Abstract: A seal arrangement (40) between relatively movable components (42,48) includes at least one magnet (54) on a first component (48) and at least one magnet (56) on the second component (42). A clearance (55) is defined between the at least one magnet (54) on the first component (48) and the at least one magnet (56) on the second component (42). Springs (58) bias the at least one magnet (54) on the first component (48) and the at least one magnet (56) on the second component (42) towards each other. The at least one magnet (54) on the first component (42) and the at least one magnet (56) on the second component (42) are arranged to repel each other against the spring (58) to control the clearance (55).

Abstract: An environmental control system which is particularly suitable for use in aircraft comprises an air compressor (22) and an expansion turbine (36). The air compressor (22) is electrically driven at its optimum speed to deliver compressed air to the turbine (36). The compressed air expands through the turbine (36), thereby reducing in temperature as it drives the turbine (36). An electrical generator (44) is driven by the turbine (36). A condenser (33) is provided to condense water vapor in the air exhausted from the compressor (22).