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MARPA Air Carrier Committee Seeks Clarification on post-AD PMA Parts

The MARPA Air Carrier Committee, led by Michael Rennick, Delta Air Lines Component Engineering Manager, is hard at work supporting PMA users and MARPA members.  In June, members of the MARPA Air Carrier Committee, including Air Wisconsin, American Airlines, Republic Airways, US Airways, Air Canada, and Delta Air Lines, submitted to the FAA a letter seeking clarification on the issue of PMA parts that are alternates to post modification Airworthiness Directive (AD) related parts.

This clarification is necessary because confusion has sometimes arisen between operators and local regulators over the need for an Alternative Method of Compliance (AMoC) for post-modification AD-related PMA parts.  It is the position of the MARPA Air Carrier Committee that if the PMA is an alternate to an OEM part contained in a post-AD configuration, no such AMoC is required.

When a PMA is issued for a replacement part for a post-modification AD-related OEM part, it is uncommon for the PMA applicant to request an AMoC to the AD, or for the FAA to note the AD on the PMA approval.  This makes some sense because a post-AD PMA part is inherently an alternative method of compliance without being described as one. However, an issue arises because many ADs call out only the modified OEM part as a means of compliance.  Because ADs are technically regulations under Part 39, alternate approvals such as PMAs might not satisfy the regulatory requirement and so an AMoC may be required.

It would be beneficial to both operators and PMA manufacturers to see this change.

The OEM part is the source of the condition giving rise to the AD.  The post-modification part must resolve the condition in order to satisfy the AD. During the PMA approval process for the same part, the AD is also taken into consideration..  In order to receive PMA approval, the subject PMA part must resolve the condition resulting in the AD, just as the post-modification OEM part does.  There should be no need to call out an AMoC for the PMA part related to the AD; the underlying condition that necessitated the AD has changed because the approved PMA part has replaced the post-AD OEM part. The PMA should be a valid terminating action for the AD.

There are limited circumstances in which this reasoning may not apply, but these limited circumstances are not the subject upon which the Air Carrier Committee seeks clarification.  For instance an AMoC may be necessary in a scenario in which an AD applies to a higher level component or assembly. In this scenario the PMA replacement for the OEM part may not address the AD for the higher assembly because it is a replacement at the piece-part level, and thus an AMoC may be necessary for the higher assembly.

Generally, however, an AMoC should be inherent in an approved PMA part and therefore unnecessary as a separate approval.  This is the policy clarification that the Air Carrier Committee seeks in the form of a formal FAA communication.  If an approved PMA part is a replacement for a post-AD OEM part, the FAA’s policy should clearly state that the approved PMA is a terminating action for the AD and that no additional approval or discrete AMoC is required. In the alternative, an AMoC could automatically issue for each post-AD PMA to show compliance.

MARPA greatly appreciates the Air Carrier Committee’s work on this project.  MARPA will be working with the FAA and the Committee to determine whether future ADs will list an approved PMA as a valid terminating action, or whether an automatic AMoC should automatically issue with a PMA to show compliance to the AD, or some other solution is desired.  We will keep our members apprised of these developments.

If you are a MARPA member air carrier and want to get involved with the Air Carrier Committee, please email Katt Brigham at katt@washingtonaviation.com.  If you are not yet a MARPA member but would like to get involved, visit our membership application page.  MARPA membership is free for air carriers!

Edited to clarify that ADs are regulations and identify possible solutions to the issue raised in the Air Carrier Committee’s letter.

Mike Rennick Talks PMA Reliability at Delta Air Lines

Those who attended MARPA’s inaugural European conference last month in Istanbul were treated to an excellent presentation by Delta Air Lines Manager of Component Engineering and MARPA Air Carrier Committee Chairman Mike Rennick on the impressive reliability benefits of PMA parts in Delta’s fleet.

As many know, Delta operates a very diverse fleet of aircraft, which are on average older aircraft than many other carriers’ fleets.  Yet Delta also operates one of the most reliable mainline fleets in the world.  In 2014, Delta had an impressive 169 maintenance cancellation free days; a metric that has improved each of the last three years.  Mr. Rennick pointed out that one of the important contributing factors to this success was the widespread use of PMA parts.

