is broad, spaced repetition is especially valuable — it keeps earlier systems fresh while you add new ones — and full mock exams at the real 75% pass mark confirm your readiness before you sit the official paper.
Drill ECQB-aligned 021 questions with worked explanations, track your readiness across all thirteen topics, and rehearse with full mock exams at the real 75% pass mark.
