referring now to fig1 , there is shown a simplified schematic of a typical oil lubrication and scavenge system for a gas turbine engine is illustrated . the system comprises an oil tank or reservoir 2 from which lubrication oil is drawn by a pump indicated at 4 . the particular system on which the illustration is based is of the pressure relief type in which the pressure of the oil flow to bearing chambers ( not shown ) is controlled by a pressure relief valve 6 . the pressurised oil passes through a filter 8 and then a heat exchanger 10 before being distributed to oil supply jets , generally indicated at 12 , located in a plurality of bearing chambers , the engine gearbox , etc . the oil feed pump 4 is a positive displacement pump that delivers a known flow , proportional to pump speed . oil pressure is generated by resistance to oil flow in the oil supply pipes backed by the bearing chamber pressures . the desired flow of oil to a component can be achieved by use of a suitably sized restriction known as an oil jet 12 at the end of the oil line . the design of the jet can provide either a ray or a targeted , coherent stream of oil , directed to a component or to a catching feature that will then feed the component . lubrication oil supplied to the bearings etc . is evacuated from bearing chambers and the like and returned to the oil tank 2 by a scavenge system . in the first step of this return cycle oil is drained from bearing chambers , or wherever it has been utilised , to one or more collection chambers where it is directed into a scavenge - offtake 14 where the oil is picked - up by a scavenge pump 16 and returned to the oil tank 2 through a scavenge filter 18 . the return path includes a de - aerator to remove entrained air from the oil . oil tank 2 provides a reservoir of oil to supply the oil system . the de - aerating device may be incorporated within the oil tank 2 or the return passageway for example adjacent the scavenge filter to remove air from the returning scavenged oil . scavenge pumps 16 generally follow the same construction as the oil feed pump 4 . each bearing chamber is serviced by a dedicated scavenge pump 16 except where bearing chamber pressure or gravity can be used to drive the oil to a shared sump . the capacity of a scavenge pump 16 is usually much greater than the oil flow it is required to return to the tank 2 , in order to accommodate non - linear flow / speed relationships and aeration of the oil . engines designed to operate for extended periods in zero or negative gravity flight conditions will have oil tanks that incorporate features ensuring a continuous supply of oil . fig2 shows a schematic diagram of a bearing chamber and its associated scavenge off take arrangement . a supported shaft 20 is journaled in a rolling element bearing indicated generally at 22 , the inner race 24 of the bearing is fixed to the shaft 20 and the outer race 26 of the bearing is fixed in a bearing housing . a small sump region or collection chamber 30 surrounding the shaft 20 is formed between the bearing 22 , a shaft seal 32 and bounded by the bearing chamber wall 28 on its radially outer surface . set into the chamber wall 28 is a scavenge off take port 34 and passageway 36 leading to a scavenge pump ( not shown ). although only one scavenge port 34 is shown there may be a plurality of such orifices spaced apart around the chamber wall 28 leading into the scavenge passageway 36 . similarly , there may be more than a single passageway . facing scavenge port 34 is a scavenge pumping element 38 in the form of a disc carried on the shaft 20 . the periphery of element 38 is aligned with the scavenge port or ports 34 so that centrifugal force arising from rotation of the shaft 20 and element 38 forces oil contacting the disc into the scavenge port ( s ) 34 . oil may drain into the collection chamber 30 from the bearing 22 and through at least one drainage port 40 in bearing chamber wall 28 at the exit of drainage passages 42 that communicate with spaces ( not shown ) within a structure surrounding bearing housing in which lubricating oil may accumulate in some or all orientations of the engine . the passage or passages 42 are formed to drain the contents of such spaces into a convenient space , such as collection chamber 30 from which the oil may be scavenged . in fig2 the illustrated arrangement has the axis of shaft 20 oriented in a horizontal direction , i . e ., across the page in a left - right direction . this is considered to be a normal orientation for an aircraft propulsion engine in cruise operation . a civil aircraft propulsion engine normally spends the majority if not all of its operating life in this orientation with the axis of its main shaft , such as shaft 20 , within a few degrees of horizontal . the greatest excursion from a substantially horizontal orientation occurs during a climb phase when an engine has a nose - up attitude at a greater angle . the capacity of the oil system , in particular the oil tank ensures a sufficient supply of oil . however , certain types of