A History Of Fly By Wire

A History Of Fly By Wire Abstract This research report provides a historical portrait of the development and implementation of fly-by-wire flight control systems. The report explains to the reader what flight controls are. It provides an overview of major innovations in flight control systems. It then goes on to explain what a fly-by-wire flight control system is and discusses the NASA development program that made fly-by-wire a reality. It then discusses the F-16 Fighting Falcon which was the first mass produced aircraft to utilize a fly-by-wire system. The benefits of fly-by-wire flight control are discussed as is the expansion of fly-by-wire flight control systems into commercial and general aviation. Finally, a conclusion on the substance of this report is provided. 1. Introduction Purpose This historical research report describes the development and implementation of fly-by-wire flight control systems in order to satisfy the formal report requirements outlined in the course syllabus for EGR 3350, Technical Communications for Engineers and Computer Scientists. 1.2 Background Ever since the dawn of powered human flight was realized by Orville and Wilbur Wright in December 1903, engineers and aeronautic innovators have sought to institute more efficient and safer methods of aircraft flight control. The evolution of flight control systems from human powered mechanical linkages to fly-by-wire computer systems constitutes a marvelous display of aeronautical engineering progression. Fly-by-wire flight control systems signaled a great leap in aeronautical thinking and design from mechanical linkage and large hydraulic systems to computer-aided electrical flight control systems. An article by Gray Creech of NASAs Dryden Flight Research Center explains how [1] these systems created enormous benefits for the aerospace industry allowing overall reduction of weight and aircraft system redundancy increasing safety of flight. NASAs fly-by-wire development program was the first program to successfully institute an electrical flight control system without a mechanical b ackup. This programs success led to the first mass produced fly-by-wire aircraft, General Dynamics and Lockheed Martins F-16 Fighting Falcon, the space shuttles fly-by-wire flight control computer, and many other advancements in fly-by-wire flight control that are now being realized in the commercial and general aviation industries. 1.3 Scope This report will explain to the reader what flight control is and detail a brief history of aircraft flight control and the innovations that preceded fly-by-wire system development. This report will then discuss NASAs fly-by-wire development program and the initial deployment of this technology in the F-16 Fighting Falcon. This report will explain the many benefits inherently derived from employing a fly-by-wire flight control system. Finally, this report will detail how this flight control system evolved to be used in the commercial and general aviation industry. This report will not cover future trends of fly-by-wire flight control systems. 2. Discussion 2.1 What is Flight Control? The control of flight of an aircraft is determined by control surfaces on the aircraft body that are adjusted in coordinated movements by a flight control system that orients an aerospace vehicle around three axes of motion. These axes of motion are referred to as yaw, pitch, and roll. Figure 1 illustrates these axes. Figure 1. Aircraft Axes of Motion Dr. William Elliot gives a great synopsis on how these axes of motion are affected by control surfaces. [2] 1. Normal (vertical) axis, perpendicular to the surface of the wings. Movement about the vertical axis in flight is called yaw. In most modern aircraft, stability in yaw is affected by a fixed vertical fin in the rear; active control in yaw is accomplished by a movable rudder fixed behind the vertical fin. 2. Longitudinal axis, passing through the fuselage from front to back. Movement about the longitudinal axis is called roll. Stability in roll is taken care of by wings fixed at a slightly upward angle (dihedral); active flight control in roll is done by flaps (ailerons) behind the outer wings. 3. Lateral (horizontal) axis, passing through the wings approximately from tip to tip. Movement about the horizontal axis is called pitch. Stability in pitch is conferred by a fixed horizontal tailplane; flight control in pitch is accomplished by elevators mounted behind the tailplane. In controlling these surfaces, a pilot utilizes various control mechanisms such as mechanical linkages, hydraulics, trim tabs, actuators, and, in the case of fly-by-wire systems, electricity and computers to create the desired output on the flight control surfaces based on the pilots input. 