Aircraft Structural Design: Ageing Aircraft Program - Coursework Example

Aircraft Structural Design: proposal for an Ageing Aircraft program Table of Content 0 Introduction.....................................................................................................................3 2.0 Aircraft Current Capacity.................................................................................................4 2.1 Structure of the Aircraft Maintenance team.......................................................5 2.2 Specification of the aircraft technician and their duties......................................5 2.3 Inspection programs that are run (aircraft checks).......................................................................................................................7 3.0 Proposal for the Aging Aircraft Program........................................................................9 3.1. Why Ageing Aircraft Programs...................................................................................................................9 4.0 Legal Requirements.........................................................................................................11 4.1Repair Assessment Programme...........................................................................................................................12 4.2 The widespread fatigue Damage....................................................................................12 4.3 Supplemental Structure Inspection Program (SSIPs).........................................13 4.4.Ageing Aircraft Safety Rule................................................................................13 4.5 Corrosion prevention and control program (CPCP)...........................................13 5.0 AAA Case Study.............................................................................................................15 5. Case 1: Grumman Turbo Mallard Sea Plane in-flight failure and separation of the right wing.....................................................................................................................................15 5.2 Case 2: Boeing 747 SR-100 Failure of the vertical Stabilizer..............................................................................................................................15 6.0 Conclusion....................................................................................................................17 7.0 References.....................................................................................................................18 Introduction Most aircraft that are operated either in the military or commercially at some point approach a state that can be referred to as aging. Aging of the aircraft does not refer to it being obsolete. An aircraft might end up becoming obsolete before reaching a state of aging or reach the aging state before becoming obsolete. For a commercial airplane, it can become obsolete whenever its capability no longer competes with the potential of adversaries (Wang, 2011). As often is the case, time upon which an aircraft reaches an aging state is quite difficult to determine. It is essential to have a distinction between the properties of the structure of an aging aircraft and a young aircraft. In this regard, a young aircraft is one that keeps being airworthy with the available programmes meant for maintenance often prescribed during the time of manufacturing (Hempe, 2008). Aging aircraft might be characterized as that which the effects of cracking and corrosion from fatigue needs modifying the maintenance programs for purposes of making sure they retain the adequate structural integrity. In this context, the term adequate implies the number of expected failures becomes less than whatever is often given a given fleet of aircraft. As the aircraft gets to accumulate the calendar time, as well as flight time, corrosion effects, cracking due to fatigue and accident damage makes it undergo repair. Cracking due to fatigue may also be widespread to the extent that it leads to degradation of the integrity of the entire aircraft structure (Gordon, 1991). With this occurring, the aircraft reaches a point where it is said to be in the state of widespread fatigue damage (WFD) (Vermeeren, 2012). At this point, it has to undergo some modifications in order to have the problem solved. Additionally as an aircraft increases accumulating the flight time it can exceed the design time it was meant for. At this point in time, maintenance programs would require modification in order to include other structural inspections. In cases where initial maintenance programs need modification from events aforementioned above then an aircraft might be considered as being in a state of aging. Aging aircraft has continued being in operation despite many odds (Smallman and Bishop. 