An interesting thread. Were it not for the desperate need to shoehorn it into a Spitfire, the saga would be reasonably well structured. Where, apart from your a priori decision, does it say ‘Spitfire’ except that it ‘needs’ to be for you? Let go of ‘Spitfire’ and follow the evidence. IF that leads you to a Spitfire, so well and good…

The Spitfire was one aircraft the RAF had under development – among several others. Throughout the Spitfire’s service in the RAF it was usually among the fastest aircraft, but there were several periods where it was lagging well behind – 1944 with the V-1s for instance. That doesn’t matter. There was not a period where an ASI was needed by the Air Min for one ‘fastest’ type. Again the focus on ‘Spitfire’ is simply preventing a look at Air Ministry instrument-fitted aircraft, which is the question.

Thankyou for your comprehensive reply I am glad its got a debate going. You missunderstand me in the respect of trying to prove its Spitfire. I don’t mind what it turns out to be I just want to know what, and the Spitfire being the fastest around at the time it seems logical although I only say its likely. I also mentioned that the Spitfire was fastest RAF aircraft for MOST of the early War.
In 1938/9 no-one foresaw the enormous development the Spitfire type achieved, and that we now know of – a classic case of hindsight misleading the theorist. The 1939 Air Ministry knew that the future lay with the Typhoon, Tornado and the ‘Crikey’ Whirlwind. They were wrong, as we now know. However I can see orders being placed in 1939 for ‘a dial that goes up to 11’ to fit to forthcoming types quite easily.

Good point and question. But art history students (for instance) are always told that ‘just because we have one of something doesn’t mean it was rare or unique originally’. A huge batch could have been made and blown up in an air raid… They could have been faulty… and so on. It’s probably a one-off or a rarity, but we don’t KNOW it is.

I agree but in my experiance and those of the people contacted have not seen another, my point is this instrument was not in general operational use in 39 or 40 and therefore is very rare. This being the case I believe it was produced for a special application. Possibly MKIII but like you say its not proven.

Apart from ‘it has to be a Spitfire’ what gives you the view that: ‘ The MkIII Spit seems to be the most likely candidate’?

I believe its possibly MKIII because it flew in 1940 and was capable of 385 in level flight.

It could have been for forthcoming prototype aircraft (plural) a short batch made for types that were expected to need them.

I agree totally thats the main point but what?

I don’t agree with your PRU conclusion. From memory, throughout 1939 the PRU were very unofficial and being run by Cotton who had a somewhat cavalier and ‘get things done’ approach, and very erratic support from the Air Min. Properly made speed gauges were the least of his concerns – although fuel gauges certainly would be critical. In 1940, it was a different story…

This is new information and if we can get rid of the PRU theory so much the better, the search narrows. However i thinks its likely the PRU aircraft were stripped of armour and guns and therefore faster but as i say i cant find any info on their performance. PRU could be a number of aircraft not just spit and I accept this point.

No. The quote, which requires a reasonable theory to start with is: “…when you have excluded the impossible, whatever remains, however improbable, must be the truth.” (Sherlock Holmes: “The Adventure of the Beryl Coronet”) There’s a more than subtle difference in logical analysis there. There’s a big gap between ‘unlikely’ and ‘impossible’ and between ‘improbable’ and ‘it’s a Spitfire part’. 😀

Ah i knew it was something like that thankyou for the correction.

Off the top of my head I can see it being made for the Speed Spitfire (an abandoned project that needed a ‘bespoke ASI’ above 400mph) or (much more credibly for the evidence – dates, need, the HN Racer was est to get to 480mph, etc) the 1938 Heston Napier Racer. Of course we can’t prove that. IF it were off one off those, it’s a lot rarer than another Spitfire dial. 😉

Sorry i dont know about either of these can you expand?

At a guess, it’s for a 1939 era prototype British aircraft – probably RAF, and one could come up with a very interesting list of candidates, including, but not limited to, Spitfires.

Again I agree, perhaps it was produced for a number of prototypes, it would be interesting to start a list of 1939/40 of aircraft approaching or exceeding 400 in level flight. Ill get it going
They aren’t all Spit Bits, remember?

Your right and it wouldn’t be half so much fun if part identification were that easy. 😀

Quite right.
Cheers

MK III Spitfire
Hawker Tornado

Whilst the hypothesis is that, in 1939 no RAF fighter could exceed 400mph in level flight, they all could in a dive ; the asi is a very useful instrument when you need something to tell you when the wings are going to come off!

It is quite possible, that the 480mph asi wasn’t fitted early on, to discourage competition between pilots looking for the fastest dive speed, and in so doing, “pull the wings off” at the bottom, once past 400mph, its just guess work.

