Subsonic And Transonic Flight

Subsonic And Transonic Flight There are basically three speed ranges for the flight of aircrafts, namely; subsonic, transonic and supersonic. All the three speed ranges were taken taking the speed of sound in a medium as a reference point. In this analysis, more emphasis is given to the former two which are subsonic and transonic flight. Subsonic flight refers to flying the aircraft at speeds less than the speed of sound with no formation of shockwaves. This is the speed range where most of the commercial aircrafts operate. The ratio of the speed of the aircraft and the speed of the sound is known as the Mach number. In technical terms for subsonic flight, the aircraft is flying at mach numbers which are less than Mach 1.0 since the aircraft is travelling at relatively lower speeds than the speed of sound. There are no shockwaves for aircrafts flying at subsonic speeds. This is because the acoustical disturbances generated by the passage of a subsonic aircraft, and the sound waves suffer attenuation with distance from the aircraft due to spherical spreading (Crocker, 2007). On the other hand, transonic flight deals with flying at higher subsonic speeds ranging from Mach 0.7 to approximately equal to Mach 1.0 (Aircraft Research Association, 2012). In transonic flight an aircraft flies at speeds less than the speed of sound, but with the presence of shockwaves. This leave a question of how is it possible that shockwaves form at speeds less than the speed of sound? But the answer to this question is explained by the movement of air around the aircraft. Far upstream from the aircraft, the motion of air is in uniform manner, all at the same speed. As the air come in contact with the aircraft, some regions of the air speeds up especially the air moving above the wings, creating a differential airspeed around the aircraft. These accelerate the air molecules and they end up moving very fast. These regions move faster than the speed of sound at transonic speeds, and these regions at all times end in a formation of a shockwave. DESIGN FEATURES THAT DELAY TRANSONIC FLIGHT PROBLEMS Different aircrafts are built in different ways, so the transonic region for a particular aircraft will depend on its design characteristics. There are many design features that can be employed in aircrafts to delay the transonic wave drag. In this analysis more emphasis will be on the use of thin aerofoils, use of low aspect ratio wings and the use of swept back wings. THE USE OF THIN AEROFOILS For transonic flow the wave drag rise is roughly proportional to the square of the thickness-chord ratio (NASA, No Date). This implies that when thinner aerofoil sections are used, the flow speeds around an aerofoil will be less than those for the thicker aerofoils, due to the minimum curvature of their upper and lower cambers. This give a clear indication that even at higher free-stream mach numbers, flight is possible before a sonic point appears and before the drag divergence Mach number. The drag divergence Mach number is the Mach number at which the aerodynamic drag increases rapidly as the Mach number continues to increase. It can be concluded that thinner aerofoils delay the drag divergence Mach number to a greater value. Thin aerofoils have got some disadvantages associated with their use even though they are very useful in solving transonic flow problems. Firstly, in the subsonic range of speeds they tend to be inefficient in producing lift. Also, given that the wing is too thin, it can accommodate less structure such as the structural support and fuel tanks of which means for such structures as the fuel tank they have to be embedded maybe under the fuselage. Aircrafts with thinner aerofoils also face common landing accidents due to their landing speeds which are particularly high. THE USE OF LOW ASPECT RATIO WINGS The wings aspect ratio is another factor that control the critical Mach number and the transonic drag rise. Aspect ratio is the ratio of the wingspan to its mean chord length. When looking at the aircraft from above the aspect ratio refers to the measure of how long and slender the wing appears. It is linked to the wing plan form arrangement as opposed to its cross-sectional arrangement. In this case the wingspan is the straight line distance connecting the two wingtips. Strike (2008, pp.45) clearly stated that high aspect ratio wings have an advantage in that they form low trailing edge vortices and thus reduce the induced drag. He further explain that induced drag is inversely proportional to aspect ratio, which implies wings with high aspect ratio produces low induced drag and the ones with low aspect ratios creates high induced drag. The picture below shows the configuration of both low aspect ratio wings, moderate aspect ratio wings and high aspect ratio wings. NASA (No Date) claims that an aircraft with an aspect ratio less than about four