THE ORIGINS OF THE TERMS

CONSTRUCTOR'S NUMBER
&
MANUFACTURER'S SERIAL NUMBER

WHICH IS CORRECT?

by Ron Cuskelly and Trevor Boughton

 

Data Plate from Hudson Mk V AM681
Data Plate from C-121C VH-EAG
Data Plate from B707-138 VH-EBA

 

 


Compiler's Introduction

When I first became aware that "aeroplanes ain't aeroplanes" and that they each have their own unique identity, I was confronted by that now familiar term "c/n". But what did it mean? I was aware that aircraft had "serial numbers", so did users of the term really mean "s/n" or did they not know how to spell "serial"? One thing was immediately clear, it wasn't intended to represent "cereal number" which might have been some sort of roughage quotient. Thanks to my mentors I was soon acquainted with the term "Constructor's Number" which is usually abbreviated to "c/n" and presented in lower case separated by an oblique.

Sometime in 2018, I posed the question; Who invented c/n? If anyone would know the answer it would be Trevor W. Boughton, one of Australia's foremost aviation historians and renowned stickler for detail and accuracy. There ensued many weeks of correspondence between us. We never reached a definitive answer but we did establish to our mutual satisfaction that it was a British invention, it was totally legitimate and it went "way back". To support this conclusion, much evidence was collected but for various reasons it never saw the light of day. Sadly, Trevor Boughton passed away unexpectedly on 6th October 2019. This page is based on the latest of several draft documents which summarised our investigations to Trevor's satisfaction. This page is dedicated to Trevor's memory.


Who invented c/n?


A random review of images of aircraft data plates reveals that the following descriptors were in use at various times:

NUMBER
NO.
SERIAL
SERIAL NO.
MACHINE NUMBER
MAKER'S NO.
FACTORY NO.
MANUFACTURER'S SERIAL NO.
MFG. SERIAL NO.
MANUFACTURER'S NO.
MFG. NO.

A Douglas data plate for an R4D-8 delivered in 1952 records a "Manufacturers Serial No." and a "Customers Serial No." in acknowledgement of the fact that the aircraft had a serial number issued by the manufacturer as well as a serial number issued by the customer, in this case the U.S. Navy. Modern convention suggests that "Serial Number" is a purely military identifier although this was clearly not the intention when many aircraft were built. Military serial numbers of aircraft built in the USA are alternatively known as "Tail Numbers" even though the number physically painted on the tail can be a truncated form of the actual serial number. Aircraft of the United States Navy carry serial numbers allocated by the USN Bureau of Aeronautics and these are usually described as Bureau Numbers often abbreviated to BuNo.

Given the wide variety of terms used on data plates, it is clear that a central registration authority would have been faced with either adopting one of these terms or coining a new term which was devoid of any ambiguity arising from the use of the common descriptor "Serial Number". While the manufacturers continued to operate in splendid isolation, the registration authorities in the UK and the USA did achieve some degree of standardisation, although each chose a different standard terminology. It would appear that the UK opted for "Constructor's Number" and the USA adopted "Manufacturer's Serial Number".

The significant difference between "Constructor's Number" or "Manufacturer's Serial Number" and "Serial Number" is that a C/N or MSN does not change during the lifetime of a particular airframe. On the other hand, a "Serial Number" issued by the military can change if the aircraft continues in military service after being sold to another nation with a different numbering system.

As far back as 1910, the Paris International Convention on Air Navigation recognised the need for all civil aircraft to be registered. International implementation was delayed by WWI but in 1911 a Draft Air Navigation Bill was introduced in the UK stating that with effect from 20 April 1919 all British civilian aircraft must carry registration markings. As an interim measure, British civil aircraft would use a continuation of the RAF serial system beginning at K-100. A listing of these registrations published as recently as 1986 uses the term "C/N" (Constructor's Number) to define individual aircraft. It is not known if this term was used in the original document or if it was applied retrospectively by the compiler.

As an indication of what requirements had prevailed, an Australian document titled "Application for Registration of an Aircraft" issued under Aerial Navigation Regulations 1915, requires the applicant to describe the aircraft but not define the aircraft. It makes no provision for a serial number of the airframe or the engine, requiring only the year built and approximate number of miles flown.

A provisional form for "Certificate of Registration" was issued by ICAN sometime prior to 1922 and this document has provision for a "Maker's No."

When the first formal British Register came into effect on 22 July 1919, all aircraft previously registered with K series registrations were re-registered beginning at G-EAAA. A listing of these registrations published in 1986 again uses the term "C/N".

