When the no 1 switch is actuated the start fuel and

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When the No. 1 switch is actuated, the start fuel and ignition systems are shut off. When the No. 2 switch is actuated at 110 percent speed, the main fuel solenoid valve is closed, and this shuts off fuel to the engine. 186
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d . Turbine exhaust thermal switch . A thermocouple projects into the exhaust gas stream at the aft end of the combustor. If an over temperature occurs, the contacts normally closed in the turbine exhaust thermal switch will open, close the main fuel solenoid valve, and shut the engine down. e . Tachometer generator . The APU tachometer generator is mounted in tandem with the speed switch on the accessory drive assembly. A synchronous rotor in the tachometer generator produces three-phase ac voltage proportional to the speed at which the rotor is turning. This voltage is transmitted to a tachometer indicator in the cockpit which indicates the engine speed in percent of rated rpm. f . Hour meter . Engine operating time is recorded by the hour meter attached to the engine. The meter operates on 24v dc supplied by the aircraft bus. 6.12. SUMMARY The T62 is used on the CH-47 and CH-54 helicopters as an auxiliary power unit. The engine consists of a combustor, turbine, and reduction and accessory drive assemblies. Both the compressor and turbine rotor are mounted on the same shaft. A fuel control, hydraulic starter motor, and ignition unit are mounted on the engine. Operating time for the APU is maintained separately from the aircraft engine time by an hour meter mounted on the APU. The T62 is equipped with protective devices that shut the APU down if any of the operating limitations are exceeded. If the oil pressure, rpm, or exhaust temperature limits are exceeded, a light on the instrument panel will be illuminated and the APU shut down. 187
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Chapter 7 ALLISON T63 7.1. INTRODUCTION The T63 series turboshaft engine is manufactured by the Allison Division of General Motors Corporation. The T63-A-5A is used to power the OH-6A, and the T63-A-700 is in the OH-58A light observation helicopter. Although the engine dash numbers are not the same for each of these, the engines are basically the same. As shown in figure 7.1, the engine consists of four major components: the compressor, accessory gearbox, combustor, and turbine sections. This chapter explains the major sections and related systems. 7.2. OPERATIONAL DESCRIPTION The T63 turboshaft engine, being an internal combustion engine, requires intake, compression, combustion, and exhaust, as does a reciprocating engine. Figure 7.2 is a cutaway view of the T63 engine. By looking at the letters in the arrows in figure 7.2, you will be able to follow the air's path through the engine. Air is routed to the compressor assembly by intake ducts on the aircraft. The (A) compressor assembly "squeezes" incoming air to high pressures. This compressed air is discharged through twin air-transfer tubes (B) into the combustion chamber (C) and mixed with fuel which is then burned. The exhaust gases expand through the compressor turbine (D) which extracts energy from these hot gases to drive the compressor (A). The power turbine (E) takes the remaining energy to drive
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  • Fall '19
  • Internal combustion engine, Gas turbine, Gas compressor

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