(6) The start system interfaces with the sequencing oil pressure switch, speed switch, APU control unit and APU switch. During APU start, the starter is energized and APU rotates. The ignition exciter is energized by the action of the sequencing oil pressure switch(this switch ensures that combustion cannot be initiated during an APU start until a minimum lubricating oil pressure has been buildup during APU start, with increasing oil pressure, this switch closes at 4 psig oil pressure and provides 28 volt dc power to the fuel solenoid valve and the ignition exciter). The starter and ignition circuits are de-energized by the action of the speed switch during APU engine acceleration. During normal engine operation, the exciter remains de-energized.

起动系统连接着程序化的滑油压力开关、速度开关、 APU控制组件及 APU开关。 APU起动期间，起动器被接通， APU转动。点火励磁器通过程序化的滑油压力开关（此开关确保在 APU起动到建立最小的滑油润滑压力期间不会燃烧。在 APU起动期间，随着滑油压力增加，当滑油压力达到 4PSIG时，开关关闭，并且提供 28伏直流电给燃油电磁活门及点火励磁器）动作被接通。起动器及点火线圈在 APU发动机加速期间通过速度开关被释放。在发动机正常操作期间，励磁器保持断开。

(7) The APU exhaust conducts the engine exhaust gas overboard and reduces the noise level of the high velocity gas flow. The exhaust duct consists of a

heat shield and a muffler. The muffler is inside the heat shield. A felt metal liner is installed on the inside surface of the muffler for noise reduction. At the forward end ,the heat shield has a drip pan and is supported by the engine shroud. There si a gap between the muffler and the APU engine exhaust. At the aft end ,the exhaust duct is supported by the aft fairing .
APU排放口引导发动机排出气体到外面并降低高速气流的噪音。排放管道包括一个加热保护罩和一个消音器。消音器安装于加热保护罩内部。一个绝缘金属垫片消音器内表面上，用来降低噪音。在加热器前端有一个集油盘并被发动机保护罩支持。在消音器与 APU发动机排气口之间有一个间隙。排气管道后端由后整流罩支撑。
LESSON 19 AUXILIARY POWER UNIT（2）
一、单词
首先  Primarily 供给  Furnish 接线端  teminal
中线  Neutral 导线  Lead 在 …外面  Outside
放电器  Discharger 开缝的  slotted 频率  Frequency
得到  Achieve 跳开关  Breaker 闭合  Closing
松开  Tripping 永久磁铁  Permanent magnet 帮助  Assist
锁定  Latch 弹簧  Spring 保持  hold
触点  Contact 接触器  Contactor 信号  Signal
获得  Gain 应用  Application 允许  Allow
短暂的  Momentary 通电  Energize 线圈  Coil
极性  polarity 插座  Receptacle 汇流条防护  Bus protection panel
充电器  Charger 主要的  Essential 缺席  Absence
柱螺栓  stud

二、TEXT
(1) the APU driven generator is mounted on the foreard face of the APU accessory drive gearbox. The APU generator produces the AC power required by the airplane systems primarily for ground operation, the generator can also be used as a backup generator in flight. APU is used to furnish 60 KVA of electrical power on the ground and used as AC power source of 50 KVA in flight.