will experience a considerable increase in the critical Mach number. This become useful at high transonic speeds as the drag divergence Mach number is delayed as the critical Mach number is increase which means an aircraft can fly at high speeds before shockwaves form. Low aspect ratio wings are used at transonic speeds as there are structurally strong since the distance from the wing tip to the fuselage is not that big allowing agile manoeuvrability at high speeds. Nevertheless, the main disadvantage with low aspect ratio wings is the difficulties they face at subsonic speeds because of the higher induced drag. THE USE OF SWEPT WINGS Wing sweep as one of the aircraft design features has an important role in delaying the transonic flight problems. Most importantly swept wings can delay and reduce the effects of compressibility. The idea of swept wings in supersonic flight was put forward by Adolf Busemann in 1935 (NASA, No Date), the idea which most of the best aerodynamists didnà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢t agree with at first. In transonic flow, swept wings delay the formation of shock waves to a far much higher Mach number. This reduces the wave drag over all these mach numbers. Shockwaves depend on the span component that is 900 to the trailing edge, and this is a far much smaller component than actual airspeed in swept wings. Aircraft wings can be swept both forward and backwards. The disadvantage of forward sweep is its ability to lose stability and handling characteristics at low speeds. In backward sweep, the wing experiences early separation and stalling at the wing tip sections resulting in ailerons loosing roll control effectiveness. The figure below shows swept wings on a two-seat F-15E strike eagle. With swept wings, the major disadvantage is the span-wise flow along the wings and for sweepback the boundary layer will thicken towards the wing tips and towards the root for sweep-forward. This span-wise flow can be reduced in a number of ways. Firstly, stall fences can be used at wing tips. These are parallel plates to the axis of symmetry of the aircraft. Stall fences helps to prevent the build-up of a strong boundary layer over the ailerons, allowing effective functioning of the ailerons. Wing twist can also be another solution to the span-wise flow condition. EFFECTS OF ICE AND SNOW ON AIRCRAFTS The build-up of ice and snow on an aircraft can have catastrophic effects on the ground and in flight. This ice and snow can form on the parts of the aircraft during flight where the aircraft will be flying on very harsh weather conditions which can allow the freezing of water molecules at high altitudes since the temperatures are always very low. Ice can also form on an aircraft on the ground during taxing or when the aircraft is not in use and is not housed on a hangar. On cold and rainy day, rainwater can freeze on the upper surfaces of the wings and if not removed, this ice can have many different effects on the aircraft. In this section the effects of snow on the aircraft is going to be analysed fully. Ice is one of the foreign object debris which when left on the aircraft can pose a very critical threat to the aerodynamics and performance of an aircraft. It can also hinder the performance of the pilot who is controlling the aircraft. Considering the aerodynamics effects of ice, it can reshape the surfaces of the lift producing parts of the airplane thus the wings and the tail. This changes the aerodynamics of these parts completely such that more drag is produced and less lift. This increases fuel consumption. Wind tunnel and flight tests have been carried and it showed that frost, ice and snow on the upper surface of a wing can reduce lift by as much as 30% and increase drag by as much as 40% (CAA, 2000). The amount of the lift produced depends on the angle of attack thus the angle between the aerofoil chord line and the relative airflow. As the angle of attack is increased, the wing generates more and more lift until a certain angle where air cannot flow over the upper surface and the wing experiences aerodynamic stall. The point where stall commences has to do with the contour of the aerofoil. If the surface is contaminated with ice and snow it will be slightly rougher and this reduces the lift and alters the point at which stall takes place. Borrell (2009) claims that for scheduled air carriersà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢ commercial passenger airlines inclusive icing has been a major factor in 9.5% of fatal air carrier accidents. During ground activities aircraft contamination with ice and snow lead to potential risks during takeoff and subsequent flight. These hazards are mostly sourced by the hindered flight controls or instruments and the deteriorated aerodynamic performance. If an aircraft has engines mounted at the rear of the fuselage, clear ice that has formed on the wings may become