Your figures don`t take into account the weight and bulk of additional equipment that was put onto the Spit`s during which +12 lbs was authorized in a limited scale.
These included adding of rear armor, front armor glass (-6 mph), adding of IFF aerials (-2mph) etc.
This aeroplane was fitted with a bullet-proof windscreen, armour plating over the petrol tank and externally, apart from the radiator, was similar to the Rotol Spitfire I, N.3171, previously tested at this establishment.
Also the Spit II`s engine was noticably more powerful than that of the Spit I`s.
Spitfire VB. W3134 did 291 mph at SL at +9 lbs, which means it had apprx. the same or even more power than the Spit I at +12 lbs.
So I think AH2`s speed values are very generous, considering they model the latest and rarest variant of Spit I and not that one that did most of the fighting in `39-40.
Originally posted by Nashwan
Yes, that is taken into account.
Note the Spit II test: http://www.fourthfightergroup.com/eagles/spit2.html
What it doesn't take into account is the speed increase from removing the mirror, which AH doesn't model.
The Merlin XII was less powerful than the Merlin III below critical altitude, but had a higher critical altitude, when run at the same boost.
The Spitfire II tested at 9 lbs boost did 290 mph at sea level. The Spit I at 9 lbs would have been slightly faster, the Spit I at 12 lbs would have been considerably faster.
The Spitfire did very little fighting in 1939. In 1940, the vast majority of it's fighting was done with 100 octane fuel.
According to Wood and Dempster, Fghter Command used 22,000 tons of 100 octane 10th July to 10th October.
That's something over 6300 Spit or Hurri sorties per week, the average number of combat sorties was something under 4000 per week.
The fact remains, the Spit I should go from approx 280 mph at sea level at 6.25 lbs to 305 - 310 mph at sea level on 12 lbs. It only manages 291 mph.
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.
As for the removed rear view mirror, I haven`t seen too many Spits without it.
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...?
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
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.
It says :
- the XII is more powerful below FTH than the III (exact opposite what you claim)
- the Mk II Spit is 6-7mph faster below FTH (exact opposite what you claim)
Frankly 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.
Yes that`s the mantra and the claim. And where`s the Spit I flight test at +12 lbs...?
with only every 4th fighter having the ability to use 100 octane fuel... "vast majority" you say.
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
Probably it has to do something that they couldn`t secure a solid import of 100 octane at that time anyway...
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).
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.
22 000 tons for 3 entire months of heavy fighting? That`s a ridiculus amount, Nashwan, only 7000t per month.
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.
Here`s a relevant qoute Pips found at the Australian War Memorial Archives
310 mph at SL is a wet dream, nothing more. Good luck convincing anybody about your 'facts' without backing them up with real facts.
“AH II now models it with the correct 12 lbs boost”. Are you just referring to the boost gauge?
Check the FTH. That will tell the story. If its around 18,000 ft, which I expect it is, the FM would not reflect +12 boost.
In regards the 310 mph@SL claim, I find it deeply puzzling that then why did the RAF need to introduce the Mk V. at all, when it would be 20 mph slower than the allegadly 310mph Spit I at SL, in it`s initial +9lbs form..?