Introductory Guide to PMA Sealants
Building Familiarity & Confidence in PMA Sealants
“Today, although cost remains a consideration, it is no longer the motivating factor in seeking out PMA parts. Offering improvements to products, cutting long lead-times, and improving reliability are all important factors measured by operators when choosing suppliers and selecting new PMAs.”
—Craig Barton, VP of Technical Services at American Airlines at MARPA Annual Conference 2019
Table of Contents
Over the years, many of our customers have expressed frustration with their lack of choices when purchasing aerospace sealants and choosing vendors. Customers were experiencing long lead times, delayed schedules, and higher prices, but they didn’t have an equivalent sealant to use in place of the industry-standard sealants like PPG/PRC. The result? Lower profit margins and frustrated customers.
When you’re telling your customer that you’re pushing the delivery date, we all know that even if it’s because of vendor issues, the buck stops with you. It’s your relationship with the customer that’s strained.
In the early 2000s, we began to look for solutions, narrowing in on the idea of PMA sealants. If PMA parts are used throughout the aviation industry, then why do none exist for sealants? We pursued the idea, and in 2008, we received the FAA’s approval for the first PMA sealant line.
In this article, we’re aiming to provide an introductory guide to PMA sealants and how the aerospace industry can leverage them. We suggest this guide for anyone who works at a MRO, airline, aircraft OEM, or maintenance shop in the following departments:
Because there is still some uncertainty and unfamiliarity with the concept of PMA and particularly PMA sealants in the aerospace industry, the purpose of this guide is to begin to remedy that. We will make clear to you the legitimacy and authority of PMA sealants as granted by the FAA. It’s equally important that we illustrate the safety and quality of PMA sealants, which are already in use by some airlines and MROs. A clear indication of their trust in the part’s performance.
Before we jump into anything, we need to get acquainted with a few terms that could be foreign to someone not familiar with the PMA process.
2. Key terms
Here are a few key terms specific to understanding PMA and PMA sealants.
PARTS, ARTICLES, PRODUCTS: The terms “parts, articles, and products” are used interchangeably within the aviation community. All require controlling documentation such as a Drawing(s) or Technical Data Sheet(s). In 2014, the FAA released Advisory Circular 21.303-4 confirming that sealant is indeed an “article,” but for the sake of this guide, we will use the term “part.”
PMA: Parts Manufacturer Approval. See the broader, more detailed explanation of PMA below.
OEM: Original Equipment Manufacturer. See the broader, more detailed explanation of OEM below.
FAA: Federal Aviation Administration
Conforms to: The part meets the requirements that the FAA has set in place.
Equivalent to: The part is not identical to another part, but it will have the same “form” “fit” & “function” as its equivalent.
Supplement number: Unique number assigned by the FAA when the PMA part is approved.
Eligible manufacturers: In the case of PMA sealants, eligible manufacturers are aircraft OEMs (like Boeing) that the FAA has approved for the use of PMA sealants. On the PMA supplement, you can find the list of eligible manufacturers and their specific aircraft models (like a Boeing 737) on which the sealant can be used.
Non-critical part: A part that DOES NOT perform “a function of such significance (critical function) to the aircraft on which it is installed that, if it failed, the airworthiness of the aircraft would be degraded to the extent that would preclude continued safe flight or landing (per FAA AC 43-18).” See below for a further explanation of the definition of non-critical.
Airworthiness approval: An approval granted by the FAA that identifies the airplane as suitable for flight. Parts contribute to an aircraft being ruled airworthy or not.
Now that we have a handle on terms specific to the PMA process, we can talk about what a PMA is.
3. What’s a PMA
PMA can be a confusing term to those who are just getting into or are unfamiliar with the Federal Aviation Administration and alternative and replacement parts. But it is not all that difficult when broken down properly.
Think of it like this; you know how Walgreens has their generic pain killers that are an equivalent to Tylenol but cheaper? Like 30% – 40% cheaper? Both products are FDA tested and approved pain relievers made up of acetaminophen. The difference is the name on the bottle.
The concept of PMA parts is similar. PMAs are usually cost-saving alternative products that can be safely used in place of an original part. PMA manufacturers have to go through a rigorous process with the FAA in order to ensure that their parts are airworthy. PMA parts will function exactly the same or better than OEM parts.
PMA parts are now a key component of the airline industry. They had brought competition to OEMs when there were none beforehand. More recently, PMA sealants have been introduced and provide cost savings like JIT and lower pricing.
One of the myths regarding PMA parts is that they are not as safe as OEM parts. We address this and other PMA myths and misconceptions in a section below. But first, let’s address the question, what’s the actual difference between OEM and PMA parts?
4. OEM vs PMA parts
OEM parts are the first parts to be designed and produced to perform a specific function. It is often thought that PMA parts are inferior to OEM parts, but that is simply not true.
PMA parts are parts that perform the same function as the OEM part and can be used in exchange but are made by other manufacturers. PMA parts require the same FAA regulations that apply to the OEM parts. This includes FAA oversight inspections and audits, similar to those of the aircraft or engine they are used on.
“No person may produce a modification or replacement article for sale for installation on a type-certificated product (an aircraft, engine, or propeller) unless this article is produced in accordance with a PMA issued by the FAA under 14 CFR part 21 Subpart K (sections 21.301 through 21.320)”.
