FTA of Main Landing Gear Systems

FTA of Main Landing Gear Systems FTA OF MAIN LANDING GEAR SYSTEMS Main Landing Gear System For any aircraft landing gear is the undercarriage which support the craft when it’s not flying, until it to take off and during landing. Landing gear hold net weight of whole aircraft during taxing without any damage. Fig: A380 main landing gear configuration Components of landing gear The materials used to construct gear components are of great importance and are selected as per their properties The main components of landing gear are: Down-lock and drag brace Retraction actuators, Rotational actuators Trunnion Forward trunnion braces Metering pin extension Rotational Lockpins Aft braces Oleo cylinder Oleo piston Axle beam fold and compensation actuator Brake assembly Tires and wheels Sensing wheel Axle beam assembly Failure of lading gear In this part we discussed about the Ductile and Brittle Failure, Stress Corrosion Cracking, Stress Rapture, Fatigue Cracking Failure Dynamic Failure, Landing gear Spring Failure and Wheel Failure. We analyzed these possible problem and construct suitable fault tree analysis in order to identify failure condition in brief. The objective of constructing the fault tree is to investigate and analyze the possible failures and different components and systems of the landing gear with their consequences and solutions. In the case of mechanical failures: There are 12 types of failures Excessive, deflection , thermal shock, impact creep, relaxation, brittle fracture, ductile fracture, wear, spring, failure, corrosion, stress corrosion cracking, and various type of fatigue. On the basis of this problem that can occurs in main landing gear we construct the fault tree to identify the failure condition and met the requirements. Materials for landing gear The materials used for the landing gear are High strength steel Titanium Aluminum Failure mechanism of landing gear Fatigue cracking failure Mostly aircrafts and military experience serious damage and the fatigue. Stress corrosion cracking This SCC is caused by synergy between a corrosive environment and a mechanical tensile stree Dynamic failure When aircraft land on the ground tricycle landing gear and load affected by the ground/pavement response are distributed on the and can cause problem. Landing gear spring failure Here micro cracks acted as stress concentration as well initiation crack site leading the spring to fracture due to fatigue Wheel failure During landing wheel experienced a lot of pressure. Due to this over pressure that could damage 4.2 The fault tree of typical main landing gear system: The main purpose of constructing fault tree is, in order to identify the possible failure of any system which can occurs in any manner. In case of main landing gear, fault tree can be construct on the basis of two main conditions: Fault tree analysis for failure condition 511: one or both MLG fail to extend and down lock with false down and locked indication. Fault tree analysis for failure condition 511: one or both MLG fail to extend and down lock. Between these two failure conditions of main landing gear, I choose to analyzed fault tree analysis for failure comdititon511: one or both MLG fail to extend and down lock with false down and locked indication. The analysis based on fault tree My main object of constructing this fault tree is to identify the typical failure condition of main landing gear in order to save aircraft from it’s hazardous failure As we need to take safety procedure for every parts of aircraft, landing gear is also aspect which cause aircraft in a dangerous mode So in order to overcome this failure of landing gear and for the safety of aircraft, I finally decide and came to know the purpose of failing landing gear and what can be the cause for this. With the help of fault tree analysis, we analyzed the each and every problem inside the landing gear and try to overcome by constructing fault tree In case of LH or RH or both MLG fail to extend and down lock with false down and locked indication, pilot receive alert. So while construction fault tree we take as a main event by using event symbol as shown in fault tree. After we decided main event than we analyzed for the cause of it by using the Boolean symbol called AND gate. We use AND gate so that we could analyze all next true lower