Unusual Three Letter Registrations

[Noha307]

I was just looking through the Grumman photographs thread and I came across a page with a couple of interesting pictures that show Grumman G-36's with the apparent registrations "NXG7" and "NXG8" outside of a Roosevelt Field hangar:


(Source: Warbird Information Exchange)

It reminded me of another picture I found on a Secret Projects thread a while back that showed a Martin Baltimore III with the registration "NXM53":

(Source: Secret Projects)

Another picture of the aircraft with the same unusual registration - and a rudder in RAF camouflage - appears in the book Weapons and Warfare:

(Source: Bernard Fitzsimons, ed., Weapons and Warfare, vol. 3, 24 vols. (New York: Columbia House, 1977), 268.)

While American aircraft registrations began with two letters until 1948, outside of the above instances I have never seen three letters.[1] (As an aside, it reminds me a bit of the three digit Wright Field designations in that they both appear to be an extension of existing systems outside of the "rules".) The original poster of the Baltimore picture was confused as to what the "M" could have stood for. However, with two data points, I have a theory: the third letter was taken from the manufacturer's name. In other words, "G" for Grumman, "M" for Martin. Furthermore, both of the pictured aircraft were likely intended for export. As proposed by someone in the Secret Projects thread, it appears as though these were temporary registrations. To speculate a bit further, it is worth noting that the pictures were likely taken before the United States was involved in the war. (As evidence of this, another G-36, NX-G1, was pictured with French roundels. These would have been replaced with the British ones seen above when France capitulated - in 1940.) Equally important, both aircraft types were acquired by the "Anglo-French Purchasing Board". At this time, the United States was still trying to appear nominally neutral and forced the commission to purchase materiel via the "cash and carry" policy. Therefore, taken as a whole, the civilian registrations seem to be an attempt to have a façade of neutrality. In other words - unlike under the later lend-lease program, where aircraft were nominally taken on strength with the U.S. military and briefly given a USAAF serial number before delivery - the G-36 and Baltimore were being sold by private companies, under civilian registrations, to a foreign government, that the United States government was in no way involved with.

[k5083]

I guess my first question would be, how sure are we that those IDs are really official civil registrations?

My understanding of N-numbers is that regardless of the prefix letters, the following sequence beginning with the number has to be unique. That means that if there were really an NXG6, there couldn't be an NX6, NC6, NR6, etc. At least that was true with the version of the system that carried through after the 1940s. I'd want to check CAA-FAA records to see if these registrations really existed or were just corporate/military designations that look sort of like civil registrations.

I know there is a rule against painting a letter/number sequence on your plane that looks like it could be a civil registration, which is why the CAF's Spitfire used to sport only the letters H749 of its serial NH749. But more recently I notice it displays the whole serial, so apparently you can get a waiver. It wouldn't have been hard for the military and aircraft corporations to get such waivers if they wanted to further that facade of neutrality you mentioned.

August

[Noha307]

I guess my first question would be, how sure are we that those IDs are really official civil registrations?

I toyed with the idea that they could be some other identification marking, but nothing else seemed to fit. For example, I briefly considered that they could be British military serial numbers. However, as far as I can tell, the British never had serials that began with three letters either. Furthermore, the Martlets used serial numbers that began with AL, AX, BJ, and BT.[1]

It's interesting that the one in French markings has a hyphen in the registration: "NX-G1". However, the Spirit of St. Louis's registration, N-X-211, has no less than two. So it's not out of the question.

My understanding of N-numbers is that regardless of the prefix letters, the following sequence beginning with the number has to be unique. That means that if there were really an NXG6, there couldn't be an NX6, NC6, NR6, etc. At least that was true with the version of the system that carried through after the 1940s. I'd want to check CAA-FAA records to see if these registrations really existed or were just corporate/military designations that look sort of like civil registrations.

Other than asking for standard copies of aircraft paperwork of CD, I haven't done much research with the FAA and I don't know how accessible records like that would be.

I know there is a rule against painting a letter/number sequence on your plane that looks like it could be a civil registration, which is why the CAF's Spitfire used to sport only the letters H749 of its serial NH749. But more recently I notice it displays the whole serial, so apparently you can get a waiver. It wouldn't have been hard for the military and aircraft corporations to get such waivers if they wanted to further that facade of neutrality you mentioned.

It's actually something that I've considered in regards to the restoration of aircraft where the registration, since it was painted so large on the wing, could be considered part of the paint scheme of the aircraft. For example, a regular Piper Cub being restored to resemble a Flitfire, but the registration of the aircraft being replicated, for whatever reason, is not available. The rule you mentioned can be found in 14 CFR 45.22, which allows exemptions from the normal marking rules. (I presume partially based on justification similar to that behind the Living History Flight Experience.) The same section states that if normal marking is impossible under any of the existing regulation, requests for exemption may be applied for on a case-by-case basis. I guess the next question would be whether the same rule existed under the CAA in 1940.