2009). Besides the enormous cost of acquiring a new aircraft, there are limited reliable manufacturer around the world. Therefore, for safety, as well as for economic purposes, the aging aircraft would continue being in service for a period longer than expected. In line with this argument, this paper seeks to investigate and bring to the fore the Aircraft current capability alongside the proposal for ageing Aircraft programme. It is worth noting that, like any other machine, aircraft requires maintenance for purposes of making sure safety of those who use them becomes guaranteed. This can be achieved through the introduction and implementation of stringent rules and regulations aimed at keeping them airworthy. The Aircraft Current Capability There are regulations that have been put in place in making sure the aircraft remain airworthy. One such regulation is the aircraft maintenance program, which provides a guideline for the current capability of putting in place systems that are deemed to be relevant to the Aircraft maintenance. There are regulations that have been put in place in making sure the aircraft remain airworthy. One such regulation is the aircraft maintenance program, which provides a guideline for the current capability of putting in place systems that are deemed to be relevant to the Aircraft maintenance. Generally, certified staff is categorized into four levels basing on the regulation of the Joint Aviation Regulation. These levels basing on knowledge, and experience include, the level one general familiarization best described below as junior level technicians, Aircraft maintenance Technician, who are often licensed belonging to level two Transit and Ramp whose function is described below, the aircraft sheet metal Technician and the Trim and Fabrication Mechanics The structure of aircraft maintenance team The aircraft maintenance team is responsible for airworthiness of the aircraft. For this case, Aircraft Maintenance Engineers are tasked with make final decisions as to whether the aircraft is ready or not for flight. This decision is often governed by a principle called “Safety first”. Maintenance team is, therefore, involved in various aspects of airline activities, from how to fly, when and where to fly. As often is the case, Air maintenance teams, are, more often than not required to complete a high technical work that cuts across repairing, maintenance of the aircraft, and operating the aircraft engines and systems, alongside taxiing the aircrafts. Various skilled trades are often involved in the process of maintenance of the aircrafts. As a practice, previous experience is needed for one to qualify as a mechanic, technician or engineer in the area. However, it is worth noting that from time to time there are openings available for grab for candidates who have low technical experience in line with aircraft maintenance. For such like cases, applicants are often classified or absorbed in the junior classification. Specification of the aircraft technician and their duties Junior Technicians Employees can easily progress from this junior position to the level of mechanical or technical classification. Education requirements of a junior are basically high school completion. Although candidates who, additionally have completed a likely technical course at any recognized institution are given preference. Aircraft maintenance Technician Aircraft Maintenance Technicians are tasked with the responsibilities of performing certain scheduled maintenance, troubleshooting company, defect rectification and customer aircraft. While working on a ramp and in a hanger, the technicians are often involved in the repair of things such as landing gear, hydraulic system, flight control systems and fuel systems. The candidates that are hired as Technicians of the Aircraft are required to have a certificate in Aviation maintenance, or have an equivalent schooling the ministry of Transform. For one to be eligible for any promotion above this level of a Technician, there is needed suitably professional rated Aircraft Maintenance Engineer (AME), M License, which can be sought after a period of 4 years of a documented work experience. The Aircraft Sheet Metal Technician The Aircraft Sheet Metal Technician are responsible of assessing corrosions and damages of structures; modifying sheet metal, replacing, and repairing composite structures. Those candidates that are often hired as structural Technician need to have a college certificate in aviation. For eligibility for promotion beyond the level of the Technician, one is required to have a suitable rated Aircraft Maintenance Engineer “S” license, which is sought following 3 years documentation. Trim and Fabrication Mechanics Trim and Fabrication Mechanics are often engaged in repairing the aircraft furnishing, and the fabric work. This includes panelling, chairs, drapes and carpets. These mechanics are also involved in the maintaining the interior of an aircraft including replacement of the evacuation slides, windows, doors, and windshields. Candidates that were hired for this work needed a High School trade certificate with preference being given to the candidates who were part of Aviation Maintenance council. Inspection programs that are run (aircraft checks) There are measures put in place to make sure aircrafts are inspected regularly. In regard to this, Aircraft maintenance checks, which entail periodic inspections of the Aircrafts, are done on all civil/commercial aircraft after a stipulated period of time of usage. This involves both detailed and routine inspections. Inspections commonly referred to as checks are of the following: D check, B check, checks C and check D. C and D are often considered the heavier checks, and A and B checks are considered the lighter checks. A Check For this inspection, it is often performed at approximately every 200-400 cycles or 500 to 800 flights hours. Fundamentally, it requires about 20 to 100 man-hour. As a routine, it is performed overnight at hangar or airport gate. The real occurrence of this check always vary with the type of Aircraft, cycle count, or number of hours the