BoB Spitfire 100 Octane fuel
 

BlackSix,

Firstly, thank you very much for all your efforts on behalf of your customers in response to our feedback. This flight sim (please see link below) appears to provide a good example of the Spit 1A with regard to the aircraft flown in the Battle of Britain. Is there any chance that we could have the Spit represented something like this, as it was in the battle with 100 Octane fuel in CloD too? Many flight sim lovers are missing this in CloD at the moment.

http://www.a2asimulations.com/store/solo/spitfire/

For example, the link includes the following statistics for the Spit:

General Information - Supermarine Spitfire Mk IA
The Spitfire Mk IA was the initial production version with some minor modifications. It utilized the Merlin III engine, and with the availability of high-octane fuel, was able to be overboosted to 12 psi of manifold pressure using a boost control cutout. This greatly increased the top speed, but was discouraged in all but the most dire emergencies. In the event, most pilots considered any form of air combat a dire emergency, and the overboosting of the Merlin III became routine. This aircraft also made use of the Rotol constant speed propeller which improved performance substantially as compared to the original, two-bladed wooden props fitted to the Mk IA.
• Empty Weight: 4,999 lbs.
• Wingspan: 36.8 feet
• Wing Area: 242 square feet
• Normal Takeoff Weight: 6,050 lbs.
• Maximum Takeoff Weight: 6,250 lbs.
• Top Speed @ sea level: 289 mph TAS
• Top Speed @ sea level: 340 mph TAS (War Emergency)
• Top Speed: 354 mph TAS @ 20,000 feet MSL
• Top Speed: 410 mph TAS @ 20,000 feet MSL (War Emergency)
• Stalling Speed, clean (6,000 lbs.): 81 mph IAS
• Stalling Speed, landing (6,000 lbs.): 69 mph IAS
• Service Ceiling: 34,700 feet
• Powerplant: Rolls-Royce Merlin III, 1300 HP War Emergency, 1025 HP for takeoff.
• Armament: (8) .303 caliber machine guns with 300 rounds per gun.

note the difference in top speed at sea level when boost cut-out is operated. This is the sort of historic experience many of us would like to see when we fly the Spit 1A in CloD; just like when we read the real life combat reports.

Happy landings,

Talisman

Great post Talisman, love CoD and what the developers are doing with the new series of IL2 and the advances they are making taking forward ww2 flight simulation. Accurate FM of the aircraft are essential and I trust the developers will improve the current crop, especially the Spit 1a which feels particularly undermodeled.

Sry Talisman but posted data used by A2Asimulations for Spitfire MK1 are totaly wrong expecially with Emergency Power. Even Spitfire MKIX wasn't such fast :P

Hi Talisman,

Good that you started a new thread (instead of the mellee I see in the Friday Update thread) :)

It gives me the opportunity to ask the question I always wanted to, but never dared:

How many octanes does the fuel the SpitII flies with, has?


~S~

As you know Kwiatek, A2A simulations state that their Spitfire MkI is of a particular period March-May 1940 with 2-pitch props, and claim they were light enough to achieve these speeds although they do admit the 410mph in the handbook is a typo, their model doesn't actually achieve that speed. If I can quote them:
"The majority of Spitfire I testing at RAE etc was done pre 12 lb boost.You need to be very careful when analysing tests to match conditions to dates. Most tests done early were only at 6 1/4 and LOW weights, making those aircraft (March 1940) much faster. There was a steady drop off in speed as the marque progressed and the Mk II was slower again. What changed (and what was MUCH more important) was the climb rate.

2 pitch airscrews gave faster speeds than ROTOL (much lighter) but the climb was inferior. Given that climb to altitude was the main problem, the heavier props won out even though they delivered lower speeds. "

As you also know, they do not take the Spitfire MkIX max 335mph max as an indication that their lower powered MkI is incorrect because the MkIX was much heavier and therefore presumably slower.

To me its just more examples of just how complex these issues become without reference to specific configurations and perhaps the A2A configuration and results aren't relevant to what we are trying to get hold of: 100 octane CSP Spitfire Ia's of the BoB period July-October 1940.

I think its best to leave it to the devs to come up with the correct data for the given configuration and loadouts from everything that is available 'out there', or more likely an amalgam of it.

BlackSix has already said that the whole 100 octane/boost matter has been referred to Luthier for consideration.