loose during flight due to flexing of the wings and may be ingested by the engines causing a possible engine blow or failure. In most cases engine failure is the result of icing within the engine fan blades or is because ice that has formed on the engine inlet has been ingested. Icing on the propeller blades can also cause a dangerous imbalance. It is vital therefore, that no aircraft should take-off before the pilot has ascertained that all the surfaces of an aircraft are ice/snow free. Ice can also cause an uncontrollable rolling and pitching motion on an aircraft and recovery might be impossible in cases where there is too much ice. These may lead to the airplane stalling at much higher speeds and lower angles of attack than normal. The other effect is that it can cause antennas to vibrate so severely that they break end up breaking. These can result in a communication barrier between the pilots on the aircraft with air traffic controllers on the ground or other pilots. These on its own has an upper hand of causing an aircraft crash. As ice forms on the windshield, the pilotà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢s visibility may be lost leading to the pilot controlling the airplane on imagination which in most cases is a very dangerous threat. According to Brandon (2000), the weight of25mm of ice on a small general aviation aircraft would be about 30-40kg, which shows how much a little ice can have on the weight of the whole airplane, so there is no such thing as a little ice. SOLVING ICING PROBLEMS Aircraft icing problems can be overcome in a numerous ways which can be classified under the two sub topics of de-icing and anti-icing. De-icing are measures that are put in place to get rid of the ice that have already formed on the aircraft structure. This procedure of de-icing can be done with mechanical or pneumatic tools or with employment of warmed de-icing fluids. Mechanically, de-icer boots are fitted in sections along the leading edges of the wing, and horizontal and vertical stabilisers. The boots are made from natural rubber and fabrics made of rubbers between which are inflatable tubes closed at the ends. The tubes are then connected to the air supply. When in operation air is pushed in to the boots using the tubes hence increasing the pressure and as a result the bond between ice and the aircraft weakens and ice falls off. For de-icing using fluids, the liquid is applied along the centreline of the upper part of the fuselage, and then over the sides. The problem with allowing the aircraft structures to ice and then rely on de-icing is that some will be invisible to the human eye and sometimes left on the aircraft resulting in catastrophic effects during flight. On the other hand, anti-icing is a preventive way of not allowing the build-up of ice on the surfaces of the aircraft structures. Glycols act an important role in this operation because of their non volatile characteristics, non-toxic, non-corrosive and having low freezing points. Anti-icing is usually performed before takeoff as the liquid is usually effective for 10-20 minutes (RIA Novosti, 2013). Anti-icing systems on flight are usually turned on before approaching an icing zone. This systems are typically, carburettor heating, fuel vent heat, pitot heat and windshield heat. Anti-icing on the wings is done by spraying the fluid from the leading edges to the trailing edges of the wing. Anti-icing as a preventive measure is the method of the two since the user is assured of no ice formation on the aircraft hence minimum or no adverse effects of ice and snow build-up on aircraft structures. BIBLIOGRAPHY AOPA Air Safety Foundation (2008) Aircraft Icing. USA: Bruce Landsberg. Civil Aviation Authority of New Zealand (2000) Aircraft Icing Handbook. New Zealand: CAA. Crocker, J. M. (2007) Handbook of noise and Vibration control. Canada: John Wiley Sons. Fly Folker (2009) Ground Icing. The Netherlands: Folker Services. Kermode, A.C. (2006) Mechanics of Flight. 11th Edition. England: Pearson Education Limited. Perk, L., Ryerson, C.C. and Martel, C.J. (2002) Army Aircraft Icing. Hanover: U.S Army Engineer Research and Development Centre. Aircraft Research Association (2012) Experimental Aerodynamics. Available at: www.ara.co.uk/services/experimental-aerodynamics (Accessed: 02 February 2013). Brandon, J. (2009) Icing Conditions in Flight. Available at: http://www.pilotfriend.com/av-weather/meteo/thnder.htm (Accessed: 01 March 2013). Borrell, B. (2009) How Does Ice Cause an Airplane to Crash. Available at: http://www.scientificamerican.com/article.cfm?id=ice-flight-3407 (Accessed: 01 March 2013). NASA (No Date) Introduction to the Aerodynamics of Flight. Available at: http://history.NASA.gov/SP-367/chapt5.htm (Accessed: 03 February 2013). RIA Novosti (2013) De-icing of Airplanes. Available at: http://www.en.rian.ru/infographics/20110114/162128519.html (Accessed: 12 March 2013).

