helicopter is interconnected with the collective pitch lever, so ensuring that an increase in pitch is accompanied by an increase in engine power,7.The fuel system (Part 10) incorporates a high pressure fuel shut-off cock to provide a means of stopping the engine. This may be operated by a separate lever, interconnected with the throttle lever,or electrically actuated and controlled by a switch on the pilot's instrument panel.
8.A turbo-jet engine fitted with a thrust reverser usually has an additional control lever that allows reverse thrust to be selected (Part 15). On a turbo-propeller engine, a separate control lever is not required because the interconnected throttle and P .C.U. lever is operated to reverse the pitch of the propeller.
INSTRUMENTATION
9.The performance of the engine and the operation of the engine systems are shown on gauges or by the operation of flag or dolls-eye type indicators. A diagrammatic arrangement of the control and instru-mentation for a turbo-jet engine is shown in fig. 12-2.
Controls and instrumentation
135
Fig. 12-2Diagrammatic arrangement of engine control and instrumentation.
转螺旋桨的桨距。 5．对于装有加力燃烧室的发动机，仍保持使用一根操纵杆的控制，但是需用另一个燃油系统来供应及控制给加力燃烧室的燃油。
6．对于涡轮螺桨发动机，油门杆和螺旋桨控制装置是联动的，因而保持用一根杆操纵发动机。同样，直升机的油门控制杆与总距操纵杆是联动的，所以能保证桨距增加时同时增大发动机功率。图12-2 发动机控制和仪表的布置图
仪表板
压缩
燃烧
排气
飞机 油门杆燃油流量计燃油 加温器
油门开关
滑油散热器
滑油泵
Controls and instrumentation
136
Fig. 12-3Electro-mechanical E.P .R. transmitter.
线性电压差变压器 (L.V.D.T.)
电信号
平衡架
传感器
构架
放大器
真空膜盒
轭
伺服马达
电位计
传感器
真空膜盒
放大器
通向发动机压比指示器
电位计
输出电压
参考电压
伺服马达
机械信号 (齿轮系)
图12-3 电机械式发动机压比(E.P.R.)传感器
发动机推力
10．发动机的推力用推力计来指示。推力计有两种基本类型，第一种测量涡轮出口或喷管压力，第二种称为发动机压比(E.P.R.)表，测量两种或三种参数之比。当测量发动机压比时，该压比通常是喷管的压力与压气机进口压力之比。但是，对于风扇发动机来说，该压比可以是涡轮出口和风扇出口的综合压力与压气机进口压力之比。
11.不论对于哪一种情况，都要给出推力输出的指不，虽然当只要测量涡轮出口压力时，仍然必须对进口压力的变化加以修正。然而，这两种类型都可能需要对外界大气温度的变化作修正。为了对外界大气条件作补偿，可能要对仪表的刻度设定一个修正值，因而对所有工作状态下的最小推力输出都可以作检查。
12.适当安置的一些皮托管感测压力或一些与从发动机测取的指示类型相称的压力。这些皮托管可以直接连接在指示器上，也可以连接到压力传感器上，再通过电路连接到指示器上。13.仅显示涡轮出口压
力的指示器基本上是这样一块表，盘面上可能刻有每平方英寸的磅数，汞柱的英寸数，或最大推力的百分数。
14.发动机压比既可以由电机械式，也可以由电子式传感器来指示。对于这两种情况，传感器的输入是发动机的进口压力(P1)及由风扇出口压力和涡轮排气压力构成的综台压力(P INT )。有些情况下单独使用风扇出口压力或者涡轮排气压力取代P INT 。
Engine thrust
10.The thrust of an engine is shown on a thrust-meter, which will be one of two basic types; the first measures turbine discharge or jet pipe pressure, and the second, known as an engine pressure ratio (E.P .R.) gauge, measures the ratio of two or three parameters. When E.P .R. is measured, the ratio is usually that of jet pipe pressure to compressor inlet pressure. However, on a fan engine the ratio may be that of integrated turbine discharge and fan outlet pressures to compressor inlet pressure.
