Controls and instrumentation

振動

44.渦輪噴氣發動機具有極低的振動水平，由于即時發生的或部分的故障所引起的振動可能會不被發覺而通過。因此，許多發動機上裝了振動指示器，它持續地監視發動機的振動水平。該指示器通常都是一個毫安表，它通過放大器接收從裝在發動機上的傳感器傳來的一些信號（圖12-11）

圖12-9 滑油溫度和壓力傳感器和指示器
Fig. 12-9 Oil temperature and pressure transmitters and indicators.
Fig. 12-10 Fuel flow transmitter and 圖12-10 燃油流量傳感器和指示器
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．儀表上記錄的振動水平是拾取處感測的總振動量。更精確的方法會區分出各個轉子頻率范圍之間的差別，從而保證振動源能被孤立出來。對于多轉于發動機來說，這尤為重要。
45.在發動機的機匣上安裝一個振動傳感器，與放大器和指示器用電路相連。振動感測元件通常是一個電磁傳感器，它將振動的大小轉換成為電信號，這些信號使指示器指針的移動與振動水平成正比。儀表板上的一個警告燈被設置在系統中，用于在有不可接受的振動正在臨近時向駕駛員報警，以使發動機停車，從而減少損壞的危險。
47．為用于多轉子發動機，已經研制成功了一種晶體式振動傳感器，它能提供更可靠的振動指示。在通向振動儀表的電路上裝了一個濾波器系統，這就有可能將所得的振動對照已知的頻率范圍進行比較，由此能找到振動源的位置。一個多選擇位置的開關使駕駛員可以選出一個特定的區域，以獲得該振動水平的讀數。
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.

圖12-11 振動傳感器及指示器
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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