SAE R-225-1998 Fly-by-Wire A Historical and Design Perspective (To Purchase Call 1-800-854-7179 USA Canada or 303-397-7956 Worldwide).pdf

1、r / * I if * r Phase IIE. Precision Aircraft Control Technology and Reliability/Maintainability of SFCS Fly-By-Wire; and Technology Transitions and Application. Gavin Jenney was Director of Air Force In-House Facilities, including the B-47 Program. Gavin also designed the fly-by-wire system used on

2、this program and was one of the flight test team. He is author of many Air Force technical documents on fly-by-wire and is currently President of Dynamic Controls, Inc. He reviewed and made numerous suggestions to improve this book. F/L Paul Sutherland, a Canadian Air Force exchange officer, came on

3、 the scene at a very opportune time. He took over Phase II of the B-47 In-House Program and Phase II of the Sperry Phoenix Effort. He orga- nized and chaired the Government-Industry Symposium on Fly-By-Wire given at Wright-Patterson Air Force Base. Major General Robert R. Rankine, HQ AFSC, while ser

4、ving as a Major during his early military career, was a Section Chief in the Control Elements Branch of the Flight Dynamics Laboratory. He offered early encouragement of this publication, as illustrated by this excerpt from a June 11, 1992, letter to HQ AFMC: Technology for fly-by-wire was developed

5、 by Wright Laboratory in the 1960s and first saw application in a production airplane in the F-16. Mr. Harry Hillaker, formerly of General Dynamics and now a viiAcknowledgments member of the Air Force Scientific Advisory Board, has told General Yates that fly-by-wire in the F-16 would not have been

6、possible without the Flight Dynamics Lab (now part of Wright Lab). . . . I believe a monograph on this subject would be of considerable value to the AFMC technical community, since it represents a USAF-led technology development that has had a significant impact on world aviation. . . . I believe su

7、ch a monograph would be popular with a multitude of engineers throughout the aero- space industry who have been working fly-by-wire issues for decades. Ed Snyder and other personnel of the Air Force Materials Laboratory indoctrinated the McDonnell Douglas engineers on the survivability aspects of hy

8、draulic fluid Mil-H-83282 over Mil-F-5606 (the then standard Air Force fluid), mainly the performance at higher temperature and the higher bulk modulus. The new fluid was used in A/C 12200 throughout the Fly-By-Wire Program and is now the standard hydraulic fluid in Air Force aircraft. There are man

9、y other individuals who deserve to be mentioned as they played a part in establishing the technology we use. However, I feel we must set a limit, and sincerely hope theyll understand the situation. I offer special thanks to my wife, Betty. With WordPerfect, helpful suggestions, encouragement, and ma

10、rital sup- port, she made this book possible. Vernon R. Schmitt Former AFFDL Project Engineer, Task 822503 viiiChapter 1 Introduction Fly-by-wire in aircraft flight control design is more than adding a simple wireit is a sophisticated system that changes the way aircraft are designed and the way the

11、y fly. Previous works on fly-by-wire have omitted or inadver- tently bypassed many of the details and explanations of the systems design, choosing instead to highlight only its application. Our purpose then is to fill this void by describing the “how“ and the “why.“ This book was prepared and writte

12、n by people who directed or staffed the fly-by-wire research and development programs because, as time passes, without a formal account of the key events and activities of the initial R work referred to as “in-house“ was accomplished at Wright-Patterson Air Force Base (WPAFB) in Dayton, Ohio, by con

13、tractor and Air Force military and civilian personnel. The Air Force spent millions and millions of dollars to promote and advance fly-by-wire technology to a level where it could be used as a practical design technique on new aircraft. Furthermore, had these programs not been undertaken and had the

14、y not been successful, fly-by-wire would not have been used on the design of flight control systems of military aircraft for at least for another 30 yearsand perhaps not even then. Unlike some design techniques that can be proven by mathematical models, computers, simulators, and perhaps lab- orator

15、y models, fly-by-wire required the design, construction, tests, and flight tests of flightworthy hardware. With many R it was computer designed, installed, and flight tested with good results. On the F-16 the neutral stability point was moved and with movement of the leading edge slats (computed), w

16、e have relaxed static stability. Experimentally on the F-111 we created the MAW (mission adaptive wing), which permitted changing the wing camber in flight. 2. The all-important action for changing concepts into reality is mechanization. Mechanization was accomplished on the B-47 program. In fact, t

17、he Survivable Flight Control System mechanization on the 680J Program made fly-by-wire a reality. 3. The B-2 and F-117 both employ this part of fly-by-wire. Thus, when we start to blend signals that are computerized (or computed) we can blend the various systems: avionics, flight control, and so on,

18、 ad infinitum. In the future, we can adapt such techniques to automatic flight for take-off, cruising, and landing. 2Chapter 2 Background of Fly-by-Wire Definitions What is meant by fly-by-wire? A simple, abbreviated description might be: fly-by-wire is a flight control design wherein a mechanical l

