Small Aircraft Troubleshooting Procedures Starter motor $_{runs, but do}$ $^{es not }$turn crankshaft Starter drags Starter  excessively  noisy Probable Cause Isolation Procedure Remedy Starter will  not operate • Repair circuit.  • Replace switch or wires.  • Adjust starter lever in accordance   with manufacturer’s instructions.  • Remove and repair or replace   starter. • Adjust starter lever in accordance   with manufacturer’s instructions. • Replace defective parts. • Replace defective parts. • Charge or replace battery. • Replace with serviceable unit. • Repair or replace starter. • Turn down commutator. • Replace starter drive. • Replace crankshaft gear. • Check master circuit. • Check switch circuit continuity. • Check starter lever adjustment. • Check through items above. If   another cause is not apparent,   starter is defective. • Check starter lever adjustment. • Remove starter and check starter   drive and overrunning clutch.  • Remove and check pinion gear and  crankshaft gear. •   Check battery. •   Check contacts. • Check starter brushes, brush spring   tension for solder thrown on brush   cover. • Clean and check visually. • Remove and examine pinion. • Remove starter and turn over engine   by hand to examine crankshaft gear. • Defective master switch or circuit • Defective starter switch or switch   circuit • Starter lever does not activate switch  •   Defective starter • Starter lever adjusted to activate   switch without engaging pinion with   crankshaft gear • Defective overrunning clutch or drive • Damaged starter pinion gear or   crankshaft gear •   Low battery • Starter switch or relay contacts   burned or dirty  •   Defective starter • Dirty, worn commutator • Worn starter pinion • Worn or broken teeth on crankshaft  gears Figure 5-13. Small aircraft troubleshooting procedures. Figure 5-14.  Typical gas turbine engine starting sequence.  5-10 Electric Starting Systems and Starter  Generator Starting System Electric starting systems for gas turbine aircraft are of  two general types: direct cranking electrical systems and  starter generator systems. Direct cranking electric starting  systems are used mostly on small turbine engines, such as  Auxiliary Power Units (APUs), and some small turboshaft  engines. Many gas turbine aircraft are equipped with starter  generator systems. Starter generator starting systems are  also similar to direct cranking electrical systems except that  after functioning as a starter, they contain a second series of  windings that allow it to switch to a generator after the engine  has reached a self-sustaining speed. This saves weight and  space on the engine.  The starter generator is permanently engaged with the engine  shaft through the necessary drive gears, while the direct  cranking starter must employ some means of disengaging  the starter from the shaft after the engine has started. The  starter generator unit is basically a shunt generator with an  additional heavy series winding.  [Figure 5-16]  This series  winding is electrically connected to produce a strong field  and a resulting high torque for starting. Starter generator  units are desirable from an economic standpoint, since one  unit performs the functions of both starter and generator.  Additionally, the total weight of starting system components  is reduced and fewer spare parts are required.  Time (seconds) Compressor rpm Exhaust gas temperature (°C) Idle EGT Peak starting ECT Exhaust gas temperature versus time Compressor rpm versus time Starter cuts out Ignition off Engine attains self-accelerating speed Ignition on Fuel on Engine lights up EGT rise indicates light up Engine attains idle rpm