Aerospace Actuators 2

Signal-by-Wire and Power-by-Wire

Jean-Charles Maré

• Publisher: Wiley-ISTE
• Year: 2017
• Print ISBN: 9781848219427
• eBook ISBN: 9781119407188
• Edition: 1
• Topic: Mathematics
• Subtopic: Mathematical Analysis
• Index: Mathematics

This book is the second in a series of volumes which cover the topic of aerospace actuators following a systems-based approach.
This second volume brings an original, functional and architectural vision to more electric aerospace actuators. The aspects of signal (Signal-by-Wire) and power (Power-by-Wire) are treated from the point of view of needs, their evolution throughout history, and operational solutions that are in service or in development.
This volume is based on an extensive bibliography, numerous supporting examples and orders of magnitude which refer to flight controls and landing gear for various aircraft (fixed or rotorwing, launchers) in commercial, private and military applications.
The topics covered in this set of books constitute a significant source of information for individuals and engineers from a variety of disciplines, seeking to learn more about aerospace actuation systems and components.

 

1
Electrically Signaled Actuators (Signal-by-Wire)

The objective of this chapter is to present the architectures for the transmission/processing of information associated with actuation functions. The “flight control” application is used as the basis for this exploration because it is much more complex, and in many ways richer than other applications (e.g. landing gear, engines, etc.). This chapter will explain the evolution of flight controls from purely mechanical to all electrical signaling. To illustrate the importance of the electric transmission of information and power in modern aircraft, it is best to start off by stating a few orders of magnitude:

• – the Airbus A380 has nearly 500 km of electric cables. The 120 miles of electrical cables for the Boeing B787 has a mass of 4 tons;
• – Daniel [DAN 07] considers that on current long range aircraft, we can count 13,400 functional power lines (for both power and signal) for a total length of 240 km and with a total mass of 1,800 kg (we have to add 20% mass for connectors and fasteners). The part pertaining to the transmission of information is typically comprised of 7,800 lines, 170 km long and with a mass of 700 kg. This consists of 5,400 mono wire cables for analog and discrete signaling, with 2,050 twisted pair cables and 350 coaxial or quadraxial cables;
• – for helicopters, [VAN 07] indicates that the Sikorsky S-92 is comprised of 295 kg of electrical cable, including 193 kg for information transmission and with 1,200 cable/aircraft interfaces. The mass of electrical cables increases to 612 kg on the CH-53K model, representing 3.5% of its empty weight.

1.1. Evolution towards SbW through the example of the flight controls

As indicated at the end of the previous chapter, the electrification of the information chain took place “gradually”. Whatever the application (fixed wing or rotor wing; commercial, military or private), when the electric information chain was first introduced, the mechanical information chain was maintained as a standby. The latter gradually disappeared, as redundancies applied to the power information chain allowed for the new alternative to reach the level of reliability required. The richness of this evolution, as illustrated by flight control, is analyzed below. It also attempts to embrace other actuating functions associated with the landing gear (steering and braking) or the engine (control of air and fuel flows, geometry and thrust reversers).

1.1.1. Military applications

The trends towards the uptake of more electrical information chains were initially driven by the need to autopilot flight in situations with zero visibility (military aircraft) or without an actual pilot (missiles and space launchers). For military aircraft, reducing vulnerability and increasing maneuverability have also been major reasons for the electrification of both the information and the control chains. This is illustrated in Table 1.1, which has mainly been sourced from [RAY 93].

Table 1.1. Evolution towards an all-electric information chain for the flight controls of military aircraft

Year	Manufacturer model	Advancements (from the previous model)
1943	Boeing B17E	3-axis autopilot with electrical output, mechanical summation on pilot commands by an electromechanical actuator
1959* 1964**	Dassault Mirage IV	Electrohydraulic elevons, analog electric signaling with mechanical backup
1964* 1967**	General dynamics F-111	Electrohydraulic spoilers
1974* 1978**	General dynamics F-16	Analog quadruplex FbW to increase relaxed static stability Quadruplex electronics with middle value logic Side-stick
1974* 1982**	Panavia Tornado	Triplex digital electronic FbW and mechanical backup channel
1978* 1983**	McDonnel Douglas F/A-18	Quadruplex digital electronic FbW Separation of electrical and hydromechanical fault detection and isolation Backup mechanical signaling for pitch control
1974* 1986**	Rockwell B1-B	Combination of full authority SCAS and purely hydromechanical control chains Structural Mode Control System (or SMCS)
1979* 1984**	Dassault Mirage 2000	Electrohydraulic actuators, and quadruplex analog FbW, electrical backup
1986* 2001**	Dassault Rafale	Electrohydraulic actuators, triplex digital FbW and analog backup Side-stick
1989* 1997**	Northrop B2	Quadruplex digital electronic FbW 4 Actuator Remote Terminal (or ART) in the wings, communication by multiplex bus Performance level kept in case of failure of an actuator electronic channel by changing the loop control gains of remaining healthy channels

*First flight, **Entry into Service (EIS)

1.1.2. Commercial aircraft

Table 1.2 shows the incremental evolution of flight controls for commercial aircraft, using European aircraft as an example. Note that it took a cumulative total of over 40 years to completely replace the mechanical information chain with all-electric information chain.

Table 1.2. Evolution towards an all-electric information chain for the flight controls of European commercial aircraft

Year	Manufacturer model	Advancement (from the previous model)
1969* 1975...

Table of contents

• Cover
• Table of Contents
• Title
• Copyright
• Introduction
• 1 Electrically Signaled Actuators (Signal-by-Wire)
• 2 Signal-by-Wire Architectures and Communication
• 3 Power-by-Wire
• 4 Electric Power Transmission and Control
• 5 Electro-hydrostatic Actuators
• 6 Electro-mechanical Actuators
• Bibliography
• Notations and Acronyms
• Index
• End User License Agreement