2.2 Brief History of Flight Control System Progression Dr. Elliot continues to explain that after [2] Glenn Curtisss patent of the aileron, the basics of modern flight control were firmly established, and the result was a standardized cable-operated control system. [2] In this standard arrangement, a single control column (or stick) was used to operate both elevators and ailerons through a series of cables and pulleys; in a similar fashion, the rudder was moved by foot pedals. The physical strength of the pilot was all that was required to augment these control surfaces in flight for slow moving aircraft. The physical limitations of pilots began to be realized as aircraft became faster and heavier. [2] This problem was initially solved by the installation of small flaps (tabs) on primary control surfaces. These surfaces utilized the airflow acting on the tabs to move the main control surface they were attached to. The development of automatic piloting systems was also on going at this time and [2] steady advances in autopilot technology led to the development of mechanical boosters to assist pilots in moving control surfaces of very large aircraft. [2] Successive aircraft produced during the late 1940s and early 1950s continued to make great advances in hydro-mechanical flight control systems. [3] During this time period hydro-mechanical control systems developed into 3000 psi hydraulic systems as seen in Figure 2. Figure 2. Flight Control System Innovation Timeline [3] Technology Military Commercial Un-Powered: 1910s 1920s Powered Boost: 1940s 1940s 3000 psi Hydraulics: 1940s 1950s Auto Pilots: 1950s 1950s Fully Powered, w/*Reversion: 1950s 1960s (Boeing 727) Fully Powered, w/out *Reversion: 1950s (B-47) 1970 (Boeing 747) Fly-By-Wire: 1970s (F-16) 1980s (A-320) Digital Fly-by-Wire: 1970s 1980s (A-320) 5000 psi Hydraulics: 1990s (V-22) 2005 (A-380) Power-By-Wire: 2006 (F-35) 2005 (A-380) *Reversion: Servo actuators unlock allowing pilot mechanical control. [3] Figure 2 details the engineering progression of flight control systems over the last 100 years. Interestingly, prior to the institution of fly-by-wire flight control systems, [2] artificial feel systems were incorporated in flight control systems to necessitate the need for pilots to feel as though they were still mechanically connected to the aircraft flight control system even though hydraulic systems broke this connection between pilot and control surface. These advancements in flight control technology culminated in the desire for an electrical means of flight control system execution. 2.3 What is a Fly-By-Wire (FBW) Flight Control System? [2] Aerospace Recommended Practice (ARP) defines FBW as a flight control system wherein vehicle control information is transmitted completely by electrical means. A FBW control system is a computer system that monitors pilot control inputs, various parameters such as airspeed, altitude and angle-of-attack, and outputs flight control surface movements with the objective of keeping the aircraft within its designated flight envelope. Literally, this computer interprets electrical signals via pilot control and sensor input and outputs electrical signals to actuate the corresponding control surface in order to achieve the desired flight orientation. The flight envelope refers to the safe operating characteristics an aircraft is designed to fly at given different speeds, altitudes and other variables. The actuation of a fly-by-wire system is effectively the same for all such systems, namely; the system employs electrical signal inputs to create electrical signal outputs. However, these systems can be deployed with a varying array of design elements or control law algorithms that decide how the system will react in a given situation as well as what entity, human or computer, has superior control of the aircraft at a given time. This subject will be elaborated on in a later section. 2.4 NASAs Digital Fly-By-Wire (DFBW) Development Program On May 25, 1972 at NASAs Dryden Flight Research Center, the first flight to successfully demonstrate a digital FBW flight control system without a mechanical backup was conducted. [1] Support for the concept at NASA Headquarters came from Neil Armstrong, himself a former research pilot at Dryden. He served in NASAs Office of Advanced Research and Technology following his historic Apollo 11 lunar landing and knew electronic control systems from his days training in and operating Apollo spacecraft. Armstrong suggested that the Dryden DFBW team adapt an Apollo program digital flight control computer. It wasnt long, however, before the DFBW program developed a digital flight control computer that significantly advanced the state of the art. This was demonstrated by the fact that for the Space Shuttle, designers turned to the DFBW