(3)
At 4°C (39°F) and below -Failure of INL ANTI-ICE ON advisory legend to illuminate indicates a system malfunction. Do not .y the aircraft in known icing condi-tions.
b.
At engine power levels of 10% TRQ per engine and below, full inlet anti-ice capability cannot be provided due to engine bleed limitations. Power to operate the valves is normally provided from the No. 1 and No. 2 dc primary buses, respectively, through circuit breakers marked NO. 1 and NO. 2 ENG ANTI-ICE, respectively. During engine start, power to operate the No. 1 engine inlet anti-ice valve is provided from the dc essential bus through a circuit breaker marked NO. 1 ENG START. The #1 and #2 INL ANTI-ICE ON advisory legends receive power from No. 1 and No. 2 dc primary buses, through circuit breakers, marked NO. 1 and NO. 2 ENG ANTI-ICE WARN, respectively.
2.23 ENGINE OIL SYSTEM.
Lubrication of each engine is by a self-contained, pres-surized, recirculating, dry sump system. Included are oil and scavenge pump, emergency oil system, monitored oil .lter, tank, oil cooler, and seal pressurization and venting. The oil tank is a part of the main frame. Each scavenge line has a screen at the scavenge pump to aid fault isolation. A chip detector with a cockpit warning legend is in the line downstream of the scavenge pump.
2.23.1 Engine Emergency Oil System. The engine has an emergency oil system in case oil pressure is lost. Oil reservoirs built into the A and B sumps are kept full during normal operation by the oil pump. Oil bleeds slowly out of those reservoirs and is atomized by air jets, providing con-tinuous oil mist lubrication for the bearings. A #1 ENG OIL PRESS or #2 ENG OIL PRESS caution legend will go on when indicated oil pressure drops below 25 psi on helicopters without modi.ed faceplates on the instrument panel or below 20 psi on helicopters with modi.ed face-plates. Power for the caution legend comes from the No. 1 and No. 2 dc primary buses through circuit breakers marked NO. 1 and NO. 2 ENG WARN LTS respectively.
2.23.2 Oil Tank. The oil tank is an integral part of the engine. Tank capacity is 7 US quarts. The .ller port is on the right. Oil level is indicated by a sight gage on each side of the tank. Servicing of the tank is required if the oil level reaches the ADD line. Overservicing is not possible because extra oil will .ow out the .ller port. The scavenge pump returns oil from the sumps to the oil tank through six scavenge screens, each one labeled for fault isolation.
2.23.3 Oil Cooler and Filter. The oil cooler (Figure 2-9) cools scavenge oil before it returns to the tank. Oil from the chip detector passes through the oil cooler and is cooled by transferring heat from the oil to fuel. After pass-ing through the oil cooler, oil enters the top of the main frame where it .ows through the scroll vanes. This further cools the oil and heats the vanes for full-time anti-icing. The vanes discharge oil into the oil tank. 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 to a disposable-element .lter. As the pressure differential across the .lter increases, the .rst indi-cator will be a popped impending bypass button. As the pressure increases further, this indication will be followed by an indication in the cockpit #1 or #2 OIL FLTR BYPASS, after which a .lter bypass will occur. Power for the caution legends is from the No. 1 and No. 2 dc primary buses respectively, through circuit breakers marked NO. 1 and NO. 2 ENG WARN LTS. During cold weather start-ing, or on starting with a partially clogged .lter, the high-pressure drop across the .lter will cause the bypass valve to open and the caution legends to go on. The impending bypass indicator has a thermal lockout below 38°C to pre-vent the button from popping. A cold-start relief valve downstream of the .lter protects the system by opening and dumping the extra oil to the gear box case.
