Electric Starting Systems and Starter Generator Starting System in Engine Starting Systems
Starters for gas turbine aircraft systems are most often either direct cranking electrical systems or starter generator systems. These two types are most commonly used for gas powered engines and utilize magnets or direct current electric motors to start the aircraft engine. Understanding the differences between the two types and how they function can help you decide which the best system for your aircraft is.
Direct cranking electric systems
Direct cranking electrical systems will most often benefit a small turbine engine, turboshaft engine, or APU. These starters operate from battery voltage which actuates and initiates the system operation with a set value of cranking torque applied to the engine. Once the engine has started and reaches a set speed, direct cranking electrical systems then undergo disengagement from the starter automatically.
Starter generator systems
Starter generator systems contain brushes, windings, a stator, and an armature. The wires are wound around the armature and make a field coil. Voltage is induced into this coil and passes through the brushes and armature to generate a magnetic field. This activates the stator which then starts the engine. After the engine is started, a separate set of windings can then take over and act as a generator for the aircraft.
Difference between Direct cranking electric systems and Starter generator systems
One disadvantage to both systems is that they require some sort of power to initiate operation. Starter generators, however, only need the battery in the beginning to initiate functionality and then are self-reliant. As compared to starter generators, direct cranking electrical systems do hold some differences that set them apart. Starter generators do not need to disengage the starter from the shaft, as they are permanently engaged to them. Due to the fact that starters also function as a generator after initiation, they can be an economical choice over direct cranking electrical systems.
Nevertheless, both systems provide similar functions with their different operations and choosing the right system may depend on the type of aircraft you are flying, as well as the type of engine starter you desire.