Official Fulqrum Publishing forum - wep on RAF planes awol???? boost levels??? no 100 octane fuel:(

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- - wep on RAF planes awol???? boost levels??? no 100 octane fuel:( (http://forum.fulqrumpublishing.com/showthread.php?t=19754)

Quote:

Originally Posted by fruitbat (Post 245196)

good work Biggs:)

just did another test with the mkIIa and they show (compared against the tests from SpitfirePerformace) that the mkIIa seems to be pretty much spot on for climb rate and top speed. (this plane really is fun to fly)

its the mkI thats off for some reason.

the other thing i noticed is that u cant fly the mkII in anything other than the black and white undersides... which is pretty ironic as is was the EARLIER mkIs that flew in that paint scheme...completely minor issue i know :-P

LUTHIER lets get this mkI issue sorted please!

yep, the day/night scheme was changed between end of Dunkirk and beginning of the BoB, sometime in early June.

for the record The Spitfire Story, by Alfred Price lists the diff between 87 octane fuel and 100 as

"giving no improvement at or above 16,500 foot full throttle height of the merlin II and III engines fitted to the spitfires, below that altitude the maximum boost pressure could be raised from 6 1/4 pounds to 12 pounds without causing detonation in the cylinders; the resultant extra power increased the maximum speed by a useful 25mph at sea level and 34mph at 10,000 feet"

and being supplied to frontline squadrons from spring 1940.

ABSOLUTE BONKERS!!!!!

the mkI is BETTER than the mkIa.... i did this twice cause i didnt believe it the first time...

at 18k WEP boost (4lb) coarse pitch.... i can hit ~260 IAS thats what...340TAS?

at the SAME at SAME boost and pitch... i can only hit 220 ISA in the mkIa

260IAS is still 20mph too slow but its a whopping 40 faster than the 'a' version (which should be the SAME as the mkI in terms of top speed)

:confused::confused::confused:

Edit: i even think the climb rate is better for the mkI vs mkIa but im not sure

bump... Has anyone else tried this yet? I want to make sure its not just me and my bad flying skills. :-P

Quote:

As it turned out, aviation spirit was to prove no worry for the R.A.F. By July 11th, 1940, the day after the Battle of Britain opened, stocks of 100 octane petrol used in the Merlin engine stood at 343,000 tons. On October 10th, twenty-one days before the battle closed, and after 22,000 tons had been issued, stocks had risen to 424,000 tons. With other grades of aviation spirit total stock available on October 10th, 1940, was 666,000 tons. Oil reserves were 34,000 tons.

All this information is courtesy of Mike Williams Spitfire site:

http://www.spitfireperformance.com/spit1vrs109e.html

Most of the benefit of 100 octane fuel in the Hurri I and Spit I was at lower altitudes, there was no gain above the rated alt of these planes. Only when the Spit II appeared with a higher boost supercharger at high alt, was there any gain up high.

Thanks for all the info Buzzsaw:cool:

Spitfire: The History

According to RAE trials 12lbs boost would reduce engine life to 10 hours at 3000rpm ground level.

Following trials of 95 and 100 fuel, the decision to supply 100 Octane fuel was made on 16 March 1939. 16 fighter and 2 bomber squadrons were supplied by September 1939

Merlin II produced 1030hp @ 16250ft (42.6" MP) and 1160hp @9000ft (54.3" MP)

Trying to find some performance figures from the Supermarine trials.

OK, Handling trials held for gun configuration, Martlesham Heath 20th July 1939

K9787 (8 brownings)
Merlin II, 2 blade wood fixed:
time to 20kft = 9.4min
Speed@18.5kft = 363 mph
CEILING = 31,900

K9783 (8 brownings)
Merlin II, 3 blade DH 2 pitch (5/20 bracket):
time to 20kft = 11.4min
Speed@18.5kft = 367 mph
CEILING = 34,400

L1007 (2 hispano, no brownings at all)
Merlin III, 3 blade DH type 5/21 bracket (that is not a CPS unit, it's a later 2 speed bracket for the Merlin III):
time to 20kft = 10.7min
Speed@18.5kft = 364 mph
CEILING = 34,500

So, there's not a massive difference between the types. The difference is in take off distance, acceleration and pilot workload. All spitfires were converted to the 5/29 and 5/30 brackets for CPS during June and July 1940

Quote:

Originally Posted by Osprey (Post 245528)

yep... well the mkIs in this game dont really come close to that.. i got 260IAS @18ooo with the mkI... but thats still about 20 IAS off.

def needs MOAR BOOST!!!!