Where Do Your Floats Come From?

by Rachel Obermoller
Pilot, MnDOT Office of Aeronautics
Published in Midwest Flyer – April/May 2017

There are several ways, which floats, or really any additional equipment, can be certified for aircraft. When an aircraft is initially certified, a Type Certificate (TC) is issued. Sometimes, many similar aircraft will be grouped together. For example, the Type Certificate Data Sheet (TCDS) Number 3A24 lists the Cessna 185, 185A, 185B, 185C, 185E, and 185F, as well as some special configurations of those models. The TCDS lists limitations and design limits of these models in various configurations. If your aircraft was certified per the TCDS to include floats, the models will be specified, as well as those items on the TCDS which change when floats are installed. In the case of the Cessna 185, the TCDS lists EDO 2790 amphibious floats and EDO 2960 straight floats, which begs the question, what about all of the other float models you can put on a 185?

The answer to that question lies in the Supplemental Type Certification process.  As you might guess, a Supplemental Type Certificate (STC) is an amendment to the Type Certificate for the aircraft. The manufacturer may have elected to not include certain supplemental equipment in the original type certification process, or it may have been approved after the original type certification, possibly by a third party. Sometimes, when a new aircraft is delivered from the factory, there may already be several STCs on the aircraft, depending on the equipment the owner specifies. For the Beechcraft Bonanza, a new G36 Bonanza with a G1000 avionics suite installed will have an STC for ADS-B in order to make the aircraft ADS-B compliant. Similarly, float manufacturers who manufacture floats for certificated aircraft (non-experimental) will apply for an STC for their equipment on an airframe.

The waters can start to get a little muddied when you have multiple STCs on one airframe, as is the case with older aircraft, and those with more modifications installed. Your aircraft may end up with STCs for common things like alternators, vacuum pumps, engines, propellers, avionics items, engine analyzers, and interior and exterior lighting in addition to things like floats, skis, tundra tires, or gross weight increases. As you can imagine, some of these items, and the additional limitations they include, may interfere with or contradict one another.

For this reason, it is particularly important for an owner or pilot to be familiar with the equipment on their aircraft, how it was certified, and any limitations in the flight manual supplement for those items, and to have a mechanic they trust who also understands the intricacies of their aircraft’s paperwork and can help them wade through the questions they may have. Some STCs explicitly state they are not compatible with certain others, while others may be a bit more vague and require some careful consideration before they are installed on the aircraft.

So far we’ve just talked about the paperwork compliance side of all of this, but I wanted to drill down a little more into how equipment is actually certified, so I got in touch with a former student of mine who is an engineer at Wipaire, the world’s largest float manufacturer located in South St. Paul, Minnesota.

Elliot Bishop is a private pilot and holds a seaplane rating in addition to being a Designated Engineering Representative (DER) Flight Analyst. His interest in math, science and space got him into aerospace engineering. In his past 6 years at Wipaire, he’s found that seaplanes and the variety of projects that go with his work has made his job both challenging and interesting and keeps him engaged and busy.

There is a lot of work that goes into certifying floats, or any supplemental equipment for an aircraft, and it all starts with figuring out how to comply with the certification requirements. Whether you are aware of it or not, FAR Part 23 has recently undergone a significant rewrite with the goal of streamlining certification activities and reducing costs while maintaining the same or better level of safety. The new Part 23 will be effective in August of 2017, and changes the standards and rules that TC and STC holders and applicants will use from prescriptive requirements to performance-based requirements.

Elliot explained that while this may sound more onerous than just complying with the previous rules, the hope is that it will provide greater flexibility, allow for easier adoption of new technologies both in testing and designs, and lead to a faster and less expensive process as a result.

One of the possible means of compliance is the ASTM International specifications, and since these are not part of the Federal Aviation Regulations, they can be more quickly revised to adopt new technology. While there will likely be a learning curve to adopt and fully utilize the new process, the hope is that as new technologies advance such as electric aircraft, distributed propulsion, and new materials and methods for manufacturing, the new regulations will provide the needed flexibility for the manufacturer to either apply an existing standard as means of compliance, or specify their own means of compliance as part of the application.

