NX numbers

[montauk1989]

I have an experimental exhibition category deHavilland chipmunk. It's basically stock except for the radio and transponder. I'd like to use the NX tail number in lieu of the "EXPERIMENTAL" sign. I understand that my plane qualifies but I'm not clear on whether or not I need to send anything to the FAA. Can I just change my "N" to "NX"?
Thanks
Dave

[mustanglover]

Sec. 45.22

Exhibition, antique, and other aircraft: Special rules.

(a) When display of aircraft nationality and registration marks in accordance with Secs. 45.21 and 45.23 through 45.33 would be inconsistent with exhibition of that aircraft, a U.S.-registered aircraft may be operated without displaying those marks anywhere on the aircraft if:
(1) It is operated for the purpose of exhibition, including a motion picture or television production, or an airshow;
(2) Except for practice and test fights necessary for exhibition purposes, it is operated only at the location of the exhibition, between the exhibition locations, and between those locations and the base of operations of the aircraft; and
(3) For each flight in the United States:
(i) It is operated with the prior approval of the Flight Standards District Office, in the case of a flight within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for the takeoff airport, or within 4.4 nautical miles of that airport if it is within
Class G airspace; or
(ii) It is operated under a flight plan filed under either Sec. 91.153 or Sec. 91.169 of this chapter describing the marks it displays, in the case of any other flight.
(b) A small U.S.-registered aircraft built at least 30 years ago or a U.S.-registered aircraft for which an experimental certificate has been issued under Sec. 21.191(d) or 21.191(g) for operation as an exhibition aircraft or as an amateur-built aircraft and which has the same external configuration as an aircraft built at least 30 years ago may be operated without displaying marks in accordance with Secs. 45.21 and 45.23 through 45.33 if:
(1) It displays in accordance with Sec. 45.21(c) marks at least 2 inches high on each side of the fuselage or vertical tail surface consisting of the Roman capital letter "N" followed by:
(i) The U.S. registration number of the aircraft; or
(ii) The symbol appropriate to the airworthiness certificate of the aircraft ("C", standard; "R", restricted; "L", limited; or "X", experimental) followed by the U.S. registration number of the aircraft; and(2) It displays no other mark that begins with the letter "N" anywhere on the aircraft, unless it is the same mark that is displayed under paragraph (b)(1) of this section.
(c) No person may operate an aircraft under paragraph (a) or (b) of this section--
(1) In an ADIZ or DEWIZ described in Part 99 of this chapter unless it temporarily bears marks in accordance with Secs. 45.21 and 45.23 through 45.33;
(2) In a foreign country unless that country consents to that operation; or
[(3) In any operation conducted under Part 121, 133, 135, or 137 of this chapter.]
(d) If, due to the configuration of an aircraft, it is impossible for a person to mark it in accordance with Secs. 45.21 and 45.23 through 45.33, he may apply to the Administrator for a different marking procedure.


Sec. 45.23

Display of marks; general.

(a) Each operator of an aircraft shall display on that aircraft marks consisting of the Roman capital letter "N" (denoting United States registration) followed by the registration number of the aircraft. Each suffix letter used in the marks displayed must also be a Roman capital letter.
[(b) When marks include only the Roman capital letter "N" and the registration number is displayed on limited, restricted or light-sport category aircraft or experimental or provisionally certificated aircraft, the operator must also display on that aircraft near each entrance to the cabin, cockpit, or pilot station, in letters not less than 2 inches nor more than 6 inches high, the words "limited," "restricted," "light-sport," "experimental," or "provisional," as applicable.]

[montauk1989]

Thanks for the reply. My question, because I've gotten mixed answers, was whether or not any one that's converted from "N" to "NX" had to notify the FAA of the change. The "X" of the "NX" is not as I understand it a part of your actual N number.
Dave

[mustanglover]

Thanks for the reply. My question, because I've gotten mixed answers, was whether or not any one that's converted from "N" to "NX" had to notify the FAA of the change. The "X" of the "NX" is not as I understand it a part of your actual N number.
Dave

I talked to my FSDO PMI and we both read the regulations and he agrees that you can apply the "NX" + registration number by yourself without having to notify the FAA.

This rule applies to aircraft over 30 years old (classic?) and makes the condition that you do not have to apply the "EXPERIMENTAL" decal which would detract from the display of the aircraft.

[ProfromDover]

The important part of the N number for the FAA is the basic number and letter suffix itself. That is reflected in the certificate of airworthiness as just "N1234", etc.

The FAA considers the addition of X, L, R, or C as ornamentation to be addressed in the above part 45 excerpt.

Changing the external markings from N1234 to NX1234 does not constitute any concern from the FAA as long as the additional letter matches the certification basis for the subject aircraft (i.e. X on an experimental aircraft)

[montauk1989]

Thanks for the replies. The number was changed last week so no need for the "experimental" sign. It a pity the FAA couldn't have made it XN instead of NX. It was a bit of challenge to make the change but it turned out great.
Dave