Maintenance and Certification
- ISSUE 4/2007
- Copyright and Credits
- Guest Editorial
- To the Letter
- Winter Operations
- Flight Operations
- Maintenance and Certification
- Recently Released TSB Reports
- Accident Synopses
- Regulations and You
- The Civil Aviation Medical Examiner and You
- Flight Crew Recency Requirements — Self-Paced Study Program
- Full HTML Version
- PDF Version
- The National Aircraft Certification Branch, Project Management Division
- Why "Simple" NDT Is Not All That Simple!
The Project Management Division is the primary point of contact within the National Aircraft Certification Branch for individuals or organizations seeking type certification for their aeronautical products in Canada. These products are designed by Canadian companies, as well as foreign companies seeking to sell their products to Canadian operators. As such, the Division is the voice of the Branch on both the domestic and international stage. With approximately 22 employees, consisting of engineers and technical support staff, the Division provides a project management function for all matters related to aeronautical product certification.
The Chief, Project Management oversees five project management teams and one additional team responsible for type certificates and project information systems. The five project management teams, each led by a senior project manager, are divided by aeronautical product type, that is, large transport fixed wing, executive/business, general aviation, rotorcraft, and engines/propellers/appliances/ supplemental type certificates (STC). With dozens of certification projects running concurrently in each of the product types, each project management team will juggle several issues with many different clients on any given day.
The certification of aeronautical products is a process, and you could say that the Project Management Division is the owner of that process. Being the owner, the Division establishes, implements, manages and constantly develops the process elements and tools that are used in the complex activity known as aircraft certification. The process may start with a phone call from an operator or manufacturer, and culminate in the issuance of a type certificate for a new aircraft (the prerequisite for the aircraft to achieve its first certificate of airworthiness) several years later.
Project managers in the Division assemble and coordinate teams of technical specialists from the engineering, flight test and maintenance disciplines at Transport Canada. These specialists work with their counterparts in industry to ensure that new and modified aeronautical products comply with appropriate design standards and regulations, which is essentially what the type certificate represents. Project managers in the Division are themselves engineers with backgrounds in various disciplines, and all have experience in the design, maintenance or operation of aeronautical products. In fact, many have previously worked elsewhere in the National Aircraft Certification Branch as technical specialists themselves. This technical background is crucial for project managers, to allow them to effectively facilitate technical challenges, to formulate sensitive and effective correspondence on highly technical subjects, and to inherently understand the needs of the technical specialists within their teams.
The Project Management Division’s clients consist of the general public, type certificate and STC applicants, airlines and operators, and other divisions within the National Aircraft Certification Branch, most typically Engineering and Flight Test. As managers of the process in which these clients are key players, the effectiveness of the Division’s project managers within any given certification project depends on an understanding of a set of expectations:
- Have and display detailed knowledge of process elements and tools;
- Be a guide to technical specialists on all matters related to the certification process and project information;
- Be facilitators, as required, in technical disputes amongst internal resources or with applicants;
- Apply appropriate filtering/buffering between technical resources and applicants/operators;
- Perform technical vetting of decisions prior to delivery to clients;
- Lead the project, yet at the same time serve the needs of technical specialists;
- Proactively pursue solutions to problems (systemic or project-specific) that impact progress.
The Type Certificates & Aeronautical Products Group is responsible for the preparation of all certificates issued from the National Aircraft Certification Branch, the accompanying type certificate data sheets that define the limitations, the accompanying approved documentation for any given certificated product, as well as managing the National Aeronautical Product Approval System (NAPA). This is a national database of project information and is in fact the system from which type certificates and STCs are issued. The Aircraft Certification Regional Offices use this system as the backbone of their project management activities.
In summary, the Project Management Division within the National Aircraft Certification Branch is responsible for all process and project management matters dealing with the certification of aeronautical products at Transport Canada Headquarters. The Division plays a key role in facilitating the issuance of approvals for all aeronautical products that operate in Canada, and for Canadian products operating in Canada and abroad.
Most aircraft maintenance engineers (AME) are somewhat familiar with the term "non-destructive testing" (NDT), and know that it encompasses the penetrant, magnetic particle, eddy-current, ultrasonic and radiographic inspection methods. In many cases, AMEs also have some specific knowledge of the penetrant and magnetic particle methods, which are frequently thought of as the "simple methods" of NDT. This has mainly come about as the result of economics; both of these methods have been in use for over fifty years, are relatively cheap to utilize, and are therefore cost-effective ways of adopting a higher level of inspection for surface defects. In the aerospace industry, penetrant inspection in particular has flourished, since it answers the need for finding surface flaws in non-ferrous material, and is "simple to use." This last statement deserves some analysis in order to place the use of the word "simple" in perspective, since there are misconceptions about what the word means, and how it affects the performance of this inspection method.