As an aside, if any marking starting with an "N" is considered some level of problematic by the FAA, how about having two airworthy aircraft painted with the same registration? To go back to the Spirit of St. Louis for a second, there are multiple airworthy replicas of the airplane, and at least both the EAA and Old Rhinebeck examples have "N-X-211" painted on the wings and rudder. However, only the former is actually registered as the modern equivalent: N211. The latter is N211XC.

Not to get too off topic, but one other instance to wonder about: The registration of Amelia Earhart's Lockheed 10E Electra, NR16020, was permanently retired by the FAA in 1988. Indeed, if you look up the modern equivalent, N16020, on the FAA database it reads "permanently reserved". If the goal was for it to "never...be used by anyone ever again", then why was the Museum of Flight's Lockheed Electra allowed to fly while marked as it? To be clear, technically the aircraft was registered as N72GT, but allowing the marking to be applied seems to violate the intent of removing it from use.

EDIT: So, I found a 1939 copy of 14 CFR 02 and there is nothing that specifically mentions a third letter. There is a "domestic aircraft for foreign delivery" section, but it just states that aircraft may display the registration of a foreign country, not a modified version of an American one. The only provisions for non-standard markings appear to be a cross, +, to indicate aircraft owned by a foreign individual and a bar, _, to indicate an uncertified aircraft. (Note, the latter is depicted in the text as an underscore, but seems possible that it is meant to represent a hyphen. This may explain the odd use of one on a Boeing 707 as mentioned in a different thread.)

[k5083]

Clearly the FAA permits some historic aircraft to display the same registrations as the originals but to actually be registered something else. I believe one of the airworthy NYP replicas actually is registered NX211 (or we would just say N211 nowadays), the others are likely granted permission to wear one registration while displaying the other more subtly, probably on a case-by-case permission basis. The UK does the same thing, I think.

But, I think only one aircraft can really be registered N_211 at a time, whether it's N211, NX211, NC211, or whatever. Also, even though the second letter doesn't count any more you are still allowed to display it, as you can see on countless antique aircraft. Hyphens within the registration, as far as I can tell, don't count at all. N-X-211, NX211, and N211 are all the same to the FAA.

So there can only be one N_6. I checked this site:

http://www.airhistory.org.uk/gy/reg_N.html

I don't know where this guy pulls his info, but two interesting points here. First, the numbers N1 through N25 are reserved by the DoC, basically for government use. This seems to have been true from the beginning through this day. I have seen a few of the current ones, Reagan KDCA is a good place to spot them.

According to the above list, there was a Travel Air BW (i.e., a 4000) registered NC6 and a Stinson SR registered NS6. It doesn't give the dates each registration was active; I assume they were not current at the same time. Probably they acquired the Travel Air in the 1920s, sold it or wrote it off, and the Stinson took up the registration in the 1930s. Who knows how long the Stinson lasted; conceivably through the war.

Then, according to the below, the DOT owned a DC-3 registered N6 from 1948 to 1975.
http://www.aviationdb.com/Aviation/Aircraft/6/N6.shtm

The number has since been worn by a Citation operated by the FAA, and likely other aircraft. All government owned.

My suspicion is that there never was an aircraft registered NXG6. or any other numbers shown in these pics. I think it was just painted on these planes built for export, which probably were test flown without any true military or civil registration, so the manufacturer could keep track of them. The NX in front was just to make them seem like civil aircraft at a glance. Maybe with the informal blessing of the CAA. The fact that at least two manufacturers used what appears to be the same system is interesting. Maybe this was coordinated; maybe one just imitated the other.

I could be wrong, maybe there is a musty document in the FAA's archives somewhere with a record of this shadow registry, but my default assumption would be that these were simply bogus civil reg numbers.

August

[Archer]

In the UK, aircraft without a full CofA were/are permitted to fly with a test serial, see here: https://en.wikipedia.org/wiki/United_Ki ... st_serials
Could this be a US variant perhaps? Or a UK issued test serial used on US built airframes during WWII? The format does not fit any of the systems mentioned on the Wiki page unfortunately.
To me, the assumption in the first post would make sense, with the third letter denoting the manufacturer. That would make these experimental civil registrations allocated to Grumman (NXG) numbers 7 and 8 with the Martin Maryland using the Martin variant of this.

