HUD Announces New Defect Taxonomy Effective January 1, 2020 Weiner Brodsky Kider PC

The resulting categorised defects are listed in Table 2. We informally validated this list by discussion with expert maintenance practitioners. This list is considered to be comprehensive for all engine blades, independent of the blade type, engine model and manufacturer. A detailed description of each defect is provided in Appendix Table A1. Then, we integrated our findings in an initial single comprehensive defect list. This list was further enhanced by our own insights gained from observation and personal communication with industry experts.

definition of defect taxonomy

The inter-relations were then identified and the causes assigned to the defects. Identification of the cause–defect relationship was done by analysis of the research literature, discussion with expert maintenance practitioners, reference to the maintenance manuals and general engineering principles. Hence, this set of relationships has a degree of validation, and provides a sufficient representation of the complexity of the real situation. Surface damages describes deviations from the nominal surface, such as roughness, waviness, lay and flaws . This may include material separation and/or loss of base material or coating .

Software trustworthiness evaluation model based on a behaviour trajectory matrix

Some find it easier to think of them as classifications. Azevedo, C.R.F.; Sinatora, A. Erosion-fatigue of steam turbine blades. Ilcewicz, L. Composite damage tolerance and maintenance safety issues. In Proceedings of the FAA Damage Tolerance and Maintenance Workshop, Rosemont, IL, USA, 19 July 2006. Surface and/or structural damage due to excessive heat, visible as stain or discolouration and, in severe cases, by loss or flow of material. The third limitation is that even though the ontology can show all potential causes and loops of causalities, it cannot describe to what extent each factor contributes towards the defect.

For example, for bird ingestion, we did not differentiate between say a sparrow and an albatross as the expected type of defect remains the same; only the extent of damage increases with increasing size of the ingested item. Another potential application is for the ontology to be used as an inspection support tool to analyse engine and maintenance history for unexpected events. For example, if it were known that an engine had suffered a bird ingestion, then the ontology could be interrogated to identify the possible defects.

Regarding productivity, manual FL obtains 3.43%/min, which improves automated FL significantly. Finally, there are no significant differences in satisfaction for both treatments. The trajectory of software behaviour is represented by a matrix and converted into a grayscale image, whose processing method is used to evaluate the trustworthiness of software behaviour more objectively and accurately.

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They developed cause-effect usability problem classification model that consists of three causal attributes and four effects attributes . However, in the absence of formal usability evaluation in OSS projects, the trigger attribute as suggested in the model cannot be sufficiently justified. Additionally, the use of pre-defined values for some of the attributes may introduce selection bias and users are likely to select incorrect values. Usability is one of the prominent software quality characteristics that measures the understandability, learnability, operability and attractiveness of the software products .

Borescopes are the most important optical aid to visually inspect the inside of the engine, which is otherwise inaccessible. Causal – Since no formal usability evaluation is usually conducted in OSS projects, usability problem triggers cannot be identified. In OSS projects, usability defects are most often reported from online user feedback facilities and results of developer black-box testing. Considering this limitation, definition of defect taxonomy instead of looking at trigger attributes, we study the failure qualifier of the problem. This information could help software developers to understand the reason why a user considers the problem as a valid usability defect. However, Keenan’s approach to classification relies on a high quality defect description which, as our earlier work demonstrates , are rarely present in open source usability defect reports.

ISO 9126 Quality Characteristics Taxonomy

What matters is that we are collecting, analyzing, and categorizing our past experience and feeding it forward to improve our ability to detect defects. Taxonomies are merely models and, as George Box, the famous statistician, reminds us, “All models are wrong; some models are useful.” Witek, L. Numerical stress and crack initiation analysis of the compressor blades after foreign object damage subjected to high-cycle fatigue. Vardar, N.; Ekerim, A. Failure analysis of gas turbine blades in a thermal power plant.

  • First, we examined the open literature on engine defects and failures, with a particular focus on engine blades.
  • The inter-relations, causal links and cascade effects lead to a complex network of defects and causes.
  • The unclear separation between the keywords can lead to misclassification of defects that will eventually affect the identification of root cause and similar resolution strategies.
  • A precise defect description is often not possible due to other factors, such as the cleanliness or discolouration of the part, the experience of the inspector and the limitation of visual inspection, without additional inspection aids .
  • Additionally, some defects are closely related and only differ in dimension, for example, their degree of depth, length or curve radius.

Each is subjective based on the experience of those who created the taxonomies. If they are used in similar circumstances, an additional benefit to having a taxonomy is that later on, test cases can be built on them. Simply put, a tester with taxonomy at his disposal has higher chances of success.