11.In each instance, an indication of thrust output is given, although when only the turbine discharge pressure is measured, correction is necessary for variation of inlet pressure; however, both types may require correction for variation of ambient air temperature. To compensate for ambient atmospheric conditions, it is possible to set a correction figure to a sub-scale on the gauge; thus,
the minimum thrust output can be checked under all operating conditions.
12.Suitably positioned pilot tubes sense the pressure or pressures appropriate to the type of indication being taken from the engine. The pilot tubes are either directly connected to the indicator or to a pressure transmitter that is electrically connected to the indicator.
13.An indicator that shows only the turbine discharge pressure is basically a gauge, the dial of which may be marked in pounds per square inch (p.s.i.), inches of mercury (in. Hg.), or a percentage of the maximum thrust.
14.  E.P.R. can be indicated by either electro-mechanical or electronic transmitters. In both cases the inputs to the transmitter are engine inlet pressure (P1) and an integrated pressure (PINT) comprised of
Controls and instrumentation
137Fig. 12-4A simple torquemeter system.
在将传动扭矩传给螺旋桨时，扭矩计靠液压测量斜齿轮产生的轴向载荷
斜齿轮
轴向推力
发动机滑油压力 扭矩计滑油压力
图12-4 简单的扭矩系统
扭矩计活塞
螺旋桨轴
15.电机械式系统对压力改变的指示方式是采用传感器膜盒（图12-3）使压力传感器的中心轴偏移，导致轭架相当于A.A 轴旋转。这一运动由线性可调电压差变压器感测，并转换成为交流电信号，经过放大后作用在伺服马达的控制绕组上。16.伺服马达通过齿轮改变通向发动机压力比指示器的电位计输出低压信号，同时驱动平衡架沿着与轭架的原始运动相同的方向运动，直到通向马达的线性可调电压差变压器信号消失和系统稳定在新的位置为止。
17.电子式发动机压比系统采用两个震动筒式压力传感器，它们感测发动机空气压力，并在与这些压力相关的频率下振动。依据这些振动频率，计算出发动机压比的电信号，然后将信号输入发动机压比表和电子式发动机控制系统（第10章）。发动机扭矩
18.发动机扭矩用以指示涡轮螺桨发动机发出的功率，该指示器称作扭矩计。发动机的扭矩或扭转力矩与马力成正比，经由螺旋桨减速齿轮传递出来。
19.一种扭矩计系统示于图12-4。在该系统中，由斜齿轮产生的轴向推力与作用在活塞上的滑油压力相抵消，抵消轴向推力所需的压力被传给指示器。
20.除了提供发动机的功率指示之外，扭矩计系统还在由于功率故障造成扭矩计滑油压力降低时，用于自动控制螺旋桨顺桨系统。对于某些安装条件下，它还用于协助喷水系统的自动操
作，以便在外界温度较高或在高海拔飞机场恢复或增大起飞功率（第17章）。
fan outlet and turbine exhaust pressures. In some cases either fan outlet pressure or turbine exhaust pressure are used alone in place of PINT.
15.The electro-mechanical system indicates a change in pressure by using transducer capsules (fig. 12-3) to deflect the centre shaft of the pressure transducer causing the yoke to pivot about the axis A.A. This movement is sensed by the linear variable differential transformer (L.V.D.T.) and converted to electrical signal which is amplified and applied to the control winding of the servo motor.
16.The servo motor, through the gears, alters the potentiometer output voltage signal to the E.P.R. in
dicator and simultaneously drives the gimbal in the same direction as the initial yoke movement until the L.V.D.T. signal to the motor is cancelled and the system stabilizes at the new setting.
17.The electronic E.P.R. system utilizes two vibrating cylinder pressure transducers which sense the engine air pressures and vibrate at frequencies relative to these pressures. From these vibration frequencies electrical signals of E.P.R. are computed and are supplied to the E.P.R. gauge and electronic engine control system (Part 10).