I think your right about the ASI reading, exceeding 400MPH in a MKI or II probably wouldn’t be a good idea, I am not sure what speed the wings come off but I think they had canvas covered elevators that got very heavy at high speed. Airframes were strengthened as BHP increased. The MK VII/IX didn’t get anywhere near 480 in level flight, I think 410 was flat out at the optimum alt. 480 was probably close to structural failure but there are allot more people better qualified than me on this forum to answer that one.
The more I think about it the more I think it’s for PRU Spit’s. There were quite a few operating in 1940. Its frustrating that there doesn’t seem to be any info on their performance.

Graham,

I think the point being made is that in 1939 it was clear that aircraft would be exceeding 400mph fairly soon – the Tornado was on the cards, as were more powerful Spitfires and other developments (the specification for the Gloster E.28/39 was put out in 1939), so it was considered wise to start producing gauges even if there was not an immediate application for them. Better to have a stockpile when the aircraft requires them, rather than having aircraft fitted with instruments that don’t have a sufficient range!

Its a valid point however there are flaws in this suggestion. Firstly it doesn’t take very long to modify an ASI. A 400 MPH or any similar could be modified to 480 in no time at all, simply produce a new face and recalibrate the instrument an aircraft manufacturer could achieve this in a few days tops. Second it took at least until 1941 until a 480mph was needed in operational aircraft, they might as well have started using 480’s in MKII’s ect (and discontinue the 400’s) if they had started full scale production. 480’s werent introduced until at least the MKV in Spit’s and logic follows therefore that the Spit always being the fastest RAF aircraft during this time that it wouldnt be introduced in other models earlier. Why would they start to store ASI’s in 39 when resources were very stretched, for aircraft that would take another two years development before they were needed? I have spent a good deal of time checking dates on various instruments:o because it is a good clue to their use. You really don’t find the dates on the instruments earlier than the operational introduction of the aircraft they were intended for, this surports the idea that they could be produced ready for use and not stockpiled.
Why arent there allot more around? I have been collecting for twenty years and have had quite a few of these instruments pass though my hands. The type face is different and i have never seen one dated earlier than 41. My feeling is this instrument was produced in small numbers for a special project/projects and or PRU use. The question is what? The MkIII Spit seems to be the most likely canidate, although perhaps the Tornado and some other early developing designs. I do not believe for a moment this instrument was fitted to any known stock aircraft type operating in 39 or 40. If we discount the stock piling idea, I think the most likely application is PRU use, we should be looking for PRU performance figures for these dates, as i said earlier i have looked and cannot find any info.:) reminds me of an old saying “if you disprove all the other possibilities, then the one you are left with is the answer no matter how unlikely”😉

Totally agreed with that, and not to forget that this gauge (even if some could have been equiped with 0-400 MPH gauge) was also used on Beaufighters (first, were handed over to the RAF on 27 july 1940) Whirlwind (handed over on july 1940), Mosquito.
My own research on the subject shows that pilot’s notes are not the ultimate proof about instruments use, the operational use could be different.
Cheers,

Olivier

I agree instruments had widespread uses although I didnt know the 480 was used in Mosquito’s or Beaufighters, never heard of a Tornado will have to look that up, interesting. I have seen quite a few 480 ASIs over the years but have never seen one earlier than 1941 before.:D

Ok Spits had a 30 Gallon,a 40 Gallon,a 90 gallon and a 170 Gallon jettison/slipper tank IIRC.Now are they made by the same manufacturer as the Main fuel tanks.If so then they might have an idea what it is,that,s if they are still around.;)
In regards to dumping.Here at Oakey during the big cleanup lorries were loaded up each morning and would leave the base and return back empty in the afternoon.This area is rich of stories,furfies,myths and legends of parts chucked down any number of pits/coal shafts/rivers/holes/quarries etc…Yes the armed forces did strange things sometimes and perhaps the parts you recovered might have been spares kept in stores and told to be rid of them.:)

I am sure they were from the stores as they were all in one area. These rumours of dump sites are rife, I have documented evidence of 50+ cat E burried Merlins, I know they are there as I have the paperwork and it says they were left, it does not give the location I have searched for 5 years without success, an airfield is a big area to search.Even using a deep scan metal detector you can end up digging allot of deep holes only to find rubbist or an old drain. The place i dug the fuel bits according to an eye witness, was where they were smashing up aircraft setting fire to them and burying them. There isnt anything bit there i suppose the big remains were picked out and sold as scrap.

????

Strange one isnt it? according to my part list 65 is aux fuel wether that means drop tank is another matter its just a educated guess based on allot of Culmhead spits using drop tanks. I find it hard to believe stuff was shipped to Culmhead to destroy it. Its in the middle of no where. Like I mentioned earlier i bought some bungs/caps from ebay and its not the first time I have seen them advertised (the bungs that is not the parts) so I think it must be a fairly common Spit part. Its a strange looking thing but i cannot figure out what it could possibly be used for ? with my limited knowledge I have never seen a fuel part like it?? perhaps a baffle? I have a complete parts list for a PRU Spit and its not in there?? Anyway i have several so if anyone IDs it I am going to send them one for the info, you’ll have to clean it yourself though they polish up really well.;)