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Tales from the DAR Side

Attack of the Placards

Joe Norris

Last month, I discussed the “EXPERIMENTAL” marking and passenger warning placard. Beyond those items there’s a general requirement for placards and markings called out in 14 CFR 91.9. While there’s no specific guidance for these markings, the idea is to make it obvious what each switch, control, fuse, or circuit breaker does. Plus, a follow-up to some of your questions about N numbers. Read more

I’m still getting a number of calls and e-mails with questions on N numbers, so before I move to our subject of this month’s column, I want to touch on N numbers one more time. Specifically, there continues to be some confusion on when the “NX” prefix can be used. Let’s try to clear things up.

First and foremost, you’re only allowed to use the “NX” prefix on aircraft that are at least 30 years old, or on aircraft which are replicas of small U.S. aircraft that are at least 30 years old. Remember, a replica in the eyes of the FAA is an aircraft that has the “same external configuration” as the aircraft being replicated. That means it has to be the same wingspan, length, shape, etc. Scale replicas don’t meet these criteria. We’re talking full-size replicas here.

With that in mind, let’s take a look at a few examples. There are many popular homebuilt designs that have been around for at least 30 years. The Wittman Tailwind, Pietenpol, Baby Ace, Fly Baby, Midget Mustang, and Pitts Special all come to mind. Other “legacy” homebuilts are also included in this group, such as the Thorp T-18, Breezy, EAA Biplane, Acro Sport, and many others. But there are also some homebuilts that aren’t normally considered when discussing legacy designs. Aircraft like the RV-3 and RV-4, the VariEze and Long-EZ, the Sonerai II, and even the original tailwheel Glasair are all 30-year-old designs, so builders of these aircraft have the option of displaying their registration mark with the “NX” prefix, which then eliminates the requirement to put the “experimental” marking near each entrance.

Builders can’t stretch the replica definition to include aircraft that are just about the same. “Close enough” doesn’t count. For example, just because the RV-4 design has been around for over 30 years, it doesn’t give an RV-8 builder the option of displaying “NX.” The RV-8 design looks like a close relative of an RV-4 for sure, but it isn’t a replica of the RV-4 in the FAA’s eyes. RV-8 builders will have to wait until 2025 before they can use the “NX” prefix for their registration mark.

For those of you who do have aircraft that meet the criteria for displaying “NX” as the prefix for your registration number, remember that it’s only used to mark the number on the aircraft. “NX” won’t appear on the aircraft’s registration certificate or on any of its paperwork. The FAA records will just show the N number in its usual form, with the N followed by the registration mark of the aircraft. So if you’re requesting a custom N number for your homebuilt, don’t ask for “NX,” as you’ll only confuse the issue. Just request the N number you want and then mark it on the aircraft with the “NX” prefix. You don’t have to change anything on the registration application or other paperwork.

Okay, I hope that clears up everything on the N number issue. Now let’s turn our discussion back to the topic of proper placards and markings. Last month, I discussed the “experimental” marking and passenger warning placards. Beyond those items there’s a general requirement for placards and markings called out in 14 CFR 91.9. While there’s no specific guidance for these markings, the idea is to make it obvious what each switch, control, fuse, or circuit breaker does. Think about it from the viewpoint of a person sitting in the aircraft who has never seen it before. The idea is to mark each control, etc., so that there’s no question as to what it does and how to work it. For example, you would mark the throttle control with the word “Throttle” and include an instruction on how to use it, such as “push to open” for a panel-mounted knob or “open” with an arrow pointing in the appropriate direction for a throttle lever. Same goes for “Mixture,” “Propeller,” or “Flaps.” This idea carries on to switches and other items in the cockpit.

There’s no specified way to incorporate these placards and markings, so it’s up to the builder to choose the method they may wish to use. Here are some examples I’ve seen in aircraft I’ve inspected.

Placard 1

This builder used a combination of placards off the sheet provided in the EAA Amateur-Built Certification Kit and others made with a standard label maker. Using the placards supplied in the kit is a very common way to go. Using a standard label maker is quite common as well.

Placard 2

Sometimes the placards are made on a clear background so that the color of the instrument panel shows through, as in this example.

Placard 3

This builder has marked the purpose of each switch directly on the panel, then placed a universal “on” and “off” above and below the switches as appropriate.

Placard 4

Here we see a builder who used individual letters to make the placards. A lot of work, but nice results.

Placard 5

This builder used material similar to that used for plastic name badges to make the placards. This is a very clean and professional look.

As you can see, there are many ways to meet the placarding and marking requirements in the cockpit. It really doesn’t matter how you do it, so long as you do it! A good job of marking everything will help make your final inspection go smoothly.

One often-forgotten marking is the fuel filler. Each filler location should be marked with the minimum allowable grade of fuel and the capacity of that individual tank. Here are two examples of how this can be done.

Placard 6

Placard 7


Don’t forget to indicate any special fueling requirements, such as mixing two-stroke oil with the fuel if required. Here’s a way to meet that requirement.

Placard 8

You should also placard any special instructions or limitations. For example, if there are rpm ranges where your engine/propeller combination shouldn’t be operated, you should either put a placard on the panel or mark a yellow arc on the tachometer (or both). If you place limit or range markings on the instrument glass, you need to include a slippage mark so that it will be readily apparent if the glass slips or rotates in the instrument. A slippage mark is usually a small white mark at the bottom of the instrument that is partially on the glass and partially on the instrument bezel. If the white line is broken, the glass has slipped and the pilot knows the limit and range markings are no longer accurate.

Here are a couple of examples of instrument slippage marks.

Placard 9

Placard 10

You’re now ready to properly mark your homebuilt! We’ve talked about data plates, N numbers, and required placards and markings. Having all these markings properly placed will help make your final inspection a breeze!


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