MARPA and its members frequently tout the many benefits PMA provide to operators.  Operators are generally aware of the lower prices offered by PMA parts.  They are also aware that PMA parts may be their only option, or one of very few options, for replacement parts for legacy aircraft. However, operators may not be aware of the significant reliability benefits that PMA parts also provide.

Mr. Rennick explained that in order to maintain its fleet to the level it requires Delta wants options.  Service experience has demonstrated that PMA parts match, and in some cases exceed, the performance of OEM parts.  Based on this experience Delta has found PMA parts to be acceptable for use throughout the aircraft, components, and engines.

Mr. Rennick’s presentation included exciting metrics showing an upward trend in Mean Time Between Unscheduled Removals (MTBUR) and Mean Time Between Failures (MTBF) on certain applications in which Delta had utilized a PMA solution.  Metrics like these indicate the great value proposition that PMA’s can offer air carriers; not only from a purchase price standpoint, but importantly, from a reliability standpoint.  These metrics, along with shortened lead times, are part of the greater holistic value proposition offered by PMA parts and something we should remember to emphasize when talking to potential customers.

Mr. Rennick also stated that because of Delta’s close cooperation with its vendors it is able to address issues more quickly than might otherwise be possible.

Delta’s comfort level born of experience with PMA parts has led to the carrier using PMAs in even very critical applications, including engine gas path and rotating parts, life limited parts, and power generation.

The emphasis on the reliability of PMA parts is one that we, as an industry, should be sure to promote to our customers.  Cost savings means more than just lower prices (an obvious benefit of PMA!)  Keeping aircraft safely and reliably operating without unscheduled removals and increasing time between failures generates cost savings for operators by allowing them to get planes turned quickly and keeping their passengers happy.  MARPA always makes it a point to emphasize the reliability benefits of PMA wherever we go.

If you were unable to join us in Istanbul you will still have a chance to see this great presentation on the reliability benefits of PMA parts.  We anticipate Mr. Rennick giving a similar presentation at the 2015 MARPA Annual Conference.  This will be a great opportunity for PMA manufacturers to hear directly from Delta on the air carrier’s take on PMA parts, and an excellent opportunity for operators to see how one carrier is making PMA parts an important element of their maintenance program success. Register today to take advantage of Early Bird rates!

New Draft FAA Guidance: replacing vacuum-driven attitude instruments with electronically-driven replacement indicators

The FAA has published new draft guidance for public comment.  The guidance is meant for instruments and indicators designed for small (Part 23 or CAR 3) aircraft.  It is a policy statement that describes acceptable compliance methods for replacing vacuum-driven attitude instruments with electronically-driven replacement indicators. Electronically-driven attitude indicators include indicators that use electrical power to (1) excite an internal gyro, or (2) replace the operation of the gyro with microelectronics.

The policy notes that electronically-driven attitude indicators may replace the existing attitude indicators used in VFR or IFR airplanes.

Comments are due to the FAA by August 21, 2015.

You can email comments to: leslie.lyne@faa.gov

Comments can also be delivered by mail or hand to:
Federal Aviation Administration
901 Locust St
Room 301, ACE-114
Kansas City, MO, 64106

Please send a copy of your comments to MARPA, so that the Trade Association’s response can support your concerns.  Please also let the Association know if this is guidance that is important to your business.

Customers Customers Customers!

The customers will be there in Istanbul in twelve days – will you?

MARPA and the Association of European Airlines (AEA) will co-host a PMA meeting in Istanbul on May 25-26.  By my count we have 29 customer-personnel attending the conference – these are air carriers and MROs that are interested in PMA solutions.  You can see the current “early registration list” online to see who has already committed.  And we are hoping to confirm a few more European carriers before the end of this week.

“29 customer representatives in an intimate setting like that?  Unlimited access to air carrier and MRO purchasing representatives?  I can’t think of a better networking opportunity for a PMA company that wants to sell into Europe”

Customer attendees will include (but not be limited to):

  • DHL
  • KLM
  • Lufthansa Technik
  • Pegasus Airlines
  • SunExpress
  • Turkish Airlines
  • Turkish Technik

Why are they gathering?  To learn more about PMA and to network with PMA companies that can provide them with solutions.  Why have AEA and MARPA gone to the effort to bring these air carriers together?  To help educate the world about PMA and to help our members make sales to air carriers in the region!

If you’ve been dying for an opportunity to have one-on-one time with air carriers and MROs that are eager to learn more about PMA, then this is the conference for you.  If you aren’t yet registered for the conference, then you should be.