Akbar The Great Essay example -- Religious History

Jalal-ud-Din Muhammad Akbar was born on October 14, 1542 in Sindh. In 1540, his father Humayun was forced into exile by Afghan leader Sher Shah and Akbar had to spend his childhood in Afghanistan with his uncle. His childhood was spent in fighting and running instead of learning how to read and write, though he was very interested in art, architecture, music and literature. His father, Humayun, died when Akbar was very young and Akbar was crowned a Mughal emperor around the age of thirteen or fourteen. He was a Mughal emperor from 1556 to 1605. Under his rule the Mughal’s had most of the Indian subcontinent under their power. Akbar did not consolidate his power until he successfully won two battles, one which was with the descendants of Sher Shah Suri and the other one was with the Hindu King Hemu of Panipat. Before he consolidated his power Akbar was assisted and advised by Bahram Khan in running the affairs of the country. Bahram Khan was soon removed and Akbar freed himself from external influences and ruled supreme. In order to preserve unity of the Mughal Empire, he had adopted many programs that won the hearts and loyalty of the Muslims and non-Muslim people of his realm. Along with his numerous military conquests, he had introduced a sequence of reforms to help consolidate his power. One of the great known reforms of Akbar was his religious tolerance aimed at Hindu-Muslim unification through the introduction of a new religion known as Din-i-Ilahi. His tolerance is said to be influenced by a great Sufi leaders and his surrounding of people with liberal views, which this paper is going to explore how Akbar’s religious tolerant policies were a direct result of his influence by Sufism and the concept of Solh-... .... http://www.biography.com/people/akbar-the-great-9178163 Pritchett, Frances . "Religion at Akbar's Court ." Columbia University in the City of New York. N.p., n.d. Web. 2 May 2012. . Garbe, Richard Von. Akbar, emperor of india. S.l.: General Books, 2010. Print. "Jalaluddin Muhammad Akbar." Scribd. N.p., n.d. Web. 2 May 2012. . "Din-i Ilahi". Encyclopedia Britannica. Encyclopedia Britannica Online. Encyclopedia Britannica Inc., 2012. Web. 04 May. 2012 . Ghodratollahi, Eshan . "Akbar, The Doctrine of Shol-i-Khol and Hindu-Muslim Relations." Journal of Religious Thought: A Quarterly of Shiraz University 21 (2007): n. pag. Archive of SID. Web. 2 May 2012.