program for a flight computer for the Orbiters. The result was a classic case of in-house technology transfer. The original digital flight control computer deve lopment from Apollo proceeded to the DFBW program and then back again into space aboard the Shuttle. The program utilized a Navy F-8C Crusader for testing which incorporated the use of computers in making the flight control surface deflections that corresponded to the pilot input. [3] NASAs DFBW program, consisting of 210 flights, lasted 13 years. Figure 3 [6] shows the avionics bay of the test aircraft where the computers that managed the flight control system were installed. Figure 3. F-8C Test Aircraft Avionics Bay 2.5 F-16 Fighting Falcon Originally developed by General Dynamics and now produced by Lockheed Martin, the F-16 was the first mass produced aircraft to use a FBW flight control system. The F-16 has seen multiple upgrades since its service debut in the 1970s. These upgrades are typically called blocks and are designated by a number. In the F-16s case, [4] the F-16 A/B model consists of blocks 1, 5, 10, 15, 15OCU, and 20 while the F-16 C/D model consists of blocks 25, 30, 32, 40, 42, 50, and 52. There also is F-16 E/F block 60 models developed for the United Arab Emirates, an F-16 MLU (Mid Life Update) block, and various other F-16 models developed for special purposes or foreign customers. These blocks signaled upgrades in areas such as avionics, engines, engine inlet area, and weapons capabilities to name a few. According to Joe Sambor, a Lockheed Martin aero field service engineer, [5] all F-16 block designations developed prior to block 40 utilized analog flight control computers while all later blocks in cluding block 40 utilized digital flight control computers. The difference between analog and digital computers lies in the way they process information. Analog computers work in a continuous time environment where data can take on an infinite set of values which results in no loss of transmitted data; however, its implementation is cumbersome requiring an extensive hardware configuration. Moreover, this hardware configuration is difficult to upgrade. Digital systems operate in a discrete time environment where data values are finite. Loss of data is augmented by high resolution and sampling rates which effectively renders data transmission loss negligible. The benefit in system implementation is mainly software based providing smooth transitions for system upgrades and reduction in overall system cost and maintenance. The F-16 utilizes four separate flight control computer systems which work together to select the proper flight response output at any given time. This flight control configuration is considered practically immune to failure as long as power is applied to the aircraft. 2.6 Benefits of Fly-By-Wire Flight Control Systems One of the great benefits FBW technology brings to the aviation industry is the ability for aerospace engineers to design an aircraft to be inherently unstable allowing for increased maneuverability. Prior to FBW, aircraft had to be designed to inherently want to return to straight and level flight. This meant that maneuverability was diminished due to the fact that, in order for the aircraft to maneuver, the aircraft had to first overcome its inherently designed stability. FBW systems are able to monitor aircraft flight in real time allowing aircraft that could never fly with simply the skill of the pilot because of the aircrafts instability the ability to take to the skies. Also, [6] aircraft weight is reduced with the removal of mechanical linkages and reduction in hydraulic system components. Enhanced safety is provided by the redundancy design of electrical circuits as well as the computers ability to respond to an adverse flight condition much faster than a pilot. The overall c ost of the system is reduced as less hardware and mechanical parts are required, fuel efficiency of the aircraft is increased, and passengers experience greater comfort derived from the increased aircraft handling characteristics. Furthermore, the system can be designed to control the flight envelope keeping the pilot from making control inputs that would put the aircraft outside its safe operating capability. Also, digital FBW control systems can accept input from any aircraft sensor reducing rigidity constraints in system design. 