Thursday, September 18, 2014

Blog #6 Wrapping up my project with a conclusion.




Conclusion
            The end state is whether we have to live with aircraft structural mishaps and for the time being yes.  Aircraft have come a long way.  Engineers continue to develop better products, with greater physical properties that will allow us to live with aircraft structural issues and even though we don’t like it, it will be able to control.  After these issues are further conquered, the FAA will continue to make the industry one of the strictest to preserve life and the machines. Aircraft mishaps do happen like the two mentioned accidents, but if the industry is refined then the rate of structural mishaps will continue to slowly subside.  Through the assistance of experienced investigators and their data collection processes, it will allow for refinement of the industry.  This refinement, will allow for the death toll of passengers caused by air mishaps to steadily fall (Rodrigue, 2013). 
            Since 1918 it has been conclude by the Aircraft Crashes Records Office (ACRO), located in Geneva that most mishaps were caused by humans (67%), technology (20%), and the last 13% by atmospheric conditions that resulted by weather.  Respectively, 50% off all accident took place within 10 km of the airport of which the aircraft took off from and 21% was a result of the aircraft landings.  1970 was a milestone for the aviation because before 1970 air travel was on the rise and proportionality so was mishaps.  After 1970, with the number of air travel being substantially higher, fatalities decreased rapidly.  The results of all this is due to aircraft design being better, improved training for aircrew, advanced control and navigation systems, to include comprehensive accident management teams who strive towards identifying all probable causes to conclude strategies towards mitigation (Rodrigue, 2013).
References
Rodrigue, J-P (2013), The Geography of Transport Systems (3rd ed.). New York, NY: Routledge.

Friday, September 12, 2014

Blog #5; Discuss Two Accidents Pertaining to your Subject; Structural Failure

Aircraft Mishap #1: Stress Failure Suspected in Air Mishap
On February 25, 1989, at 1:34 a.m., United Airline flight 811, a Boeing 747-100 departed Honolulu International Airport enroot to Auckland, New Zealand with 336 passengers and 18 crewmembers on board. At Approximately 2:29 a.m., flight 811 made an emergency landing back at Honolulu airport with a gapping 10 by 40 foot hole on the right side of the aircraft towards its nose. This aircraft that Boeing had designed was meant for a long life of service with structural integrity in mind (Stress failure suspected in air mishap, 1988).

Reports came back that passengers had heard sounds of hissing (escaping air) coming from that side of the aircraft, when suddenly a large portion of the aircraft ripped away taking the passenger in those seats with it. Approximately 9 passengers got sucked out and fell 5,500 meters to their death in the Pacific Ocean. By the time the aircraft had landed, out of the four engines, 2 remained and 14 other passengers sustained injuries (Stress failure suspected in air mishap, 1988).

After the initial reports, investigators from the National Transportation Safety Board (21 member team with 2 Boeing experts) were still not sure what exactly happened but they were leaning towards structural failure. The root cause could have been stress fractures compounded by maintenance personnel’s doing repairs in that since the rip of the skin appear close to a fresh rivet line.  A service difficulty report was filed with the FAA from United on this particular aircraft and it cited that the 19 year old aircraft after a recent inspection had found corrosion and cracks near number 3 engine pylon (Stress failure suspected in air mishap, 1988).


Figure 1. The color picture depicts United Airline flight 811, a Boeing 747-100 safe on deck with a 10 by 40 foot gaping hole in the right forward portion of the fuselage. Adapted from “Stress failure suspected in air mishap.” 1989, The Windsor Star, Copyright 1989 by The Windsor Star.

Aircraft Mishap #2: Roof Ripped Off Jet in Apparent Structural Failure; Flight Attendant Lost, 61 Injured

            On April 28, 1988, Aloha Airlines flight 243, a Boeing 737-200 took off from Hilo to Honolulu International Airport with 95 passengers on board. When the aircraft had reached 24,000 feet altitude, and leveled off, the upper forward portion of the fuselage ripped and tore itself free from an apparent failure of the structured aircraft. During the chaos that ensued, one flight attendant, Mrs. Clarabell Lansing was sucked out of the aircraft when pressure broke and fell 24,000 feet to her death below in the Pacific Ocean (Parker, 1998).  
           
