Maintenance and Certification
- ISSUE 1/2011
- Copyright and Credits
- Guest Editorial
- Air Taxi Floatplane Operations Workshop Brings B.C. Operators Together
- Flight Operations
- Maintenance and Certification
- Recently Released TSB Reports
- Accident Synopses
- Regulations and You
- Debrief: From the FAA: Loose Equipment in the Flight Compartment and on Glare Shields
- National Aviation Day (poster)
- Take Five: NOTAMs
- Full HTML Version
- PDF Version
- Used Parts Obtained from Foreign Sources
- Compressor Washes—Maintaining Engine Reliability and Performance
by K. Bruce Donnelly, Civil Aviation Safety Inspector, Maintenance and Manufacturing Standards, Civil Aviation, Transport Canada
This is the latest in a series of interrelated articles addressing the maintenance of Canadian-registered aircraft and parts intended for installation thereon. This article focuses specifically on the use of used, repaired or overhauled aeronautical parts (used parts) that are obtained from foreign sources.
In recent years, we have seen an emerging trend with respect to the globalization of the aviation industry. Transport Canada has entered into aviation agreements with various States. These high-level agreements are normally complemented by subordinate agreements, such as Maintenance Implementation Procedures (MIP), which specify the requirements that must be met for the mutual and reciprocal acceptance of each party’s aircraft and parts maintenance certifications.
Consequently, Canadian operators and maintainers now have improved access to foreign sources of maintenance and used parts; however, more awareness and diligence is required by the industry with respect to verifying the specific certification requirements for used parts. TCCA is aware of circumstances where repaired or overhauled parts and components that did not actually meet the eligibility criteria were inadvertently installed on Canadian-registered aircraft.
Generally, with respect to the installation of used parts, the Canadian Aviation Regulations (CAR) prescribe that any part that has undergone maintenance must be accompanied by an Authorized Release Certificate or similar document containing a maintenance release for the work performed on that part. This requirement applies equally to privately and commercially operated aircraft. The person providing the maintenance release must be authorized to sign the release by the holder of an approved maintenance organization (AMO) certificate. When the maintenance is performed outside of Canada, the person must be authorized to sign under the laws of a State that is party to an agreement or a technical arrangement with Canada and the agreement or technical arrangement must provide for such certification. This is an important distinction; not all aviation agreements provide for such a recognition.
The installer is responsible for ensuring that a used part is eligible for installation. He or she carries out that responsibility by requesting the appropriate documentation from the supplier, establishing the part traceability to the maintainer of the used part. The installer must also ensure that the maintenance is performed by an appropriately rated AMO or foreign equivalent that is specifically approved by TCCA under the authority of an aviation agreement to certify the maintenance that was performed on the part. The installer must therefore be aware of the specific used part certification requirements that are applicable in the respective circumstances.
Although the documentation may differ in appearance and naming convention, the requirements—in terms of the part identification, traceability and certification information, that are to be recorded on the Authorized Release Certificate, which accompanies the used foreign part—are the same as those for an Authorized Release Certificate (also known as Form One and formerly known as form number 24-0078).
|Used, Repaired or Overhauled Part Certification Requirements by Jurisdiction|
|Canada||United States||European Aviation Safety Agency (EASA)||Brazil||Israel|
|Completed Form One Authorized Release Certificate with signed CAR 571.10 maintenance release||Completed FAA 8130-3 Authorised Release Certificate or maintenance release document, e.g. FAA form 337, repair station tag or work order or signed maintenance record entry||EASA Form 1 from TCCA-approved and EASA-approved Part 145 Repair Station, with TCCA approval number indicated in block 13||Completed DAC Form SEGVÔO 003 from TCCA recognized DAC Brazil AMO with specific release statement and approval number indicated in block 13||Completed Civil Aviation Administration of Israel 8130-3 form|
Used foreign parts procured from jurisdictions with which Canada does not have an aviation agreement are not eligible for installation on Canadian-registered type-certificated aircraft because these parts do not comply with the applicable regulatory requirements. Installers should first inquire as to whether an agreement exists between Canada and the country of origin. The technical agreements can be viewed on the TC Web site. In addition, installers should not rely on the mere fact that an agreement does exist; the repaired or overhauled part might still be ineligible for installation. The used part certification requirements differ by country of origin due to the differences in the respective bilateral or other technical agreements. The requirements identified in the preceding table are not exhaustive; the table is produced here for convenience to illustrate some of the differences by country of origin.
