FM 1-506 Fundamentals of Aircraft Power Plants ... - Survival Books

WWW.SURVIVALEBOOKS.COMFM 1-506supplied to the critical areas. An oil inlet temperatureindicator is frequently provided to show the oil temperatureas it enters the engine-bearing compartments. Oilinlet temperature also indicates proper operation of theengine oil cooler (Figure 9-12).established on a thrust-measuring ground test standbyvarying the exhaust nozzle area of the engine to achievethe desired EGT.AIR TEMPERATURE INDICATORThe air temperature indications (Figure 9-13) currentlyused in aircraft are free air temperature (FAT),outside air temperature (OAT), ram air temperature(RAT), total air temperature (TAT), and static airtemperature (SAT). Regardless of which temperature isinstrumented in a specific aircraft model, the flightmanual shows how to use it, along with applicable chartsor tables, to set the EPR values which provide rated thrustlevels. The EPR setting varies with the thrust leveldesired and with the true TAT existing at the front of theengine (T t2). Some aircraft have instrumentation whichindicates T t2values that may be used without correctionto determine EPR settings.ENGINE THRUST INDICATIONThe way a pilot sets and monitors the thrustproduced by the engine has been mentioned before(Figure 9-14). Thrust indication is discussed in detailbelow.On some engines, engine RPM and exhaust gastemperature (EGT) are used to indicate and set thrust.On such engines, the pilot receives the full rated thrust ofthe engine for takeoff at 100 percent RPM and a specifiedEGT. The specified EGT at 100 percent RPM isOn centrifugal compressor engines, notably themilitary J48, thrust is indicated by RPM alone. Full ratedthrust for takeoff is obtained when the tachometer reads200 percent. The J48 has a fixed nozzle area which isestablished at manufacture. While there is an EGT limitfor takeoff and for the other engine ratings, a J48 willnormally operate at EGT below the applicable limit forthe thrust rating used by the pilot. If the EGT reaches theallowable limit, the engine deteriorates or malfunctions.Most afterburning and non-afterburning turbojetsand turbofans with single or dual axial-flow compressorsuse engine ratio to measure engine thrust. EPR indicatorscompare total turbine discharge pressure to total9-9