2.7 Expansion of Fly-By-Wire Systems in Aviation Currently, DFBW flight control systems are available in every aspect of government, military, and commercial aviation. These systems are deployed on helicopters, fighter jets, stealth bombers, and commercial airliners. Even general aviation is starting to see the benefits that DFBW technology has to offer. Mark Tatge, a writer for Forbes magazine, explains that [7] small-piston aircraft and business jets are undergoing a radical upgrade. Digital technology developed for combat fighters and commercial aircraft 20 years ago is finally making its way into the cockpits of small aircraft, often at a fraction of the cost of the electronics currently installed in Boeing jumbo jets. Major airlines like Airbus and Boeing have already begun moving their fleets toward the DFBW domain. Airbus made this move with its A320 aircraft, [6] the first commercial airliner to have DFBW technology. Boeing subsequently followed suit by employing DFBW technology on its 777 and 787 aircraft models. It is interesting to note however, that Airbus and Boeing differ in the employment of their respective DFBW flight control systems and algorithm control laws. An article written by Brian Palmer summarizes the differences between the two aircraft manufacturers. Palmer explains that [8] Airbus employs a joystick that electrically connects the pilots input to the flight controls where Boeing employs the standard yoke that still uses cables to deliver pilot input commands. Airbus also utilizes control algorithms called flight envelope protection that keeps the aircraft from flying outside its designed operating area. Boeing gives more latitude to the pilot in being able to push the envelo pe when appropriate. Palmer also goes on to explain how [8] it is unclear as to whether flight envelope protection makes air travel safer. Palmer cites two aircraft incidents; namely, China Airlines Flight 006 and the crash of an American Airlines jet in November 2001 where flight envelope protection could have hindered the aircraft flight control recovery or could have prevented the crash, respectively. 3. Conclusion 3.1 Summary The employment of flight control systems over the past one hundred years has seen quantum leaps in the design and theory behind how a pilot actually controls the flight of an aerospace vehicle. DFBW technology has exponentially increased the safety of flight for millions of people. This area of engineering owes its continued refinement and evolution to countless individuals and organizations who have taken on the challenge of developing the control systems that advance the safety and efficiency of flight. It is amazing to look back in history on the evolution of aerospace vehicles and recount that within fifty years of human beings first successfully completing powered flight that autopilots were flying planes without human pilot commands from Canada to England. That physical power of flight controls was supplanted by hydraulic actuation which in turn was augmented with electrical circuits. That the advent of seemingly unrelated hardware such as microprocessors and logic circuits wou ld have such a profound place in designing an aircraft to fly. That the innovators in this field had the vision and courage to trust their knowledge and engineering skill in putting the lives of capable pilots in the hands of a computer system. The flight control systems currently deployed in aviation constitute some the most well engineered, capable and, failure resistant electrical systems ever created. However, it should be noted that such systems seem to still be in their adolescence and much discovery and improvement is left to the next generation who endeavors to improve upon and invent the future of aerospace flight control systems. Sources Cited [1] Creech, Gray. Digital Fly By Wire: Aircraft Flight Control Comes of Age. http://www.nasa.gov/vision/earth/improvingflight/fly_by_wire.html. Jim Wilson. NASA Dryden Flight Research Center, September 30, 2007. Internet. October 24, 2012. [2] Elliot, Dr. William. The Development of Fly-By-Wire Flight Control. Air Force Material Command: Office of History, AFMC Historical Study No. 7, December 1996. Print. [3] Greetham, Tom. Evolution of Powered Flight Controls. http://mae.osu.edu/sites/mae.web.engadmin.ohiostate.edu/files/uploads/ME888Presentations/evolution_of_powered_flight_controls_seminar.pdf, February 10, 2012. Accessed November 10, 2012. Internet. [4] F-16.Net. Production Blocks and Experimental Versions. http://www.f-16.net/f-16_versions.html. Accessed December 2, 2012. Internet. [5] Sambor, Joe. F-16.Net Forum. http://www.f-16.net/f-16_forum_viewtopic-t-6605.html, October 22, 2006. Accessed December 2, 2012. Internet. [6] Philippe, Christian. The Impact of Control Technology. T. Samad and A.M. Annaswamy (eds.), IEEE Control Systems Society, 2011. Internet. October 23, 2012. [7] Tatge, Mark. Fly By Wire. http://www.forbes.com/forbes/2005/1128/083.html. November 11, 2005. Accessed December 2, 2012. Internet. [8] Palmer, Brian. Boeing Vs. Airbus. http://www.slate.com/articles/news_and_politics/explainer/2011/07/boeing_vs_airbus.html. July 11, 2011. Accessed December 2, 2012. Internet.