 

 

Looking for more opportunities like this one?  Take a look at everything that MARPA is planning for the remainder of the year to help promote YOUR export sales.

Treasury Makes It Easier to Comply, When Exporting

PMA manufacturers who are exporting their parts from the U.S. need to ensure that they remain in compliance with the U.S. export regulations.  In addition to the BIS and DDTC regulations that apply to aircraft parts, exporters also need to remain in compliance with Treasury Department regulations.

Some of those Treasury Department regulations include lists of people and entities that you ought not to do business with.  Every agency has multiple lists that you need to examine, but Treasury is doing something to consolidate its lists and make it easier to review them. This consolidation should make it easier to search to ensure compliance, whether you are searching on line or using a computer program to automatically research your business partners.

The Treasury Department office with jurisdiction over export programs is the Office of Foreign Asset Control (OFAC).  OFAC has a list of Specially Designated Nationals (SDNs) as well as other (non-SDN) sanctions lists. OFAC is now offering all of its non-SDN sanctions lists in a consolidated set of data files called the Consolidated Sanctions List. This consolidated list will include the following:

  • Non-SDN Palestinian Legislative Council List
  • Part 561 List
  • Non-SDN Iran Sanctions Act List
  • Foreign Sanctions Evaders List
  • Sectoral Sanctions Identifications List

OFAC announced that it plans to discontinue some of these lists as separate lists, so they will only be available as part of the consolidated list.

Persons seeking to check whether there are OFAC sanctions that might apply to their transaction should be sure to check their export business partners (by personal name and company name) against the Specially Designated Nationals List and the Consolidated Sanctions List.

One can also use the Sanctions List Search which consolidates both lists into a single searchable database. This tool is useful because it can automatically search for names that are close (bot not exact matches) and can be set to find matches with different levels of confidence (which will then be reviewed by a human to assess whether they actually match).

Exporters should also check the details of their transaction (including destination country) against the Sanctions Programs and Country Information page, which list sanctions programs based on country and on certain other criteria.

FAA Publishes Designee Management Policy for Public Comment – All Manufacturers Need to Review and Comment

Do you rely on a Designated Engineering Representative (DER) to approve data for your business? Do you use DMIRs for issuing 8130-3 tags?  If you do, then you know how critical designees can be to the parts approval process.  Often, though, designees are required by the FAA to do things that the FAA employees themselves are not permitted to do, like require paperwork that is not required by law or regulation (this can be a violation of the Paperwork Reduction Act), or impose standards of conduct that are not required by law or regulation (this can be a violation of the Administrative Procedures Act). When this happens, the designee has no choice but to obey the instructions from the FAA-Advisor … even if they would be illegal if undertaken by the FAA’s employees.

Want to make sure that designees are not used to do things that FAA employees can’t do (by law)?  The be sure to take the time to offer comments to the FAA Designee Management Policy that is now out for comment.  The FAA has issued for public comment a draft change to the guidance document affecting designees.  Although only parts are changed, it is a potential opportunity to comment on the entire document.

The original guidance is called “Order 8000.95, Designee Management Policy.” It was first issued in April of 2014.

This guidance document provides a wide variety of guidance on how to manage FAA designees. It has not and does not appear to cancel FAA Order 8100.8 (Designee Management Handbook), although some of the guidance appears to address some of the same issues as that guidance (failure to cancel 8100.8 might have been an oversight).

As a practical matter, designees (who are the people most directly affected by this guidance) will not be able to write comments that are critical to this guidance. This is because designees can be terminated for cause or without cause, at the discretion of the FAA. So the FAA can terminate a designee for exercising his or her First Amendment freedoms (as long as they come up with any other pretext for the action, including a termination ‘not for cause’). Designees are well aware of this and they regularly self-censor their comments because of the chilling effect that the FAA’s discretionary termination power has had. In some cases, designees have contacted me because they know that I will protect their anonymity.

The real-world issue us that designees rely on their designation from the FAA to ply their trade. If they are terminated (for-cause or not-for-cause) then they cannot simply be a designee for someone else. They need to choose a entirely different career path. So the process for reviewing designee termination is very important. And both the current policy and the draft policy are woefully inadequate, because they offer no standards for review, so the FAA employees are able to rubber stamp any termination decision on review. Honest review depends 100% on the personal integrity of the reviewing personnel – and there is no formal training for the employees who act as reviewers in that process (by comparison, state court judges typically attend judicial training).

