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Parker: Remote Electronics Unit

January 21, 2021

Parker Aerospace designs and manufactures a family of adaptable and scalable controllers such as their remote electronics unit (REU). REU products and technologies are used in the most advanced fly-by-wire systems today providing precise closed-loop actuation control. With the worldwide trend toward reduced aircraft wire weight, the REU provides for local actuator control signaled by high integrity data buses, significantly reducing the amount of aircraft wire needed.

Parker’s pedigree in actuator controllers is well established, supplying all of the primary actuation control on Bombardier’s C Series, the Embraer Legacy 450/500, and the Gulfstream G650, as well as other aircraft. In addition, Parker specifies requirements for the design and fabrication of basic REU controllers based on system requirements and functionality required. The Parker family of adaptable and scalable REUs are proven products that meet or exceed all applicable certification requirements levied by the world’s certification agencies. Parker offers a variety of REU versions to fit specific applications as listed below.


For the baseline Parker flight control system, the REUs provide a high level of functionality to allow continued safe flight and landing without the primary flight control computers (FCCs). This is accomplished through the use of independent flight deck inceptor interface modules (IIMs) which excite and demodulate the pilot control sensors, digitize the signals, and send them via two different data buses to both the FCCs and the REUs.

The direct mode control laws that reside in the FCCs are replicated in the REUs such that control is maintained. Other functions such as yaw damping and gain scheduling based on aircraft speed (actual or synthesized) are supported in the REU. In addition, the REU provides a local force fight mitigation function as well as monitoring and test functions. Communication with the FCCs is by way of a high speed data bus with an alternate, dissimilar data bus link being provided.

The REU design includes a control lane that performs the actuator control loop closure, and a monitor lane that verifies the control lane function. Both control and monitor lanes verify each of their individual interface signals from the FCC and the actuator. Both lanes have the ability to disable the associated actuator.

The designs are coupled with state-of-the-art packaging and enclosures for installation outside the pressure vessel in harsh environments. The units can also be mounted directly to the actuator or manifold.


Parker offers dual channel REUs that supports two hydraulic actuators and two motor controllers (MCE). The basic design is similar to the single channel high functionality version. The additional functions provided in the dual channel version include:

  • • Data bus selection and cross-REU data exchange
  • • Two hydraulic actuator servo loop control
  • • Up to two motor control electronics command signaling
  • • Local force fight equalization


The advantage of the dual channel REU is a reduction of the aircraft level line replaceable unit (LRU) count, and the ability to also signal motor control for the purposes of horizontal trim control, high lift motor control, and electric/hydraulic motor control.

Like the single channel version, the dual channel remote electronics unit is designed to operate outside the pressure vessel. The dual channel REU is intended to be installed at a convenient location somewhere between the two actuators it supports.


In some fly-by-wire flight control systems, the FCCs are certified as essential for continued safe flight and landing (even if the system can maintain continued safe flight and landing without them) and the REUs are made as simple as possible (no embedded control laws or local force fight mitigation, for example). Parker has designed and promoted such an REU and has also specified a simplified REU that is designed and built by a sub-tier supplier for use on one of our customer’s aircraft.

  • • Typically includes only a single data bus and no cross-REU connections
  • • Provides only single hydraulic actuator servo loop control
  • • Basic monitoring and built-in-test
  • • Units are most often installed directly on the electro-hydraulic servo actuator


The single channel REU design emphasizes simplicity, high reliability, low-cost and durability.


Parker’s REUs can be used on the following fly-by-wire or power-by-wire aircraft flight control applications:

  • • Business jets
  • • Commercial transports
  • • Military fixed wing aircraft
  • • Military and commercial helicopters



Parker REUs offer proven technologies that have met or exceeded customer requirements for high reliability, high durability, adaptable (for families of aircraft), and have met the most stringent certification requirements faced by any suppliers for full time flight critical systems and equipment.




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