            That was not the only issue that the pilots dealt with while trying to maneuver the aircraft into Maui; an engine fire broke out as well while they descended and landed safely at the airport. In total, 61 out of the 94 passengers on board sustained injuries and only one was in critical condition (Parker, 1998).  
           
            The Boeing 737-200 has an overall length of 100 feet and the hole ripped a huge 20 by 11 foot hole in the top of the aircrafts fuselage. The NTSB describes the aircraft looking like a convertible with wings. Their predication was that the aircraft had suffered from numerous small cracks in the skin and fuselage or be a result of metal fatigue.  The investigation began and they found out the Boeing had put out a bulletin three months earlier for an inspection of the upper-fuselage around panel joints for cracks. The FAA stated, “If the cracks suddenly joined together…extensive structural damage and rapid depressurization of the plane could result.” The bulletin was put out for the older 291, 737-200 with more than 30,000 landings (Parker, 1998).

            Flight 243’s aircraft was number 152 in production and the second highest aircraft with the most landings. Aloha flights make a substantial number of landings since they make nonstop commuter flights around the island. Plane number 152 had made over 89,193 landing in 35,310 flight hours. The 19 year old plane pulled up nothing that was out of the ordinary and investigators conclude with structural failure due to fatigue (Parker, 1998).



Figure 2. The color picture show Aloha Airlines jet with a large section removed from the roof of the fuselage, in Hawaii after an emergency landing from 24,000 feet. Adapted from “Roof Ripped Off Jet in Apparent Structural Failure; Flight Attendant Lost, 61 Injured: [FINAL Edition].” By L. Parker, 1988, The Washington post, Copyright 1988 by The Washington Post Company.

Reference

Parker, L. (1988, Apr 30). Roof ripped off jet in apparent structural failure; flight attendant lost,
61 injured. The Washington Post (Pre-1997 Fulltext) Retrieved from http://search.
proquest.com.ezproxy.libproxy.db.erau.edu/docview/307009366?accountid=27203

Stress failure suspected in air mishap. (1989, Feb 25). The Windsor Star Retrieved from http://
           search.proquest.com.ezproxy.libproxy.db.erau.edu/docview/253750800?accountid=27203

Thursday, September 4, 2014

Blog #4; Chapter 8 Structural Materials and Characteristics of Fire



            For this week’s assignment we had to either review the chapters assigned to up or Air Detective tip #14. I decided to choose chapter 8 because it is relatively associated with my topic of structural failures. When broken down to the materials utilized for building an aircraft, engineers and designers have to take in the ideas of what materials to use and specific areas that high temp materials will be utilized. Aircraft materials that are commonly utilized with aircraft construction have certain melting points and an overall temperature range that has to be adhered to. Below in Figure 1, is a reference chart of these common metals.

Figure 1. Melting Points of Common Aircraft Materials Utilized for Aircraft Construction. Adapted from “Fire Investigation.” by  R. H. Wood and R. W. Sweginnis, 2006, Aircraft accident investigation, 2nd ed., p. 67. Copyright 2006 by Endeavor Books.

Aircraft Materials

            As aircraft over time have been developed to withstand the structural forces associated with flight, a need for metals to withstand the speed and temperatures associated and thus a melting point must be higher. The author Pol Duwez (1954) stated, “This immediately imposes a drastic limit on the possibilities. Of the 92 natural elements, not more than 20 have melting points above 3,000 degrees” (p. 100). He continued to test his theories and concluded that the intrinsic property of metal cannot be altered be any means, the elements melting point is set. But, by creating chemical compounds, this could be achieved and oxides and carbides would be used for their property includes a high melting point. Now for aircraft construction theses chemical compositions would have to retain all physical strength and be chemically inert to high temperatures (Duwez, 1954). 

