The power transfer unit (PTU) is a device used to transfer hydraulic power from one system to another system without sharing fluid between those systems. The PTU consists of two axial-piston rotating groups, housed separately but connected by a common driveshaft and mounting adapter. The PTU mechanically couples two hydraulic systems so that when activated, hydraulic pressure from system one drives the hydraulic motor, which then transmits rotational power through a common shaft to the hydraulic pump, which in turn converts the rotational energy back into hydraulic pressure for system two.

The motor-side is slightly larger in displacement than the pump-side to make up for mechanical losses (breakout performance) within the unit while maintaining system pressure. The pump side includes a case-drain port to route internal leakage, cooling, and idle bypass flow back to the reservoir. The idle bypass flow permits the PTU to operate smoothly and continuously at all demand flows from zero to rated. When idle bypass flow is not properly established by design, the PTU may operate intermittently during low-flow conditions and cause audible noise throughout the aircraft.

The simplest and most common PTU configuration in use on aircraft today consists of two fixed-displacement rotating groups that rotate in only one direction, thus transferring power in only one direction. Other Parker Aerospace applications utilize variable-displacement rotating groups and operate bi-directionally, thus providing the capability to transfer power in either direction. These units are significantly more challenging, requiring complex hydro-mechanical controls to allow proper operation.

APPLICATIONS:
Parker Aerospace PTUs can be found in a variety of commercial and military aircraft including the Embraer 170/190, Bombardier CRJ-700/900, COMAC ARJ-21, Mitsubishi Regional Jet, Bombardier C Series, Boeing 737, Gulfstream family of business jets, plus the Boeing C-17 and KC-10.

FEATURES AND ATTRIBUTES:
• Minimized weight and envelope
• Low noise design
• Mature designs in use on the world’s most active fleets

OPTIONAL FEATURES:
• Bi-directional design option
• Variable displacement design option
• Compatible with all major hydraulic fluids (phosphate ester, hydrocarbon)
• Can be provided with isolation mounts to minimize vibration transmission to structure
• Can be provided with an attenuator at the pump outlet to minimize pressure ripple
• Can be provided with PTU selector valve and priority valve when integrated into Parker Aerospace systems