Netw360 Lab Week 2

Week 2 Lab Report 1. Read through the lab instructions before executing the lab steps and creating the reports. 2. Follow all procedures in the lab instructions for the items you will need to include in your report. 3. After executing all steps contained in the lab instructions, submit a one Word document for each project containing your report to the Dropbox. Create your reports using the template starting on page 2 and submit it to the Week 2 Dropbox by the due date. Have fun while learning! Thanks Your NameJeret BurnettNETW360, Professor’s Name Mario  Kosseifi Current Date July 15, 2012 Lab #2 Part 1, Antennas Lab Report Case Project 3-1 Antenna Type Using the internet and other resources, research the different types of antennas that are included under the three main categories: omni-directional, semi-directional, and highly-directional. Draw or print an example of each type and summarize when it is used, what is its maximum transmission distance, and it’s advanta ges and disadvantages. Omni-Directional [pic] When it is used?This antenna can be used for indoor and outdoor access points. It is an excellent solution for RV parks, Marinas, Resort Wi-Fi, and other general outdoor area where other wireless access is needed but unable to be achieved by the small antennas on a router. What is its maximum transmission distance? The range of this antenna is 3000 feet. However, a longer rage is possible with additional antennas on the receiving end. Advantages and disadvantages? The main advantage to this antenna is that you can receive wireless signal in areas that were not available before.Everyone has heard of internet â€Å"Cafes†, but with this antenna you could make an internet â€Å"Cafe† literally in the middle of a campground. The disadvantage is that trees, building and hills can reduce the signal and in somecases can completely stop the signal from getting through. Also, to get this antenna high enough to cover some areas the l ength of the coax cable will reduce the signal; thus making the antenna less effective. Semi-Directional [pic] When it is used? Semi-directional antennas are ideally suited for short and medium range bridging.If you want to connect two office buildings that are across the street from one another and need to share a network connection semi-directional would be a good choice. Or if you have a long narrow room where you need coverage throughout the whole room you can mount the antenna on an end wall. This is because the side-to side signal will not travel as far but the forward signal will travel quite far. What is its maximum transmission distance? Semi-directional range can vary greatly but is commonly used in situations that call for a range of a few hundred feet to two miles.Advantages and disadvantages? The main advantage of a semi-directional antenna is that in some cases a semi-directional antenna can provide such a long range coverage that they eliminate the need for multiple a ccess points. The main disadvantage is that if you need coverage over a large open area, such as a cubical office where the entire floor is open, a semi-directional antenna would not be the best choice because not every computer will receive coverage. Highly-Directional [pic] When it is used?It’s main usage is for point-to-point communication links where wired or other directional wireless coverage is not possible. What is its maximum transmission distance? Highly-directional antennas can operate at a range of up to 35 miles. Advantages and disadvantages? The main advantage is if you need to transmit wireless signal over a very long range without the signal going all over. Such as a person that is quite wealthy, they may have their own private island and want internet connectivity, but does not want to go with satellite internet and wired connectivity is out of the question.Another advantage is that if you are located in a building where wireless signal is very hard to get, a highly-directional signal may be the answer because since it is so focused in such a small narrow margin it may be able to basically blast through the wall. The main disadvantage is that the dish antenna is subject to damage from weather, especially if not mounted correctly. Highly directional antennas, for the most part, require a clear line-of-sight between ends. Your NameJeret Burnett NETW360, Professor’s Name Mario  Kosseifi Current Date July 15, 2012 Lab #2 Part 2, RF Behavior Lab ReportDetermining the behavior of an RF signal can be an aid when troubleshooting a WLAN that does not function properly. In this project you will use several online calculators to computer the RF behavior. 4. 30dBm 7. 8. 4 11. -81. 538 19. -5. 474469367710745 |Name |Power Output | |Cell Phone |. 6 W | |Cordless phone |10 mW | |Garage Door Opener |100 W |

English Architecture During Medeival Times essays

English Architecture During Medeival Times essays English Architecture During Medieval Times Architecture is the practice of building design and the technology applied in constructing a building. Medieval or, English architecture is very appealing in the variety of castles and cathedrals throughout England. Each structure has its own feature and aspects in reflecting the Gothic style of architecture. English architecture is based on the Gothic principal of architecture that has designed the vast castles and cathedrals from early to the late Gothic structures. The most popular form of architecture in England, early Gothic style is referred to as the Bay Design. This design consisted of simply a large building and a collection of different bays throughout the span. The building consisted of a single roof, one central ridge with two planes of rafters. This Medieval form is called a single span. (Braun 91) The most important feature in English architectural punctuation consists of buttresses, broad pilasters to form a sound system for the structure. The buttresses were slender strips employed by architects that supported the main walls. Broad pilasters added great dignity to the wall surfaces and were stepped in place at various angles of the building to propose a sturdier forum. ( Braun 99 ) During the 14th and 15th centuries advanced roofing technology enabled the spans of buildings t be increased. ( Braun 98 ) this meant that enormous cathedrals and castles could be constructed and still retain the strength of smaller structures. The large galleried churches of the tenth through the twelfth centuries were scientifically designed to have many windows to light the gallery floor. By the early Gothic period the row of rounded windows was accepted for being the main principle for lighting. The early Gothic or bay unit design was merely the popular design chosen throughout the early Gothic times in England. The Gothic form of architecture was developed upon th...