level condition which can possibly occur. Possible cause of man landing gear are false LG down position indication and LH or RH MLG fail to extend and down lock. Still there are some cause to fail these two components, which we will define by Boolean logic symbol call OR gate. The purpose of OR gate is to identify among of various possible problem if any of one or more of the next lower level event are true for failure of above condition. In fault tree analysis we solved the problem and come to the conclusion with what if, and with the help of various Boolean logic symbols. The main event that I mention in the top is not only the problem that cause landing gear to fail but also the lower level parameters which fails landing gear fails. When we look from external and if landing gear is not extend during landing than we conclude that the landing gear doesn’t work. But besides engineer who work in the field of safety assessment, other observer will just guess just the landing gear fail. We never thought of what cause the landing gear fails. As per landing gear consists various components so the probability of failure also high. If small components for example spring fails, than the landing gear fail.so in order to overcome these all possible failure fault tree is constructed. Among of various symbols and representation, AND and OR gate plays vital role to make all possible decision for failure. Determination of minimal cut set for fault tree analysis Minimal cut set is define as a combination of primary events sufficient for the top event, on other words intersection of primary event. The main objective of representing a fault tree in terms of various Boolean equations is that these equations can then be used to determine the fault tree’s minimal cut sets and minimal path sets. While we obtain the minimal cut set, the quantification of the fault tree is more or less straightforward. For every fault tree will consists of finite number of minimal cut sets that are unique for that event. There are two kind of minimal cut sets which can occurs the top event to occur. One components minimal cut sets, if there are any, represent those single failures that will cause the top event to occur. Whereas two-components minimal cut sets represents the double failures that together will cause the top event to occur. Similarly for an n- components minimal cut set, all n components in the cut set must fail in order for the top event to occur. The calculation of minimal cut-sets The minimal cut sets expression for the top event can be written as in the general form T = M1 + M2 +†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦+Mk, Here the terms T is the top event and Mi are the minimal cut sets. Whereas for the each minimal cut sets for n-components minimal cut set can be represents as Mi = X1X2.,†¦Ã¢â‚¬ ¦ Xn Here the X1 and X2 , etc represents the basic components failure in the fault tree analysis I represents my above failure events as ABC, T is top event caused by all lower level events. Here I want to mention the example of top event expression is T = A + B.C Here A, B and C are components failures. In this example [A] represents the one-components minimal cut set whereas [B.C] represents the tow-components minimal cut set. In order to determine the minimal cut sets of a fault tree, the tree should be translated first to its equivalent Boolean equations. Here I want to mention the example of calculation the minimal cut set to my fault tree The procedure to calculate the minimal cut sets of fault tree T = E1.E2 being AND gate E1 = A+ E3 being OR gate E3 = B+C being OR gate E2 = C+E4 being OR gate E4 = A.B being OR gate Substituting the top down first the expression of minimal cut can be expressed as below T = (A+E3) . (C+E4) = (A.C) + (E4.C) + (E4.A) + (E3.E4) Substituting for E3, T = (A.C) + (B+C).C + E4.A + (B+C). E4 = A.C + B+C + C.C + E4.A + E4.B + E4.C Here according to idempotent law, C.C = C, substituting this value to above equations T = A.C + B.C + C + E4.A + E4.B + E4.C. Again according to the law of absorption twice, A.C + B.C + C + E4.C = C Then the above results become, T = C + E4.A + E4.B Hence, substituting for E4, applying the law of absorption twice, T = C + (A.B).A + (A.B).B = C + A.B The minimal cut sets are thus C and A.B where, [C] is one- components and [A.B] is two-components minimal cut sets.