aircraft flows since it was last checked. This occurrence might at time be delayed by an airline in case certain predetermined condition are fully met B Check This check is often done at approximately every 4 to 6 months. It requires approximately 150 hours, and on most occasions, it is done 1 to 3 days at the airport hangar. Just like in check A, similar measures apply to check B. It is worth noting that B checks might become incorporated into a successive A checks so that A-1 extends to A-10 completing all the B necessary check items. C Check This check is more often than not done at every 15 to 21 months or at a specified amount of the actual flight hours according to the manufacturer. This sort of maintenance check is somewhat more extensive compared to B check. This is because; about the entire aircraft is often inspected. The check helps put the aircraft out of service until when it is completed, it is stipulated that the aircraft cannot leave the maintenance site. This check, as well requires some more space as compared to B and A checks. Time required for the completion of such a check is about 1 to 2 weeks. The effort that is involved might require to about 600 man-hours. It is noted that for this check, the schedule for the occurrence involve much more factors, as well as components considering the processes involved, and it varies from one aircraft category to the other. D Check This check is by far regarded as the most comprehensive. It is also the most demanding for an aircraft. It is commonly referred to as Heavy maintenance Visit. It occurs approximately after a period of five years. It is the check that to a larger extend takes the whole aircraft apart for purposes of overhauling and inspection. Additionally, if need be, paint on the aircraft might be completely be removed to pave the way for further inspection on issues such as fuselage metal skin. For such a check, about 40,000 man hours are required and can even take up to two months for it to be completed. This depends on the type of the aircraft, and the number of technicians that are involved in the whole process. By and large, the check requires most space of the four maintenance checks. Due to this, it has to be performed at a given suitable maintenance base. Considering the requirements of check D alongside the tremendous effort that is involved, it becomes the most expensive maintenance check having total costs for a visit being much within a million-dollar range. Given the nature, as well as the cost of this check, for most aircrafts, in particular, those that have a relatively larger fleet, need to plan D checks in order for their airplane years in advance. More often than not, the older aircraft that may deem to be phased out of a certain fleet of airlines are stored or scrapped after reaching this D check because of the high costs that are often involved when compared with the value of the aircraft. Averagely, a commercial aircraft can undergo about 2 to 3 checks before it becomes retired. It has been noted that most repair, Maintenance, and Overhauling shops seem to suggest that is almost impossible to have a D check performed profitably at any shop located on the street. Proposal for the Aging Aircraft Program Why Ageing Aircraft Programs It is widely cited that the United States Air force has a number of aircrafts that age between 20 to 35 years old and even older. Although, there have been planned to have the old Aircrafts be replaced with the new ones, it has been noted that due to the foreseeable economic losses, replacement for the remainder is not planned. These aircrafts constituted the majority of the total operational aircraft force. With plans to retire these aircrafts and replace them with new ones, the question has been what impact would these have economically and could we maintain the aging aircrafts. In the context of this discussion, it is proposed that the aging aircraft program is of paramount importance and, therefore, adopted. It is worth contenting that in case the life of the existing aircrafts is extended at some reasonable cost, there would be substantial saving realized by the companies that own these airplanes, at least, the cost deferments. Research has indicated that protracted depot maintenance and operations along with other life extension programs can decrease the fleet readiness. However, most commanders have always been reluctant to have the planes removed from service until when their timely return is assured. The extended service lives for the older aircraft becomes possible only by maintaining aggressive repair and maintenance and implementing the aircraft modification programs, which might be somewhat labour intensive, costly and often depend on the high levels of skills and craftsmanship. Research has indicated that one of the pervasive challenges with the old aircraft is corrosion. According to the Air Force surveys done in 1990 and 1997, corrosion related costs of maintenance were worth millions of dollars in any given year and such costs are on a steady increase (Vlot, 2001). This thus implies that if the advanced technologies are implemented, corrosion would be significantly reduced, and it would also help improve the field and procedures for the depot maintenance. Additionally, it would help ensure there is the safe operation of the older airplanes. Considering the past records, various aircraft forces have been informed of the challenges that face the management and updating of the aging fleet for some time. The United States Air force, for instance, sponsored a certain research body called the National Research Council study which came up with promising technologies, as well as research opportunities that can help address the critical structural issues that surround the aging of the fixed-wing aircraft. This was in particular issues to do with fatigue, inspection, corrosion, and repair (Smallman and Bishop. 