In October 1938, the British Air Registration Board printed a form titled "Nationality and Registration Marks". This appears to mark a transition from a ledger to a card system for maintaining the Register. This form has a heading "Constructor's No." The card for G-EAAA (and many others) is stamped;

"THIS ENTRY COPIED on 1st JANUARY, 1939, From FORMER REGISTER".

About 1928, Australia changed its Certificate of Airworthiness (Form C.A. 14) from a burgundy coloured card to a new four page paper CofA document while retaining the same form number. The burgundy card made provision for "Name of Constructor" and "Description of Aircraft" but made no provision for an identifying number. The revised four-page document made provision for a "Constructor's Number". This new form layout was almost identical to the UK CofA (Form 59) used in 1932 and possibly earlier.

An "Application for Certificate of Airworthiness" issued under Australian Air Navigation Regulations 1921 has a heading "Constructor's No. or Late Service No." This would appear to provide for aircraft that had a military serial number but no serial number issued by the manufacturer. In some instances, applications were submitted (and accepted!) quoting a military serial number when it should not have been too difficult for the applicant to determine that the aircraft did indeed have a "Constructor's Number". Although issued under 1921 legislation, this form does not reveal a printing date so the term "Constructor's Number" could have been introduced anytime after 1921.

Although it is suspected that Australia used the term as early as 1921, the earliest documented Australian use of the term "Constructor's Number" is 1928, although without access to the original UK Register of 1919, it remains highly likely that the term was in use in the UK as early as 1919.

Australian practice is believed to have followed British practice with the use of "C/N" until approximately 1936 when Australian documents began to use the term "Manufacturer's Serial Number". At this time there were widespread changes to Australian air navigation legislation resulting from legal action brought against the Commonwealth by the private pilot Henry Goya Henry (1901-1974).

By the fifties, data plates issued by Lockheed, Douglas and Boeing were using the term "Manufacturer's Serial Number" but this probably commenced much earlier.

To add to the mix, a Certificate of Registration of Aircraft (CA Form 71) issued by the U.K. Civil Aviation Authority on 27 February 1976 for Cameron Balloon G-BDSE registered to British Airways, provides a column headed "Aircraft Serial Number".

Therefore, it is concluded that the terms "Constructor's Number" and "Manufacturer's Serial Number" are both well established and equally valid methods of defining the same numerical descriptor used to identify an individual airframe. Today, "Manufacturer's Serial Number" (MSN) is the descriptor of choice for Airbus and Boeing.

The abbreviations for "Constructor's Number" and "Manufacturer's Serial Number" can be presented in upper case or lower case but upper case has been adopted here for consistency. Traditionally, the abbreviation for "Constructor's Number" is presented in lower case letters separated by an oblique. Some writers have used the term "Construction Number" but this variation does not appear on any official documentation sighted by the compilers. For the full expression, most official documents show the possessive apostrophe but this is sometimes omitted (notably on data plates) presumably for simplicity.

The compilers' review of readily available aircraft data plates revealed only one which used the term "Constructor's Number" and this was for a Vampire built in Australia in 1950. Despite a wider search, the compilers were unable to find any use of the term "Constructor's Number" by an American manufacturer or agency.

 

THE ORIGINS OF THE TERM CONSTRUCTOR'S NUMBER

 