Airworthiness Notice B-073 is also a useful reference guide and provides more detailed information with respect to part certification requirements for parts obtained from different sources; however, installers should be aware that it also does not cover all of the respective agreements that are in place. Installers should consult the appropriate technical agreement and familiarize themselves with the specific used part certification requirements that are applicable in their circumstances.
Some agreements, such as the Administrative Arrangement on Maintenance between TCCA and EASA, require the foreign AMO (such as EASA-approved Part 145 repair station) to submit a supplement to their existing approved manual to TCCA for approval. The approval number must appear on the Authorised Release Certificate. If it does not, the part is not eligible for installation. Installers must be vigilant in ensuring that the organization is in fact approved by TCCA and that the approval has not expired, as the approvals must be renewed by TCCA every two years.
Installers are also reminded that where one country has an agreement with another country and one of those countries has an agreement with Canada, the terms of the agreement between Canada and that country are not extendable to the other country. For example, a country in Africa that has an agreement with EASA has the ability to issue an EASA Form 1 Authorised Release Certificate for maintenance performed on a part. The part is not eligible to be installed on a Canadian aircraft despite the fact that Canada has an agreement with EASA, because Canada has no agreement with that specific African country.
It is therefore very important for organizations that procure used parts from foreign jurisdictions to be vigilant in requesting the proper documentation from the part supplier to support the used, repaired or overhauled part installation eligibility. If any doubt exists as to whether a used or repaired part obtained form a foreign jurisdiction is eligible for installation, installers are encouraged to consult with their principle maintenance inspector (PMI) or local Transport Canada Centre (TCC) for advice.
by Joe Escobar, Editor, Aircraft Maintenance Technology (AMT) on-line magazine (www.amtonline.com). This article originally appeared in the September 2007 issue of AMT Magazine and is reprinted with permission.
Compressor washes are a routine procedure for those who work on gas turbine engines. Some mechanics might think it is just another mundane task we must do. But why do we do compressor washes? Well, the answer is more than, “because it is written into our operations procedures.” Let’s take a look at compressor washes and how they affect engine performance and life cycles.
Taking a look back at what we learned in A&P [airframe and powerplant] school, we see that thermal efficiency is a prime factor in gas turbine performance. AC 65-12A [A&P Powerplant Handbook] tells us that thermal efficiency is the ratio of net work produced by the engine to the chemical energy supplied by the fuel. The three most important factors affecting thermal efficiency are turbine inlet temperature, compression ratio, and the component efficiencies of the compressor and turbine. Other factors that affect thermal efficiency are compressor inlet temperature and burner efficiency.
Contamination to the compressor section affects the thermal efficiency, and therefore the performance of the engine. Not only does it affect performance, but damage to the blades caused by contamination can lead to engine failure.
So, what causes contamination? Well, it has to do with the atmospheric environment. The atmosphere, especially near the ground, is filled with contaminants. There are fine particles of dirt, oil, soot, and other foreign matter in the air. Because of the large volume of air introduced into engine compressors, a lot of this contamination is introduced into the engine. The centrifugal forces of the compressor throw this contamination outward so that it builds up to form a coating on the casing, vanes, and the compressor blades.
The accumulation of these contaminants reduces the aerodynamic efficiency of the blades, resulting in deteriorating engine performance. The efficiency of the blades is reduced in a way similar to the way ice buildup reduces the lift efficiency of a wing. This loss of efficiency can lead to unsatisfactory acceleration and high exhaust gas temperature (EGT). Contamination, especially in high-salt operating environments, can also lead to corrosion of the engine components.
In order to maintain engine performance and reduce the corrosive effects on the engine, the debris that builds up in the compressor needs to be removed. We do this through routine compressor washes.
So, how does a compressor wash remove contaminants from an engine? AMT talked with Bruce Tassone, president of ECT Inc. ECT manufactures R-MC compressor wash. “The chemicals in a compressor wash solution break down the organic bonds of the contaminants,” Tassone shares. “This then allows the air stream and/or the fresh water rinse to remove the contaminants out of the engine.”
The OEM [original equipment manufacturer] specifies which chemicals can be used to wash the compressor. The approved list can vary from manufacturer to manufacturer. “Some OEMs have a specific list of approved washes,” says Tassone. “Others refer to a military specification like MIL-C–85704 or set specific chemical parameters.”
Tassone stresses the importance of using proper chemicals like R-MC. “There are different parameters you have to meet with a compressor wash,” he shares. “Using unapproved engine washes could cause damage to the engine or airframe such as corrosion, acrylic crazing, hydrogen embrittlement, stress corrosion cracking, and other defects.” In order to avoid damaging the engine, be sure to use only authorized chemicals. “You should ask your supplier or overhauler for certification that they meet the engine and airframe OEM specifications,” stresses Tassone.