2009). According to NRC report, there is the need to implement near-term actions that range between 3 to 5 years for purposes of improving the management and maintenance of aging aircraft. It also recommended that near-term research need be sponsored. In implementing these recommendation, the decision was reached upon which a new aging aircraft program, which was to be under the AATTs oversight, (a new Technology transition program) would take shape. The program as estimated was budgeted at $5 million in the year 1999 and $14 million in the year 2001, which was subject to an increase. Since the implementation of this report, the impact of this program has yielded positive returns. It has been noted that, through this program, it has made it possible for the NRC recommendation to be acted upon and more is expected t o be addressed. By adopting the aging aircraft program, various technical objectives shall be achieved. These includes correcting the structural deterioration that might at some point be a threat to the safety of an aircraft, preventing or minimization of structural deterioration that might end up becoming excessive economic burden or otherwise adversely affect the readiness of the force, and predicting for future planning purposes, whenever the burden of maintenance becomes too high or the availability of the airplane becomes so poor such that retaining the airplane within the inventory ceases to be of economic value. Legal Requirement It is worth contenting that Aging aircraft has been known to have various challenges. One of such challenges is corrosion. It has been widely cited that millions of dollars are spend on aircrafts due to corrosion, repair, and corrosion prevention. Structural fatigue cracking has also been cited as one such key challenge. These problems have safety implication besides the economic challenges. Besides the wiring safety, aircraft subsystems are also said to be a great challenge that have a serious impact on the availability of an aircraft. Prompted to solve the issues of widespread fatigue damage (WFD), corrosion, as well as, cracking due to fatigue and accident damage, there were legal FAA requirements for such aircrafts to meet. They include Repair Assessment Programme, the widespread fatigue Damage and APP and the Repair Assessment Programme. Repair Assessment Programme This rule as stipulated and published in the Federal Register on 2nd of January 1998, stated that a damage tolerance inspection need to be carried out for repairs on fuselage pressure boundary, which encompass bulhead webs and doors skin, for purposes of maintaining safety of the passengers. This law was limited to various ageing aircrafts for instance the Boeing type 707/720, 727, 737, 747, Fokker F-28, and Lockheed L1011, the A300, and the group of McDonnell Douglas ranging from DC-8, DC-9/MD-80 to DC-10. According to this regulation, operators are prohibited from flying any of the aircrafts listed above for the validated flight cycle performance time, unless all the necessary operation specification for the given aircraft is revised to the referenced repair assessment (http://www.faa.gov/regulations_policies/orders_notices/index.cfm/go/document.information/documentID/13746). Widespread Fatigue Damage (WFD) & Ageing Aircraft Program (APP) With a view to deal decisively with the issue of WFD, the NPRM was developed by the Aviation Rule Advisory Committee aimed at ensuring that the large aircraft is only operated within the stipulated time frame. This, therefore, brought about the introduction of the Ageing Aircraft Programme alongside the supporting Organization Maintenance programme. The programs were aimed at correcting issue such as corrosion of the aircraft and the control program, supplementing the structural inspection program, emphasizing on structural repairs, along with the program to have WFD precluded from the fleet, and structural modification of the aging aircraft. Additionally, the Airworthiness Assurance working groups were required to investigate the aircrafts that at the moment were found to be lacking ALS and ask them to make sure they have one (http://www.faa.gov/regulations_policies/orders_notices/index.cfm/go/document.information/documentID/13746). Supplemental Structure Inspection Program (SSIPs) The SSIPS was developed for the Ageing Aircraft fleet following the mishaps of the Aloha airline. It was resolved that each of the team of manufacturers of large transport aircraft come up with own programs for different Aircrafts. However, changes have been made on these regulations upon changing the AC 91-56A. A team that was constituted to oversee the SSIDs program was the responsibility of overseeing the RAPAASR in finding out the impact such rules has on the SSID programs (http://www.faa.gov/aircraft/air_cert/design_approvals/transport/aging_aircraft/media/faapitch.pdf).. Ageing Aircraft Safety Rule These rules came in on 2nd April 1999 as a notice number. 