SEI Risk Identification Taxonomy

Other defects may be more apparent when the deposits are removed, e.g., surface damage. Further, the findings of the induction borescope inspection at the MRO shop determines whether or not to commit to a costly disassembly of the engine. The maintenance of aero engines is intricate and time-consuming and even one maintenance episode may be an appreciable proportion of the engine list price . Consequently, there is an ongoing need for more effective and efficient inspection processes.

definition of defect taxonomy

One of the first defect taxonomies was defined by Boris Beizer in Software Testing Techniques. It defines a four-level classification of software defects. The general goal of a defect taxonomy is to reduce the number of product defects that reach customers. Although this goal could be accomplished by implementing excessively long beta and internal testing using certain sets of customers as “permanent” beta … Mishra, R.; Thomas, J.; Srinivasan, K.; Nandi, V.; Raghavendra Bhatt, R. Failure analysis of an un-cooled turbine blade in an aero gas turbine engine. Rao, N.; Kumar, N.; Prasad, B.; Madhulata, N.; Gurajarapu, N. Failure mechanisms in turbine blades of a gas turbine Engine—An overview.

Whittaker s How to Break Software Taxonomy

The crack in turn can result in material lift-up or breaking away of a significant piece of the blade. No application of blade defects is apparent in the literature. The literature review revealed that most studies present the defects in alphabetical order and do not provide a categorisation system. Moreover, they analyse engine blade failures after a particular event has occurred. There appears to be no existing work that systematically describes root-causes of blade defects and the interrelations.

definition of defect taxonomy

Notably, the new Taxonomy removes fraud that the lender did not know or could not know about from Tier 1 and places it in Tier 4, thereby removing the requirement that the lender respond in the Loan Review System. HUD also substantially altered the definitions within each defect tier level. These new and revised definitions are broader in some cases, covering additional conduct. Similarly, the causes listed in each defect category have been substantially changed providing for additional and more specific findings in most defects. Hierarchical system of categories designed to assist in the classification of defects. They are hierarchical lists with root causes, failure signs, and other defect-related elements.

Using a Distributed Heuristic Evaluation to Improve the Usability of Open Source Software

•an evaluation of the taxonomy by practitioners to understand its strengths and weaknesses. Testing can be done without the use of taxonomies or with a taxonomy to guide the design of test cases. The Software Engineering Institute has published a “Taxonomy-Based Risk Identification” that can be used to identify, classify, and evaluate different risk factors found in the development of software systems. Key PointA taxonomy is a classification of things into ordered groups or categories that indicate natural, hierarchical relationships. A crack is often an expansion of a pre-existing defect such as a nick, scratch or gouge. Was funded by a PhD scholarship through this research project.

Aspects that can be used in forming the taxonomy

The third level is only representative as there are, for example, hundreds of objects that may cause a dent. We felt it was not useful to list all those items, which only results in a massive ontology. Likewise, we did not further split up root-causes in subcategories.

Analysis of the Textual Content of Mined Open Source Usability Defect Reports

It is often aggravated by high air temperature, humidity, moisture and contaminated environments, such as salt from sea or de-icing treatments. Maintenance activities cannot be completed without locating the set of software artifacts that realize a particular feature of a software system. Manual Feature Location is widely used in industry, but it becomes challenging (time-consuming and error prone) in large software repositories. To reduce manual efforts, automated FL techniques have been proposed. Research efforts in FL tend to make comparisons between automated FL techniques, ignoring manual FL techniques. Moreover, existing research puts the focus on code, neglecting other artifacts such as models.

Second, we proposed a new classification system for both engine blade defects and root-causes. The defects were categorised based on the type of damage, and the causes based on their nature and resulting damage. These two categorisations were combined into a blade defect–cause taxonomy.

These investigations focus on specific engine blade stages or a single, often fractured blade that caused the event to happen. Only a few attempts have been made to analyse all possible failures of engine blades. This includes research by Rao and Carter , which takes different failure modes and failure mechanisms into account, but does not further describe the defects.

A total of 41 evaluators from 26 to 55 years of age participated in the evaluation of the OSUDC taxonomy. As shown in Table 5, most of the evaluators are computing students and academic researchers, accounting for 48.8% and 29.3%, respectively. Almost 80% of the evaluators had received training or certification related to usability evaluation/ HCI/ UX. However, as indicated in Table 6, the majority of evaluators had limited familiarity in handling usability defects. Even if formal usability evaluations were to be conducted, OSS projects would still lack an effective mechanism to conduct the evaluations, mainly for two reasons.

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