The process of certifying a new float starts with the concept in terms of the applicable aircraft, desired characteristics of the float, and known specifications. They then design a properly sized float, which they believe will fulfill the concept, and figure out how to attach it to the airframe. This involves designing the appropriate rigging, creating the internal structure for the float, and designing the systems associated with the float, such as the water rudder controls or hydraulic pump for amphibious floats. Running concurrent to the design process is the need to get the certification plan approved by the FAA, write the test plans to satisfy the various requirements, execute and document the testing, write the appropriate reports, and generate drawings and other technical documents which will be part of the STC approval. While this sounds straightforward and somewhat linear, there are quite a few places where the process can hit a snag, and changes must be made.

In flight and static testing, it can be hard to anticipate exactly how an aircraft or component will perform with a given modification, and when an issue arises, they have to find a way to improve the design to solve the problem. As you can imagine, for someone who likes a good challenge and solving problems, the certification process presents a lot of opportunities to exercise their skills.

There is a lot of testing which goes into certification, and this occurs both on the ground and in flight. Landing loads must be tested for the components, rigging, fittings, and other components, anything which cycles must be evaluated for wear and performance, electrical loads on the system must be assessed, plumbing and routing of cable, wires, and lines must be evaluated for interference, and components which attach to the airframe must be evaluated to ensure they withstand the loads they are rated for.

Certification of a new float on an aircraft requires repeating many of the flight tests that were done when the original aircraft was certified. The flight manual supplement includes performance charts or adjustments, which must be developed. There are also limitations for performance in various conditions including crosswind, service ceilings and flight conditions, which must be considered. Stall characteristics may be affected which in turn can impact other operational speeds for the aircraft, and even if they remain the same, many things must be evaluated to ensure the impacts of the modification are accounted for.

Whether you fly a stock Piper Warrior or a Cessna 206 with all the bells and whistles, you can imagine, understanding the aircraft certification process helps a pilot understand how the aircraft was designed, tested, and certified, and gives meaning to the limitations, operating practices, and instructions found in the flight manual and supplements. Each manufacturer should also provide updates to these documents as needed, instructions for continued airworthiness, which may include maintenance manuals and service bulletins, and be a resource for parts and support for aircraft owners and maintenance personnel.

If you’re not sure whether your documentation is in order or you have the right supplements in your plane, it’s a good conversation to have with your mechanic, or the manufacturer of the aircraft or component to ensure you have the whole picture.

As you can imagine based on everything that goes into the design of an aircraft or modification, there are a whole host of careers related to the engineering field which are accessible to someone with an interest in aviation.  In the Engineering Department alone at Wipaire, they employ people with drafting and CAD modeling skills, those with manufacturing and maintenance experience who develop and prototype parts and components, and technical writers, as well as engineers. Just because someone has an interest in aviation doesn’t mean they are locked into a career as a pilot, mechanic or engineer, either. Every aviation business has a need for people skilled in things like accounting, sales, administrative support, marketing, manufacturing, customer relations, human relations, web development, graphic design, and IT services.

In Minnesota, there is a great program for high school students called the Minnesota Aviation Career Education (ACE) Camp. ACE Camp is a weeklong summer camp where students get to experience many different careers in aviation, learn about a wide variety of careers and tour employers in Minnesota, experience flying in a general aviation aircraft, and complete a host of hands-on activities to learn more about aviation. It sounds like a lot of fun, even for adults, but unfortunately it’s only available to high school students. For more information about cost, dates, or to apply, visit www.mnacecamp.org

The MnDOT Office of Aeronautics is a great resource for your local airport, flying club, EAA chapter or other aviation group interested in helping promote aviation safety. Chris Meyer schedules the safety seminars our office presents, and in particular, the presentation “Test Pilot 101 – Returning Your Aircraft to Service” is a great option to learn more about the aircraft certification, documentation, and maintenance return-to-service process. You can reach Chris at 651-234-7224 or christopher.meyer@state.mn.us and he would be happy to arrange a time to bring this or one of our other WINGS safety seminars to your group.

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