99-02 and was required to end on 2nd of August 1999, however, it was extended until October in 1999. This regulation has been instrumental in helping reduce the airworthiness of ageing aircraft operating as air transport by the DT analysis. According to this rule, made sure all aircrafts start operating in part 121, the United states registered aircraft operating in part 129 and all the multi-engine aircrafts to become operated in a certain scheduled operation in part 135 (http://www.faa.gov/aircraft/air_cert/design_approvals/transport/aging_aircraft/media/faapitch.pdf). Corrosion prevention and control program (CPCP) This rule requires that inspection and maintenance done on fleets that were operating under Part 121. Similarly, the US registered multi-engine aircraft operated either by the foreign company or foreign person under Part 129 and all multi- engine aircraft under Part 135. This was done for purposes of the Aging Aircraft This regulation make it possible for operators to add a CPCP program for a given period of two years, and the operation was later changed from OST to OMB (http://www.faa.gov/aircraft/air_cert/design_approvals/transport/aging_aircraft). AAP case study Case 1: Grumman Turbo Mallard Sea Plane in-flight failure and separation of the right wing On 19th December 2005, the Grumman Turbo Mallard Sea Plane came into a reality of experiencing a loss of control due to the right hand wing in-flight separation at Miami Port, in Florida, USA. This fatal and dramatic is an ideal example for the structured fatigue. In this specific case, 58 years old Grumman G73T and Turbo mallard Seaplane shed its right hand wing following a failure of the main spar. Investigation revealed that the right wing of this Aircraft separated from it due to various pre-existing fatigue cracks and fractures, which caused a reduction in the residual strength of the structure of the wing. At the time, Flight 101 was one of the scheduled passenger flights operating on a regular basis to Bimini Bahamas having 18 passengers over board and two flight crew attendants. It was certainly operating under provisions of the fourteen Code of the Federal Regulation and part 121 of the visual rules flight plan. The investigation done by the national Transportation safety Board revealed that the cause might have probably been the in-flight failure alongside the right wing separation of the right wing when in normal flight. Figure 01 showing the Crushing of Grumman Turbo Mallard Sea Plane following in-flight failure and separation of the right wing (http://www.airliners.net/search/photo.search?album=7018) Case 2: Boeing 747 SR-100 Failure of the vertical Stabilizer On 12th August 1985, Boeing 747 SR -100 experienced a loss in the control, which was attributed to the vertical stabilizer loss. Having declared an emergency, this aircraft maintained its flight for a period of 30 minutes and eventually impacted terrain in at Gunma Prefecture, Japan (mountainous region). According to an official report, this aircraft got involved in the tail-strike incident at the International Airport of Osaka way back in 1978, which had a damaging effect on the rear pressure of the aircraft. Repairs made on the pressure bulkhead failed to conform to the approved repair method of Boeing. The procedure for Boeing requires that a continuous doubler plate along with 3 rows of rivets for enforcement of the damaged bulkhead. However, the technician who performed the repairs on the given aircraft instead used 2 separate doubler plates. One had 2 rows of rivets while the other one had only one row. Because of this, the resistance of the parts was significantly reduced to metal fatigue by about 70 percent. Thus, when the bulkhead happened to give way, resulting explosive decompression caused the rupturing of the four hydraulic system lines. Following the rupturing of the control surface of the aircraft, it became uncontrollable to have the aircraft put under control. Figure 1 showing the Lost portions of a vertical fin or stabiliser, which is indicted by the hatched lines. Phugoid motion, which indicate variations in longitudinal motion centre mass of the aircraft . Figure 2 showing a lost portions of a vertical fin. The source of the image is Image Official AAIC Report on the accident. Figure 2a showing the crashing of Boeing 747 SR-100 following a Failure of the vertical Stabilizer (http://aviation-safety.net/database/record.php?id=19850812-1) Conclusion Considering the enormous cost of acquiring a new aircraft, alongside the existing limited reliable manufacturer around the world, the aging aircraft need be maintained in service for a period longer than expected. However, for this to be effective there is need to ensure stringent rules and regulations aimed at keeping them airworthy are followed to the later. This would help guarantee safety of passengers overboard References Hempe, D. W. 2008. Parts Manufacturer Approval Procedures. 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Retrieved on 24th April 2013. http://aviation-safety.net/database/record.php?id=19850812-1. Retrieved on 24th April 2013. http://www.faa.gov/regulations_policies/orders_notices/index.cfm/go/document.information/documentID/13746. Retrieved on 24th April 2013. http://www.federalregister.gov/regulations/2120-AI05/aging-aircraft-program-widespread-fatigue-damage. Retrieved on 23rd April 2013. http://www.faa.gov/aircraft/air_cert/design_approvals/transport/aging_aircraft/media/faapitch.pdf. . Retrieved on 25th April 2013 http://www.faa.gov/aircraft/air_cert/design_approvals/transport/aging_aircraft/. Retrieved on 24th April 2013. Read More