Module 3 Electrical Fundamentals case studies
Module 3 Electrical Fundamentals · Put your knowledge to work in context.
Module 3 Electrical Fundamentals is one of the foundational knowledge modules in the EASA Part-66 aircraft maintenance licence syllabus, and it underpins almost every later module a candidate will meet. It is written for trainee and practising aircraft maintenance engineers working toward a Category A, B1, B2 or B3 licence, and for anyone who needs to demonstrate a solid grounding in electrical principles before moving on to airframe, avionics or systems content. The Module 3 Electrical Fundamentals case studies are 5 cases and about 4,023 words.
1Cabin Lighting Feeder: High-Resistance Joint or Undersized Cable?
A 28 V DC essential bus supplies a cabin lighting load through a 6 m feeder run of two conductors, each rated at 5 mΩ per metre. The load is three identical lamp units in parallel, each drawing 4 A at 28 V.
754 words, about 4 min2Missing Freewheeling Diode on a Fuel Shut-Off Valve Relay
A 28 V DC fuel shut-off valve is energised by a relay whose coil measures 220 Ω and 120 mH. The coil is switched on the low side by an NPN transistor, and a suppression diode is fitted at the relay socket with its cathode to the coil positive terminal.
810 words, about 4 min3Ageing Reservoir Capacitor: Out of Tolerance, Hot, and Short of a Spare
A 28 V DC avionics supply uses a 4700 µF, 40 V, 105 °C electrolytic capacitor as the reservoir across the rectified output of a 400 Hz transformer-rectifier unit. After nine years in service the full-load ripple has risen from 40 mV to 180 mV peak-to-peak and the capacitor can is slightly domed.
814 words, about 4 min4Galley Inverter Tripping: kVA, Power Factor and an Extra Load
A 115 V, 400 Hz, single-phase inverter on a twin turboprop is rated at 1.5 kVA and trips at 13.0 A rms output current. Its load is a galley heater and fan drawing 1.2 kW at 0.75 power factor lagging.
845 words, about 4 min5Nickel-Cadmium Emergency Battery: One Hot Cell and a Mis-set Float Voltage
A 20-cell nickel-cadmium battery rated 25 Ah supplies an emergency communications installation. A capacity check is run at the 5 A rate to a cut-off of 20 V.
800 words, about 4 min