The FAA’s failure to have effective standards actually undermines the FAA’s own interests. One example arises in the context of designee termination. The lack of effective standards means that individual FAA employees can cause the termination of a designee for any reason, including a reason that would have been considered to be illegal if it was used to terminate an employee, as long as the party who initiates the termination offers a pretextual reason. There is no formal inquiry into such pretext – it is taken at face value – and the VERY short time period for presenting a defense means that it is tough to be effective in assembling a defense: the full appeal including all supporting evidence must be submitted within 15 days – while the designee is given the charges, he or she has no opportunity to review the FAA’s underlying evidence. In comparison, the appeals panel has 45 days to consider the appeal and then another 15 days to notify the designee of their decision for a total of 60 days. We have seen evidence that FAA inspectors will use this period to gather more evidence to refute the defense and bolster the ‘prosecution’ so clearly the FAA is not bound to any sort of deadline for presenting its own case.

There is plenty that could be improved in the designee management process.

This is a great opportunity to help the FAA to better manage the designee community using effective processes that ensure fairness for everyone. MARPA members should strongly consider reviewing and commenting on this draft guidance.

Comments are dues to the FAA by January 7. Please send comments to MARPA, as well, so we can sure that our comments reflect your concerns.

Comments Due: 01/07/2015
How to Comment: Deliver comments by mail or hand to:
Susan Hill
1625 K Street NW
Suite 300
Washington DC, 20006Email comments to: Susan.ctr.hill@faa.gov
Email CommentsFax comments to:
(202) 223-4615, Attn: Susan Hill

UPDATE:

My comment on the cancellation of FAA Order 8100.8 failed to take into account FAA Notice 8000.372.  That Notice directs all AIR manufacturing personnel who oversee designees to stop using Order 8100.8 and being using 8000.95 on a schedule.  The schedule reflects the implementation of the Designee Management System (DMS) in those offices.

Under that schedule, all MIDOs with designee management responsibilities should have transitioned to Order 8000.95 during the summer (of 2014).  So Order 8000.95 will have supplanted 8100.8 for MIDOS (but not necessarily for ACOs and FSDOs).  This means that DMIRs and DAR-Fs have transitioned.  But DERs should still be under 8100.8 until they are formally transitioned (at which time they will fall under the instructions of 8000.95).

Special thanks to William Denihan for pointing this out!

Be sure to Request the Referenced Service Bulletin in Airworthiness Directives!

Have you ever been frustrated to learn that an AD went out that references a service bulletin, and (too late!) you later learned that the service bulletin made disparaging remarks or provided inappropriate directions about your company or your parts?

How do you prevent this situation?  You need to get a copy of the service bulletin that is cross referenced by the AD, and review it before the AD rule becomes final.  But sometimes no one will provide the service bulletin to you!

That just shouldn’t be the case.  If an AD might indirectly affect you because of the cross referenced service bulletin, then you should be entitled to review the service bulletin before it becomes part of a regulation.

The U.S. government agrees!!

The U.S. Office of the Federal Register has published a new rule designed to make government rules more transparent.  It accomplishes this by addressing incorporation-by-reference.

What is Incorporation-by-Reference?

Incorporation-by-Reference (or IBR) is the term for regulations that make reference to some other document that is not published in the rule. Historically, incorporation-by-reference came about because it cost money to print the Federal Register, and wasting a lot of pages on a standard that could easily be obtained outside of the Federal Register. But today, most people access the regulations and the Federal Register on line, so there is not as much of a burden associated with publishing such documents. Incorporation-by-reference can be an issue for the public because when an incorporated document is merely technically available – but it is not really available – then this can make it difficult or impossible for an affected person to comply with the regulation (and can make it impossible for the affected person to even know that (s)he is subject to the regulation).

In short, unavailable-but-incorporated documents can reflect secret regulations that are impossible to comply with.

With this in mind, the Administrative Conference of the US began to study what could be done to update the rules to reflect modern technology. This ultimately led to the Office of the Federal Register looking into potential changes to the rules on incorporation-by-reference.

