FINAL EXAM (ESSAY) - INSTRUCTOR KEY

POOL/QUESTION BANK 1 (1.1) According to the text there are numerous Service Life issues that can lead to progressive failures in structures. What are those issues and what are the two that are major concerns in an actively used fleet of aircraft? Explain the concerns. Chap 35, Page 406, speaks to this. The issues are fatigue, corrosion, wear and creep. Of these, corrosion is the biggest concern due to the fact aircraft work in harsh environmental conditions, such as marine, dust, altitudes, dirt, acid rain and other factors. Another major concern is fatigue due to repeated flight cycles e.g. take off landings, pressurization cycles, etc. As aircraft age, duty cycles must be scrutinized with inspections to find indications of fatigue as well as inspecting all repairs made in regards to fatigue cracking etc. Examples are Aloha Airlines and the recent Southwest airline fatigue crack issue occurring in flight. (1.2) According to the text, what two Service Life Issues bear extra scrutiny and investigative examination in aging or high use aircraft? Explain in detail how these issues are potential hazards. Chap 35, Page 406, speaks to this. The issues are fatigue, corrosion, wear and creep. Of these, corrosion is the biggest concern due to the fact aircraft work in harsh environmental conditions, such as marine, dust, altitudes, dirt, acid rain and other factors. Another major concern is fatigue due to repeated flight cycles e.g. take off landings, pressurization cycles, etc. As aircraft age, duty cycles must be scrutinized with inspections to find indications of fatigue as well as inspecting all repairs made in regards to fatigue cracking etc. Examples are Aloha Airlines and the recent Southwest airline fatigue crack issue occurring in flight. (1.3) Define and explain the growth phases of fatigue cracks. Chap 35, Page 407-409 speaks of this. Basically, there are three phases associated with metal that evolves from progressive fatigue to instantaneous fatigue. They are; crack initiation phase, which is microscopic, crack propagation phase, which is macroscopic, critical length stage where the structure can no longer support the load. Evidence of progressive fatigue can often be detected by seeing benchmarks and striations on failed structures. This study source was downloaded by from CourseH on :56:18 GMT -05:00 (1.4) Explain the evolution of progressive fatigue in terms of stages or phases as mentioned in the text. Chap 35, Page 407-409 speaks of this. Basically, there are three phases associated with metal that evolves from progressive fatigue to instantaneous fatigue. They are; crack initiation phase, which is microscopic, crack propagation phase, which is macroscopic, critical length stage where the structure can no longer support the load. Evidence of progressive fatigue can often be detected by markings on the failed structure called benchmarks and striations. These observations, confirmations are the disciplines of trained metallurgists. POOL/QUESTION BANK 2 (2.1) According to an Air Detective Tip, what are some of the issues and as well importance of collecting data from cockpits with analog gauges and switches? Air Detective 16: Student should provide some of the following: Obtaining pre-impact information from cockpit instruments is helpful, but not always reliable. Impact damage and