Composite Materials

            A composite material is the end result, a combination of different materials (non-homogenous) that make it stronger then separate individual materials. When the materials are combined especially in any metallic alloys, each separate material in the combination will retain its mechanical, chemical and physical property making it stronger, stiffer and lighter. This combination becomes a matrix and reinforcement. But composites due tend to leave engineers with headaches because of their high costs (Campbell, 2010). With those high costs, different attributes of materials to make up the composites that engineers are picky over, such as; elasticity and overall stiffness.  The overall shape and genetic makeup of the composites utilizes does help save costs though because they are well suited for certain environments and the end buyers (Michaels, 2013). 

            The two main elements that make up current aircraft structure for composites are carbon fiber and fiberglass. These two items can be utilized to make up a sandwich construction of layered non metallic or metallic core. But, it can be utilized in conjunction with each other or separately. When utilized, the aircraft becomes stronger and is more susceptible to withstand higher temperatures of fire, but at 1,200 degrees Fahrenheit it will melt. Regardless, the actual reaction of carbon fiber to fire will be depended on the resin (resin burn point is 1,100 degrees Fahrenheit or less) utilized to bond the fibers. In accordance with the authors, Wood & Sweginnis, (2006) “The temperature at which liberates the fibers or reduces their structural integrity…a characteristic frequently considered proprietary among manufacturers” (p. 66).Since it pure carbon, the fibers will melt but in general it will not decompose further. To understand more of what leading builders, Boeing and Airbus are doing to bring their jumbo jets into the future, please see figure 2 (Wood & Sweginnis, 2006).  


Figure 2. The picture depicts leading manufactures, Boeing and Airbus with their new class of jumbo jets and the genetic makeup of their fuselage (structure). Adapted from “Their New Materials: Using the latest alloys and composites is only part of the answer for today’s manufacturers.” by  D. Michaels, 2013, The wall street journal, Copyright 2013 by The Wall Street Journal.

Aluminum Alloys

            Most of aircraft taking to the skies today, their structures are comprised of 95% aluminum alloy and 5% zinc or copper and other small amounts of trace elements. When thinking about the chemical properties of the aircraft structures, the alloying elements, associated stress on the structure, exposure time, the overall temperature and the configuration (cast structure/heavy forged vs. thin layers of paneling) will determine how it will behave in a fire(Wood & Sweginnis, 2006). 

            Initial heating.   Aircraft strength can be severely jeopardized when exposed to heat. Regardless if the fire was a slow burning one that started in the cargo hold, thriving for one of the elements of fire (oxygen, fuel and heat), or a violent high temperature fire, it’s only a function of time. Time of exposure is only a guess of an assumption that engineers can determine when generating the correct chemical composition for aircraft structural materials. Testing the alloy for hardness and make temperature calculations, allows for them to predict the function of hardness loss over the specified alloy to be utilized (Wood & Sweginnis, 2006).  

            Eutectic melting.  Eutectic melting is when any of the alloying metals or other mixtures yield their lowest melting point, but some of the chemicals in the metal mixture remain a solid while the rest become a liquid (Eutectic, 2011). Once this point is reached and the alloy is extremely stressed, the “broomstraw effect” takes place. This phenomenon will resemble a green stick fracture of a bone because the fibers in the metal will show signs of delimitation in the failed area along the grain boundaries.  At the accident site, the investigator could determine that the stress was result of the impact and heating was prevalent from an in-flight fire. If a part or component is under a high stress load during the flight, heated then the “broom straw” fracture could not be 100% presumed by the investigator to prove that an in-flight fire occurred. 890 degrees Fahrenheit is aluminum alloys eutectic melting point (Wood & Sweginnis, 2006).  

            Melting.  During an accident investigation, the investigator could be mislead by structural bending of aluminum alloys because at 850 degrees Fahrenheit, it becomes plastic and will begin sagging at post impact fires. If the fire is burning hot enough, around 1,175 degrees Fahrenheit, aluminum alloy will liquefy and at this point the molten remnants will follow either gravity or if the plane is still in the air, the slipstream, see Figure 3. Investigators would be able to determine the casual factors of molten aluminum in the slipstream because tiny droplets will impinge on the structure of the aircraft. For gravity now, aluminum droplets will be larger than that of what slipstreams do (Wood & Sweginnis, 2006). 

