Mk. XX vs Mk. 20
 

When did the British Air Ministry change the roman numerals of aircraft versions for arabic numerals?
And why?

Thanks in advance.

Chris

Re: Mk. XX vs Mk. 20
 

IIRC sometimes 1942-43, and the change aplied only to future contracts. Why? A wild guess, the war and massive expansion of RAF had meant that smaller % of supply etc officers had got classical education in public schools, so roman numerals were potentially source of misunderstandings which might have had serious consequences.

Juha

Re: Mk. XX vs Mk. 20
 

The change actually occurred in 1948. You may be thinking of the introduction of role prefixes (as in F.IX) which occurred in 1942. As for the reason, I suspect it was just easier to write the Arabic numerals, especially when you got up to numbers like XVIII. Also easier to tell apart 7 and 8 than VII and VIII.

I should add that the RCAF switched earlier, in 1945. This was largely due to mark number blocks being allocated in the 10s and 20s for licence built British aircraft in Canada. Can you picture the problems with hand written correspondence requesting what part numbers to use for the Mk. XXIV, XXV and XXVI?

Re: Mk. XX vs Mk. 20
 

Hello Bill
to the end of 1942 roman numbers, then new variants in Arabic numbers, from 1948 all a/c variants with Arabic according to Alfred Price. I also recall a 1943 letter from 5th Sea Lord to Air Ministry, which is quoted in Morgan’s & Shacklady’s Spitfire book, in which the Sea Lord used designation F.21, when talking on newest version of Spits in test-phase. He wanted a naval version of it as soon as possible, even if that meant non-folding wings. But it clearly isn't quite clear-cut. Price begin to use Arabic on Mk 18, M & S on F. 21.

Juha

Re: Mk. XX vs Mk. 20
 

Mk. XIX still used Roman number, all after the type 20 Spitfires used Arab numbers.

Re: Mk. XX vs Mk. 20
 

I suspect Juha's comment should be qualified to new variants planned after the end of 1942, for clearly new variants entered service with Latin numbers much later than that date.

Re: Mk. XX vs Mk. 20
 

Hello Graham
Price in his The Spitfire Story, year 2000 print, ie reprint of the 1995 revised edition, writes "From 1943 until 1948 the new a/c entering service carried arabic mark numbers while the older types retained their roman numerals."

IMHO it maybe would be better to replace "entering service" with "initiated during that period", if even that is entirely correct. Anyway I'm with Pilot and Morgan & Shacklady that initially Mk XVIII and Mk XIX were known with the roman mark numbers, but I'm not a Spitfire specialist.

Juha

Re: Mk. XX vs Mk. 20
 

Juha- I am also not very informed about Spitfire but in this moment I completing illustrations for the book about the recce Spitfires and gentleman who are authors state this mark for the Mk. XIX and the later was marked different. By the way- Alfred Price is great author.

Cheers :)

Re: Mk. XX vs Mk. 20
 

There is also engines. There was the Merlin XX but the next Merlin was the 21.

The Mosquito used Roman numerals after B. XX.

I would think someone came to their senses, to keep the number of characters down. ie Mosquito NF. 38 > Mosquito NF. XXXVIII

Re: Mk. XX vs Mk. 20
 

I suspect there may not be a single answer. To get away from Spitfires, as far as I know the Halifax continued to use Latin numbers up to the final A Mk.IX, which even as a idea post-dated 1943.

Re: Mk. XX vs Mk. 20
 

Well, Graham, it may not be when it was built but when it was ordered, since it was at that time that the AM applied a new Mark number if relevant.

Re: Mk. XX vs Mk. 20
 

Yes, that was my original point. However, was the precise development of the later marks of Halifax accurately predicted before 1943? The Mk.III was on the way by then, and future development depended entirely on its success. It is probably that the Mk.IV was already seen as a non-starter, but that could have lead to an entirely different development history for the type. It is fairly certain that the Mk.VI with its superior engines had been foreseen. However, the Mk.VII was a Mk.VI but with reversion to the earlier engines due to a shortage of the better ones, something unlikely to have been preplanned in 1942. The C. Mk. VIII and postwar A. Mk.IX were later still.

I agree it is very important to appreciate how the decisions to place orders for one aircraft/development or another are made well in advance of their appearance, especially when major changes/improvements are foreseen. In these specific circumstances should we go back over two years for the allocation of mark numbers to what were fairly minor variants of a then unproven development? Perhaps so..... in this case I think not, but two years is perhaps not so long after all.

Re: Mk. XX vs Mk. 20
 

Was there a different policy for mark numbers with regard to aircraft and engines? Merlin 45 entered service in Spitfire V in 1941. Some documents called it Merlin XLV, but the Arab numeral was certainly used by the end of 1941.