Aircraft General Knowledge: 1-hour targeted help
PPL Aircraft General Knowledge Tutoring | Systems & Instruments Help
PPL Aircraft General Knowledge tutoring — systems, instruments and powerplant
Section titled “PPL Aircraft General Knowledge tutoring — systems, instruments and powerplant”Aircraft General Knowledge covers a wide range of technical content and the exam reflects that breadth. Students often find the instrumentation section particularly difficult — understanding how a gyroscopic instrument actually works, why an altimeter has errors, or how a pitot-static system behaves in icing conditions requires a clear mental model, not just a memorised answer.
A 1-hour session is well suited to targeting a specific system or instrument type that isn’t making sense. The 3-hour intensive covers the full UK CAA and EASA AGK syllabus: airframe and systems, powerplant, and the complete range of flight instruments from air data and gyroscopic through to radio and warning systems.
The instrument errors covered in AGK — particularly altimeter errors, pitot-static failures and gyroscopic instrument behaviour — connect directly to Principles of Flight. Understanding how an instrument fails mechanically helps explain what the pilot experiences aerodynamically, and examiners in both subjects test the same scenarios from different angles.
Choose your session
Section titled “Choose your session”Use a 1-hour session to solve a specific problem or choose a 3-hour session for a deeper, structured lesson. Both options are available for this subject below.
Aircraft General Knowledge: 3-hour intensive session
Frequently asked questions
Section titled “Frequently asked questions”Why do students struggle with the instruments section of the PPL AGK exam?
Because instrument questions test how a device works, not just what it measures. An altimeter question might describe a blocked static port and ask what the instrument reads during a climb — which requires understanding the pressure mechanism, not just knowing that an altimeter measures altitude. The same applies to gyroscopic instruments: questions on precession, rigidity in space, wander and topple require a clear model of how a gyroscope behaves. Students who have only read definitions without building that model tend to guess on these questions. A focused session on instrument principles resolves this quickly.
What is the difference between a direct-reading compass and a remote-reading compass in the PPL exam?
A direct-reading compass (also called a magnetic compass) uses a magnetised element suspended in liquid to align with the Earth's magnetic field. It is simple and requires no power but is subject to errors including turning error, acceleration error, magnetic dip and deviation. A remote-reading compass (flux valve or slaved gyro system) uses a flux detector to sense the magnetic field and feeds the signal to a gyroscopic indicator, giving a more stable and accurate heading display. The PPL(A) AGK exam tests the errors of the direct-reading compass in detail, particularly the turning and acceleration errors and the conditions under which they occur.
What are the main errors of the altimeter tested in the PPL AGK exam?
The PPL(A) exam tests four main altimeter errors. Instrument error is a manufacturing tolerance. Position error (also called pressure error) arises from the static vent location causing inaccurate static pressure readings at certain speeds or attitudes. Lag error occurs because the aneroid capsules take time to respond to rapid pressure changes. Blockage errors occur when the static port is blocked by ice or contamination — the altimeter then reads the altitude at which the blockage occurred and does not change. Temperature error is also tested: in cold air, true altitude is lower than indicated because the air is denser than ISA standard.
How does a pitot-static system work and what happens when it fails?
The pitot-static system supplies pressure to the airspeed indicator, altimeter and vertical speed indicator. The pitot tube measures total pressure (static plus dynamic). The static port measures ambient static pressure. The ASI uses the difference between the two. The altimeter and VSI use static pressure only. If the pitot tube blocks (e.g. from ice), the ASI freezes or behaves like an altimeter — reading higher in a climb and lower in a descent. If the static port blocks, the ASI, altimeter and VSI all freeze at the values they held when the blockage occurred. The PPL(A) AGK exam tests these failure modes and the effect of the alternate static source.
What powerplant topics are most commonly tested in the PPL Aircraft General Knowledge exam?
The most frequently tested powerplant topics in the UK CAA and EASA PPL(A) AGK exam are: the four-stroke cycle and valve timing, carburettor icing (conditions, symptoms and use of carb heat), mixture control and the effect of altitude on mixture, magneto operation and the pre-takeoff magneto check, oil system functions and oil pressure/temperature limits, and the causes and effects of detonation and pre-ignition. Questions on fuel grades (AVGAS 100LL) and the consequences of using incorrect fuel also appear regularly.
Syllabus
Section titled “Syllabus”Aircraft General Knowledge
Section titled “Aircraft General Knowledge”Airframe Systems & Powerplant
- Airframe
- Systems
- Powerplant
Instrumentation
- Air Data Instruments
- Gyroscopic & Magnetic Instruments
- Display & Warning Instruments
- Radio Instruments
- Fuel, Temperature and Pressure Instruments