 
Figure 3. Temperature Ranges of Metals and Aftermath Appearance. Adapted from “Fire Investigation.” by  R. H. Wood and R. W. Sweginnis, 2006, Aircraft accident investigation, 2nd ed., p. 68. Copyright 2006 by Endeavor Books.

References

Campbell, F. (2010). Structural composite materials. (p. 1). Materials Park, OH: A S M International. Retrieved from http://site.ebrary.com.ezproxy.libproxy.db.erau.edu/lib/
            erau/docDetail.action?docID=10439480
Duwez, P. (1954, September). High temperatures: Materials. Scientific American, 191(3), 
            98-106. Retrieved from http://www.nature.com.ezproxy.libproxy.db.erau.edu/
            scientificamerican/journal/v191/n3/pdf/scientificamerican0954-98.pdf
Eutectic. (2011). In The American Heritage Science Dictionary. Retrieved from http://
            ezproxy.libproxy.db.erau.edu/login?url=http://search.credoreference.com/content
            /entry/hmsciencedict/eutectic/0
Michaels, D. (2013, June 17). Their new materials using the latest alloys and composites is only part of the answer for toda'ys manufacturers. The Wall Street Journal, Retrieved from http://online.wsj.com/news/articles/SB10001424127887323844804578530982555671760
Wood, R., & Sweginnis, R. (2006). Aircraft accident investigation. (2nd ed., pp. 61-74). Casper, WY: Endeavor Books.

Friday, August 29, 2014

Blog #3; Addition to Chapter 21 and AD #13, Review http (link) in citation for an interesting review on tolerated fatigue damage

         
 Articles

           Article 1: If you wish to view a great free article; copy the following link, paste it in your browser and enjoy. http://www.skybrary.aero/index.php/Ageing_Aircraft_-_Structural_Failure

           Article 2: Enclosed is a pretty impressive article on how we live with structural fatigues and damages to our aircraft. Follow along with the author Jaap Schijve by highlighting:  http://ac.els-cdn.com/S0142112308001461/1-s2.0-S0142112308001461-main.pdf?_tid=49af11ea-2fe1-11e4-b9f1-00000aab0f01&acdnat=1409360717_363e7907ce7a35b3b440ca7e8ffd8204. Its going to ask you to purchase but if you log on to ERAU, you will be able to view in the Hunt Library. 
     
Reference

Schijve, J. (2008, April 28). Fatigue damage in aircraft structures, not wanted, but tolerated?. International Journal of Fatigue, 31(6), 998-1011. Retrieved from http://ac.els-cdn.com/S0142112308001461/1-s2.0-S0142112308001461-main.pdf?_tid=49af11ea-2fe1-11e4-b9f1-00000aab0f01&acdnat=1409360717_363e7907ce7a35b3b440ca7e8ffd8204

SKYbrary.aero. (2014, April 1). Ageing aircraft - structural failure. Retrieved from http://www.skybrary.aero/index.php/Ageing_Aircraft_-_Structural_Failure

Blog #3; Chapter 21 review and Air Detective Tip #13



            For this week blog, I have been tasked with choosing one of the chapters out of my text book titled: Aircraft Accident Investigation, second edition, written by Richard H. Wood and Robert W. Sweginnis. Also, I have to discuss air detective tip #13 and post a relevant article on my subject.  For this task I have chosen to discuss chapter 21, Operations and Maintenance. This chapter is very interesting because the analytical aspect and comparisons of my subject, Structural Failures.
             
            This chapter is broken down into three subjects and the authors surmised, Wood and Sweginnis (2006), “MAN-MACHINE-MEDIUM approach” (p. 165).  Each of these areas covers different analytical aspects of an aircraft mishap investigation. Under the first part “MAN,” it takes a deep look into the certification/qualifications of all aircrew that were aboard the aircraft at the time of the accident. “MACHINE,” breaks down the facilitated maintenance plan of the aircraft, the state of the aircraft and where it was worked on before the accident.  Finally, “MEDIUM” is split into two areas of concern, operations; who and how the pilot flew and operated the aircraft, while maintenance covered the initial status of the aircraft before the accident (Wood & Sweginnis, 2006).  

