Engine Oil Pressure & Other Pressure Systems PDF

**Engine oil pressure** The most important instrument used by the pilot to perceive the health of an engine. Oil pressure is usually indicated in pounds per square inch (PSI).  In reciprocating and turbine engines, oil is used to **lubricate** and **cool** bearing surfaces where parts are rotating...

**Engine oil pressure** The most important instrument used by the pilot to perceive the health of an engine. Oil pressure is usually indicated in pounds per square inch (PSI).  In reciprocating and turbine engines, oil is used to **lubricate** and **cool** bearing surfaces where parts are rotating or sliding past each other at high speeds. **Green Arc** is the \"safe\" range. When the oil pressure needle is in this area, it means everything is working as it should. The engine is getting the right amount of oil pressure for smooth operation. **Red Dial Lines** indicate the minimum and maximum safe operating limits. If the oil pressure needle is on or beyond this line, it means there's a serious issue, like the engine not getting enough oil or too much pressure, which could lead to engine damage. **Manifold Pressure** In reciprocating engine aircraft, the manifold pressure gauge indicates the **pressure of the air in the engine's induction manifold**. This is an indication of power being developed by the engine. The higher the pressure of the fuel air mixture going into the engine, the more power it can produce. **Engine Pressure Ratio**  Turbine engines use an **Engine Pressure Ratio (EPR)** gauge to show how much power the engine is making. The EPR gauge **compares** the **exhaust** pressure with the air pressure at the engine\'s **intake.** Adjusting for things like temperature and altitude, it gives an indication of the engine\'s thrust. Since it compares two pressures, it\'s called a differential pressure gauge. This gauge gets its data from a pressure ratio transmitter or, in digital systems, from a computer. The transmitter measures the pressures and sends an electric signal to the gauge. A. An analog EPR gauge from a turbine engine B. A digital EPR indication and other turbine engine parameters on a flight deck digital display screen  C. Engine pressure ratio transducer **Fuel pressure** While direct-sensing fuel pressure gauges using Bourdon tubes, diaphragms, and bellows sensing arrangements exist, it is particularly undesirable to run a fuel line into the flight deck, due to the potential for fire should a leak develop. Therefore, the preferred arrangement is to have whichever sensing mechanism that is used be part of a transmitter device that uses electricity to send a signal to the indicator in the flight deck. **Hydraulic Pressure ** Hydraulic systems are commonly used to raise and lower landing gear, operate flight controls, apply brakes, and more. Sufficient pressure in the hydraulic system developed by the hydraulic pump(s) is required for normal operation of hydraulic devices. **Vacuum Pressure** Gyro pressure gauge, vacuum gauge, or suction gauge are all terms for the same gauge used measures the vacuum pressure that powers air-driven gyroscopic flight instruments. Air is pulled through the instruments, making the gyros spin. For the instruments to work properly, the gyros must spin at the right speed, which depends on the vacuum pressure. The gauge shows how much less pressure is in the system compared to the outside air, measured in inches of mercury. This gauge is very important for aircraft using vacuum-operated gyroscopic instruments to ensure they function correctly. **Pressure Switches** A pressure switch is a simple device usually made to open or close an electric circuit when a certain pressure is reached in a system.  It can be manufactured so that the electric circuit is normally open and can then close when a certain pressure is sensed, or the circuit can be closed and then opened when the activation pressure is reached. **Pressure measurement ** involves some sort of mechanism that can sense changes in pressure.  A technique for calibration and displaying the information is then added to inform the pilot Three fundamental pressure-sensing mechanisms 1.**Bourdon tube** used to measure relatively high pressures 2.**diaphragm or bellows** most often used to measure relatively low pressures. 3.**Solid-state sensing device** are used in modern aircraft to determine the critical pressures needed for safe operation. Most Bourdon tubes are made from **brass, bronze, or copper**. Alloys of these metals can be made to coil and uncoil the tube consistently numerous times.  Some of the instruments that use a Bourdon tube mechanism include the **engine oil pressure gauge, hydraulic pressure gauge, oxygen tank pressure gauge, and deice boot pressure gauge.** Diaphragms, aneroids, and bellows pressure sensing devices are often located inside the single instrument housing that contains the pointer and instrument dial read by the pilot on the instrument panel. Thus, many instruments that make use of these sensitive and reliable mechanisms are direct reading gauges. But, many remote sensing instrument systems also make use of the diaphragm and bellows.  Examples of instruments that use a diaphragm or bellows in a direct reading or remote sensing gauge are the **altimeter, vertical speed indicator, cabin differential pressure gauge (in pressurized aircraft), and manifold pressure gauge.** **Aneroid** is an evacuated sealed diaphragm, retaining absolutely nothing inside. **Crystalline piezoelectric sensor** -- this type of sensor uses crystals that are naturally piezoelectric materials.   **Piezoresistor** -- is a type of sensor that works by changing its electrical resistance when a mechanical force, like pressure or stress, is a applied.    **Semiconductor chip sensors** -- are devices made from semiconductor materials that changes its conductivity depending on conditions like temperature, pressure, or light. **Pressure** is a comparison between two forces. **Absolute pressure** exists when a force is compared to a total vacuum, or absolutely no pressure. **Gauge pressure** This is the most common type of pressure measurement. This is the difference between the pressure to be measured and the atmospheric pressure.  **Differential Pressure** When two pressures are compared in a gauge, the measurement is known as differential pressure and the gauge is a **differential pressure gauge** **Standard Pressure ** In aviation, there is also a commonly used pressure known as standard pressure. This refers to an established or standard value that has been created for atmospheric pressure.  Standard pressure value    **29.92 inches of mercury (\"Hg)**    **1,013.2 hectopascal (hPa)**    **14.7 psi**