Ask the DAR

Pilots operating handbook, the most common builder error, and adding vortex generators.


Question: Is my RV-8 required to have a pilot’s operating handbook (POH)? I see some builders create them.

Answer: Although a POH is nice to have and can be very handy, one is not required for an Experimental/Amateur-Built aircraft. The operating limitations issued with your airworthiness certificate complies with the POH requirement.

Question: As a DAR and technical counselor, what do you think is the most common error you see as people are building their aircraft?

Answer: On metal aircraft, by far the most common problem I run across is the lack of proper deburring. When sheet metal is cut, drilled, or punched, the edges are left somewhat jagged. This makes it necessary to smooth these edges and holes to prevent later stress cracks.

Lack of proper deburring is influenced by several things. One is with the increased availability of pre-punched kits, many builders think that they don’t need to deburr the holes.

The quality of pre-punching is very dependent on the sharpness of the kit manufacturer’s tooling. A new, sharp punch will leave a very nice, clean hole. As the tool dulls, the holes become more and more in need of deburring.

Another factor is that as kits get easier to build, they are attracting builders who are not particularly interested in becoming familiar with common “acceptable methods, techniques, and practices” for aircraft construction and repairs. These acceptable methods, techniques, and practices, by the way, can be found in FAA AC 43.13-1 and -2.

A few years ago, it was noted that many people were over-deburring, i.e., rounding sheet metal edges and countersinking holes that were not meant to be countersunk. Recently it seems that we have reached the other side of the circle and people are now under-deburring.

If you run your hand across the edge of the metal or a hole, you should never feel roughness. It should feel very smooth. Almost every crack that I’ve found when inspecting a mature aircraft can be traced to insufficient deburring.

I always recommend that all builders-yes, even experienced ones-get a tech counselor visit very early in the building process. At this point, the TC can stop you from proceeding down the wrong road. If you disagree with anything a TC suggests, then by all means, get another opinion. After all the TC is only an advisor, but he/she is an experienced advisor. And as said in a particular TV insurance commercial, “It’s free!”

Question: We are considering buying a Zenair 601HDS that is built, but hasn’t had its final inspection and signoff for testing. If we purchase the aircraft, would we be able to add VGs (vortex generators) to the wings to lower the stall speed? We are, of course, not the builders, but we would install a third-party VG package that has already been tested on the HDS.

Answer: There should be no problem installing VGs on your aircraft. You do not have to be the primary builder to make changes to an Experimental/Amateur-Built aircraft. You can install the VGs before or during Phase I flight testing. Just be sure to document everything during flight testing. Also be sure that you receive a builder’s log and all required documentation from the original builder to show compliance with the 51% rule.

Please send your questions for DAR Asberry to [email protected] 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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