questions about modifying a factory built aircraft

Opotions are few, John. Not knowing what you have in mind, there are a few things possible.

1. Check the Type Certificate Data Sheets (TCDS) for the type. There might be something listed under "optional equipment" that you may be able to use. On the FAA home page, click on "Aircraft" and drill down. The M20s are listed as 2A3.      OR,

2. Check for an STC that you can use.    OR,

3. If you are planning to certify something of your own design, read FAR 23.785 and set aside some months or years. Seats and belts are intensly looked at by the FAA certification folks.

If you only want to remove a seat, it usually only needs a log book entry and a W&B Chart C update.

Bob

John

Seating on a Mooney M20 is going to be relatively easy because it is certified under CAR 3. You don;t have to comply with the current Part 23 regulations, just CAR 3. Look those up, they are pretty striaght forward.

Now as for sticking that thing in experimental.. don;t  do it until you talk to someone that knows what they are doing. Conventionally, this requires a complete FAA aircraft conformity check to return to standard. This would clearly suck on numerous levels (feel free to jump in here Joe N.. this is your DAR bag of tricks)

There is a thing we call a "pocketed right up" that might work for test flights, but honestly, with seating I can not envision a need for a test flight. Before you mess with your nice white standard certificate, talk with someone that knows what they are doing before you get stuck with a pink one.

John I echo the other  comments you've gotten. Although I'm not a DAR, I was faced with a similar issue when I modified my J5A Cub with PA-12 wings, PA-20/22 stabilizers/elevators, PA-12 fuel system, etc. The FAA told me at first my only practical option would be experimental exhibition. There is no other category of experimental that our situations would fit; experimental amateur built is not applicable because you did not build at least 51% of your Mooney. Experimental exhibitiion is very restrictive - you are allowed to fly only to-from airshows, with  prior FAA permission, and practice fights with 30 miles of airport, etc. If I were you and you really want to modify your aircraft, I would consider obtaining an STC. A one-time STC applicable to your serial nunmber only would save you engineering costs. That's what I did with my Cub. If you actually went through the time and expense of an STC for all Mooney M20C Rangers, you might recoup expenses by selling the mod to other Mooney owners.

-Joel Marketello   

Thank you for your responses!  It sounds like experimental is not the way to go with this project.  I had heard rumors that a one-time STC was offered by the FAA but I don't know much about the process.  I will have to read up on that.  "Been there and done that" advice is hard to find these days which makes me thankful for EAA!

Keep the dirty side down, unless you're into aerobatics....

JA

A one time STC is applicable to only one airplane. You can use this process for all kinds of modifications, but the work going into that STC is about the same as for a regular STC. You have to prove that the airplane still meets the applicable regulations. You have to document the modifications and test or otherwise prove they are ok. It is neither easy or inexpensive.

Sonja

Been there, done that (on Mooneys)

Thanks Sonja, as with most things in aviation, it will probably be better to build a different plane, or buy a different one that suits my needs.  The more I consider gross weight, and cabin space, I doubt my idea would've worked for long anyway.

JA

For any project that will change a type certificated product, the first thing is to define the outcome of the project completely. In the sample case, the seating arrangement is the proposed project. Once the scope is defined, identify everything that will be touched by those changes. Next go to Order 8900.1 Volume 4 Chapter 9 figure 4-67 and follow the flow chart to determine if you will need an STC, or if the project could be done with a Field Approval. Next go to the same document and look at figure 4-68 and use this table to determine what level of support will be needed in developing the proposed modification. The next thing would be to have a meeting with the appropriate FAA office for the project. If it can be done via Field Approval, then your FSDO Airworthiness Inspector is the go to guy. If you need an STC, then you will have to go the an Aircraft Certification Office. In either case, the FAA will identify all the relevent FARs that you will have to show compliance with in order to gain approval. Since the case at hand is a CAR 3 airplane, that is the Certification Basis and for the most part, those are the regulations you will be required to comply with. In some cases, you may be asked to comply with the current FAR 23 regulations, but only for certain items.

If it is determined that it can be done by Field Approval, the process is much easier, but may still require hiring a DER to work the structures and systems issues.

Once you know what you will need to comply with you can start the detail design, or thow out the idea based on cost or feasability. With the detail design finished, build the prototype (if its a one time, the prototype is the finished product) and if the modification changes limitations, aerodynamics, or systems, you may be required to show compliance with the FARs by flight testing. If the design is really radical, you may even have to go Research and Development to prove the design will even work.  A Manufacturing DAR is required to issue an Experimental Show Compliance airworthiness certificate for you to perform the tests required (with a formal test plan). Either a Manufacturing or Maintenance DAR can issue an Experimental R&D certificate (consistant with their letter of authorization). When the test plan is complete and documented, that package would be sent to the ACO, and they would issue the STC. This process can take months, and the aircraft can not be returned to standard category unless you have the STC in hand, or you remove the modification and return the airplane to the original configuration.  To go back to Standard either with the STC, or modified back to original, you need a Maintenance DAR. Not an easy or inexpensive process, but do able.

All in all, you may have to hire a couple different DERs based on their areas of authorization, and a couple different DARs to get the job done.

http://fsims.faa.gov/PICResults.aspx?mode=EBookContents is the link for Order 8900.1

Hope this helps for anyone that is planning on making mods to their airplane.

David Schober DAR-T