The Cell Phone Invention :: Expository Essays Research Papers

The Cell Phone Invention We have all seen and used cell phones. However we have probably taken the technology for granted. The cellular telephone has evolved and improved a lot over the years. Before we get into the history let us first get the definition for 'cellular'. It's called cellular because the system uses many base stations to divide a service area into multiple 'cells' (1). Each base station consists of a tower and at the base is the equipment to send and receive signals. Now that it cleared up we will look back into the history. To find the first "cell phone" in history we look back to 1928. In 1928 the Detroit Michigan Police Department made the earliest significant use Mobile radio in a vehicle in the United States. The system operated at a frequency close to 2 MHz. The channels soon became overcrowded (3). This seems like a small and weak signal but at the time it was evolutionary. Nothing like this had ever been done before. It also seems like a crude method but it was just the beginning. The police, different companies, and public agencies were the only ones that got to use the mobile technology, but in 1945 the technology was made for public use. The mobile equipment was not sophisticated enough to prevent interference (3). The concept of using small cells wasn't looked at until 1947. Research found that this would increase the traffic capacity of mobile phones, however the technology didn't exist at that time (1). Also in 1947 AT&T tried to get the FCC to put aside a large band of radio-spectrum frequencies so that widespread mobile telephone service would become feasible (1). The FCC didn't like the idea and didn't back the technology at the time and limited the amount of frequencies. Twenty-one years later, in 1968, the FCC reconsidered AT&T's offer. They stated that, "if the technology to build a better mobile service works, we will increase the frequency allocation, freeing the airwaves for more mobile phones" (1). This is when AT&T and Bell Labs proposed the first idea of 'cells'. There would be many low frequency towers and calls would be passed from tower to tower as phones traveled across the area. Until this time, we have to realize that cell phone research was not a major or popular area. It was probably seen as a worthless study that wouldn't amount to much if anything.

What are the main features of child directed speech and how does it help language acquisition?

The language traits that characterise child-directed speech tend to facilitate the acquisition of language. Children start their lives without language and are faced with the challenge of emerging into a world in which they cannot effectively communicate. From the time a child is born, however, they will begin to associate what happens around them with meaning. As time passes, they will begin to associate unknown verbal forms to known meanings. Parents show a unique type of speaking that is referred to as child-directed speech, motherese, or, more commonly, baby talk for example â€Å"moo-cow†.This speech has many unique characteristics that distinguish it from adult-directed speech. One feature of child language acquisition is that children master language by making mistakes until they fully acquire the skills. This ‘trial and error’ approach shows that learning is taking place, however, phonological development seems also to depend on physical ability to produce sounds. Some phonological errors used by children are deletion in words such as â€Å"do(g)† and â€Å"cu(p)†. Although some add on extra vowels, for example â€Å"doggie†.A lot of young children change one consonant or vowel for another, known as an assimilation such as â€Å"gog† instead of â€Å"dog†. These errors show that as a child learns a word is substitutes the sound of a letter for a different one. In phonology there are a variety of features used by parents for language acquisition such as higher pitch in the parents voice, a greater range of frequencies in the tone, a slower speed of speech, clearer enunciation, emphasis on one or two words in a sentence, and special pronunciations of individual words.This is more common from the mothers as it comes naturally to them and is done in order to allow infants time to process the information being conveyed to them. Rhythm is also emphasized when talking to a child and is used closely with th e emphasis of various syllables. One children can produce sounds effectively they can use these skills to form real words that others can recognize. Proto-words have meaning for the child and the parents so a child needs to acquire the vocabulary that will help them be understood by a wider audience. Also achild needs to learn the meanings of words in order to link objects and ideas. The rate of lexical development in children at 12 months is that they know 50 words which increase to 2,000 at 36 months which shows that language is aquired in the early stages. Parents also tend to use some lexical features in speech such as â€Å"mama† and â€Å"dada† to encourage the child to start speaking, as these words are usually the first two the child says in their early months. As the child starts to progress, the parent uses diminutives like â€Å"doggy†, â€Å"kitty†, â€Å"potty† for the child to understand easily.Children can link a word and the referen t easily as they can usually see it, or see a visual representation in a book. The social and interactive nature of many