Premix or concentrated?
Compressor wash can come in either premixed or concentrated forms. How do you know what type is right for you? “Some customers buy premixed if they are concerned with either the labour associated with mixing and/or the quality of water they can secure,” Tassone tells AMT. “If they have space concerns, such as inventory storage, or they want to be a little more cost-effective in terms of the transportation, and they have the capacity to blend the chemical in regards to labour pool and water quality, they may tend to go with concentrate.”
Water quality is an important part of effective compressor washes. Whether it is for mixing the concentrate or for the rinse portion of the wash, proper water needs to be used. “We, as well as the OEMs, always recommend de-ionized or de-mineralized water,” says Tassone. Don’t be tempted to use tap water. Doing so can introduce contamination back into the engine you are trying to clean out.
Establishing a wash schedule
Compressor wash schedules will vary from one operator to the next. The frequency of wash events relates to the amount of contaminants being ingested into the engine.
Operating environment and the types of flight profiles both affect contaminant levels. “High cycles impact the engine,” shares Tassone. “But flight patterns also do. If you are dealing with a commuter such as a turboprop, where you are doing shorter runs at lower elevations more closely tied to the city, then your fouling curve is going to increase. If you are looking at trans-Atlantic flights, your fouling curve may not be as steep, but you may have ancillary impacts such as the inorganic and salt buildups. So you have multiple effects with respect to the engine.”
Each operator needs to develop a compressor wash schedule that best meets their operating situation. “Most operators set compressor wash schedules with regards to their specific situation,” Tassone tells AMT. “They will look at what their degradation curve is. And either individually or with us, they will do an economic analysis of what the breakpoint is for the best wash frequency, and then tie that task in to whatever would be the appropriate checkpoint in their maintenance schedule. In a salt environment, it could be a wash every day because our product has corrosion inhibitors. It could also be on up to a three- to six-month cycle.”
Tips for effective washes
Compressor wash procedures vary from manufacturer. A typical compressor wash involves three steps—a chemical wash, a water rinse, and an engine run.
After connecting the appropriate fixtures to the engine, a chemical is injected in the engine while the compressor is turned. Firms like ECT manufacture the wash equipment to conform to the OEM flow rate and pressure recommendations. This allows the chemical to be ingested into the compressor section where it breaks up the molecular bonds of the contaminants. The wash is followed by a fresh water rinse. The rinse ensures that all of the contaminants dislodged by the wash are flushed out of the engine. This is followed up by an engine run. The airflow from the engine run helps further clean out the dislodged contaminants, and dries out the engine.
Tassone shares the following tips for effective washes: “First and foremost, they should always refer to the OEM procedures, because they are engine specific. Second, products that are biodegradable and nontoxic yield high cleaning efficiency while improving personnel safety and lowering disposal costs. If solvents are used, make sure the proper collection, disposal, and government reporting are maintained. Third, we can’t emphasize enough that high-quality water, both for mixing and for rinsing, is very important. Finally, they should be using injection hardware and equipment that is approved by the OEMs or their engineering group to ensure they are getting a proper wash and not introducing FOD [foreign object damage] hazards. The mechanics should inspect to ensure all hardware is secure so that foreign objects are not ingested into the engine. Using correct servicing equipment also ensures proper pressure and flow during the compressor wash.”
Performing proper compressor washes can result in many benefits. Removing the contaminants restores engine efficiency, resulting in better fuel economy (Tassone says a 1 to 4 percent fuel savings can be realized). It also results in lower EGT, lower corrosion, and restored performance. It’s more than just a mundane task after all.
New! The Civil Aviation Safety Alert
Until recently, Transport Canada (TC) was distributing aviation safety information to stakeholders through the use of several types of documents, such as Service Difficulty Advisories and Service Difficulty Alerts. TC identified a need to consolidate these safety documents into one single document, now entitled the Civil Aviation Safety Alert (CASA).
On October 1, 2010, the CASA became the new vehicle for TC to disseminate, in a timely manner, specific safety issues to targeted stakeholders. The new CASA address various subjects such as flight operations and is not restricted to service difficulty topics.
CASAs are non-mandatory notifications used to convey important safety information and recommended action items. The information contained in CASA is critical and recipients are expected to take the CASA recommendations into consideration during ongoing operations and maintenance.
For more information, visit http://www.tc.gc.ca/eng/civilaviation/opssvs/managementservices-referencecentre-1187.htm.
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