19、ink is replaced by an electrical one. Obviously, this description must be expanded to com- prise the links purpose or function and the items being linked. In some respects, a better understanding of fly-by-wire might be obtained if one were to visualize the pilot moving the controls. On the controls

20、 are attached electrical devices that generate and transmit electrical signals to another member that is remotely located in the aircraft. The controlled member moves in step with the pilots commands. Further, when sensor and computed outputs are added to the pilots commands, the pilot has the capab

21、ility of con- trolling the aircraft motion about its referenced axes. Sensing components, such as gyros and accelerometers, along with computing devices and actuators are part of a fly-by-wire flight control system. Over the years a number of definitions of fly-by-wire have been proposed. In 1967, t

22、his was the accepted definition: “A fly-by-wire flight control system is an electrical primary flight control system employing feedback such that the vehicle motion is the controlled parameter.“ Eventually, this definition was superseded. As of 1995, the one now accepted as standard and used by U.S.

23、 industry is as follows: Fly-by-wire A flight control system wherein vehicle control input is transmitted completely by electrical means. (This definition applies to digital designs as well as analog.) Other terms used with fly-by-wire systems are: Flight control system A system that includes all ai

24、rcraft subsystems and components used by the pilot or other sources to control one or more of the following: aircraft flight path, attitude, airspeed, aerodynamic con- figuration, ride, and/or structural modes. Autopilot A portion of the aircrafts flight control system that automatically initiates f

25、light corrections by sensing deviations from a fixed reference; the autopilot performs the necessary functions, including computa- tions and actuation, to maintain the aircraft on a steady preset course and attitude without assistance from the pilot. The term “autopilot“ is short for automatic pilot

26、. Pseudo fly-by-wire A fly-by-wire control system with a mechanical backup that is normally disengaged. 3Fly-by-Wire: A Historical and Design Perspective Redundancy. The existence of more than one means for accomplishing a given function. Power-by-wire actuation An integrated servoactuator that inco

27、rporates an electric motor to receive power from the aircraft main electric power system in lieu of an actuator connected directly to the aircraft main hydraulic system. Definitions for other frequently used terms can be found in documents listed in the References section. History World War II Autop

28、ilots Fly-by-wire has been around in one form or another for at least 50 years. In 1943 the C-1 Autopilot was developed and installed in the B17E bomber aircraft for use during World War II. The primary purpose of this equipment was for bombing. It provided a stable platform for the bombardier to do

29、 the proper target sighting, and it eliminated undesirable motion of the aircraft at the time of the bomb release. The pilot could also make use of the autopilot, especially on long mission flights over water. The C-1 Autopilot was electrical. There were potentiometer-type transducers on the vertica

30、l and directional gyros to sense changes in roll, pitch, and yaw. Voltages from these transducers were fed to electronic amplifiers, the output of which operated solenoids or servomotors which, in turn, had cable drives attached to the flight control surfaces (the elevator, rudder, and ailerons). Th

31、e pilot would trim the aircraft for straight and level flight, then engage the autopilot. Thus, in a sense, he was flying on a fly-by-wire system. The C-1 Autopilot was built by the Honeywell Corporation. The E-4, used on other military aircraft, was built by the Sperry Corporation. The A-12 Autopil

32、ot, also built by Sperry and used on operational aircraft in 1946, is representative of the type of equipment that was installed and flying on operational aircraft. Figures 1 and 2 give some basic data about its oper- ation. Fig. 1 shows a cutaway view of the vertical gyro. Fig. 2 shows the electric

33、al signal flow of this autopilot. The flight amplifiers shown in the figure are electronic types. The actuators are electromechanical, with a clutch and cable drive connected to the flight control surface. The Guided Missile Era After World War II, the guided missile era started about 1947 and exten

34、ded into the 1960s. The Matador, a ground- to-ground missile, the Snark, a ground-to-ground missile, the BOMARC, a ground-to-air missile, the RASCAL, an air-to-ground missile, and the Falcon, an air-to-air missile, all used a control system of the fly-by-wire type. The experience gained by the manuf

35、acturers of electronic components and by users of this equipment afforded an oppor- tunity to establish more technology for fly-by-wire control systems for aircraft. For example, some of the environ- mental extremes these missile systems had to meet gave the designers the know-how when similar desig

36、ns were required for manned vehicles with less harsh operational requirements. In 1956, when Aviation Week interviewed personnel of the Air Force Flight Control Laboratory, it was quite appar- ent that a number of hurdles and roadblocks had to be overcome if fly-by-wire were to become a reality: The

37、 time may not be far away when the complex mechanical linkage between the pilots control stick and the airplanes control surface (or boost system valve) is replaced with an electrical servo system. It has long been recognized that this “fly-by-wire“ approach offered attractive possibilities for reducing weight 4