words also indicate the importance of interacting with others, suggesting that pragmatic awareness is vital to language development. The reduplicative such as â€Å"quack quack† and diminutives like â€Å"mummy† show the bridge between phonological and lexical development. Child directed speech features a unique syntax. Parents usually use short utterances rather than full sentence structures in order to convey meaning to their child.They are often repeated so children have practice in a particular concept. Child directed speech helps infants to detect syntactic boundaries and makes linguistic patterns easier to recognize. Children begin to understand word order through child directed speech which slowly expands into a deeper understanding of sentence structure. However, communicating with children can be difficult if you can’t maintain their attention, so you need to talk about a topic that interests them.For example if you are washing them you could talk about all the different body parts whilst washing them, if they splash talk about the splash. Ask a lot of questions and let them reply as this speeds the acquisition of verbal auxiliaries by the child. Parents should use lots of names for things and many words for actions as they play an important role in later language development. Conversations with children are mostly about the present, here-and-now, rather than topics pertaining to another time, past or future.Regarding grammar, in the first three or four years there is not much point in correcting them as it will just confuse them and may do harm to their confidence and self-esteem. It is best to let the child correct themselves spontaneously when they are ready. However you could drop hints to help them out in correcting what they are saying. In order to relate to a child during â€Å"baby talk†, a parent may deliberately fabricate some words, and may pepper the speech of non verbal utterances. The parents might refer only to objects and events in the immediate surrounding area, and will often repeat the child’s utterances back to them.Children employ a wide variety of phonological simplifications, usually assimilation or reduplication, in learning speech, where the child seizes on a stressed syllable, and repeats it to form a word. Within the context of normal conversation with their children caregivers use a variety of techniques to encourage the continuance of that conversation. Repetition is one of the most frequently used methods of prolonging conversation, as well as one of the particular traits of child-directed speech.Frequently heard words for objects will be better remembered and better articulated than other words once the child begins to develop a productive vocabulary of real words. The more times a child hears a sentence clearly modeled, the more that child†™s language learning is facilitated. The expand and recast technique serves as an alternative to repetition, and, is a method parents often use as it gives children new ideas and helps with the formation of grammar, as well as prolonging the conversation by recasting the prior topic into a new form.Turn-taking is another technique used in child-directed speech. Used early in the child’s development, turn-taking provides infants with the opportunity of learning the structure of conversations. The parents use cues such as exaggerated pauses to help infants learn to take their turns. Routines of turn-taking also serve other functions in linguistic development. Babies gain experience in vocalizing, and participate in situations in which that vocalizing becomes more language-like.

The Relationship Between The Narrator And His Wife

Cathedral The relationship between the narrator and his wife was acrimonious at best. He does not care enough for her to be nice to a house guest who is a friend of hers as evidenced by his comment â€Å"I wasn’t enthusiastic about his visit. He was no one I knew. And his being blind bothered me.† (Carver, 1983, p.2679). In point of fact he seems to be a jerk overall with his comment about the man being blind. I have always believed prejudice is based in ignorance and I think this is a perfect example. He is bothered by a blind man and freely admits to not having any blind friends. He is afraid of what he does not know and of someone who is different. The wife’s comments back to him also divulge a sourness towards their relationship. He writes â€Å"My wife looked at me with irritation† (Carver, 1983, p.2683) and â€Å"My wife gave me a savage look† (Carver, 1983, p.2679) bolstering the conclusion made with the narrators comments above. I think their relationship should change after this. She should leave the jerk and find someone who actually gives a damn about her! Having said that, my training and experience as a former Firefighter/EMT tells me things will only get worse until some big event happens at which point they will get divorced. The significance of the blindness is that he has so much to teach others. It is ironic that the narrator is â€Å"bothered† by this man’s blindness and feels a certain amount of defeat in his inability to describe a Cathedral to him. There is also some shameShow MoreRelated Threatening Relationships in Carver’s Cathedral Essay1235 Words   |  5 PagesThreatening Relationships in Carver’s Cathedral  Ã‚     Ã‚  Ã‚   Although many critics have written numerous accounts of Richard Carver’s Cathedral as being about revelation and overcoming prejudice, they have overlooked a very