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Section 1.4 - Hydraulic Pressure Regulated Power System

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The system in drawing below represents a pressure regulated power system comprised of two parts:
1) the power system, and
2) the actuating system part of the overall hydraulic system.

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This type of system was used in all aircraft between 1937 and 1945. The system had a pressure regulator which "knew" when to withdraw horsepower from the engine when it was needed.  The concurrent blue-red system drawn in that manner because when the bypass part of the system was used, the blue-red part of the system acted as the return line to the reservoir and, thus, was "blue".  However, the power system was used to produce hydraulic power, the blue-red part of the system was filled with high pressure oil and, therefore, was "red".

 Functions of Parts of the Power System

  1. Reservoir -- holds an extra supply of fluid for system from which oil was drawn when needed, or oil was returned to it when not needed.
  2. Accumulator -- absorbs pulsation within the hydraulic system and helps reduce "linehammer effects" (pulses that feel and sound like a hammer has hit the hydraulic tubes).  It is an emergency source of power and it acts as another reservoir.
  3. Filter -- removes impurities in the hydraulic system and in the reservoir.  The reservoir has one big filter inside the tank.
  4. Power Pump -- it changes mechanical horsepower (HP) to hydraulic HP.
  5. System Relief Valve -- relieves pressure on system as a safety.measure and takes over as a pressure regulator when pressure regulator fails.
  6. Pressure Regulator -- as the name implies, regulates the pressure in the hydraulic system.  When it senses a built-up in pressure in the lines to the selector valves, it acts so that the system automatically goes to bypass.

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Updated: March 12, 2004