Operations
             
            At first, the inspector needs to gather all the information off of the important documents. These documents would include licenses, medical certifications and if applicable, logbook. Since these are labeled as perishable items, they need to be collected as soon as possible. Other items for collection could include but not limited to: flight manuals, plans, check-lists, charts and maps. All of these collected items could help paint a picture for the investigator as to how the pilot was physically, overall experience and if he or she was actually qualified to operate and fly that aircraft (Wood & Sweginnis, 2006).

Procedures
             
            Every company has a set of protocols that spells out what and how the pilot will be operating the aircraft. With this they are able to track, follow and train their pilots to ensure that they stay current in Federal Aviation Agency (FAA) guideline. But, not all companies follow these regulations and might have become indolent. As a mishap investigator, areas of focus need to be in the following areas: training and competency, flight data, communication and summation of the flight history that took place (Wood & Sweginnis, 2006).
           
            Training and Competency.  Everything is dependent on how the aircraft was actually operated. If the pilot was operating the aircraft for company transport or commercial paints a good picture. All pilots should be current and in compliance with both company training regulations and Federal Aviation Agency (FAA) training requirements. Investigators should look up previous grade sheets from simulator training and instructor pilot remarks. While doing this, the instructor could be asked for a better understanding of the pilot’s overall competency to operate the aircraft. Without the help of the instructor, most companies do not keep logs or records of all their pilots’ competency reports (Wood & Sweginnis, 2006).
             
            Flight Data.  Determining the load plan of the aircraft needs to take place. Investigators can collect the flight manifest of the passengers and cargo on the plane and statements from the ground crew who actually loaded the aircraft. By doing this, the gross weight (GW) and center of gravity (CG) can be calculated. Once calculated, it can be determined if it’s a causal factor of the accident, it would back up why the aircraft crashed shortly after takeoff. If not, one can assume that the load plan was within limits (Wood & Sweginnis, 2006).  

            Now that the load plan is determined, the file flight plan from the FAA can be copied. Air-to-ground communications can be factored as to where the plane was going, deviations from the flight plan, and what GPS system was utilized. A step by step approach can be determined of the course of action the pilot lead the aircraft on (Wood & Sweginnis, 2006)

            Communication.  Transcripts from the FAA can be obtained to determine any causal factors. Different frequencies could have been utilized and so a review of all relevant ones will be necessary. Also a copy of the tape can be obtained to see if any other noises or data was transmitted before/after the transcript took place. It might be strange to think that all this in necessary but to a trained ear, it can paint a clear picture of the situation. But, the FAA has all their tapes on a 15 day cycle and so you have to request hastily otherwise the tape could be recycled. Tapes and transcripts allows for a pretty accurate timeline because every time the pilot keyed their microphone, its recorded based on time (Wood & Sweginnis, 2006)

            Flight History.  Under the active operation investigation, a detail flight history of the accident is created to be submitted into the report. All the facts gathered from the beginning of the flight to the accident are logged in chronological order with the help of all other investigators. This detailed flight history is only of actual facts and not the detailed analysis that one might think it’s used for (Wood & Sweginnis, 2006). 

Maintenance

            The maintenance of the aircraft is paramount when determining the causal factors of the mishap. A thorough investigation of the life of the aircraft is going to be conducted to figure out if it complied with the strict requirements of the FFA and manufactures maintenance protocols. With this, applicable service bulletins and directives will need to be gathering from the manufacture and FAA. Going through the aircraft data book will depict the maintenance that was conducted on the aircraft in a detailed chronological listing (Wood & Sweginnis, 2006).