Spring Days Ahead

Spring is a magical season for me. I love the sound of birds chirping, the smell of rain in the air, and the vibrant colors of the flowers starting to bloom. It awakens the senses. The winter cold is gone, yet the unbearable heat and humidity of summer in the south has yet to arrive. I love that daylight savings time puts an end to the long dark evening hours of winter. The phrase â€Å"spring forward† is a reminder to set our clocks ahead one hour during spring. Springing forward is what the season is all about and what I look forward to the most. The increased sunlight and ability to spend more time outdoors brings a new outlook on life and lifts my spirits. My husband and I become rejuvenated as we begin to get outdoors more and take pride in renewing our home and yard. Whether it is a small project, such as giving the front door a fresh coat of paint, or starting a garden, we look forward to it with excitement. Spring has been called â€Å"the season of growth† and it is when I start a new vegetable and flower garden each year. There is nothing better than freshly picked vegetables from my garden. The vegetables are free from pesticides and provide a healthy snack for our family. The smell of fresh cut flowers in a pretty vase on my kitchen table reminds me of the small pleasures in life. The beautiful colors of the flower garden help bring color and vibrancy to the world. Spring is a busy time of the year for my family. Spring brings on a fresh round of taking the children to school, sporting events, and birthday parties. Trying to keep up with two young children can be exhausting. The occasional spring rainstorm provides a welcome relief from all this activity and gives me a badly needed break. There is nothing better than curling up on the couch with a good book, listening to the rain beat upon the roof, and enjoying the feeling of not being rushed to get somewhere. Spring is my favorite season. New color and life appear in the world. The long dark nights of winter are behind us. Everyone and everything is filled with a new sense of urgency and vibrancy. Others prefer the oppressive heat of summer, the dark cold of winter, and the dreary days of fall, but I will take spring over them all.

The Road Not Taken - 1211 Words

The Road Not Taken By: Robert Frost Imagine that your making a decision and you are stuck to choose between two things that could change and impact your life greatly. What would you do? What pathway would you take? Robert Frost wrote ‘The Road Not Taken’ in 1916 at the age of 42 in New England, Massachusetts. ‘The Road Not Taken’ is one of his most popular works due to the ideology of choices that people would have to face in their life. In the early 20th century, Robert Frost based the majority of his poems from rural life in New England, where he grew up. Robert Frost was highly regarded for his deep, realistic understanding of rural life and using elaborate social and philosophical themes in his works. This poem explores a†¦show more content†¦For the second stanza, the traveller is describing that both pathways are equally the same through the used of extended metaphors, personification and metaphors. On third stanza, the poet is providing additional information on the season by â€Å"And both that morning equally lay, in leaves no step had trodden black†. This imagery of the season autumn symbolises the perfect layers of yellow leaves on the path as for a long period of time no one has walked on it yet. On third line, onomatopoeia was used which is â€Å"oh† that illustrates an emphatic tone for the decision that he made. The traveller is now regretting the decision that he made. On the last two lines, an extended metaphor was used, â€Å"Yet knowing how way leads on to way†, â€Å"I doubted if I should ever come back†. These last two lines of the third stanza, heightens the attention of readers that he hopes that he could try the other path as the traveller knows ‘how one road can lead to another’. Also, the traveller is having doubts as it is impossible to retrace steps as other choices or decisions can lead to other options in life. The third stanza raises the awareness to readers as he decided to stick with the decision that he made but still with a bit of regrets. The last stanza, Robert Frost uses a number of poetic techniques, in order to demonstrate the fear and regrets as he already made which path to go and now, there’s no turning back. In the first line onomatopoeia was used andShow MoreRelatedRoad Not Taken752 Words   |  4 PagesPoetry Essay ENGL 102: Literature and Composition MLA Thesis Statement: Every adult faces the challenge of a life-altering decision. In â€Å"The Road Not Taken† by Robert Frost there are many metrical devices used to portray the poet’s major theme of decision making. Outline for â€Å"The Road Not Taken† I. Introduction A. Influence of decision making B. Problem faced by the character II. Body A. Theme of decision making B. Setting (1) Why is this symbolic? C. Title Read MoreThe Road Not Taken1084 Words   |  5 PagesClara