Who invented the term "C/N"

[Fris B. Fairing]

I am wondering about the origins of the term C/N for Constructor's Number. It has been suggested that it was first coined by Air Britain to describe the serial number assigned to an airframe by its manufacturer and to differentiate that number from a subsequent "serial number" as assigned by the military. So who was first to use it and when?

[chevvron]

I saw it used in 'Air Pictorial' from about 1960.

[WHBM]

More common in general engineering is MSN for Manufacturers Serial Number, but it seems that certain air forces got there first using the word Serial, with their own numbering scheme being known as Serial Number, so another term arose to avoid confusion. USA refers to Tail Number rather than Serial Number.

[megan]

More common in general engineering is MSN for Manufacturers Serial NumberI think there is a different interpretation between MSN and C/N, though the MSN is incorporated within the C/N. I'll use the P-51 as an example.

The aircraft was produced under the following North American factory identities - NA-73, 83, 91, 97, 99, 101, 102, 103, 104, 105, 106, 107, 109, 110, 111, 122, 124, 126. Missing numbers were either P-51 projects cancelled or other NA non P-51 projects.

The P-51D was produced as NA-106, 109, 110, 111, 112, 122, 124. 107, 127 and 138 were cancelled or transferred projects, 107 was cancelled and transferred to 103 for production as a C model.

A constructors number (C/N) for a particular P-51D in its entirety thus might be NA-122-30972, the 30972 being the serial number. Four thousand NA-122 aircraft were built.

[Fris B. Fairing]

Thanks everyone who has responded.

Megan, I think the terms C/N and MSN are interchangeable as they mean essentially the same thing. Noting your example of the P-51, it is not unusual for manufacturers to combine the model number with the Constructor's Number or the Manufacturer's Serial Number. Lockheed, Cessna and Piper are other examples that come to mind. Given that these are all American manufacturers it is more likely that the resultant number would be described as a Manufacturer's Serial Number or just simply a Serial Number. I have not found an example of an American manufacturer using the term C/N. If anyone can show evidence of such use I would be very pleased to see it.

It looks like the term C/N is a British invention which stems from late 1938 or maybe even earlier. In October 1938 the Air Registration Board introduced a card with a column headed "Constructor's No."

So the objective is to find British use of the term C/N earlier than 1938 or American use at any time.

Rgds

[DaveReidUK]

To muddy the waters further (well why not :O), Boeing jet airliners all have two numbers allocated by the manufacturer: a 5-digit number that is unique across all Boeing jets and another number indicating the aircraft's sequence in the production of the type concerned (commonly referred to as the "line number")

For example just landed at Heathrow is one of Singapore Airlines' Boeing 777s, 9V-SWU, which has serial number 42235 (unique) and line number 1124 (specific to the 777). United have a 747 with the same line number, and it's been used for two 737s (for a -300 Classic and a -800 NG where Boeing started again from 1).

Incidentally the FAA always refers to "serial number" in ADs, Type Certificates, etc, rather than MSN or C/N.

[treadigraph]

Now that Dave has stirred the mud a little, I always thought it odd that the Aztec shares the PA-23 designation with the Apache (certification purposes?) but has c/ns prefixed "27-" which I think was the Piper project number?

[DaveReidUK]

Now that Dave has stirred the mud a little, I always thought it odd that the Aztec shares the PA-23 designation with the Apache (certification purposes?) but has c/ns prefixed "27-" which I think was the Piper project number?

Yes, the Apache and Aztec share the same Type Certificate (1A10). The TC differentiates between the 150/160 hp O-320 powered Apaches (with 23- MSNs) and the 235/250 hp O-540 powered Apaches/Aztecs (with 27- MSNs).

[safetypee]

Adding to the muddy the water, the BAe146 / RJ used ‘set’ numbers which became airframe build numbers on assembly.
The aircraft reference consisted of a four number group, the first represented the subtype - length of centre fuselage, 1=100, 2=200, 3=300, and the last three numbers the serial number of the assembled airframe and matching sub’set’ components.
The plan was for the finally assembled aircraft to have consistent sequenced parts after the size - length, was defined by sales; nose from Hatfield, centre fuselage Bristol (the variable bit), and tail section Chadderton. e.g. 3121 was a 146-300 and 121st in ‘build sequence’ (not necessarily as built or flown).
All started well until ‘set’ 19 tail section fell off the back of a lorry on the M60. Thereafter a more general mix and match policy ensued.

The chosen numbering system, the final aircraft identification, was the master certification reference and thus influenced by the ‘home’ regulating agency - UK CAA, who required a reference and tracking system related to the aircraft type approval.
Further complications arose with the RJ because these were built under the umbrella of the 146 type certification, but with modifications applied, - there was no independent type designation. e.g. 2207 was the ‘first’ RJ (85) but built as and amongst the final 146s.

So to address the question, the designation or change of term probably relates to the requirements of certification authority (civil / military) and need to track design, build, and in-service modification.