DATE
DOCUMENT
NATION
SOURCE
REMARKS
1910
International Convention on Air Navigation held in Paris France 2 Recognised the need for the registration of civil aircraft but WWI intervened.
1911
Draft Air Navigation Bill UK 2 Stated that with effect from 20APR1919 all British civilian aircraft must carry registration markings. As an interim measure British civil aircraft would use a continuation of the RAF serial system beginning at K-100. A listing of these registrations in Source: 2 (published 1986) uses the term "c/n".
28AUG1916
Application for Registration of an Aircraft Aust MaAM 17/216 Document issued under Aerial Navigation Regulations 1915. Makes no provision for a serial number of airframe or engine. Requires year built and approx. number of miles flown.
04OCT1916
Certificate of Registration of an Aircraft Aust MaAM 17/218 Document issued under Aerial Navigation Regulations 1915. Makes no provision for a serial number of airframe or engine. Requires year built.
22JUL1919
First British Register UK 2 Under the International Convention in Paris, the new British Register came into effect. All aircraft previously registered with K series registrations were re-registered beginning at G-EAAA. A listing of these registrations in Source: 2 (published 1986) uses the term "c/n".
1922
Convention relating to the regulation of Aerial Navigation, signed at Paris, October 13, 1919, with Additional Protocol, signed at Paris, May 1, 1920 [1922] League of Nations 1 A provisional form for Certificate of Registration has a heading; "Maker's No." This term, or other alternatives, may appear in earlier ICAN documents.
07MAY1929
Application for Registration of Aircraft (C.A. Form 11) Aust NAA/TWB Has a heading; "Constructor's Number". Issued under Air Navigation Regulations 1921. For Westland Widgeon VH UKS.
16MAY1929
Application for Certificate of Airworthiness (C.A. Form 12) Aust NAA/TWB Has a heading; "Constructor's No. or Late Service No.". Issued under Air Navigation Regulations 1921. For Westland Widgeon VH-UKS.
38DEC1936
(sic)
Application for Certificate of Airworthiness for Export (Form 11-10431) USA NAA/TWB Issued by Department of Commerce, Aeronautics Branch. Has heading; "Manufacturer's serial No.". Issued for Sikorsky S.38B VH-UZE
26FEB1937
Application for Certificate of Airworthiness (C.A. Form 12) Aust NAA/TWB Issued by Department of Defence, Civil Aviation Branch under Air Navigation Regulations 1921. Has a heading; "Constructor's No.". Issued for Sikorsky S.38B VH-UZE.
12MAR1937
Certificate of Airworthiness (C.A. Form 14) Aust NAA/TWB Issued by Department of Defence, Civil Aviation Board. Has heading "Constructor's No.". Issued for Sikorsky S.38B VH UZE.
OCT1938
Nationality and Registration Marks UK WWW This form was printed by the British Air Registration Board. This form has a heading "Constructor's No." The card for G-EAAA (and many others) is stamped; "THIS ENTRY COPIED on 1st JANUARY, 1939, From FORMER REGISTER".
JUL1946
Douglas Service Bulletin USA Douglas Lists Oklahoma-built C-47s that were issued with an incorrect block of "factory serial numbers".
21APR1947
Application for Registration of Aircraft (C.A. Form 11) Aust NAA/TWB Form has a heading "Manufacturer's Serial Number". Form appears to have been printed in 1941. Issued for DC-4 VH ANF.
27FEB1976 Certificate of Registration of Aircraft (CA Form 71) UK 9 The CofR for Cameron Balloon G-BDSE registered to British Airways provides a column for "Aircraft Serial Number".
2006
Regulations and Procedures for the International Registry (2006 first edition) ICAO Doc 9864 Uses the term "manufacturer's serial number"
current
Civil Aviation Authority UK G-INFO website Serial No
This is the unique identification number of the aircraft. This may be the aircraft constructors serial number, a military serial number or a PFA project number.
current
Civil Aviation Safety Authority Aust CASA website Uses the heading Serial Number.

 

DATA PLATES

As will be seen from the following random selection of manufacturers' data plates, many terms were used to describe the individual identity of an airframe. No doubt it was this variety of descriptors that led registration agencies to adopt a uniform unambiguous term such as Constructor's Number. Significantly, only one plate has come to light bearing the term Constructor's Number.

 