Aircraft Specifics

            Aircraft Titles.  A title search is paramount just like requesting a Carfax on a used car. This will determine if the aircraft has changed hands over time. The title and serial numbers are the only important data to research because registration numbers changes over the course of its age. The FAA can assist with the search to determine the aircraft's lifespan and can look up if all service directives and bulletins have been complied with because that is a mandatory reporting procedure to the FAA (Wood & Sweginnis, 2006)

            Data Books.  Next all of the data books, service records and logs will need to be collected and gone through. This will determine if required airframe inspection and maintenance intervals were complied with. Engine logs will have entries of all hourly inspection intervals conducted, rework, repair and modifications performed. Shop service records or aircraft discrepancy books will have all the daily maintenance performed on the aircraft logged. Here any major structural, hydraulic, or corrosion discrepancies will be annotated and either be job complete, awaiting parts or awaiting further re-work. These work orders will paint a clear picture of the airworthiness, overall condition and life of the aircraft (airframe). In my previous blog, I covered the general inspections of the type of materials utilized and the effects of corrosion degradation. Included with the data books are also going to be the most up to date weight and balance of the aircraft too (Wood & Sweginnis, 2006)

            Reports.  Mandatory reporting of serious malfunctions, discrepancies or defects must be reported to the FAA, in the United States. In the Service Difficulty Reports (SDR), which is maintained by the operator with a filed copy to the FAA, is logged on the aircraft specific serial number.  In accordance with Wood and Sweginnis (2006), “In the United States, the FAA maintains two computer files that are accessible and potentially valuable to the aircraft accident investigator” (p.168). The two files are Accident/Incident files which covers if the aircraft was in a reported accident and the SDR files covers any logged incidents or component failures. SDR files are viable even though only an average of 15% gets reported (Wood & Sweginnis, 2006).

            Maintenance Outsourcing.  As the aviation industry continues to grow, maintenance outsourcing has been a problem because owners of the aircraft usually don’t perform their own maintenance. If the respected aircraft needed some type of maintenance to be performed such as an engine overhaul, the aircraft would be brought to that respected profession. From the beginning till now, licensed Airframe and Power-plant (A&P) mechanics have performed the maintenance on any type, model or series of aircraft. If in individual possessed an A&P license, it was good for their entire life time and that is where the problems began because there is no way a mechanic can stay current on all aircraft (Wood & Sweginnis, 2006)

            Aircraft mishap began to occur and still occur due to maintenance outsourcing. It’s a traceable accident that the FAA has kept an eye open for. Items such as wrong parts installed, incorrect maintenance procedures/inspections, and rush maintenance are to blame. To help with the overwhelming issue the FAA foresaw, all major inspections and overhauls must be accompanied by the operator of the aircraft to ensure that the stringent maintenance procedures are adhered too, otherwise the FAA will hold the operator responsible for any complaints or accidents. The FAA released a statement back in 2004, that the authors Wood and Sweginnis (2006) stated, “Air carriers do not lose responsibility for their independent contractors’ regulatory violations simply because the independent contractor is independently certificated by the FAA” (p. 169). Since this is a global issue, agreement on maintenance standards should be standardized on who will be providing the certification, inspections and overall enforcement of all maintenance. Outsourcing is here to stay and will not be going anywhere, anytime soon (Wood & Sweginnis, 2006)

Air Detective Tip #13

            Basically, the air detective tip #13 is in direct correlation to chapter 21 that I surmised above. It gives a detailed checklist of all the items that an investigator will need to collect from the accident site, FAA and National Transportation Safety Board (NTSB). The investigator will need to read, interpret them and secure them so that no others could possibly be tampered with.  These items collected will help figure out what the cause of the accident might have been and could possibly lead up to preventing further accidents from this cause (Lawin). 

References

Lawin, R. (n.d.). Air detective tip 13 for aircraft accident investigation. Retrieved from https://erau.blackboard.com/bbcswebdav/pid-15078061-dt-content-rid-29793014_4/institution/Worldwide_Online/SFTY_UG_Courses/SFTY_330/Air_Detective_Tips/AirDetectiveTip13_0911.pdf 
Wood, R., & Sweginnis, R. (2006). Aircraft accident investigation. (2nd ed., pp. 165-169). Casper, WY: Endeavor Books.