Kirkpatrick Mr. Woods English 102 CHA 8 November 2010 The Road Not Taken The poem â€Å"The Road Not Taken† by Robert Frost describes the dilemma in decision making, generally in life each individual has countless decisions to make and those decisions lead to new challenges, dilemmas and opportunities. In Frost’s poem, the careful traveler observes the differences of each path, one is bent and covered in undergrowth (Frost 5) and the other is grassy and unworn (Frost 8). In the end he knowsRead MoreThe Road Not Taken967 Words   |  4 PagesThe Road Not Taken by Robert Frost Two roads diverged in a yellow wood, And sorry I could not travel both And be one traveler, long I stood And looked down one as far as I could To where it bent in the undergrowth; (5) Then took the other, as just as fair, And having perhaps the better claim Because it was grassy and wanted wear; Though as for that the passing there Had worn them really about the same, (10) And both that morning equally lay In leaves no step had trodden blackRead MoreThe Road Not Taken1448 Words   |  6 Pagespoem â€Å"The Road Not Taken.† Frost, in few words, brings to light the decisions that all functioning humans will be faced with. When Frost says, â€Å"Two roads diverged in a yellow wood,† (1) these roads clearly represent two different decisions to be made. Does it have to be two roads? It, in fact, does not. The roads could be a complicated web of an interstate system; however, only one road can be taken. There is no reverse, and there are no U-turns. There is simply a single path to be taken. How doesRead MoreEssay On The Road Taken And Not Taken937 Words   |  4 PagesThe Road Taken and Not Taken Response I had to choose between playing a full-time summer sport or going on family vacations in the summer. Sports enriched my life in many ways such as creating more memories with my friends, allowing my pitching to improve, and gaining valuable team experience. Family vacations also could have changed my life as it allows for more family time, memories, and adventures. In the end, I chose to play a summer sport because it increased my games per year, practices perRead More Robert Frosts The Road Not Taken - The Significance of The Road Not Taken811 Words   |  4 Pages The Significance of The Road Not Taken  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚      My father introduced me to The Road Not Taken when I was a young teenager because he figured that I was beginning a period of my life where I would be forced to make many important decisions, and he saw this poem as a source of guidance through those decisions. This poem carries truth and edification in its words. It forms a beautiful analogy of life and all its complications. After my father finished reciting the poem, I neverRead More Road Not Taken Essay980 Words   |  4 Pages Critical essay for â€Å"The Road Not Taken† by Robert Frost Two roads diverged in a yellow wood And sorry I could not travel both And be one traveler, long I stood To where it bent in the undergrowth; Then took the other, as just as fair, Because it was grassy and wanted wear: Though as for that the passing there Had worn them really about the same. And both that morning equally lay In leaves no step had trodden black. Oh, I kept the first for another day! Yet knowing how way leads to way, I doubtedRead More The Road Not Taken Essay542 Words   |  3 Pagesfor Frost is that he has the power of standing still where he is.† There is never a straight road there are always curves and turns in which one must encounter and act upon. Readers can interpret the poem â€Å"The Road Not Taken† in many ways. It is a persons past, present and the way one see things, which determines their choices and paths they follow. This poem shows how Frost believes that it is the road that you choose that makes you the person you are. Decisions are always hard to make. It is impossibleRead MoreThe Road Not Taken Essay758 Words   |  4 PagesThe poem â€Å"The Road Not Taken,† Robert Frost employs personification to illustrate the literal scene of the poem. The personas vision as a Pilgrim Traveler, on a road with outlooks pointing in two directions that symbolize a fork in the road. Both of roads leads to two different types of a life style, and to choose the right road will make the difference. In the first stanza the personification shows â€Å"Two roads diverged,† in to choose which road to travel. While in the second stanza the personifiedRead MoreThe Road Not Taken Analysis1280 Words   |  6 PagesThe Road Not Taken As I read and analyzed this poem I became aware that it is indeed a great poem and that the reader must dig deep in order to find the true message of the poem. Careful readers shall not be tricked. The Basic Subject of the Poem The poem starts off with the title â€Å"The Road Not Taken.† At first sight this title could be used as foreshadow that the following poem will be about making a mistake, not making the right choice (not taking the right road) therefore establishing a

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