YEAR
MANUFACTURER
DESCRIPTOR
NUMBER
AIRCRAFT
SOURCE
REMARKS
1933
Lockheed NUMBER
194
Vega 5C Special MaAM 52/92. Also Revolution in the Sky by R.S. Allen
1935
Lockheed SERIAL
1051
10B NC14992 8 (Note: 1)
1936
Lockheed SERIAL
1054
10E NC14994 8 (Note: 1)
1937
Lockheed SERIAL
1107
10A VH-UZO MaAM 45/94 (Note: 1)
1937
Lockheed SERIAL
1222
12A NC18125 8 (Note: 1)
1941
Lockheed SERIAL
2763
Hudson AM681 7 (Note: 1) See image above.
1943
Lockheed SERIAL
18-2598
Lodestar 43-16438 8 (Note: 1)
1955
Lockheed MANUFACTURER'S SERIAL NO.
4175
C-121C VH-EAG MaAM 45/96. (Note: 1) See image above.
1957
Lockheed MANUFACTURER'S SERIAL NO.
182A-3227
EC-130A-55-LM 8 (Note: 1)
1965
Lockheed (Fiat) MANUFACTURER'S SERIAL NO.
6699
F-104-G 8 (Note: 1)
1937
Douglas SERIAL NO.
1908
DC-3 MaAM 52/90 (Note: 1)
1939
Douglas FACTORY NO.
2643
B-18A MaAM 45/96  
1942
Douglas FACTORY NO.
6108
C47-R1830-92 MaAM 45/94 (Note: 1)
1942
Douglas FACTORY NO.
10828
C54D MaAM 52/90 (Note: 1)
1943
Douglas NO.
26536
DC3C MaAM 52/91 (Note: 1)
1944
Douglas FACTORY NO.
27376
C54-E MaAM 52/91 (Note: 1). Also AAF Serial No.44-9150
1952
Douglas MANUFACTURER'S SERIAL NO.
43363
R4D-8 MaAM 52/91 (Note: 1). Also Customers S/N. 50826
1957
Douglas SERIAL NO.
45162
DC-7C MaAM 52/91 (Note: 1)
1939
CAC MANUFACTURER'S NO.
8
Wirraway A20-10 MaAM 53/103. Also Serial No. A20-10
1951
CAC MANUFACTURER'S NO.
1524
CA-18 Mustang MaAM 45/94. Also Serial No. A68-199
1942
Bristol SERIAL NO.
T9604
Beaufort T9604/A9-52 MaAM 53/104. Aircraft Production Commission (Aust)
1942
Northrop SERIAL
476
Vengeance A27-1 MaAM 52/92 (Note: 1)
1944
Vultee SERIAL
31422
Vengeance A27-519 MaAM 52/92 (Note: 1)
1944
Chance Vought

MFG. NO.

6296
Corsair NZ5485 MaAM 53/104 (Note: 1)
1950
DHA CONSTRUCTOR'S NO.
4077
D.H. 100 Vampire MaAM 44/59. de Havilland Aircraft (Aust)
1956
Convair MFG. SERIAL NO.
320
Convair 440 LN-KLB MaAM 53/104  
1957
Cessna SERIAL
35537
310 VH-UAL/AER MaAM 53/104 (Note: 1)
1959
Fokker SER. NR.
10134
F27.202 VH-TFI 6  
1959
Boeing MANUFACTURER'S SERIAL NO.
17696
707-138 VH-EBA 3 See image above.
1960
Bell MANUFACTURERS SERIAL NO
1801
47J MaAM 45/95 (Note: 1)
1962
Piaggio MANUFACTURER'S NUMBER
409
P.166 VH-ASA MaAM 45/95  
1965
Piaggio SERIAL NUMBER
414
P.166C VH-FSC MaAM 45/95  
1965
Victa SERIAL NO.
F81
Airtourer VH-BWI MaAM 53/105  
1966
Grumman MANUFACTURER SERIAL NO.
281C
S-2E 152812 MaAM 53/105  
1971
Pilatus Fabr No
731
PC-6 Turbo-Porter 5  
1981
Aerospatiale AVION No.
252
Rallye TB.10 MaAM 45/95  
1982
Hughes Helicopter SERIAL No.
280269D
369D P2-PHL MaAM 53/105  
1995
Piper SERIAL NO.
36-7760076
PA36-300 MaAM 53/105  

 

NOTES

1
Issued under the auspices of the Manufacturers Aircraft Association Inc.
2
Descriptors are presented verbatim including punctuation.

 

SOURCES

1
http://www.worldlii.org/int/other/LNTSer/1922/99.html
2
Appleton John, 1986, The Civil Aircraft Registers of Great Britain 1919-1985. TAHS, UK.
3
http://www.adastron.com/707/qantas/data-plate.htm
4
MaAM:
Man and Aerial Machines
No. 1, February 1989 to No. 19, February 1991 produced by John Hopton.
Man and Aerial Machines No. 21, April 1991 to No. 100b, November 2013 produced by Trevor Boughton.
(Issue No. 20 was intended to be an index but it was never produced.)
5
Exhibit at the Queensland Air Museum.
6
Photograph provided by David Thollar.
7
Plate in compiler's collection. See image at top of page.
8
Image of plate from unrecorded source on the Internet.
9
Jenkinson, Alec, 1999, BEA, BOAC & Balloons A Life in Aviation, self-published England.

 

Issue
Date
Remarks
2
18JAN20
Added the term "Aircraft Serial Number" which appeared on a UK CofR dated 27FEB76 from Source: 9.
1
22NOV19
Original issue. Compiled by Ron Cuskelly and Trevor Boughton in August 2018.

 



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