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Mule – Hydraulic Ground Power Unit

imageHydraulic Ground Power Unit – Hydraulic power units, sometimes called a hydraulic mule, provide hydraulic pressure to operate the aircraft systems during maintenance. They can be used to:

• Drain the aircraft hydraulic systems.
• Filter the aircraft system hydraulic fluid.
• Refill the aircraft system with clean fluid.
• Check the aircraft hydraulic systems for operation
and leaks.
Manufactured in many sizes and cost ranges, some have a limited range of operation, while others can be used to perform all the system tests that fixed shop test stands are designed to perform.This type of portable hydraulic test unit is usually an electrically powered unit. It uses a hydraulic system capable of delivering a variable volume of fluid from zero to approximately 24 gallons per minute at variable pressures up to 3,000 psi.

Operating at pressures of 3,000 psi or more, extreme caution must be used when operating hydraulic power units. At 3,000 psi, a small stream from a leak can cut like a sharp knife. Therefore, inspect lines used with the system for cuts, frays, or any other damage, and keep them free of kinks and twists. When not in use, hydraulic power unit lines should be stored (preferably wound on a reel) and kept clean, dry, and free of contaminants.

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