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.
圖12-2 發動機控制和儀表的布置圖
Fig. 12-2 Diagrammatic arrangement of engine control and instrumentation.
Controls and instrumentation
發動機推力
10．發動機的推力用推力計來指示。推力計有兩種基本類型，第一種測量渦輪出口或噴管壓力，第二種稱為發動機壓比(E.P.R.)表，測量兩種或三種參數之比。當測量發動機壓比時,該壓比通常是噴管的壓力與壓氣機進口壓力之比。但是，對于風扇發動機來說,該壓比可以是渦輪出口和風扇出口的綜合壓力與壓氣機進口壓力之比。
14.發動機壓比既可以由電機械式，也可以由電子式傳感器來指示。對于這兩種情況，傳感器的輸入是發動機的進口壓力(P1)及由風扇出口壓力和渦輪排氣壓力構成的綜臺壓力(PINT)。有些情況下單獨使用風扇出口壓力或者渦輪排氣壓力取代PINT。
圖12-3 電機械式發動機壓比(E.P.R.)傳感器
15.電機械式系統對壓力改變的指示方式是采用傳感器膜盒（圖12-3）使壓力傳感器的中心軸偏移，導致軛架相當于A.A軸旋轉。這一運動由線性可調電壓差變壓器感測，并轉換成為交流電信號，經過放大后作用在伺服馬達的控制繞組上。
Controls and instrumentation
16.伺服馬達通過齒輪改變通向發動機壓力比指示器的電位計輸出低壓信號，同時驅動平衡架沿著與軛架的原始運動相同的方向運動，直到通向馬達的線性可調電壓差變壓器信號消失和系統穩定在新的位置為止。
17.電子式發動機壓比系統采用兩個震動筒式壓力傳感器，它們感測發動機空氣壓力，并在與這些壓力相關的頻率下振動。依據這些振動頻率，計算出發動機壓比的電信號，然后將信號輸入發動機壓比表和電子式發動機控制系統（第10章）。
Engine thrust the minimum thrust output can be checked under all
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,
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
20.除了提供發動機的功率指示之外，扭矩計系統還在由于功率故障造成扭矩計滑油壓力降低時，用于自動控制螺旋槳順槳系統。對于某些安裝條件下，它還用于協助噴水系統的自動操作，以便在外界溫度較高或在高海拔飛機場恢復或增大起飛功率（第17章）。
圖12-4 簡單的扭矩系統
Fig. 12-4 A simple torquemeter system.
22.發動機轉速指示由發動機驅動的一個小型發電機經電路傳給指示器，它顯示出實際的每分鐘轉速（r.p.m.)，或者顯示出發動機最大轉速的百分比（圖12-5）。發動機轉速常常用于估算發動機扭力。但是，由于進口溫度和壓力狀態會影響給定的發動機轉速下的推力，所以它給出的不是推力的 指示值。
發動機轉速
21.所有的發動機都有它們的轉速指示。對于雙轉子或三轉子發動機，總是要指示高壓轉子的轉速。在多數情況下，還有另外的指示器顯示低壓和中壓轉子的轉速。
Controls and instrumentation
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 an
a.c. 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. indicator and simultaneously drives the gimbal in the same direction as the initial yoke movement until the
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