I’m happy to share what little I know, after all, what’s the point of keeping information to yourself when others could make good use of it? The problem I have is finding the time between work, child care, hitting people with lumps of steel (that’s 15c re-enactment), learning to fly, etc, etc.
I also don’t have immediate access to some of the documents I took the information from and am now aware that there are errors in the way I collated that information some 15 + years ago. I wouldn’t like to put some of the information forward without re-checking those original documents. There are some bits I’m happy with so I’ll see what I can scrape together and try and find a way of presenting some info on the earlier DH hydromatic propellers…soon…ish.
What I can do at the moment is give you the low down on the Air Ministry propeller designation system introduced about 1943 and which Pete has already done a very good job of explaining. Let’s take one of his examples D17/446/2.
Starting with the D, this tells us that it’s a deHavilland prop. R would be Rotol.
17 is for the Aircraft/Engine combination and here we have one of the slight disadvantages of this system for while D17 denotes the Tempest, you’d also find this prop on the Typhoon which already had a number of D3. I’ve found examples where the same mark of aircraft with the same mark of engine have propellers with different numbers following the D. I can only presume that the prop in these cases was originally designed with a slightly different mark of aircraft or engine in mind.
Moving on, the first 4 denotes the number of blades, the following 4 the shank size and the 6 is the shaft size. The last number, 2, tells you that this is the second version of this type of prop.
There you go, pretty much what Pete had already written.
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