TM 1-1520-238-10 2-28 2.26.7  Fuel  Pressure  Warning  System. The  engine fuel pressure warning system for each engine consists of a pressure switch that illuminates the FUEL PSI segment on the pilot caution/warning panel. The FUEL PSI ENG 1 and FUEL PSI ENG 2 segments will illuminate when fuel pressure drops below 9 psi. 2.27  ENGINE ALTERNATOR. 2.27.1  Engine  Alternator . The  engine  alternator (fig 2-16 ) supplies AC power to the ignition circuitry and the ECU. It also supplies a signal to the N_G speed indica- tor. All essential engine electrical functions are powered by the alternator. When the alternator power to the ECU is interrupted, a loss of N_p and torque indications will occur on the affected engine(s), and the engine(s) will increase to the maximum power. Percent N_p/N_r will increase above 100% and T4.5 limiting will be inoperative. When the alter- nator power providing the N_G signal is interrupted, a loss of N_G indications will occur with a corresponding engine out audio signal and warning light being activated. Actual engine operation is unaffected. A complete loss of engine alternator power results in affected engine(s) increasing to  maximum  power  with  a  loss  of  of  N_p,  N_G  indication, torque and engine out audio signal and warning light be- ing activated, and by an inability to start the engine. 2.27.2  Engine Alternator . When the engine alter- nator (fig 2-16 ) power supply to the DECU is interrupted, 400  Hz,  115  vac  aircraft  power  is  used  to  power  the DECU, therefore preventing an engine (high side) failure. N_p/torque indications will not be affected. When alternator power supply for the N_G signal is interrupted, a loss of the associated engine N_G indication and an engine out audio signal and warning light will occur. Actual engine opera- tion is unaffected. Complete failure of the alternator will cause loss of N_G indication, activation of an engine out au- dio and warning light, and inability to start the engine. Op- eration of the engine and all other indications will be nor- mal. 2.28  ENGINE OIL SYSTEM. Each  engine  is  lubricated  by  a  self-contained,  pressur- ized, recirculating, dry sump system. Included are oil sup- ply and scavenge pumps, an emergency oil system, an in- tegral oil tank, a filter, an oil cooler, and seal pressurization and venting. A chip detector that illuminates the  CHIPS ENG  1  or  CHIPS  ENG  2  segment  on  the  pilot  caution/ warning  panel  is  in  line  downstream  of  the  scavenge pump. 2.28.1  Emergency  Oil  System. Small  oil  reservoirs, built into the engine oil sumps, are kept full during normal operation  by  the  oil  pump.  If  oil  pressure  is  lost,  oil  will bleed slowly out of these reservoirs and be atomized by air jets thus providing an oil mist lubrication for the engine bearings for thirty seconds at 75% N_G. An OIL PSI ENG 1 or OIL PSI ENG 2 light on the pilot caution/warning panel will illuminate when oil pressure drops below 20 – 25 psi. 2.28.2  Oil Tank. Pertinent oil grades and specifications are in table 2-7. The filler port is on the right side of the engine (fig 2-16). The oil level is indicated by a sight gage on each side of the tank. Oil is supplied to the oil pump through a screen. The scavenge pump returns oil from the sumps to the oil tank through six scavenge screens. 2.28.3  Oil  Cooler  and  Filter. Scavenge  oil  passes through an oil cooler (fig 2-16) before returning to the tank. It is cooled by transferring heat from the oil to fuel routed through the cooler. If the oil cooler pressure becomes too high, a relief valve will open to dump scavenge oil directly into the oil tank. Oil discharged from the oil pump is routed through a disposable element filter. As the pressure differ- ential across the filter increases, the first indication will be a popped impending bypass button. As the pressure in- creases further, the OIL BYP ENG 1 or OIL BYP ENG 2 segment on the pilot caution/warning panel will illuminate. During engine starting, with oil temperature below the nor- mal  operating  range,  pressure  may  be  high  enough  to close the oil filter bypass sensor switch. In this situation, the caution light or lights will remain on until the oil warms up and oil pressure decreases. The impending bypass in- dicator has a thermal lockout below +38 ° C (100 °F) to prevent the button from popping. 2.28.4  Chip  Detector. Each  engine  chip  detector  (fig 2-16) is mounted on the forward right side of the accesso- ry  gearbox.  It  consists  of  an  integral  magnet,  electrical connector, and a housing. A removable screen surrounds the magnet. The detector attracts magnetic particles at a primary chip detecting gap. If chips are detected, a signal is sent to the pilot caution/warning panel to illuminate a CHIPS ENG 1 or CHIPS ENG 2 segment. These chip de- tectors are of the non-fuzz burning type. 2.29  ENGINE IGNITION SYSTEM. Each engine has an ignition exciter unit with two igniter plugs. The exciter unit receives power from its engine al- ternator. The MASTER IGN keylock switch on the pilot en- gine PWR lever quadrant (fig 2-19) is an enabling switch to the ENG START switches. When an