aircraft may be expected to operate at completely different attitudes of nose - up , nose - down or inverted for relatively long periods . in these cases attention is paid to identify potential oil trap spaces and to provide drainage passages through which the spaces may drain into a convenient collection chamber whatever the orientation of the engine axis . however , it has been found in practice that the efficiency of the scavenge collection system is not constant and in some instances scavenge oil is not picked up and can be prevented from draining into the collection chambers . fig3 illustrates the arrangement of fig2 rotated counter - clockwise through 90 degrees to a nose - up position . in the situation of fig3 the normal draining of oil into the scavenge collection chamber 30 may be interrupted unless special attention is paid to the positioning and layout passages of drainage passages 42 relative to the element 38 . the oil tank 2 is provided with internal means ( not shown ) to ensure oil pick - up at all engine orientation so the oil pumping system will continue to operate as normal until the contents of oil tank 2 have been distributed through the oil pump 4 . unless the scavenge system can continue to return oil to oil tank 2 the lubrication system eventually will be starved of supply . passages such as indicated at 42 must be provided and located with regard to providing drainage paths from enclosed spaces into collection chamber 30 where oil may be recirculated . however , problems may arise in the orientation of fig3 because returning oil draining from passage 42 may be forced back through port 40 by windage effects in the collection chamber 30 . as a result oil is effectively prevented from draining into the chamber 30 and being recirculated back into the scavenge offtake port 34 and passageway 36 . the solution provided by the present invention is shown in fig4 a and 4 b comprises a weir , or shield generally indicated at 44 , placed between the scavenge port 40 and the scavenge pumping element 38 . the effect of shield 44 is to help establish a flow pattern within collection chamber 30 which effectively guides oil droplets and oil mist onto the element 38 at a radial point near to the shaft 20 . this is found to be more effective at maintaining an oil film across the surface of the element 38 which is shed from the periphery of the disc under centrifugal force into the scavenge offtake port 34 . as shown in fig4 a and 4 b the shield 44 may comprise a shaped and perforated annular member of sheet metal material thickness . the component configuration illustrated has an “ l - shaped ” cross section consisting of a cylindrical portion 46 that extends in a substantially axial direction parallel to the axis of shaft 20 , and an annular portion 48 lying in a substantially radial plane at one end of the cylindrical portion 46 . for the purpose of mounting the weir the cylindrical portion is formed with a radius matching the radius of the outer surface of the outer race 26 of bearing 22 . exact dimensions depend upon the details of a chosen mounting arrangement . for example the cylindrical portion 46 could be trapped between the wall of the bearing housing and the bearing outer race 26 , or the housing wall could be at least partly recessed to receive the portion , providing bearing loads can be satisfactorily transferred to the housing wall . a number of apertures or slots 50 are formed in the cylindrical portion 46 of the shield member corresponding to the size and spacing of the scavenge intake ports 40 in the bearing chamber wall . however , such an arrangement involving an additional component , i . e ., shield 46 that has to be manufactured accurately and positioned correctly during assembly suffers inherent disadvantages . a solution is illustrated in fig5 in which the outer race 26 of the bearing 22 is extended laterally at 52 to provide a portion functionally equivalent to the shield 44 . the extension portion 52 of outer bearing race 26 is provided with a number of machined slots 54 spaced apart around the circumference of the bearing race that extend fully through the extended race wall 52 in a substantially radial direction . there are as many such slots 54 as the number of scavenge ports 40 in the bearing chamber wall . each slot permits scavenged oil from a drainage passage 42 to enter the collection chamber 30 through ports 40 . the thickness of the extended race portion 52 , i . e ., the dimension in a radial direction , is sufficient to act as an effective shield over the element 38 . scavenged oil is thus passed into collection chamber 30 and towards a more advantageous , radially inner position on the element 38 . the arrangement illustrated shows a collection chamber 30 at one side of a bearing 22 . it will be understood that a similar arrangement may be provided at the opposite side of the bearing to function in the same manner when the bearing orientation is inverted relative to the orientation illustrated in fig4 b and 5 b , i . e ., rotated through an angle of 180 degrees .