Hi all. In another thread re. (as it turns out) a dH 4500 prop spider someone mentioned a numbering convention for de Havilland prop assemblies that included the letters ‘GQ’. I hadn’t come across this before. Is this a post-war thing? I am familiar with the ‘thousand serieses’, and how that became incorporated in an assembly designation (such that a specific 4000 series hub assembly for the Whirlwind was the 4/4, for instance), and was interested to find out from that thread that come the Hydromatics the system gained further nuance to deal with shaft size differences. But the post by ‘Tonk’ was interesting – I asked about it on that thread but it is getting buried now.. any more info very welcome.
PS Anneorac, have you ever thought of writing an idiot’s guide to propellers? Niche, but it would put so many of us out of our collective airscrew-related miseries.
By: Beermat - 23rd February 2015 at 21:53
Never thought you’d actually consider doing it – thanks Anneorac. That’s the kind of generosity that makes this forum worth putting up with the occasional twits for!
By: anneorac - 23rd February 2015 at 21:14
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.
By: Beermat - 23rd February 2015 at 17:19
Thanks Pete! Oops, misunderstood 🙂 It was because it was ‘DH’.. that’s my excuse, anyway.
Ed, yes, you’d think so, wouldn’t you? But I can’t find one (would be so useful in getting a handle on DH props, as the US ones are so well documented). Similarly, blade equivalents as well. I know that there were some, at least visually – I think the Blenheim had a Hamilton 6010 blade equivalent, but cannot be certain, and amazingly it seems that neither can anybody else! It’s like the knowledge has evaporated, along with all records, within living memory. Not to mention American blade profile drawings (Hamilton Sunstrand say they have the ones I was after, but that they are ‘proprietary’ and that no-one can see them apart from operators, and there aren’t any operators as the blades in question are no longer licenced by the FAA). However, they were published to units for reference purposes during repair – according to the manuals – so they surely must be ‘out there’. Meanwhile, the best sources in the world say that the de Havilland ones really have disappeared. Newly manufactured authentic DH blades, like the 55409 blades on a recent MkI Spit, were simply copied from relics.
By: MerlinPete - 23rd February 2015 at 13:45
Matt, the “GQ” refers to Gipsy Queen, I must admit I didn`t realise that at first either!
Late war, or post war, the prop designation was changed. I don`t know what all the numbers mean, but here are some examples:
2 blade: Prentice I, D92/212/1 No2 shaft?
3 blade: Devon, D113/312/1 No2 shaft
Pembroke, D187/313/1 No3 shaft
4 Blade: Balliol D45/435/1 No5 shaft
Lincoln II, D87/445/1 No5 shaft
Tempest V, D17/446/2 No6 shaft
There are loads of these, but it seems that in the second group of numbers the first digit is the number of blades, and the third is the shaft size in SBAC. The single figure on its own is a revision or mod number.
I can`t see how they determine the shank size, but I`m quite sure that a Devon blade is a smaller shank than a Pembroke.
The Balliol and Lincoln were D shank.
Shack props have an intermediate shank size, between D and E, these props are DF178/334/1 (or2) and DB/229/336/1 where F and B are front and back.
Pete
Someone on here is probably familiar with what it all means.
By: powerandpassion - 23rd February 2015 at 10:50
PS Anneorac, have you ever thought of writing an idiot’s guide to propellers? Niche, but it would put so many of us out of our collective airscrew-related miseries.
I will buy a copy !! Great idea. Maybe a website. Happy to contribute funds to get a website going, get a geek to sit next to you so you can download.
I really, really, really want to find a parts catalogue for DH feathering airscrews that matches DH part numbers to the equivalent Hamilton Standard part numbers. Surely such a document must be out there !
Ed
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February 22, 2015 at 10:37 pm