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Aircraft hydraulic systems have progressed from simple to complex, reliable systems, and in the future, with the Mach 3 aircraft, will be called upon to perform even more tasks. A review of past accomplishments, with a presentation of areas where progress is needed is examined in this paper.

The 747 airplane, the largest commercial airliner, is the first U. S. airplane for airline service to use fully powered flight controls without manual reversion. The four hydraulic systems permit the highest degree of reliability per system operation with all major controls powered by dual-tandem actuators or having redundancy in location of operation. This airplane has 500 hydraulic hp as compared to the 87 hydraulic hp used on the 707 airplane. Each system is powered by an engine-driven pump and an air-driven pump. The latter is operated during peak demands only. In 17,000 hr of ground and flight tests, the 747 hydraulic systems have achieved and exceeded required performance and reliability.