Ask the DAR

Avionics certification, ops lims for self-designed aircraft, house paint on Experimentals.

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Question: Can you address the requirements for avionics used in Experimental/Amateur-Built aircraft for IFR operation? I have been looking at several sections of the FARs, but cannot find what I am looking for. For example, is it OK to use non-certified EFIS systems, GPS, etc. in the IFR environment? Do radios need to be certified, and must transponders be TSOd? When I owned a Piper Cherokee 180, it seemed that everything I wanted to add or replace in the cockpit had to be certified. Can you compare/contrast this with E/A-B aircraft?

Answer: Thanks for your question. Actually, this is a bit out of my expertise; I prefer sticking to the regs that I work with every day.

The requirements that you are asking about are operational requirements, not aircraft certification requirements. I personally know quite a few people operating Experimental aircraft under instrument flight rules with non-certified EFIS and avionics, and I believe they are perfectly legal. However, I can’t point you to a specific rule. Of course, the transponder must be TSOd, but to the best of my knowledge, that is not required for other avionics.

Question: I have designed and built a one-of-a-kind airplane. Where do I list V speeds and aircraft weight in my operating limitations? Does the weight need to be listed as gross weight?

I now have 35 hours on the plane and need to flight test at gross weight. Is it OK to carry another person? As I read the FARs, it seems like this is OK to do; please advise.

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Answer: If you read your operating limitations carefully, you will see that you don’t need to enter V speeds and weights in the op lims. This is an entry for the aircraft records, i.e., the airframe logbook. If you want to enter them in the op lims, that’s OK, but not necessary.

Yes, the numbers should be at the maximum weight at which the aircraft will be operated. And no, your op lims do not permit you to carry a passenger during phase I flight testing. To get the aircraft to gross weight during flight testing, you may use ballast, but not another person. You, as the designer, need to calculate what your gross weight should be and test to that number.

[Note: There is a proposed advisory circular in the works by the FAA that will allow—under specific circumstances—an additional pilot to fly along with a builder/owner during some phase I flights. The AC is expected to be released later this year after public comments and revisions are complete.—Ed.]

Question: Did you read the article in the May 2014 KITPLANES® about finishing Stewart Systems fabric with Glidden house paint? How do we know that it’s compatible or safe?

Answer: I have no way of knowing more about the safety and/or compatibility of this product than you do. The only thing you can do is talk with the manufacturer. You can ask about compatibility with whatever products you are using, and ask for references from other customers.

In the Experimental world, you are free to use anything you wish. You need to do your own research and be able to live with your final decision.

Please send your questions for DAR Asberry to editorial@kitplanes.com with “Ask the DAR” in the subject line.


Mel Asberry is an experienced Designated Airworthiness Representative specializing in Experimental/Amateur-Built aircraft. He and his wife, Ann, have built seven amateur-built airplanes including two ultralight types, a Moni Motorglider, a Dragonfly Mk2, two RV-6s and a Zenair CH 601HDS. They are currently building a scratch-built biplane.

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