Oil temperature control valve Oil inlet Fuel outlet Fuel inlet Oil return Figure 6-43.  Fuel oil heat exchanger cooler.  Figure 6-44.  Chip detector.  Return oil Permanent magnet Self-sealing housing Chip detector the engine lubrication system. In a turbine pressure relief  dry-sump lubrication system, the oil supply is carried in a  tank mounted on the engine. With this type of system, a larger  oil supply can be carried, and the temperature of the oil can  be readily controlled.  The oil pressure branch of the engine lubrication system  is pressurized by a gear-type pressure pump located in the  oil pump and accessory drive housing.  [Figure 6-45]  The  pressure pump receives engine oil at its lower (inlet) side  and discharges pressurized oil to an oil filter located on the  housing. From the oil filter, which is equipped with a bypass  valve for operation in case the filter clogs, the pressurized  oil is transmitted to a cored passage running through to the  pressure regulating (relief) valve that maintains system  pressure. The pressure regulating (relief) valve is located  downstream of the pump. It is adjusted to maintain a proper  pressure to the oil metering jets in the engine. The pressure  regulating (relief) valve is usually easily accessible for  adjustment. Then, the oil flows through the fuel oil cooler and  on to the bearing cavities through last-chance filters and out  spray nozzles to the bearings. Pressurized oil distributed to  the engine main bearings is sprayed on the bearings through  fixed orifice nozzles providing a relatively constant oil flow  at all engine operating speeds.  The scavenge system scavenges the main bearing  compartments and circulates the scavenged oil back to  the tank. The scavenge oil system includes five gear-type  pumps.  [Figure 6-45]  The No.1 bearing oil scavenge  pump scavenges accumulated oil from the front bearing  case. It directs the oil through an external line to a  central collecting point in the main accessory gearbox.  The oil return from No. 2 and 3 bearings is through  internal passages to a central collecting point in the main Pressure System Scavenge System 6-29