We’ve all seen the advertisements for penetrant products in the aircraft maintenance trade publications, and many of us know where to find these products in our shops or hangars-especially those of us who have just determined that there may be a defect in the surface of a part we’ve just inspected visually. When we locate the spray cans, a quick read of the product labels is all that is needed to refresh the memory and proceed with making a determination of acceptance or rejection of a suspect part. What could be more helpful than a quick spray of penetrant on the part surface, followed by a short wait to allow the dye to enter the suspect flaw, then a quick wipe to remove excess penetrant, and finally the application of the developer to see if a defect indication appears? True, this might be acceptable for doing a so-called "confirmation inspection" to settle doubts about evidence revealed during general visual or detailed (visual) inspections, but it certainly won’t do for penetrant inspections called out on a work card or in the scheduled maintenance section of a maintenance manual! It’s just not that simple.
Doing it, and doing it right
Way back in 1963, Carl E. Betz wrote in the preface to his book, Principles of Penetrants, about how the first fluorescent penetrant introduced by the Magnaflux Corporation in 1942, proved to be a simple solution to finding surface defects. The reason was that there was only one kind of penetrant! Mr. Betz then went on to describe (in over 450 pages of text) how complexity was subsequently designed into the process. Granted, the introduction of a large selection of different kinds of products contributed to this complexity, but there was also the small matter of recognizing how each of the various processing steps made it absolutely imperative to develop a disciplined approach during their application. This really became the hallmark of the penetrant method of inspection: the ability to stick to the precise requirements of each step of the process. Take the pre-cleaning of parts that are about to be inspected, for instance. There are still arguments about how best to achieve this! The objective is to ensure that whatever cleaning approach is used, it should not introduce factors that would prevent the penetrant from entering the surface defects that must be found. Flaws open to the surface can easily be contaminated by foreign material introduced by cleaning! So we need to think carefully about the kinds of cleaning products we choose, and the means for applying the necessary actions to remove surface contaminants. More than one defect has been missed because the cleaning actions chosen were not the right ones, and succeeded in blocking the flaw opening. And what about the possibility of contaminating a part by using red colourcontrast dye penetrant instead of the fluorescent penetrant called for in the inspection task? For final aerospace inspection applications, only the fluorescent products should be used. The red dye products may not be sensitive enough to find small flaws, and once trapped inside of a potential defect, they can reduce or eliminate the ability to find that defect using fluorescent products.
The disciplined approach may be somewhat less subject to error when we talk about parts being inspected in quantity through the use of a penetrant production process. Here we have the benefits of more controls being put in place by whoever establishes the various parameters for the process. The theory is that all parts will receive the same treatment, with little chance of process variance. Sounds simple, until one looks at the large number of variables that can affect each step of the process. How well-trained are the operators? Do they understand and practice the discipline of following the process instructions? Are the work areas free from potential contaminants? Is the timing of each step carefully adhered to? Does the quality system governing the operation function well at all levels? It can happen that persons doing the work do not even know (or care) what types of penetrant products they are using, or that nobody in the shop has been made responsible for monitoring cleanliness (including taking out the garbage!). Or what about an operation where the quality control measures being practiced by the workers are of a different standard than those prescribed by the company quality system? Believe it or not, sometimes the workers apply a higher quality standard than that practiced by the managers!
Simple it isn’t
It all starts with the regulations governing the application of NDT. They require that persons doing penetrant inspections must be trained and certified to rigid standards designed to instill a disciplined approach to doing the work. They also demand that inspection tasks must clearly state what is to be inspected and which procedures are to be followed. The work itself must be done under controlled environmental conditions to ensure that the parts and the penetrant materials are not contaminated. Finally, there must be accept/reject criteria for the parts being inspected to reduce the chances of rejecting parts unnecessarily and to ensure that parts being returned to service will not fail prior to being reinspected.
Certification of penetrant inspectors involves provision of a training program, including theoretical and practical training objectives. Candidates who successfully pass the necessary examinations, and obtain a minimum level of work experience, may be certified to specified levels of expertise. Additional training and work experience will permit certification to higher levels, eventually including the authorization to write the actual inspection procedures. The procedures for doing most penetrant inspections are already available in various recognized industry standards, but where the inspection method is being applied to portions of a large assembly, there must be well-defined steps stating the exact areas to be inspected. Simply calling up the inspection method in accordance with an industry standard will not do!
