EASA Module 3 case studies
EASA Module 3 · Put your knowledge to work in context.
EASA Module 3, Electrical Fundamentals, is one of the basic knowledge modules that a candidate must pass to qualify for an aircraft maintenance licence under the European Part-66 licensing system, in the B1 (mechanical) and B2 (avionics) categories. It is a theory module rather than a type course: it builds the physics foundation - electron theory, static electricity and conduction, electrical terminology, generation of electricity, DC sources and circuits, resistance and power, capacitance, magnetism, inductance, DC motor and generator theory, and finally AC theory including resistive, capacitive and inductive circuits, transformers, filters, AC generators and AC motors - that later modules on aircraft electrical systems, instruments and avionics assume you already hold. The EASA Module 3 case studies are 5 cases and about 3,455 words.
1The divider that wasn't faulty
A 28 V DC bus feeds a reference divider in an avionics bay: R1 = 4.7 MΩ from the bus to the midpoint, R2 = 4.7 MΩ from the midpoint to ground, giving a nominal 14 V reference. A technician connects a calibrated digital multimeter (10 MΩ input resistance, DC volts range) across R2 and reads 11.3 V.
612 words, about 3 min2Discharge time for a 300 V reservoir
An avionics power supply uses a 470 µF electrolytic reservoir capacitor charged to 300 V DC. Before the unit may be opened, the capacitor must be discharged below 50 V within 60 s of power removal, and must stay below that level while the unit is on the bench.
668 words, about 3 min3Testing a 400 Hz transformer on a 50 Hz bench
A 400 Hz aircraft transformer is marked 115 V / 26 V, 100 VA. It arrives in a workshop that has only a 50 Hz mains supply and a variable autotransformer.
644 words, about 3 min4Shunt generator that stalls at 12 volts
A 28 V, 100 A shunt-wound DC generator on a test bench, driven at its rated 3000 rpm, fails to build up. With the field disconnected the armature produces 1.8 V.
728 words, about 4 min5The filter that punctured its capacitor
A series LC bypass leg is designed to present minimum impedance at 400 Hz on a 115 V, 400 Hz supply. It uses L = 100 mH with a coil resistance of 15 Ω, and C = 1.583 µF in a plastic-film case rated 400 V DC.
803 words, about 4 min