Nope, despite you want to make it look like. The desription does not mentions the mounting of IFF aerials, so by all
likelyhood they were not present. It doesn`t mention what type of windscreen is fitted, by all likelyhood it`s an internal
windscreen.
It says an armoured windscreen.
What does it matter if they were internal or external if it was fitted with one?
Or are you claiming normal armoured windcreens were external, but you are assuming this particular one was internal?
If so, on what grounds?
As for the removed rear view mirror, I haven`t seen too many Spits without it.
Neither have I. The AH Spitfire doesn't have it though, so shouldn't have the drag from it either. A mirror is going to
cause more drag than an IFF aerial, even if the IFF aerial wasn't fitted.
Anyway, by what weird logic you want to use base the Spitfire I`s speed on the Spitfire II`s? Different planes,
different engines, haven`t you notice...?
Based on the fact they are almost identical with almost identical engines. The only difference is the Merlin XII was rated
for higher altitude and 9 lbs boost instead opf 6.25 lbs. Both used 12 lbs as a wep setting.
According to Spitfire The History:
The differences between the early Mk I and the new Spitfire were minor and apart from the Merlin XII engine running
on 100 octane fuel they consisted of a Coffman cartridge starter instead of the original electric starter of the Merlin II,
and a small fairing on the port side of the engine housing the new starter. In the air they were identical and the
designation was just a means to identify the aircraft as CBAF (Castle Bromich Aircraft Factory) built when ordering
spares
Perhaps we should ignore the figures for the Spit II because it had a different starter?
That the report you are basing your claim on says the exact opposite than you. To quote :
4.0 Level Speeds.
.......The top speed of this aeroplane is the same as that of N.3171 but is reached at 17,600 feet, 1400 feet lower than
the Mk.I Spitfire. Consequent upon this and the increase in power of the Merlin XII over the Merlin III below full throttle
height the aeroplane is about 6 - 7 miles per hour faster at heights less than 17,000 feet and about 4 - 8 m.p.h. slower at
heights above 20,000 feet. It should be noted that though the boost pressure on the Merlin XII is +9 lb. per sq.inch as
against +6 1/4 lb. per sq.inch on the Merlin III there is little difference in the engine power at heights of 16,000 feet
and above.
Little difference is not no difference. I said myself there was only a minor difference at the same boost, and of course at
high altitude the boost will be the same.
It's you who claimed at the same boost pressure the Merlin XII put out much more power.
The reduction in speed above critical alt would be because the Spit II on that test was heavier, and had the bellet proof
windscreen which the Spit I they were comparing it to didn't have.
Look at the rated altitudes from AIR 16/328 I posted above.
It says :
- the XII is more powerful below FTH than the III (exact opposite what you claim)
Isegrim, I said it was less powerfull
at the same boost pressure If you look at the test, they are running the Merlin XII at 9lbs, the Merlin III at 6.25 lbs. At those pressures, the
Merlin XII is more powerfull.
Loo at the figures from AIR 16/328 again:
Merlin III
6.25lbs boost
875hp at SL
Merlin XII
9lbs boost
990hp at SL
Of course the XII at 9lbs is more powerful than the III at 6.256 lbs, bust as I said at the same pressure the III is more powerful:
Merlin III
12lbs boost
1190hp at SL
Merlin XII
12lbs boost
1170hp at SL
- the Mk II Spit is 6-7mph faster below FTH (exact opposite what you claim)
Again, I said the MK II is slower
at the same boostFrankly we have seen quite too many examples of you overexxegaration the Spit`s performance in every possible way.
So, as long as you don`t provide credible evidence of what you say (you may start with engine charts for the Merlin III and
XII), I won`t, and I doubt anybody will accept your claims here. They are far too much unsupported.
Well, if you won't believe AIR 16/328, try this. From The Merlin 100 Series, by RR Heritage publications:
The Merlin II is essentially the same as the III except the III has a prop shaft capable of taking a CS prop.
Yes that`s the mantra and the claim. And where`s the Spit I flight test at +12 lbs...?
Here's the Spit I at 6.25 lbs:
http://www.fourthfightergroup.com/eagles/spit1.htmlN.3171 was tested with a Rotol prop, speed at sea level should be just over 280 mph.
R6774 was tested with a DH prop, the type the RAF used on the Spit I, and that was somewhat faster, although within the normal tolerances between aircraft. Note both were fitted with external armoured screens, armoured tanks etc,.
All the docs on the same page say 12 lbs boost increases speed at sea level by 25/28 mph.
There's plenty of information there that shows around 305 mph at sea level. Do you have any information that contradicts that, or just your prejudices?
with only every 4th fighter having the ability to use 100 octane fuel... "vast majority" you say.
Source?
Then also there`s Dowding`s restriction laid down upon the use of +12lbs as it wore down engines quickly, August :
http://www.fourthfightergroup.com/eagles/dowding1.jpg
http://www.fourthfightergroup.com/eagles/dowding2.jpg
Those restrictions are simply saying it's to be used in emerency only. You know, like war EMERGENCY power, W
EP
Probably it has to do something that they couldn`t secure a solid import of 100 octane at that time anyway...
Source?
Appearantly, the RAF could not convert all of it`s fighter to 100 octane until NOVEMBER 1940, by the time the BoB already ended (by British standards).
Source?
So as opposed to your claim that the Spits did their 'vast majority' of combat on +12lbs, the truth is that it wasn`t until the last two months of the year they were all capable to use it, even if there was enough fuel for that. In other words, the use of +12 lbs didn`t came into real widespread use until 1941.
Source?
22 000 tons for 3 entire months of heavy fighting? That`s a ridiculus amount, Nashwan, only 7000t per month.
It's 13 weeks.
22,000 tons / 13 weeks = 1692 tons per week
1692 tons = 3,790,000 lbs.
A Spitfire held 85 gallons of fuel, at 7.2 lbs per gallon. No drop tanks were used, so that's the maximum a spit sortie can use.
That equals 6,192 sorties per week. The RAF had something less than 700 operational serviceable fighters at any one time, so that equals about 9 sorties per fighter per week, or something over 1 per day, assuming the tanks were totally emptied each time.
In fact, the operational sorties were substantially lower than this, Hooton, Eagle in Flames gives figures of an average of 4,000 FC sorties per week.
If your numbers were correct, the RAF would have flown 6000+ sorties per week. You admitted that in fact they never flown more than 4000 sorties.
No, the 4000 number is operational sorties. To this must be added fuel used test running aircraft on the ground, ferry flights, training sorties (although only by operational squadrons, the figures don't include training command), wastage, pilots fillling their cars to go down the pub, etc.
Here`s a relevant qoute Pips found at the Australian War Memorial Archives
Why not wait and see what Neil finds in the British archives? The British archives should have more accurate info on the supply of fuel in Britain, after all.
310 mph at SL is a wet dream, nothing more. Good luck convincing anybody about your 'facts' without backing them up with real facts.
Apparently not to anyone else. HoHun has done his own calculations, which show my original statement of 305 - 310 is almost spot on. As shown above, R6774 did better than 280 at sea level at 6.25 lbs boost. The docs on MWs site show 100 octane increased speed by at least 25 mph.
The Spit II did 290 mp with 990 hp, the Spit I with an extra 200 hp is going to go quite a bit faster.
There is nothing to support your assertion 305 - 310 is wrong, other than you own assumptions.
Wotan, thanks for the info on the 109. It looks like the boost is wrong on that, but I don't know enough to tell wether the speed is out as well.
HoHun, thanks for the calculations. I've got the figures you calculated for climb from AGW as well, and I'm testing climb in AH II now.
