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EAA Experimenter

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Tales from the DAR Side

Joe Norris

My column in the January 2010 issue of Experimenter on data plates generated some good questions and comments from members. I covered some of them in last month’s column. One thing I didn’t cover is the appropriate location of the data plate, so I’ve used that as the subject for this month’s Experimenter Q&A.

Our discussion of N numbers last month gave you a good understanding of what the regulations require regarding the size and other dimensions of the individual characters. The regulation states that the N and any other letters included in the registration mark be “Roman capital.” No cursive or script fonts are allowed. The FAA wants to see this:


Not this:


Part 45 also contains some other requirements for the N number that are sometimes overlooked. For example, they must be uniform in size, have no ornamentation, contrast in color with the background, and be legible. Seems pretty understandable, but some builders get creative with some of these requirements. If you walk around any fly-in looking at paint jobs, you won’t have to look long before you see some N numbers that don’t seem to comply with Part 45. Like these for example:

N number

N number

N number


In the first picture, not only is the thickness of the characters suspect but also there is a lack of uniformity. In the second picture the N is not roman capital, and the characters are too close together. In the third picture the spacing is much too close, and of course there is no uniformity. My guess is that all of these were marked on the aircraft after the FAA inspector or designated airworthiness representative issued the airworthiness certificate.

Now that we know what the N numbers are supposed to look like, we need to know where to put them on the aircraft. Let’s start out by discussing fixed-wing aircraft. This is covered in Title 14 Code of Federal Regulations (CFR) Part 45.25. The two choices are either on the vertical tail or on the fuselage between the trailing edge of the wing and the leading edge of the horizontal stabilizer. In either location the number should be displayed horizontally, but if 3-inch numbers are used, they may be displayed vertically on the vertical tail surface. Note that when the FAA says vertically, it means this:


Not this:

N number

Note that this vertical N number also is not uniform in size and is spaced too close together. There’s actually one more problem with this one. On aircraft with multiple vertical tail surfaces, the N number is required to be on the outer surface of the outermost vertical tail surface. Note that this one is on the inner surface of the vertical tail. Again, I would bet that this was done after the FAA’s airworthiness inspection was completed.

The requirements for non-fixed-wing aircraft are called out in §45.29. There are specific requirements for rotorcraft, balloons, airships, powered parachutes, and trikes. For example, the section regarding powered parachutes and trikes reads as follows:

Each operator of a powered parachute or a weight-shift-control aircraft must display the marks required by §§45.23 and 45.29(b)(2) of this part. The marks must be displayed in two diametrically opposite positions on the fuselage, a structural member, or a component of the aircraft and must be visible from the side of the aircraft.

This wording allows enough flexibility to address the wide variety of aircraft configurations encountered in this segment.

There are special rules that apply to exhibition, antique, and other aircraft. These are called out in §45.22. I touched on these in last month’s column, and you can also see further discussion in the Q&A section of the Experimenter website.

I hope this gives you a pretty good understanding of the requirements for marking the N number on your homebuilt. Next month we’ll talk about other marking requirements, such as placards, instrument markings, etc. Until then I hope you enjoy reading this issue of Experimenter!


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