MiTasol
1st Lieutenant
This thread was inspired by a member who, incorrectly, stated that identifying part numbers was Dead easy for Spitfires as the Part number starts "300". Obviously this person got this information from someone who has never had the misfortune to work on a Spitfire so must be forgiven.
Over the years there have been a number of posts covering part numbers and serial numbers - many correct and even more which were incorrect.
I hope that those with knowledge of the thousands of aircraft types that I have never worked on will add their knowledge to this thread or expand/correct what I have written. Engine P/N deciphering needs adding - all I can say is Bristol engine part numbers start FB.
This post will set out to describe in brief detail the part number systems used by Avro, Bell, Bristol, Consolidated, Curtiss, deHavilland, Douglas, North American, Republic, Stearman, Supermarine and Vultee. You will note that I did not include Boeing because it appears that their part numbering was done by a very drunk person who had the DTs. Boeing numbers include all the systems below on the same aircraft, and even on the same major assembly - and a couple unique to Boeing.
Knowing a part number on its own is no guarantee that it comes from just one manufacturer. Bell, Curtiss, North American and Stearman all had a model 75 so all have part numbers starting 75-. Add to that the Boeing B-17 has a raft of 75- part numbers in keeping with Boeing's system of not having a system
First we need to understand the difference between Part numbers, Assembly numbers and Serial numbers.
Next - to address the Spitfire issue that inspired this post
Every new part fitted to the Mk I Spitfire had the 300 prefix but each subsequent model has its own prefix,
If part 300nn-nnn is modified, or additional, and introduced on the Mk II it will have a 329nn-nnn part number but all the parts carried over from the Mk I will still have 300 numbers. New parts introduced on the Mk V are prefixed 349, Mk VII new parts are prefixed 359 etc. New parts for the universal wing have a separate prefix as do Vokes filter, floats, drop tanks and numerous other parts. Therefore a Mk IX for example can have an assortment of parts with all those, and other, prefixes. Every model and submodel introduces new part numbers
Some common prefixes on early Spitfires are
Add to that, just to keep you on your toes, parts carried over from earlier aircraft will still have the part prefix relevant to that earlier aircraft. And yes the Spitfire does have such parts
While to some extent this appears difficult it is in fact a variation on a very common very simple theme.
Variations of the same basic concept were used by Bell, Curtiss, North American, Stearman, Supermarine and Vultee though Supermarine were the only people to have massive assemblies as the core number.
Continuing with Supermarine as an example you will get a part number like shown below - part number 30027-2517.
Breaking this down the part number consists of three segments
On Bell, Curtiss, North American, Stearman and Vultee the model number of the first type the part was used on is separated from the system number, rather than being attached to the major assembly number. With all these manufacturers the digits before the first dash indicate the model that the item was first used on.
North American - I will do this first as it is the easiest.
The five digits after the first dash indicate the individual part number with the first two digits indicating the system or section. On NAA aircraft those first two digits indicate as follows. the rest of the number is the individual part. This sort of chart is in the front of all NAA parts catalogs - this is AT-6 chart. The P-51 chart is a little simpler with no second crew member
For the B-25 the chart is essentially the same - just additions to cover the extra crew requirements and 34001 becomes the nose landing gear. I do not have a copy of the B-25 parts catalog so cannot present the equivalent page but will find a copy. Turrets were not made by NAA so the blueprints only cover the NAA made parts necessary for the installation in the 60000 group and flexible guns are 62000.
I will detail the Bell, Curtiss and Stearman systems more in a separate post on this thread.
Avro, Consolidated, deHavilland and Republic (Seversky) used a different variation on this theme with the model number followed by one or more letters representing the assembly or system.
I will detail these a little more in a separate post.
Douglas used the simplest system and there is no way to tell from the part number what aircraft a part belongs to. The first digit is the drawing size, the remainder of the number is numerical in order of being issued. Douglas had many types in production and on post production support in the early 1940s - probably about a dozen major models without counting the derivatives. so part x may be from the SBD but part x+1 could be from DC-3 or any of its twenty odd military derivatives, DC-2, DC-4, DC-5, A-20, A-26, B-18, B-23, C-33, C-68, etc, etc, etc.
Beech numbers I never managed to decipher but I only worked on a couple of B-18/C-45 aircraft for a short time.
Over the years there have been a number of posts covering part numbers and serial numbers - many correct and even more which were incorrect.
I hope that those with knowledge of the thousands of aircraft types that I have never worked on will add their knowledge to this thread or expand/correct what I have written. Engine P/N deciphering needs adding - all I can say is Bristol engine part numbers start FB.
This post will set out to describe in brief detail the part number systems used by Avro, Bell, Bristol, Consolidated, Curtiss, deHavilland, Douglas, North American, Republic, Stearman, Supermarine and Vultee. You will note that I did not include Boeing because it appears that their part numbering was done by a very drunk person who had the DTs. Boeing numbers include all the systems below on the same aircraft, and even on the same major assembly - and a couple unique to Boeing.
Knowing a part number on its own is no guarantee that it comes from just one manufacturer. Bell, Curtiss, North American and Stearman all had a model 75 so all have part numbers starting 75-. Add to that the Boeing B-17 has a raft of 75- part numbers in keeping with Boeing's system of not having a system
First we need to understand the difference between Part numbers, Assembly numbers and Serial numbers.