Also, a generalised MSN system enables additional references, dash no, to cope with different engines on the same aircraft ‘type’, additional systems, operational capability, and customer specific changes which affect certification.

[treadigraph]

Thanks Dave, hadn't realised some Apache c/ns were prefixed 27-

Incidentally, reference Boeing, Douglas Commercial also had consecutive c/ns covering all types presumably allocated as customers ordered batches of airframes - presume they also had a line number system?

[El Bunto]

Flight's archive has "constructor's number" used in correspondence from 1955 and "construction number" in the editorial text from 1960.

Nothing in Aviation Week until one reference in 2016.

[megan]

The FAA seems not to use the C/N term.

https://www.faa.gov/licenses_certificates/aircraft_certification/aircraft_registry/media/ardata.pdf I have not found an example of an American manufacturer using the term C/N

You've created confusion now Fris. The P-51 book I took the info above from uses the term C/N and is written by an American resident. The question now is his use of C/N legitimate? It was designed and built to a British requirement so perhaps they, North American, adopted the British convention.

It does seem that the term C/N has entered wide use today irrespective of the aircrafts source.

https://aviation-edge.com/database-construction-number-aircraft/

[Fris B. Fairing]

It does seem that the term C/N has entered wide use today irrespective of the aircrafts source.


Agree with you totally on that Megan. It has become a standard for aviation historians and for this reason I have no issues with its use in the Mustang book that you quote.

[Art Smass]

The CAA registration summary (see G-INFO) used the term Constructor's Number - I had a look at DH.51 G-EBIR which was registered in Jan 1924 - the pdf quotes C/n (though I guess these early sheets may have been filled out later)

Interesting though that G-INFO now uses "Serial Number"

AS

[DaveReidUK]

The CAA registration summary (see G-INFO) used the term Constructor's Number - I had a look at DH.51 G-EBIR which was registered in Jan 1924 - the pdf quotes C/n (though I guess these early sheets may have been filled out later)

Yes - as alluded to earlier, what you are looking at is the 1938 version of CA Form 113 (Aircraft Register card) retrospectively raised for aircraft that were first registered prior to that year:


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[Planemike]

Sorry for being "picky" but surely the question should read, when did the term "constructors number" come into use.
It is not a matter of "inventing" it.....

[Fris B. Fairing]

Sorry for being "picky" but surely the question should read, when did the term "constructors number" come into use.
It is not a matter of "inventing" it.....

Having got your attention, the question was then posed:

So who was first to use it and when?

Thus far it has produced many helpful contributions for which I am thankful.

[tonytales]

I am looking at a Lockheed - California Company's ID plate formerly affixed to an ex-Eastern Airlines L-1011 Tristar - quote:
MANUFACTURER'S MODEL L-1011-385-1
CUSTOMER'S MODEL 193A
MANUFACTURER'S SERIASL NO. 193A-1040
CUSTOMER'S SERIAL NO. 319
TYPE CERT. A23WE
CONTRACT NO. PROD. CERT. 600
ENGINE TYPE RB211-22CA-02
ACCEPTED 9-6-73
Note that the first L-1011, the prototype was MSN 193-1001so this particular aircraft was the 40th built. I am surprised at the engine model. The first deliveries were all fitted with RB211-22C engines. I thought they had switched to the 22B by the time this aircraft was built but it is 45 years after all. There is no overall serial number indicating what production position this aircraft placed in all of the tens of thousands of all the models of aircraft Lockheed built.
The Customer's Serial Number, 319, is what Eastern painted up front and was what the aircraft was identified as by maiontenance and others..

[DaveReidUK]

The first deliveries were all fitted with RB211-22C engines. I thought they had switched to the 22B by the time this aircraft was built but it is 45 years after all.

The -22CA was basically a -22B operated to -22C thrust levels. All -22CA engines were later converted to -22B models, but presumably there was no requirement to update the manufacturer's data plate on the airframe.

[tonytales]

Regarding the RB211-22CA engines on the early L-1011 deliveries to Eastern:
It was well a behaved engine if a bit low in power on hot days and we thought we had bought into a really good engine as our last experience with the big fan engines was the JT9D-3A on the leased B747 we operated. However, in going to 22B power, we found the engine had very little stall margin and that it would bang violently at the least provocation. Ted Fifield, the resident Rolls Royce rep assigned to Eastern at KJFK and I chased backfiring engines all over the Eastern region. We discovered that the stalls were violent enough to bend the "banana link" on the Variable Inlet Guide Vanes (VIGV) which completely messed up the vane schedule.
Please excuse the thread drift.

[Fris B. Fairing]

I'll forgive thread drift if it involves Lockheed aeroplanes.

[megan]

I'll forgive thread drift if it involves Lockheed aeroplanes Invitation accepted Fris. Sigh, my one and only true love, the wife understands. Paxed a number of times when a young teenager in this aircraft, the pilots of which were responsible for my foray into the occupation.

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