[bdk]

N1 in the FAA registry:

N-Number Entered: 1 Aircraft Description Serial Number 680-0519 Status Valid
Manufacturer Name CESSNA Certificate Issue Date 11/30/2021
Model 680 Expiration Date 11/30/2024
Type Aircraft Fixed Wing Multi-Engine Type Engine Turbo-fan
Pending Number Change None Dealer No
Date Change Authorized None Mode S Code (base 8 / Oct) 50000001
MFR Year 2014 Mode S Code (Base 16 / Hex) A00001
Type Registration LLC Fractional Owner NO

[Noha307]

In the UK, aircraft without a full CofA were/are permitted to fly with a test serial, see here: https://en.wikipedia.org/wiki/United_Ki ... st_serials

I was aware of the "slash G" for "guard" and "circle P" for "prototype", but had never heard of those before. Thanks for bringing them up.

Or a UK issued test serial used on US built airframes during WWII?

It's an interesting possibility. However, the NX-G1 "registration" first appears on a G-36 with French markings. So if they are indeed British serials, it would presumably mean they were acting as a middleman for the French.

I don't know where this guy pulls his info, but two interesting points here. First, the numbers N1 through N25 are reserved by the DoC, basically for government use. This seems to have been true from the beginning through this day.

According to the above list, there was a Travel Air BW (i.e., a 4000) registered NC6 and a Stinson SR registered NS6. It doesn't give the dates each registration was active; I assume they were not current at the same time. Probably they acquired the Travel Air in the 1920s, sold it or wrote it off, and the Stinson took up the registration in the 1930s. Who knows how long the Stinson lasted; conceivably through the war.

Then, according to the below, the DOT owned a DC-3 registered N6 from 1948 to 1975.
http://www.aviationdb.com/Aviation/Aircraft/6/N6.shtm

The number has since been worn by a Citation operated by the FAA, and likely other aircraft. All government owned.

Good point about low numbers being reserved for the government. (For what it's worth, a bunch of other short ones have been picked up by a holding company. ) However, the Baltimore registration, NXM53, would have been outside the reserved range you mentioned. (I do have to wonder if the fact that it is such a high number points to the existence of an entire series of numbers.) However, according to the above list, it appears that, at some point, the CAA may have used numbers up to NC185.

Interestingly, there's a set of Grumman G-21s from NX97 to NX108 that were all exported to Portugal. I am not sure if this means anything, but it may suggest that Grumman had experience using lower, potentially former CAA registrations for export. (As another aside, Bowers wrote an article about the reuse of registrations. Nothing that anyone here doesn't already know, but still a worthwhile read.)

My suspicion is that there never was an aircraft registered NXG6. or any other numbers shown in these pics. I think it was just painted on these planes built for export, which probably were test flown without any true military or civil registration, so the manufacturer could keep track of them. The NX in front was just to make them seem like civil aircraft at a glance. Maybe with the informal blessing of the CAA.

I think you might be right. However, the fact that low numbers were otherwise used by the CAA seems to point to their involvement in some form. If I was going to make up a fictitious registration for an airplane I was going to sell overseas and didn't have the CAA onboard, I wouldn't have picked one of the numbers that they used on their aircraft. Besides, if you're just going to use it for tracking purposes, why make it look like a registration and risk getting into trouble with the CAA? Unless you have some implicit understanding with them...

The fact that at least two manufacturers used what appears to be the same system is interesting. Maybe this was coordinated; maybe one just imitated the other.

That's the part I couldn't work out either. If this was not an official registration, how did two different companies end up using the same format? The one common variable appears to be a connection with the Anglo-French Purchasing Board. The board also purchased aircraft from just about every other major American manufacturer. If we could find pictures of these airframes, we might find more evidence of these three letter "registrations".

EDIT: Someone suggested checking out the Brewster B-339s ordered by the Belgians. While there isn't any evidence of improper registrations, I did find a page with picture of one, NX56B, with a hilariously "squished" registration. (Evidence of a haphazard and rushed implementation perhaps?) On a more serious note, it seems reasonable that the "B" on the end would have stood for "Brewster".

EDIT (22-03-29): Fixed the incorrect registration. Guess that's what I get for trying to read upside-down!

Last edited by Noha307 on Tue Mar 29, 2022 9:38 pm, edited 1 time in total.

[Chris Brame]

NX95B, with a hilariously "squished" registration.

Close.

brewster NX56B.jpg (54.28 KiB) Viewed 5797 times

[k5083]

EDIT: So, I found a 1939 copy of 14 CFR 02 and there is nothing that specifically mentions a third letter. There is a "domestic aircraft for foreign delivery" section, but it just states that aircraft may display the registration of a foreign country, not a modified version of an American one.

I think this may be an important clue, and possibly the answer.