Some Problems with Incorporation-by-Reference

The aviation industry faces many challenges related to incorporation-by-reference. An issue that can be very important to MARPA’s members is the availability of referenced documents in Airworthiness Directives(ADs), like service bulletins.  Service bulletin language can affect PMA parts, and can even disparage PMA parts in ways that are inappropriate.

Timely availability to the PMA community of these service bulletins can be a serious issue.  It is typical for the FAA’s incorporation-by-reference statement to insist that the incorporated service bulletins be obtained either from the FAA office or from the OEM who published the document. In order to test this system, I emailed an FAA office and an OEM who were described as the sources of a service bulletin (the Federal Register listed the emails and listed this as an acceptable way to make contact). The FAA response was that I should go to the OEM. The OEM response was to ask me why I wanted the service bulletin. When I responded that the service bulletin was incorporated by reference in a proposed AD, and I wanted a copy of the service bulletin to determine whether the trade association needed to file comments on behalf of the membership, I received no further communication from the OEM.  They just stopped responding to me.

MARPA Action

MARPA filed comments on the Advance Notice for this proposal and offered a number of suggestions in 2012. MARPA also participated in face-to-face meetings with the government to discuss ways to improve the current system.

The result was a new rule that clarifies obligations related to regulations that incorporate standards by reference.

What Changes Should You Expect?

It is important that incorporated material be available in proposed rules so that the public can comment on the proposed rule with full knowledge fo the proposed rule’s impact. Under the new standards (1 C.F.R. 51.5(a)), the preamble to a proposed rule must :

  1. Discuss the agency’s efforts to make the IBR materials reasonably available to interested parties, and
  2. Summarize the material it proposes to incorporate by reference in the preamble.

When the agency is ready to publish a final rule with an IBR, the agency must do the following (1 C.F.R. 51.5(b)):

  1. Ask for permission from the Office of the Federal Register to accomplish an IBR,
  2. Explain in the preamble to the final rule how interested parties can get a copy of the IBRed materials (it must be “reasonably available”), and
  3. Ensure a copy of the IBRed publication is on file at the Office of the Federal Register.

An important feature of the regulations is the requirement to discuss availability to “interested parties.” This is an expansion of the traditional language, which merely required availability to “the class of persons affected by the publication.” Interested persons should include persons who are indirectly affected (like those whose PMA parts MIGHT be affected in the case of an airworthiness directive) in addition to class of persons directly affected by the publication (which is generally operators).

The regulations continue to explain that IBR is limited to the edition that is incorporated. So if a subsequent revision of a service bulletin comes out, only the version that was approved by the Office of the Federal Register is the version that is IBRed (and not subsequent versions). 1 C.F.R. 51.1(f).

One sad omission was that the new rule does not define “reasonably available.”  The Office of Federal Register was worried that a definition might be inappropriate, so they were hesitant to offer a definition, and instead they have left it to a case-by-case analysis as defined by each agency.  But it seems certain that if you make a reasonable effort to obtain an IBRed service bulletin using the mechanism in the Federal Register, and you are denied, then you may have a claim that the service bulletin was not reasonably available.

While we did not get every change we requested, this nonetheless represents a good start on the process of providing better transparency in the situations of incorporation-by-reference.

Draft Policy Concerning § 33.83 Engine Surveys Due Next Week

We previously wrote in this space about a new Draft Policy Statement issued by the FAA concerning the vibration surveys and engine surveys required under section 33.83 of the Federal Aviation Regulations.  The draft guidance attempts to more narrowly address the FAA’s concerns about full engine test for type certificate applicants.

MARPA plans to provide comments on this Draft Policy Statement to the FAA and has sent a draft of our comments to the MARPA Technical Committee for review.  If any of our members wish to review our draft comments to provide their feedback we would love to hear from you.  Please email Ryan Aggergaard at ryan@washingtonaviation.com if there are particular issues in the draft statement you believe should be addressed so that we can incorporate our members’ concerns.

MARPA also encourages our members to file their own comments on the Draft Policy Statement.  Comments are due to the FAA by November 21, 2014.  Comments should be emailed to Dorina Mihail at dorina.mihail@faa.gov. Comments can also be mailed to her at:

Federal Aviation Administration
Engine and Propeller Directorate
Standards Staff, ANW-111
12 New England Executive Park
Burlington, MA 01803

MARPA looks forward to your comments.

New Guidance: Casting and Proof of Structure

The FAA has released two new advisory circulars that may affect the PMA community.  Both advisory circulars are issued by the Transport Aircraft Directorate and apply to Part 25 aircraft (and parts thereof).