Let’s walk through the steps by which the FAA grants its approval specifically for PMA sealants.
5. What are PMA sealants
Using the above terms, we can interpret the following definition of PMA sealants.
PMA sealants are FAA approved equivalents to OEM sealants that conform to the specification of the OEM sealant. PMA sealants are deemed non-critical parts that have received airworthiness approval. With each PMA, the FAA provides a list on the PMA supplement that contains every manufacturer and aircraft that the PMA can be used on.
As an example, and in simplified terms, this means: PMA sealant NSL1422RC can be used in place of PR1422 on a Boeing 737, because the FAA confirmed the sealant conforms to the same specifications and can be used interchangeably with PR1422 which is approved for use on Boeing 737s.
6. FAA’s PMA sealant approval process
FAA Engineering and FAA delegates verify that the replacement and OEM sealant materials are equivalent in ALL aspects and meet the requirements of the specification or technical data sheet (TDS). All the measured physical characteristic data defined on the replacement sealant TDS, like hardness, adhesion, time to cure, tensile, elongation, etc., is compared to the physical characteristic data of the OEM sealant listed on the OEM’s TDS. The data of the replacement sealant and OEM sealant are compared to any necessary commercial, industrial, and aerospace specifications for compliance.
PMA manufacturers will have to work with the FAA as well as third-party laboratories to create the necessary data. For aerospace sealants a great number of tests were performed, such as flammability, microbial at different temperatures and different environments. The data that is produced by the tests are used in the FAA’s final PMA decision. The tests that are required vary by part. Manufacturers cannot take any shortcuts, or the FAA will be able to see that in the final data and their part will be rejected.
7. Implementing PMA
Change or replacement of approved parts on an aircraft is very difficult. There are potential hurdles that you will have to jump in order to implement a PMA sealant on your aircraft. Here are just a few of the possible hurdles you will more than likely face:
- You may not be able to use a sealant that isn’t on your QPL (Qualified Product List).
- Your customers may explicitly state they don’t want PMA parts used on their aircraft.
- You may have a contract with your vendor or chemical management company that lumps together multiple parts and doesn’t allow for individual changes.
- You may not be comfortable with using PMA parts.
The initiative could require conversations with customers, engineers, maintenance directors, purchasing directors, quality, and more. It may seem like a lot, but the reward could be well worth the effort. PMAs are part of the future of the aerospace industry. With the incredible growth projected for the aerospace industry over the next decade, a monopoly on parts won’t be sustainable.
8. Why use PMA
Vendor management. Anyone in the business world knows how key this is to your operations. When you have a choice in vendors, you’re empowered to control your costs and reduce any risks caused by your vendor’s delivery habits. Here is what you can expect when you adopt PMA parts:
Better pricing: It could make it easier to meet your budget and enjoy better profit margins.
Shorter lead times: Most OEMs have incredibly long lead times that can create very real, very large problems. PMA manufacturers are focused on delivering products quickly.
Supply chain whiplash: Your business will be less susceptible to disturbances in your supply chain. With multiple vendors, your supply chain will be much more stable.
Improved product performance: In the example of PMA sealants, they provide the opportunity for faster cure times than some standard OEM sealants.
If these benefits are so plentiful, then why hasn’t everyone switched over to PMA sealants? Aside from the above-discussed reasons, OEMs have run successful smear campaigns against PMAs since they first appeared on the market. Here are some of the things you may have heard.
9. Common PMA myths
There are many falsehoods that have been spread about PMA sealants in the aviation industry. You can fly safely, knowing that they are entirely untrue.
1) PMA Parts are Inferior to OEM Parts
OEMs have tried for decades to undermine PMA parts, because PMAs eat away at their revenue. The FAA requires that a PMA part be as good as or better than the OEM part. The PMA is put through extensive testing to accumulate the data that can prove this to be true, and after the PMA is granted, PMA holders are responsible for continued operational safety. This is why we can say that PMA sealants truly perform as well as or better than the OEM sealant.
2) Sealants aren’t parts and don’t qualify for a PMA.
Over the past 11 years, the FAA has continued to confirm that sealants qualify for a PMA. In 2014, it was very clearly stated in FAA AC 21.303-4:
“This AC refers to parts and components as articles per 14 CFR 21.1. This section defines an article as a material, part, component, process or appliance. These items may include sealants, modified standard parts, brake assemblies, etc. that are in a product’s type design. Please note PMA is not for base materials, processes or inspection procedures.”
3) PMA Sealants Should be Considered Critical Parts
The definition of a critical part is that if the part fails then the entire aircraft is at risk and is no longer airworthy. A sealant does not have the necessity that critical parts do. Per the FAA, no sealant is designed or used on aircraft or engine in areas for conditions putting an aircraft at risk. If a sealant is not installed properly or fails in action, the aircraft would not “be degraded to an extent that would preclude continued safe flight or landing.” It’s as simple as that.
10. In conclusion
PMA sealants are an economical and viable alternative to OEM sealants and prevent a stranglehold on the sealant industry. MROs and airlines are starting to catch on, incorporating PMA sealants into their supply chain. As the industry continues to grow, you can bet more and more companies will be looking for alternatives in parts and suppliers, and as the aerospace industry grows, so will the PMA sealant market.