When Curtiss sold Tomahawks and early Kittyhawks and NAA sold Mustangs to the British, the only IDs they were ever given were their allocated British military serials. Presumably they were tested using just these markings, and 14 CFR 02 authorized this practice. (Later, with Lend-Lease, aircraft were also given US serials, understandably.)

So what would have been the French military serials of the Wildcats and Baltimores? Here's the French system:
http://www.airhistory.org.uk/rfc/French.html
http://www.aeroflight.co.uk/ops/mil/fre ... -force.htm

So it's an allocated manufacturer letter(s) followed by numbers starting from 1 for each manufacturer. (Nowadays there is usually a period between the letters and the numbers, and sometimes a leading 0 for numbers under 10.)

This means that if the French allocated G for Grumman and M for Martin, the French military Wildcat serials could have been G1 (or G.1), G2, G3 ... and the Baltimores M1, M2, M3 ...

So, possibly, Grumman and Martin used the serials they were given by the French and slapped "NX" on the front. Maybe because something like "G1" doesn't look much like a registration number on its own.

August

[M-62A]

The information is out there - it is just finding it.
"Air Arsenal North America" (Butler & Hagedorn)
The section on the Grumman G-36 Martlet/Wildcat begins on page 210.
The first photograph shows "Grumman G-36A No.1 of the French Navy, also wearing temporary registration NX-G1 for test flights at Bethpage in June 1940." Photograph credited to "Aviation Historical Society Collection, 382".

"Martin Aircraft 1909-1960" (Breihan, Piet & Mason)
On page 85 the photograph of first RAF Maryland II, AH280 is also marked NXM36 which the caption states "is a temporary U.S. experimental registration".
Page 88 has a photograph of "five of the thirty-five 167-B3 completed in July 1940 with British equipment and designated Maryland I. Wearing temporary NXM registrations, they await shipment via Canada."

I have not found a corresponding image of Brewster Buffalo.
Whereas the Grumman G-36 and the Martin 167 were initially ordered by the France, the Brewster 239 was initially ordered by Belgium. By agreement those aircraft not already delivered when Belgium and France fell into Nazi hands in May/June 1940, were transferred to the UK. It would interest to know if any other types were first flown with these temporary company/test marks, such as the French orders for the Curtiss Model 81/Tomahawk.

[k5083]

With respect, though, just because an author (secondary source) calls it a "registration" doesn't prove it is one. He could be assuming or speculating. That just begs the question raised by the OP, which is that given that the letters painted on the plane don't seem to conform to any known US civil registration format, it would be nice to know if there is a primary source confirming that these are, indeed, registrations, rather than just numbers painted on planes.

August

[Kyleb]

I assume the FAA granted Grumman (for instance) a block of N-numbers so they could legally fly those non-military, not certified airplanes in US airspace. Certainly, they did one or two debugging/acceptance flights before putting those aircraft on a boat to cross the ocean.

The registrations are NX, meaning Experimental, since those aircraft didn't have a standard airworthyness certificate.

The letter G would seem to represent Grumman in this instance, and the first Martlet would have been NXG1, followed by NXG2, etc.

Looks like the other manufacturers had similar blocks of N-numbers for their export aircraft too, at least up to a certain point where the number of registrations created a silly amount of paperwork with a war going on.

[Noha307]

NX95B, with a hilariously "squished" registration.

Close.

Whoops! Thanks for the correction.

This means that if the French allocated G for Grumman and M for Martin, the French military Wildcat serials could have been G1 (or G.1), G2, G3 ... and the Baltimores M1, M2, M3 ...

Interesting theory. Since certain aircraft types were only ordered by the British and others (originally) only by the French, it would be worth checking if the three letter "registration" format only shows up on the latter. If this is the case, I guess the British just didn't bother changing the marks when they took over the order.

[shrike]

Having dealt with the FAA, and assuming the CAA to have been similar, you are all overlooking one likely possibility.
There may not have been an actual recorded policy, but rather a local interpretation of regulations at the whim of one or two representatives in the flight standards office assigned to the factories.
There have been quite a few cases over the years where our form of compliance with regs has been set by an informal conversation with our current PMI without the benefit of written documentation. As he was the local authority all was good. The next one may change or reverse policy, again at no more than a personal whim or pet interpretation, and that too is good.

[k5083]

Shrike, your idea fits fine with my theory that the CAA informally allowed the letters/numbers to be painted on the plane and test flown without a real registration or under 14 CFR 02. I'm sure there was all kinds of red tape cut when test flying military airplanes in those days, and the factory and local CAA guys worked together closely.

If it comes to really assigning a civil registration to an aircraft, that's a central database, I don't think local reps get to give those out without going through DC at some point.

August