Controls and instrumentation
振动
44.涡轮喷气发动机具有极低的振动水平，由于即时发生的或部分的故障所引起的振动可能会不被发觉而通过。因此，许多发动机上装了振动指示器，它持续地监视发动机的振动水平。该指示器通常都是一个毫安表，它通过放大器接收从装在发动机上的传感器传来的一些信号（图12-11）
图12-9 滑油温度和压力传感器和指示器
Fig. 12-9 Oil temperature and pressure transmitters and indicators.
Fig. 12-10 Fuel flow transmitter and 图12-10 燃油流量传感器和指示器
indicator.
total fuel used in gallons, pounds or kilogrammes per hour (fig. 12-10). The transmitter measures the fuel flow electrically and an associated electronic unit gives a signal to the indicator proportional to the fuel flow.
Vibration
44.
A turbo-jet engine has an extremely low vibration level and a change of vibration, due to an impending or partial failure, may pass without being noticed. Many engines are therefore fitted with vibration indicators that continually monitor the vibration level of the engine. The indicator is usually a milliammeter that receives signals through an amplifier from engine mounted transmitters (fig. 12-11).
45.
A vibration transmitter is mounted on the engine casing and electrically connected to the amplifier and indicator. The vibration sensing element is usually an electro-magnetic transducer that converts the rate of vibration into electrical signals and these cause the indicator pointer to move proportional to the vibration level. A warning lamp on the instrument panel is incorporated in the system to warn the pilot if an unacceptable level of vibration is approached, enabling the engine to be shut down and so reduce the risk of damage.
46．仪表上记录的振动水平是拾取处感测的总振动量。更精确的方法会区分出各个转子频率范围之间的差别，从而保证振动源能被孤立出来。对于多转于发动机来说，这尤为重要。
45.在发动机的机匣上安装一个振动传感器，与放大器和指示器用电路相连。振动感测元件通常是一个电磁传感器，它将振动的大小转换成为电信号，这些信号使指示器指针的移动与振动水平成正比。仪表板上的一个警告灯被设置在系统中，用于在有不可接受的振动正在临近时向驾驶员报警，以使发动机停车，从而减少损坏的危险。
47．为用于多转子发动机，已经研制成功了一种晶体式振动传感器，它能提供更可靠的振动指示。在通向振动仪表的电路上装了一个滤波器系统，这就有可能将所得的振动对照已知的频率范围进行比较，由此能找到振动源的位置。一个多选择位置的开关使驾驶员可以选出一个特定的区域，以获得该振动水平的读数。
Controls and instrumentation
Fig. 12-11 Vibration transmitter and indicator.
46.
The vibration level recorded on the gauge is the sum total of vibration felt at the pick-up. A more accurate method differentiates between the frequency ranges of each rotating assembly and so enables the source of vibration to be isolated. This is particularly important on multi-spool engines.
47.
A crystal-type vibration transmitter, giving a more reliable indication of vibration, has been developed for use on multi-spool engines. A system of filters in the electrical circuit to the gauge makes it possible to compare the vibration obtained against a known frequency range and so locate the vibration source. A multiple-selector switch enables the pilot to select a specific area to obtain a reading of the level of vibration.
Warning systems
48. Warning systems are provided to give an indication of a possible failure or the existence of a dangerous condition, so that action can be taken to safeguard the engine or aircraft. Although the various systems of an aircraft engine are designed wherever possible to 'fail safe1, additional safety devices are sometimes fitted. Automatic propeller feathering should a power loss occur, and automatic closing of the high pressure fuel shut-off cock should a turbine shaft failure occur, are but two examples. On some engine types, the fuel system is fitted with a control to enable the engine to be operated by manual throttling should a main fuel system failure occur.
图12-11 振动传感器及指示器
49.
In addition to a fire warning system (Part 14), a number of other audible or visual warning systems can be fitted to a gas turbine engine. These may be for low oil or fuel pressure, excessive vibration or overheating. Indication of these may be by warning light, bell or horn. A flashing light is used to attract the pilot's attention to a central warning panel (C.W.P.) where the actual fault is indicated.
50.
Other instruments and lights warn the pilot of the selected position of the thrust reverser, the fan reverser or the afterburner variable nozzle, when applicable. Gauges also inform the pilot of such things as hydraulic pressure and flow and generator output, which are vital to the correct operation of the aircraft systems.
Aircraft integrated data system
51.
The aircraft integrated data system (A.I.D.S.) is an extension of the 'black box' aircraft accident data recorder. By monitoring and recording various engine parameters, either manually or automatically, it is possible to detect an incipient failure and thus prevent a hazardous situation arising.
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