significant aspect: the unfolding of marital drama. The story tells of how a close outside friendship can threaten marriage by provoking insecurities, creating feelings of invasion of privacy, and aggravating communication barriers. The close outside friendship between the narrator’sRead MoreA Man Becoming Prejudice Against Blind People1710 Words   |  7 Pagestrust another person.The Cathedral is a captivating story based on the lives of the narrator, his wife and a blind man. Raymond Carver is the author of this story, and he does an excellent job allowing the reader to delve into the lives of these characters. Through using the thoughts of the narrator, the reader is able to grab our attention because the story is made more realistic. The views expressed by the narrator in many senses exemplify the views of many in society and therefore the reader isRead MoreAnalysis Of Raymond Carver s Cathedral 1648 Words   |  7 Pages Cathedral is a capitivating story based on the lives of the narrator, his wife and a blind man. Raymond Carver is the author of this story, and he does an excellent job allowing the reader to delve into the lives of these characters. Through using the thoughts of the narrator, the reader is able to grab our attention because the story is made more realistic. The views expressed by the narrator in many senses exemplify the views of many in society and therefore the reader is able to make an emotionalRead MoreAnalysis Of The Narrator Cathedral 1280 Words   |  6 Pagesphysical vision, but seeing requires a deeper level of thoughtfulness. The narrator displays the capability of looking but cannot display the capability of seeing into such depths. The narrator’s whole idea of blindness came from the movies. He said blind people moved slow, were mostly led by dogs, were always serious and never laughed. But that just shows how ignorant he is against the blind. Throughout the whole story the narrator was the character that I didn t like, in fact I thought he was the antagonistRead MoreAnalysis Of Raymond Carver s Cathedral 1006 Words   |  5 Pagesis told from the perspective of a first-person narrator. Throughout the story, the narrator is self-absorbed in his own thoughts and emotions and fails in his willingness to overlook personal insecurities in order to accommodate others’ discomfort, i.e. predominantly his wife and the blind man. In general, the story lacks figurative language and is told in short, direct sentences. This basic structure leaves a lot for the reader to interpret on his or her own. I focused on two paragraphs within RaymondRead MoreCathedral Essay1479 Words   |  6 Pagesthe narrator has an attitude of being selfish, and jealous through the story. The narrator’s wife invites a blind man, Robert, to come stay in their house for a short time while the man visits family members of his own wife who recently passed. The narrator is not enthusiastic because blind people make the narrator uncomfortable, mainly because the narrator has no real experience with the blind. In addition, to his uneasiness with the blind the narrator is uncomfortable with the relationship hisRead MoreThe narrator is told by his wife that she is having her blind friend come spend a night at their1400 Words   |  6 PagesThe narrator is told by his wife that she is having her blind friend come spend a night at their house. His wife had just passed and is a very good friend with the wife and wants the blind man to come stay with them. The narrator is not very happy about the blind man coming to visit and asks the wife where she met him and to talk more about. She explains that she worked f or him, she read to him. When the blind man pulls up, the narrator is already being judgmental and prejudiced towards the blindRead MoreSummary Of The Night By Robert Wife Beulah884 Words   |  4 Pages1. Plot: The narrator is telling a story about his wife friend who is blind man name Robert. Robert wife Beulah has recently died due to cancer. The narrator wife wants Robert to spend the night at their house. The narrator wife used to work for Robert, and she is explaining the relationship between Robert and her. The husband does not like Robert because he is blind. At the end of the night Robert shows the husband how it feels to be blind and changes his views about being blind. The main incidentsRead MoreAnalysis Of IND AFF Or Out Of Love In Sarajevo878 Words   |  4 Pagesscene of the Archduke Franz Ferdinand’s assassination by Princip Bridge. The narrator is in the midst of an affair with her married professor, Peter, and over the duration of the trip, she realizes t he fragility of her relationship with him. Her realization is played out in conjunction with the historic relevance of Princip’s assassination due to the setting being in Sarajevo. As the narrator notices the parallels between her and Princip’s lives, she ultimately decides to end things with Peter inRead MoreAnalysis Of Raymond Carver Cathedral1260 Words   |  6 Pagesknown for his writing style known as minimalism, a style that often uses short phrases or sentences that convey a great amount of meaning. Carver’s â€Å"Cathedral† is full of minimalism, whether it be short and repetitive dialogue or brief thoughts that go through the narrators mind. These intentionally precise sentences are full of meaning, whether it be the importance of communication, or the lack of, the underlying tones of death and jealously, or even the psychological connection between the narrator