Electrical connection Starter drive gear Mounting bolts and alianment pin Figure 5-11.  Starter drive gear mounting holes and electrical connector.  sustain rotation or to accelerate during the initial phase of the  starting cycle. The starter must continue to assist the engine  considerably above the self-accelerating speed to avoid a  delay in the starting cycle, which would result in a hot or hung  false start or a combination of both. At the proper points in  the sequence, the starter and ignition are automatically cut  off. The basic types of starters that are in current use for gas  turbine engines are direct current (DC) electric motor, starter/ generators, and the air turbine type of starters. A typical cartridge/pneumatic turbine engine starter may be  operated as an ordinary air turbine starter from a ground- operated air supply or an engine cross-bleed source. It may  also be operated as a cartridge starter.  [Figure 5-15]  To  accomplish a cartridge start, a cartridge is first placed in the  breech cap. The breech is then closed on the breech chamber  by means of the breech handle and then rotated a partial turn to  engage the lugs between the two breech sections. The cartridge  is ignited by applying voltage through the connector at the  end of the breech handle. Upon ignition, the cartridge begins  to generate gas. The gas is forced out of the breech to the hot  gas nozzles that are directed toward the buckets on the turbine  rotor, and rotation is produced via the overboard exhaust  collector. Before reaching the nozzle, the hot gas passes an  outlet leading to the relief valve. This valve directs hot gas  to the turbine, bypassing the hot gas nozzle, as the pressure  rises above the preset maximum. Thus, the pressure of the gas  within the hot gas circuit is maintained at the optimum level.  Many types of turbine starters have included several different  methods for turning the engine for starting. Several methods  have been used but most of these have given way to electric  or air turbine starters. An air impingement starting system,  which is sometimes used on small engines, consists of jets of  compressed air piped to the inside of the compressor or turbine  case so that the jet air blast is directed onto the compressor or  turbine rotor blades, causing them to rotate.  The fuel/air combustion starter was used to start gas turbine  engines by using the combustion energy of jet A fuel and  compressed air. The starter consists of a turbine-driven  power unit and auxiliary fuel, air, and ignition systems.  Operation of this type starter is, in most installations, fully  automatic; actuation of a single switch causes the starter to  fire and accelerate the engine from rest to starter cutoff speed.  Hydraulic pumps and motors have also been used for some  smaller engines. Many of these systems are not often used  on modern commercial aircraft because of the high power  demands required to turn the large turbofan engines during  the starting cycle on transport aircraft.  Figure 5-12.  Engine starter mounted on the engine.  5-9 Starter ring gear mounted on propeller hub  Starter gear