Most difficult, is the matter of controlling the environmental conditions under which inspections are done in situ. The AME will be challenged to meet the need for maintaining cleanliness and controlling the visible light levels to avoid detracting from the quality of the inspection process, especially when using fluorescent penetrants in areas not designed for doing these kinds of inspections. It usually means having to erect a temporary (visible) light-blocking enclosure, large enough to permit adequate shielding of the area and light adaptation by the operator. The tendency is often to convince oneself that the background lighting is not serious enough to detract significantly from doing the black light inspection! In one case, this problem actually arose on a penetrant production line. Radical upgrading of the entire penetrant process resulted in the introduction of computer terminals in the final inspection areas. It was discovered that the background lighting from the computer screens, coupled with the light colour of the computer monitor casings, introduced unacceptably high levels of visible light (rest assured, this is not why so many computers are now coloured black).
Flaws vs. defects-accept or reject?
You’ve just finished applying the developer to the part, and have waited the agonizingly-long time of 20 min, so now you’re ready to commence the inspection with your trusty black light! Are you confident that the light is not producing too high a level of visible light? And is there the required intensity of black light? A quick perusal of the light intensity check records should dispel any doubts (of course the intensity checks were done!). A careful look at the part reveals a fluorescent indication, so now the fun begins. The aim is to confirm whether the indication can be interpreted to be a defect. Careful handling of the evidence will permit this determination to be made. It means having to use just the right amount of penetrant/developer removal skills, so that the surface is prepared to permit "redevelopment" of the indication. Too much removal, and the indication may be lost (thus making it necessary to effectively redo the entire inspection procedure). The idea is to be able to redevelop the indication by re-applying a light coating of developer and watching to see how quickly the indication reappears.
If it is hard to redevelop an indication, it could mean that the flaw is not a defect (i.e. does not warrant rejection of the part). Flaws frequently do not have sufficient depth to permit storage of enough penetrant. Only defects permit redevelopment of an indication, when stored penetrant repeatedly makes its way out of the defect to the surface. We’re not only talking about cracks here, but other anomalies, such as corrosion pits or laps, as well. None of this is simple! Years ago, a jet trainer lost its horizontal stabilizer when a critical (aluminum) structural fitting failed in flight. Subsequent penetrant inspections of other aircraft in the fleet revealed at least one other defective fitting. During the analysis of this fitting, other inspectors working at a different location declared the part defect-free! Subsequently, much was learned about how difficult it can be to duplicate test results. It all had to do with discipline, patience and working with an open mind.
What ultimately makes things a lot easier is the availability of accept/reject criteria. For penetrant inspections, this usually means a statement, such as "no cracks allowed." Of course, if other anomalies exhibiting defect-like properties are found, they need to be addressed in some manner as well. This is usually achieved by documenting the findings using text and illustrations (the so-called inspection report), and passing this information on to a higher level. Frequently, reinspection by using penetrants, or by some other inspection method, will enable a final decision to be made.
Report the findings!
For most AMEs, "doing the paperwork" is often the hardest part of the job. NDT is no exception. We would all prefer to continue getting our hands dirty and leave the administrative duties to someone else. This attitude persists despite the knowledge that, without a record of the inspection results and the correct disposition of the defective parts, it is possible that such parts will find their way back into service. Fortunately for the NDT specialist, there is often a reporting form provided as part of the inspection procedure. This form should describe (with the aid of diagrams, if necessary) the nature of flaws or defects found. The customer certainly appreciates having a record of the work done! Reporting should follow established company procedures to ensure that the information provided is clear and accurate. A system that identifies who did the work, and gives a clear indication of acceptance or rejection of a part, are of paramount importance.
Use the method wisely
From the above, it is clear that the use of penetrants requires sound judgement. To do a confirmation inspection may be alright in many cases, but can cause problems if the area where red dye-penetrants are being applied is also being inspected by subsequent use of fluorescent penetrants. Red dye, as a potential contaminant, therefore, goes from being an asset to becoming a liability. More significantly, the temptation to push penetrant inspection to the limit as a "simple" inspection method, invites disaster. Allowing its use for final inspection on aerospace equipment, by AMEs who are not certified to the appropriate levels, or who are inadequately supervised during its application, likewise invites major trouble. If failure of a critical aircraft component occurs because of a "false call" following penetrant inspection, and it is determined that the inspection was carried out by unauthorized persons, regulatory investigation may be the outcome. The wise application of this inspection method will be ensured as long as it is given the same status as the other NDT methods, by those who call up its use, those who supervise its application, and those who do the work.
Call for Nominations for the 2008 Transport Canada Aviation Safety Award
Do you know someone who deserves to be recognized? The Transport Canada Aviation Safety Award was established in 1988 to foster awareness of aviation safety in Canada, and to recognize individuals, groups, companies, organizations, agencies or departments that have contributed to this objective in an exceptional way.
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