Spitfire The History.
Boscombe Down 10 October 1942. BF274. Fuel consumption trials. At auw 7,100 lb in MS gear @ 174mph 6.76 air miles per gal; range 450 miles; endurance 1.95 hours at 20,000ft. FS gear @ 160 mph 6.03 air miles per gallon; range 375 miles; endurance 1.0 hr at 37,500ft. These results allow for climb to height.
Now, Spitfire the History notes that BF274 was converted from a Spitfire V to IX in August 1942, with the fitting of a Merlin 61 engine. The fuel consumption trials took place on 10th October, on 22nd October performance trials took place:
Spitfire F Mk IX Test BF274
Again fitted with Merlin 61. And are you suggesting the Merlin 66 was in use in early October 1942?
Oh, finally some useful contribution from you, and one of the red letter days when you can actually back up what you claim. I wish all days would be such.
So, it`s a F Mk IX w. a Merlin 61. It is given with a range of 450 miles on 85 gallons, and 6.76 mpg at the most economical cruise speed.
The RAF gives the range of the LF Mk IX w. a Merlin 66, with 85 gallons as 434 miles. It would appear that any difference caused by the different carb of the M66, it made it even more fuel hungry.
Based on the Merlin 61, though. I can't find any RAF range trials with the Merlin 66. Can you?
It says Spitfire IX LF, Merlin 66 (just under the range paper attachment). Based on the Merlin 61, according to whom? So now you claim you know the IXLF`s range better than the RAF itself, right?
The Merlin 66 Mk IX LF datasheet says 434 miles at most economic range.
This other British paper shows 420 miles range for the Merlin 66 IX LF
Then again, another British paper from 1945 - Spit XVI (same as the Mk IX, just with US built Merlin 66-licence engine, the Merlin 266) - 434 miles range again. Also of interest is MkXIV, with it`s greatly increased fuel capacity with wingtanks - it was only enough to make up for the greater consumption of the engine.
The other trials, which you claim to have been performed with the 'older engine Merlin 61', actually resulted in
higher range, 450 miles.
Take note it`s actually for 7100 lbs (possibly avarage flight weight), not the
It`s pretty well established I think that the Mk IX could cover 434-450 miles range on it`s internal 85 gallon capacity under the most favourable conditions (economic slow speed cruise etc.). In other words, it could not get back to it`s base from any larger distance than ca 450 miles from it`s base, much less under practical circumstances.
I know of only one test of the Merlin 66 range figures, as is usual you dismiss it because it doesn't say what you want it to say, and use instead figures for a different engine.
As shown above, you hold onto a single test which conflicts the results of half a dozen of other range data.
No, quite the opposite. If you look at the Australian tests, they are consistent. The Mustang has much better range at any speed above it's most economical speed. The Spitfire, being lighter, quite naturally has a lower most economical speed.
You are aware that as weight goes up, so does most economical cruise speed, aren't you? And that fuel consumption rises with it, and range decreases (unless the extra weight is fuel, of course)
It has nothing to do with weight. The Mustang is much cleaner aircraft than the Spitfire, so using the same amount of power, using the same amount of fuel, it can reach higher cruise speeds. Naturally, this makes it`s range much better.
The Mustang`s mileage was something like 8 mpg in the Australian test, and one would believe the Spitfire with the same engine would have much less - which is the case as the Spitfire fuel economy trials returned a milage of 6.76, consistent with the range charts etc.
Again the SU carb, again not a Merlin 66.
Let me clarify then : You claim that the SU carburrator of the Merlin 66 was so much more efficient, that it
improved fuel economy by no less than 50% , from 6.76 mpg to 10 mpg? It`s amusing given that not even swapping carburrators to direct fuel injection achieved such
unbelievable results.
It`s quite simply hogwash. Funny though the RAF firmly believe the Merlin 66, Merlin 266 Spits have the same (as a matter of fact, a bit less, ie. 434 miles vs. 450 miles) range as Merlin 61 Spits.
There is a test of the Merlin 66, Kurfurst. Why is it you reject a test of the actual engine, and instead try comparisons with other, older engines?
Well if a single test claims 50% better fuel economy, and all the other tests and range tables give the same range, it`s logical to conlclude that single test was simply abberant, the results were poorly recorded or such.
What, you mean mixture could make a difference? Getting the mixture leaner would increase range? Duh.
That`s why aircraft have engine controls like 'auto-lean' and 'auto-rich' mixture settings (at least Western Allied aircraft, LW fighter aircraft had it set fully automatic and did not need the attention of the pilot at all).
What do you think the carburettor does, Kurfurst?
Oh I am sure you know such matters much better than any of us. Tell us about the technical advanced that allow one carburrator to be 50% more fuel economic than another.
I wunder why everybody went with fuel injection in the end, and even that didn`t gave such incredibly fuel savings.
As to the mantra about 85 gallon internal fuel tanks, that's all the Spitfire was fitted with, until the RAF wanted more range. When they did, they started fitting wing tanks, a larger lower forward fuselage tank, rear fuselage tanks, and bigger drop tanks.
Sure. Yet 95% of the Spitfires in service at the end of the war still had just 85 gallon internal fuel tank. The only ones that had wing tanks were the Mk VII/IIIs, and there were very few of these around compared to Mk Vs and IXs (the latter two making up more than half of all Spitfire production IIRC, the Mk VIII less than 10%).
Well, the most numerous perhaps, but certainly not the "main" fighter. For example, a quick glance through the claims and losses lists for December 1943 shows 2 operations by Spitfire Vs, 5 by the much more capable at low altitude LF vs, and 19 by Spitfire IXs.
And please don't encourage Kurfurst on this. Last time he got into an argument on these lines, he got banned from a forum. It really wasn't nice.
Cherry picking a single operation only prevents you seeing the forest from a tree.
As for the LF V, performance was hardly inspring for 1943. It was about comparable to the Mk IX or Bf 109G close to the ground level (2-3-4000 feet), above that it`s performance fell off so badly it was inferior even compared to the Mk I. It was a desperate measure, an 'ersatz' Mk IX, due to the lack of Mk IXs.
Neil Stirling from WW2aircraftperformance.org posted the following numbers :
As of 18th May 1944.
Spitfires with Sqn's
MkV 531
MKVII 62
MK VIII 209
MK IX 996
Mk XII 22
MK XIV 61.
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Total 1881
Note that in the entire RAF, even by mid-1944, Mk IX amounted still just under a thousend, there were still more than five hundred old and outfashioned MkVs still used. The Mk VII/VIII was even less numerous, half as many of them being around than Mk Vs. And we're talking about
mid-1944 here.
'Of the 47 Spitfire Squadrons available at the beginning of 1943, only 10 were equipped with the MkIX. Owing to the difficulties producing enough engines, and demands for the aircraft from other battlefronts, it remained in short supply. This situation did not markedly improve until the second half of the year. As a result, the vast majority of home Spitfire units had to soldier on with the Mk V, even though this aircraft in most respects were totally outclassed by the opposition.'
Source : Ian Carter - Fighter Command, Chaper 5, '1943', pg 92.
They decided to switch to night bombing at the end of 1939.
In
June 1943, the RAF Fighter based in Britiain command possessed 10 MkIX Squadrons, but 34 Squadrons of Spitfire Vs, plus a Squadron of the similiar Spitfire VI. Many Squadrons operated the Typhoon, in fact the two mainstay fighters were the Spitfire Mk V and the Typhoon by far.
This is via John Foreman, author of many volumes dealing with of Fighter command, 2nd TAF etc. histories.