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By: - 25th October 2019 at 21:09 Permalink
F.18/39 resulted in the Martin Baker MB.3.
By: - 25th October 2019 at 21:26 Permalink
Most can be found at Kew.
As F.18/39 was written around the MB3 the spec may be quite short. Try AVIA 15/1341
P.S. I absolutely hate the style of this new forum
By: - 25th October 2019 at 21:37 Permalink
There’s a summary in Air-Britain’s The British Aircraft Specifications File.
By: - 26th October 2019 at 10:01 Permalink - Edited 26th October 2019 at 10:18
Thanks chaps.
AVIA 15/1341 looked promising at first but from the description it looks like it not the actual spec - the date range is 1941-1944 and it is described as "Development of fighter to specification F.18/39: policy". The problem is they now ask for cash to even look at the document, and there's no guarantee they will be able to accurately report whether or not its what I am after anyway, even after paying. Guess it's off to Kew with me.
Yes, I have various sources that state 18/39 was written for Miles but then I found this https://static1.squarespace.com/static/56c78acd0442626b2590f5ea/t/590591d02994ca1b11d96680/1493537249560/2009-2_Summer.pdf (P.13) written from a US perspective and from a pretty authoratitive source.
It seems that whether or not the specification was intended for Miles it found its way - quite deliberately - to the US. That's why it's interesting. This account claims that it was similar to Clark Millikan's 'ideal 1938 fighter' and something that NAA, just like Miles, were already looking at when the specification was released. It could be argued, perhaps, that NAA simply got there a lot quicker. One wonders how many ex-Farnborough / wider industry people worked with Miles, compared to the British cohort that 'just happened' to be in California to help with the Mustang (Thomas, Shenstone, Luttman et al).
Another question - would the mentioned Operational Requirement (OR.73) be lodged separately somewhere, at Kew again maybe? A search for 'Operational Requirement' produces nothing relevant.
Really don't like the new design either. A classic example of something that wasn't broken being 'fixed'.
By: - 26th October 2019 at 11:34 Permalink
The brief descriptions of file contents at Kew are pretty broad-brush so I think it is worth having a look to see whether the spec is included or quoted.
The article you link to doesn't actually say that F.18/39 was either viewed in the US or influential in NA's design. The brief note on this, and also the mention of Meredith's work, rather look like the author was reverse engineering the story to suggest external sources for some of the design ideas. Its a common fault with many articles ; he may be right but it is far from proven.
James Martin was notorious for not seeking or taking advice, so the MB3 is more than likely a fully in-house design. Whether UK experts had much say in the early NA work I cannot say, but I find that Shenstone's name is too often tagged onto projects without documentation to back it up. Even his role in the origins of the Spitfire is generally over-played.
By: - 28th October 2019 at 08:02 Permalink
Agreed that there's nothing proven, it all seems very 'circumstantial'. I am just keen to exhaust the sources to establish the actual British involvement. North American Aviation and nearby Lockheed had a large British cohort present because of the existing large production contracts around the Harvard and Hudson respectively. With both the P-51 and P-38 intended for the UK in even larger numbers the British Purchasing Committee seem to have been able to get a lot of technical bodies on the ground, including Shenstone who did advise on the intake - but it's all anecdotal. I am trying to find more concrete evidence of who was there and what they did.
By: - 28th October 2019 at 11:32 Permalink
There are a few errors in the paragraph regarding spec F.18/39 and research that suggest that the author made a quick skim-through of secondary sources to look for possible links with British requirements and research. He made the classic US error of mistaking the way we and Europe write dates; the spec was issued on 1st May 1939 (1/5/39 as written in Meerkoms and Morgan) and not 5th January as he read it. As Kindelberger had been in Britain in 1938, he isn't specific about the date, it feels a bit early for him to have been advised of the contents of the OR and spec, which we believe to have been written specifically around the MD3, a very different beast to the Mustang.
Meredith's report was actually R&M 1683, a RAE report published as R&M, that deals with the mathematical/thermodynamic treatment of cooling in ducts. In preceding and in parallel with this were a few patents taken out by Ellor at Rolls-Royce that are more focussed on specific aspects of duct design, with the same low/zero drag intent. The two branches are somewhat complementary and there may have been some shared, but competitive, work involved. Shenstone would have been aware of these through his involvement in the Spitfire programme but it was not a specific area of his expertise.
By: - 28th October 2019 at 13:30 Permalink - Edited 28th October 2019 at 13:42
Thanks (not for the first time). It's nice to have someone 'time served' in this area as a sounding board for all of this.
Schmued wrote "The British Air Ministry was extremely helpful. Among others they sent us Dr. B. S. Shenstone to assist us in some of the airflow problems into the radiator. The radiator, as we had it, consisted primarily of a fairing, which started at the bottom of the fuselage and enclosed the radiator. Dr. Shenstone advised us to provide an upper lip on the radiator housing, which was about 1 ½ inches below the fuselage contour. By doing this, we got a much better pressure distribution in the air scoop.” - the assistance was in how to handle the effect of the boundary layer rather than having much to do with the Meredith effect.
Curiously there was a hinged extendable spoiler on very early Mustangs that improved dive speeds by pre-separating flow ahead of the intake. This was deleted not far into the production run even though the effect of doing so, according to R&M 2222, was negative.
This is fascinating to me as it was just feasible with contemporary knowledge that this was 'designed in' as a way of improving transonic performance, which it did - but it was only ever referred to (retrospectively) as a guard against engine over-cooling, which a simple shutter would have been better at.
It is the currently un-named 'others' from Schmued's account and their contributions that I am looking to pin down, as part of a wider re-appraisal of the British approach to the P-51, politics and the whole knowledge exchange concept around the time of Tizard.
By: - 28th October 2019 at 14:29 Permalink
Yep, that sounds like Shenstone for sure. He was much in to the whole boundary layer issue and had written an article for The Aeroplane on methods to provide boundary layer suction in 1937.
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By: Beermat - 25th October 2019 at 16:15
Can anyone tell me where I can find specification F18/39? I presumed Kew, but when I had a look online it appears they don't hold these spec documents - and neither do Hendon.
It is an important one in the context of the P-51 - US aircraft could not compete for British contracts to new specifications (and potentially against UK manufacturers) for obvious political reasons, they always needed to be seen as off-the shelf stopgaps. However, it was advance notice of Operational Requirement 73 (later F18/39) that spurred Kindleberger to pursue the small Allison fighter idea.
It would be very interesting to look at the detail of F18/39 and see how Mustang-esque it was.