Engine torque
18.Engine torque is used to indicate the power that is developed by a turbo-propeller engine, and the indicator is known as a torquemeter. The engine torque or turning moment is proportional to the horse-power and is transmitted through the propeller reduction gear.
19.A torquemeter system is shown in fig. 12-4. In this system, the axial thrust produced by the helical gears is opposed by oil pressure acting on a number of pistons; the pressure required to resist the axial thrust is transmitted to the indicator.
20.In addition to providing an indication of engine power; the torquemeter system may also be used t
o automatically operate the propeller feathering system if the torquemeter oil pressure falls due to a power failure. It is also used, on some installations,
to assist in the automatic operation of the water injection system to restore or boost the take-off power at high ambient temperatures or at high altitude airports (Part 17).
Engine speed
21.All engines have their rotational speed () indicated. On a twin or triple-spool engine, the high pressure assembly speed is always indicated; in most instances, additional indicators show the speed
of the low pressure and intermediate pressure assemblies.
22.Engine speed indication is electrically transmitted from a small generator, driven by the engine, to an indicator that shows the actual revolutions per minute (), or a percentage of the maximum engine speed (fig. 12-5). The engine speed is often used to assess engine thrust, but it Controls and instrumentation
138Fig. 12-5Engine speed indicators and
generator.
发动机转速
21.所有的发动机都有它们的转速指示。对于双转子
或三转子发动机，总是要指示高压转子的转速。在多
数情况下，还有另外的指示器显示低压和中压转子的
转速。
图12-5 发动机转速指示器及发电机22.发动机转速指示由发动机驱动的一个小型发电机经电路传给指示器，它显示出实际的每分钟转速（)，或者显示出发动机最大转速的百分比（图12-5）。发动机转速常常用于估算发动机扭力。但是，由于进口温度和压力状态会影响给定的发动机转速下的推力，所以它给出的不是推力的 指示值。23.发动机转速发电机供应三相交流电，其频率取决于发动机转速。发电机的输出频率控制指示器中的同步马达的转速，位于鼓筒或阻力杯中的磁铁组件的旋转导致鼓筒的运动，进而转动指示器的指针。
24.在没有其它设备来驱动发电机的场合，可以采用可变磁阻式转速探头，它与一个音轮相接，产生感
应电流，经放大后送入指示器(图12-6)。本方法可以用于提供发动机的转速指示，而不需有单独驱动的发电机以及其相应的传动机构，因而减少了发动机的部件和运动零件的数量。
25.转速探头位于压气机机匣上，与音轮对齐。音轮是压气机轴上经机械加工的部分。每转一圈音轮外圆上的齿通过探头一次，通过改变探头中线圈的磁通量而诱导出一股电流。电流的大小由磁通量的变化率控制，因而与发动机转速直接相关。26．除了提供转子转速的指示之外，转速探头中感应的电流可以用来电亮仪表板上的警告灯，向驾驶员指示转子组件正在转动。这在发动机起动时特别重要，因为它通知驾驶员何时打开燃油开关，来向发动机供油。该灯与起动电路相连，因而仅仅在起动过程中才亮。
does not give an absolute indication of the thrust being produced because inlet temperature and pressure conditions affect the thrust at a given engine speed.
23.The engine speed generator supplies a three-phase alternating current, the frequency of which is dependent upon engine speed. The generator output frequency controls the speed of a synchronous motor in the indicator, and rotation of a magnet assembly housed in a drum or drag cup induces movement of the drum and consequent movement of the indicator pointer,
24.Where there is no provision for driving a generator, a variable-reluctance speed probe, in conjunct
ion with a phonic wheel, may be used to induce an electric current that is amplified and then transmitted to an indicator (fig. 12-6). This method can be used to provide an indication of without the need for a separately driven generator, with its associated drives, thus reducing the number of components and moving parts in the engine.25.The speed probe is positioned on the compressor casing in line with the phonic wheel,which is a machined part of the compressor shaft.The teeth on the periphery of the wheel pass the probe once each revolution and induce an electric current by varying the magnetic flux across a coil in the probe. The magnitude of the current is governed by the rate of change of the magnetic flux and is thus directly related to engine speed.
