FIRE EXTINGUISHING
20.
Before a fire extinguishing system is operated, the engine must be stopped to reduce the discharge of flammable fluids and air into the fire area. Any valves, such as the low pressure fuel cock, that control the flow of flammable fluid must be situated outside the 'hot' zone to prevent fire damage rendering them inoperative.
21.
After a fire has been extinguished, no attempt must be made to start the engine again as this would probably re-establish the fluid leak and the ignition source that were the original causes of the fire. Furthermore, the extinguishing system may be exhausted.
22.
The extinguishant that is used for engine fires is usually one of the Freon compounds. Pressurized containers are provided for the extinguishant and these are located outside the fire risk zone. When the relevant electrical circuit is manually operated, the
extinguishant is discharged from the containers through a series of perforated spray pipes or nozzles into the fire (fig. 14-4). The discharge must be sufficient to give a predetermined concentration of extinguishant for a period that may vary between 0.5 seconds and 2 seconds. The system is generally one that enables two separate discharges to be made.
ENGINE OVERHEAT DETECTION
23.
Turbine overheat does not constitute a serious fire risk. Detection of an overheat condition, however, is essential to enable the pilot to stop the engine before mechanical or material damage results.
24.
A warning system of a similar type to the fire detection system, or thermocouples suitably positioned in the cooling airflow, may be used to detect excessive temperatures. Thermal switches positioned in the engine overboard air vents, such as the cooling air outlets, may also be included to give an additional warning.
图14-4 一种典型的灭火系统
罗尔斯-罗伊斯公司
“宝石”(Gem)2发动机
Rolls - Royce Gem 2
“巨蟒”（Pyghon）发动机是从ASX轴流涡轮喷气发动机发展而来的，它于1943年4月进行了首次试车，1944年其
推力达2800磅，增设螺旋桨减速器后，该发动机产生了3600轴马力和1100磅推力，被称之为ASP。重新命名为“巨蟒”后，它投入使用，用作斯特兰公司的“飞龙”（Wyvern）S4涡轮螺桨战斗机的动力装置。
The Python was developed from the ASX axial-flow turbo-jet which first ran in April 1943 and was producing 2800 lb thrust by 1944. With the addition of a propeller gearbox the engine produced 3600 shp plus 1100 lb thrust and was known as the ASP. Renamed the Python it entered service as the power plant for the Westland Wyvern S4 turbo-prop fighter.
阿姆斯特朗·西德利公司
“巨蟒”发动机
Armstrong Siddeley Python
15: Thrust reversal
第十五章 推力反向
Contents Page
Introduction 159 Principles of operation 160 Clamshell door system Bucket target system Cold stream reverser system Turbo-propeller reverse pitch system 绪言
1．现代飞机的刹车是十分有效的，但在潮湿、结冰或被雪覆盖的跑道上，这种有效性则可能会因飞机轮胎和跑道间的附着力损失而降低。因此需要另一种方法在规定的距离内将飞机停住。
2．缩短飞机在干燥和湿滑跑道上着陆滑跑距离的一个简单而有效的方法是将排气流反向，这就是利用发动机动力作为减速力。推力反向曾经被用来在飞行中降低空速，但在现代飞机上用得并不普遍。不用反推力与利用反推力的飞机着陆距离之差异示于图15-1。
3．在高涵道比(风扇)发动机上，反推力是通过将风扇(冷气流)气流反向而实现的。由于发动机大部分推力是由风扇产生的，所以没有必要将排气流(热气流)反向。
目录
绪言
工作原理
哈壳形门系统
戽斗式盾牌系统
冷气流反推器系统
涡轮螺桨反桨系统
结构和材料
Construction and materials 166
INTRODUCTION
1.
Modern aircraft brakes are very efficient but on wet, icy or snow covered runways this efficiency may be reduced by the loss of adhesion between the aircraft tyre and the runway thus creating a need for an additional method of bringing the aircraft to rest within the required distance.
2.
A simple and effective way to reduce the aircraft landing run on both dry and slippery runways is to reverse the direction of the exhaust gas stream, thus
using engine power as a deceleration force. Thrust reversal has been used to reduce airspeed in flight but it is not commonly used on modern aircraft. The difference in landing distances between an aircraft without reverse thrust and one using reverse thrust is illustrated in fig. 15-1.
3. On high by-pass ratio (fan) engines, reverse thrust action is achieved by reversing the fan (cold stream) airflow. It is not necessary to reverse the exhaust gas flow (hot stream) as the majority of the engine thrust is derived from the fan.
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