The Changing Uses of Freak

The Changing Uses of Freak The Changing Uses of Freak The Changing Uses of Freak By Maeve Maddox As a noun, freak is documented from the 1560s with the meaning sudden turn of mind: The king, in a freak of anger, ordered the generals execution. From meaning a sudden turn of mind, freak came to mean a trick or a prank: The boy was expelled for some boyish freak. By the 18th century, freak could mean something extremely imaginative. The 1785 citation in the OED refers to a wonderful ice-palace as a freak. The expression freak of nature gained currency in the 19th century. From that phrase derives freak in the sense of something that has developed abnormally, like a two-headed calf. In modern informal speech, freak is used with a qualifying word to label someone as being extremely committed to something: health freak control freak Jesus freak vegan freak The earliest example of this formation is from 1908: camera buffs were called kodak freaks. Freak is also used as a verb: to freak out: (occas. without out): to undergo an intense emotional experience, to become stimulated, to rave, esp. under the influence of hallucinatory drugs. Also trans., to cause (a person) to be aroused or stimulated in such a way. (OED) The verb has in turn spawned the noun freak-out (also spelled without the hyphen): Horse had a freak out in the trailer and cut hocks. Freak has two adjective forms, freakish (1653) and freaky (1824). The highway official being quoted in a news story about the narrow escape of a motorist when a second lane marker came loose from the road must have been too rattled to think of either of these adjectives: this is just another freak accident, even freaker than before Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Vocabulary category, check our popular posts, or choose a related post below:50 Redundant Phrases to AvoidHow to Pronounce MobileList of 50 Compliments and Nice Things to Say!

Emotional intelligence in nursing Assignment Example | Topics and Well Written Essays - 250 words

Emotional intelligence in nursing - Assignment Example Secondly, emotional intelligence is associated with calm disposition, an important trait in dealing with mentally unstable people. Through emotional intelligence, a nurse is able to maintain relative calmness and steadiness of the mind thereby offering the necessary help to the patient. Finally, through emotional intelligence, nurses are able to work well in teams with fellow nurses and other healthcare professionals (McQueen, 2004 p. 105). Through such collaboration, nurses are able to provide relevant help to the patients by obtaining relevant help from other professionals. A mental health nurse can improve his/her emotional intelligence by reducing his/her negative emotions so that they do not end up overwhelming him (McQueen, 2004 p. 106). This aspect of self-regulation becomes an important skill when dealing with patients. Secondly, students need to connect with others emotionally at all times, socially through non-verbal communication. This is one strategy of trying to understand others thereby building lasting relationships with them. Thirdly, students need to remain connected with others in situations that might appear challenging (McQueen, 2004 p. 106). For instance, a student might use humor to maintain relationships with others in situations that are challenging. Finally, students need to exercise peaceful problem solving without hurting the other party. This also involves airing ones views and expressing emotions in a controlled

Services Based Organisation Report Essay Example | Topics and Well Written Essays - 2000 words

Services Based Organisation Report - Essay Example These developmental processes include coaching, mentoring, eLearning, action learning and blended learning (Becker and Gerhart, 2009). This paper is focused on the employee development of a firm on the grounds of eLearning and how it has been improved over the years to foster employee development and using organisational resources efficiently. The purpose of the human resource management department is not only to look after the employee acquisition and performance level, but also to ensure that the firm is able to improve the employees’ skills and knowledge. An organization with a high skilled employee base is most likely to yield a higher performance level than its competitors. Therefore, it is vital for a firm to engage in employee development to gain a competitive advantage over its rivals (Baumruk and Gorman, 2009). The advent of globalization has made the global business market a more open place; this as a result has also increased the competitiveness of the industry. Therefore the companies constantly seek out new ways to improve their operational and production process so that they can stay ahead of their competitors (Eunmi, 2009). The traditional way to achieve this is to invest in high end manufacturing process and infrastructure. The firms often overlook the importance of the individuals who run the opera tional process. Moreover, owing to the myopic vision of the organization, it is caught up in achieving short term goals only, which as a result deviates the focus from the employees. This as a result reduces the productivity and efficiency of the firm as well as the chances of its sustainability (Sugumaran, 2008). Currie and Kerrin (2010) have stated that one of the effective ways of improving the productivity of the employees is to provide them with proper training. It can be defined as the planned effort of the organization to improve the competencies and knowledge base of the employees, which includes the