26.In addition to providing an indication of rotor speed, the current induced at the speed probe can be used to illuminate a warning lamp on the instrument panel to indicate to the pilot that a rotor assembly is turning. This is particularly important at engine start, because it informs the pilot when to open the fuel cock to allow fuel to the engine. The lamp is connected into the slatting circuit and is illuminated during the starting cycle.
Turbine gas temperature
27.The temperature of the exhaust gases is always indicated to ensure that the temperature of the tu
rbine assembly can be checked at any specific operating condition. In addition, an automatic gas temperature control system is usually provided, to ensure that the maximum gas temperature is not exceeded (Part 10).
28.Turbine gas temperature (T.G.T.) sometimes referred to as exhaust gas temperature (E.G.T.) or jet pipe temperature (J.P .T.), is a critical variable of engine operation and it is essential to provide an indication of this temperature. Ideally, turbine entry temperature (T.E.T.) should be measured; however,because of the high temperatures involved this is not practical, but, as the temperature drop across the turbine varies in a known manner, the temperature at the outlet from the turbine is usually measured by suitably positioned thermocouples. The temperature may alternatively be measured at an intermediate stage of the turbine assembly, as shown in fig. 12-7.29.The thermocouple probes used to transmit the temperature signal to the indicator consist of two wires of dissimilar metals that are joined together inside a metal guard tube. Transfer holes in the tube allow the exhaust gas to flow across the junction.The materials from which the thermocouples wires are made are usually nickel-chromium and nickel-aluminium alloys.
30.The probes are positioned in the gas stream so as to obtain a good average temperature reading and are normally connected to form a parallel circuit.An indicator, which is basically a millivoltmeter c
alibrated to read in degrees centigrade, is connected into the circuit (fig. 12-8).
31.The junction of the two wires at the thermocou-ple probe is known as the 'hot' or 'measuring' junction and that at the indicator as the 'cold' or 'reference'junction. If the cold junction is at a constant temperature and the hot junction is sensing the exhaust gas temperature, an electromotive force (E.M.F.), proportional to the temperature difference
Controls and instrumentation
139
Fig. 12-6
Variable-reluctance speed probe and phonic wheel.
28．涡轮燃气温度(T.G.T.)有时用排气燃气温度（E.G.T.)或喷管温度(J.P.T)来表示。它是发动机工作中的关键参数，因而提供该温度的指示极为重要。按照理想，应当测定涡轮进口温度(T.E.T.)。但是涉及到高温，这是不现实的。但是涡轮中的温度降是按已知的方式变化的，所以涡轮出口温度通常由适当安排的热电偶测量。作为代替方式，也可以测量涡轮组件中间级的温度，如图12-7所示。
29.用于将温度信号传到指示器的热电偶探头由两种不同的金属丝构成，在一个金属套管内部连接在一起。套管上的一些传导孔允许排气流流过接点。用于制造热电偶丝的材料通常是镍铬和镍铝合金。
30.这些探头在燃气流中的配置要保证能获得良好的平均温度读数，通常将探头连在一起构成一个并联电路。在电路(图12-8)上连接一个指示器，它基本上是一个毫伏计，其读数按摄氏度作了标定。
涡轮燃气温度
27.始终要指示排气温度，以保证在任一特定的工作状态下，能够检查涡轮组件的温度。而且，通常还备有一个自动燃气温度控制系统，保证最大燃气温度不致被超过(第10章)。
31.在热电偶探头处的双金属丝的接点是“高温”或“测量”接点，而在指示器处的是“低温”或“基准”接点。假设低温接点处于恒温下，而高温接点正在感测排气温度，在电路中就会产生与两个接点的温度差成正比的电动势(E.M.F.)，使指示器的指针移动。为防止低温接点的温度发生变化，影响指示的温度，在指示器中或在电路内装有一个自动温度补偿装置。
图12-6 可变磁阻式转速探头和音轮
通向放大器和指示器
压气机厘
劳斯莱斯的标志转速探头
音轮
驱动轴