- Every part has a part number. This is usually the drawing number but some drawings cover multiple parts such as left and right hand versions of the same part or various lengths of the same part. In that case the drawing will have a note or table covering the differences.
- An assembly is a collection of parts of various numbers joined together in an assembly for ease of maintenance and repair. Sometimes all the parts of an assembly have different part numbers but more often the assembly will contain multiples of some parts. Many Assemblies have Serial numbers. Think of a seat. You obviously don't want it riveted to the main structure as you have to remove it for routine maintenance so it is made as an assembly. If you are a mechanic in the middle of the Battle of Britain you do not want to change that hard to replace casting in the middle that needs a jig to accurately position it. What you want is to requisition a complete seat so the pilot can go do his job today, not next week. Likewise with airline and other aircraft today.
- Serial numbers are used mainly on assemblies but also on some individual components. Serial numbers are only used for certain purposes:
Any part that has a "life" must have a serial number and a logbook or history card. That life can be hours or cycles before overhaul, hours or cycles before replacement (scrapping), calendar time in service and a number of other less common factors.
Any part that is part of a matched set of parts where this wing only fits this fuselage or similar
Any part that is part of a matched set of parts where this wing only fits this fuselage or similar
- Think of a seat. It is made as an assembly but usually it does not have a serial number because it is a repairable item that is completely interchangeable and has no life limitations or overhaul period. Doors and many other parts also do not normally have serials.
Next - to address the Spitfire issue that inspired this post
Every new part fitted to the Mk I Spitfire had the 300 prefix but each subsequent model has its own prefix,
If part 300nn-nnn is modified, or additional, and introduced on the Mk II it will have a 329nn-nnn part number but all the parts carried over from the Mk I will still have 300 numbers. New parts introduced on the Mk V are prefixed 349, Mk VII new parts are prefixed 359 etc. New parts for the universal wing have a separate prefix as do Vokes filter, floats, drop tanks and numerous other parts. Therefore a Mk IX for example can have an assortment of parts with all those, and other, prefixes. Every model and submodel introduces new part numbers
Some common prefixes on early Spitfires are
- Type 329 - Mk II
- Type 330 - a modification to the tail skid
- Type 331 - universal wing
- Type 337 - Mk IV
- Type 340 - Seafire Mk I
- Type 343 - Aux fuel tanks
- Type 346 - a wing modification
- Type 352 - Mk V Vokes filter
- Type 353 - PR modifications
- Type 355 - Mk V on floats
Add to that, just to keep you on your toes, parts carried over from earlier aircraft will still have the part prefix relevant to that earlier aircraft. And yes the Spitfire does have such parts
While to some extent this appears difficult it is in fact a variation on a very common very simple theme.
Variations of the same basic concept were used by Bell, Curtiss, North American, Stearman, Supermarine and Vultee though Supermarine were the only people to have massive assemblies as the core number.
Continuing with Supermarine as an example you will get a part number like shown below - part number 30027-2517.
Breaking this down the part number consists of three segments
- 300 = Supermarine Type 300 being the first model this part was used on.
- 27 = Major assembly number - fuselage complete
- 2517 = that individual part.
- G = the drawing issue (revision) letter which is not usually included in the part number in the part itself or in the parts list/catalog
- If it is included then there will be restrictions on replacing with earlier or later revision parts and this will be identified on the drawing and in the parts list. Most manufacturers just give the non-interchangeable part a new number to avoid any confusion.
On Bell, Curtiss, North American, Stearman and Vultee the model number of the first type the part was used on is separated from the system number, rather than being attached to the major assembly number. With all these manufacturers the digits before the first dash indicate the model that the item was first used on.
North American - I will do this first as it is the easiest.
The five digits after the first dash indicate the individual part number with the first two digits indicating the system or section. On NAA aircraft those first two digits indicate as follows. the rest of the number is the individual part. This sort of chart is in the front of all NAA parts catalogs - this is AT-6 chart. The P-51 chart is a little simpler with no second crew member
For the B-25 the chart is essentially the same - just additions to cover the extra crew requirements and 34001 becomes the nose landing gear. I do not have a copy of the B-25 parts catalog so cannot present the equivalent page but will find a copy. Turrets were not made by NAA so the blueprints only cover the NAA made parts necessary for the installation in the 60000 group and flexible guns are 62000.
I will detail the Bell, Curtiss and Stearman systems more in a separate post on this thread.
Avro, Consolidated, deHavilland and Republic (Seversky) used a different variation on this theme with the model number followed by one or more letters representing the assembly or system.
I will detail these a little more in a separate post.
Douglas used the simplest system and there is no way to tell from the part number what aircraft a part belongs to. The first digit is the drawing size, the remainder of the number is numerical in order of being issued. Douglas had many types in production and on post production support in the early 1940s - probably about a dozen major models without counting the derivatives. so part x may be from the SBD but part x+1 could be from DC-3 or any of its twenty odd military derivatives, DC-2, DC-4, DC-5, A-20, A-26, B-18, B-23, C-33, C-68, etc, etc, etc.
Beech numbers I never managed to decipher but I only worked on a couple of B-18/C-45 aircraft for a short time.
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