  • Casting Factors, AC 25.621-1: This AC provides guidance for meeting the requirements of 14 C.F.R. 25.621.
    • This regulation imposes limits and restrictions on casting, and also requires a design approval applicant/holder to have control over the operations of a vendor casting facility.
    • The intention of both the regulation and the AC is to drive greater levels of consistency into casting (or to mitigate inconsistencies).
    • Discusses a means of qualifying a casting process

 

  • Proof of Structure, AC 25.307-1: This AC provides guidance for meeting the requirements of 14 C.F.R. 25.307.
    • This regulation is for the demonstration of compliance for each critical loading condition.
    • The AC provides a list of factors that should be considered in deciding the need for and the extent of testing, including the load levels to be achieved.
    • The AC states that there are four certification approaches to choose from (and provides guidance on each one):
      • Analysis supported by new strength testing of the structure to limit and ultimate load.
      • Analysis validated by previous test evidence and supported with additional limited testing.
      • Analysis supported by previous test evidence.
      • Test only.

We would be interested in hearing from any MARPA member who is affected by one of these new advisory circulars.

FAA Issues Statistical Analysis Guidance – Are You Testing Enough Parts?

The FAA has issued a new advisory circular for statistical analysis.  This AC only applies to engine and APU parts.

The new advisory circular uses statistical analysis to arrive at correct sample sizes.  This sample size formula is introduced for persons who are trying to correlate two populations of parts.  MARPA had pointed out to the FAA that typically a PMA applicant does not correlate two different populations of parts – instead they derive the reasonable tolerances on one population of parts, and then design and produce within those tolerances.  The FAA would like PMA applicants to arrive at their appropriate sample size, test the parts being reverse-engineered, and then produce an equivalent number of pre-PMA parts to test for the same properties (and then correlate the two populations).  This is contrary to current FAA regulatory guidance, which requires the design to be approved and the  requires the production quality system to ensure that parts are all produced within the approved design parameters.  In essence, ACO engineers will now take control of the quality assurance system through the design process.

One of the problems with the AC is that it relied on statistical analysis for clinical trial sample size as the basis for assessing statistical analysis of reverse-engineering sample size.  Clinical trials for pharmaceuticals typically rely on populations of hundreds or even thousands of people.  Trying to test hundreds or thousands of parts in order to reverse-engineer them is simply not realistic.  Furthermore, the degree of part-to-part difference under modern quality assurance systems does not support such large sample sizes.
For those cases where the equations in the advisory circular give a lower number for the appropriate sample size, the FAA has also established minimum sample sizes.  The AC sets some minimum limits for the number of parts that must be tested in order to derive certain values (remember that you need that number of PC parts and also that number of reverse-engineered parts to meet the AC’s requirements):

Minimum Number of Parts to be Sampled

  • For basic material properties that are more dependent on alloy constituency than on part manufacture process – 10 approved parts from three separate lots with at least three parts per lot
  • For properties affected by how the material is processed during part manufacture such as high-cycle fatigue, low-cycle fatigue, creep, tensile strength, crack growth, etc. – 30 approved parts
  • For fatigue testing – at least 25 tested parts that are run until they crack
  • For parts exhibiting complex geometry or complex manufacturing variables, additional specimens may be required
  • For parts considered to have a high degree of criticality, greater sample sizes may be required

No statistical basis is offered for these minimum sample sizes.

The new advisory circular provides guidance for statistical analysis of sample-size despite the fact that no regulation actually requires such a broad-based sample.  The advisory circular appears to potentially change the regulations by increasing the burden on applicants.  To the extent that this is true, it is inappropriate.

Our concern is that despite warnings that this is non-mandatory guidance, this guidance may be used as if it were a regulation, with offices refusing to accept PMA applications that are otherwise valid, but that failed to use this AC as a basis for identifying sample size.

If you find that this AC effectively changes the application obligations imposed on you as a PMA applicant, STC applicant, or other FAA-approval applicant, then please contact MARPA so we can raise this concern with the appropriate personnel at the FAA.

AC 33-10 is known by its full title: Statistical Analysis Considerations for Comparative Test and Analysis Based Compliance Findings for Turbine Engine and Auxiliary Power Unit Replacement, Redesign and Repaired Parts.

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