According to the boost guage, 87 Octane, it does not appear to have had the modification that allows 100 octane and its +12lbs boost.

It (Spit II) does have 100/+12 performance specs though, regardless what the boost gauges show. Effectively its the same thing as Spit I with 100 octane, there was no meaningful difference between the two in performance at high boost.

OK guys,

IF you tell me that the SpitII today runs with 87 octane fuel
and it flies like an overmodelled F-16,

what do you expect its performance will be if 1C hears your comments and grants you 100 octane fuel?



Oh besides, Blacksix already posted an answer I think:
This "octane fuel" saga is becoming marvelous and I am struggling to grasp the meaning of trying to convince yourselves (first) and others (later), that a change of fuel will solve the bugs in the flight model which are the reason why your Spits get mercilessly kicked...


Just to be clear:
I am convinced that you are getting kicked in the SpitIs (and you rule in SpitIIs) because of the bad flight model bugs.
However I am not convinced that the reason lies in 13 octanes (the difference between 100 and 87 octane fuel).

~S~

~S~

I concur! So the Ia with 100 octane should have the same performance as the Spit II in the game.

But the game's Ia with CSP currently doesn't even match up to the real Ia's performance with 87 octane (source, Alfred Price - The Spitfire Story). So there's something amiss with the Ia FM that isn't simply down to fuel octane.

Also, in your opinion, is the Rotol Hurri in the game performing at 100 octane levels, as is the Spit IIa?

I'm not arguing here, by the way. I'd like to know! ;)

Where do I find that spec data for the SpitII in CoD?
I do understand that at +12lb/100 octane the Merlin III and Merlin XII have the same boost available and probably the same output.

I can't really comment on the SpitII except to say that when I did some test runs it didn't achieve the max speeds I found on the web. It was quite close but slightly under but it was close enough for me to be happy. Its probably the most accurately modelled a/c in there.

I wouldn't say it performs like an F16 but if you are comparing it with the 109s you don't, as I understand it, have an accurate 109 to compare it with (yet).

Hi Kwiatek,

Thank you for your post. I was not asking for exactly the same as the A2A Spit as I said:

"Is there any chance that we could have the Spit represented 'something like' this, as it was in the battle with 100 Octane fuel in CloD too?"

My point is that CloD appears not to have made any attempt to give us the correct Battle of Brittain Spitfire, or Hurricane for that matter. This is very dissapointing to so many flight sim enthusiasts, as 100 Octane fuel was a long term plan that the British arranged and put into action specially in time for the BoB. As I understand it, along with the Rotal prop and the way radar, air observations and intelligence was used to inform strategy and tactics, 100 Octane fuel was one of the fundamental reasons for RAF success in the air, when so much was against them.

At least on the axis side, CloD appears to have attempted to provide aircraft to the correct specification (if not actuauly achieved flight performance) and does not appear to have missed something so fundamental; of course I stand to be corrected on that as I am no expert and I must say that I have enjoyed being educated by my involvement with this sim and the community. Infact, I have found IL-2 to be a great history lesson for me, particularly on the Eastern front.

Happy landings and 'Salute' all,

Talisman

Dont belive that 2-pitch prop cause such huge difference like in data tou posted.


Here is RL analys between Spitfire MK1 with 2-pitch metal prop DH ( plane without aditional armour - so much lighter) and with Rotol constant speed prop ( plane with aditional armour, armoured windshield etc - so much heaveir)

" Conclusions.

1. This aeroplane has a much better take-off and climbs faster than other Spitfires fitted with wooden fixed pitch or metal two pitch airscrews.

2. There is a drop of 13 m.p.h in maximum level speed compared with the 2-pitch airscrew aeroplane but of this, 8 m.p.h. can be attributed to sources other than the airscrew.

3. Below full throttle height an increase in speed of about 4 m.p.h. can be attained by controlling the engine R.P.M. at 2800 instead of 3000.

4. The limiting diving speed can be reached much more rapidly with this aeroplane than with Spitfires fitted with fixed pitch wooden and 2-pitch metal airscrews. "

http://www.spitfireperformance.com/n3171.html


Spitfire MK1 with 2-stage DH prop (without addition armour) reachedmaximum speed - 367 mph ( 590 kph) at 18 600fy

Spitfire MK1 with Rotol ( with aditional armour) reached maximum speed - 354 mph ( 570 kph) at 18 900 ft.

So in level speed it would be only a few mph difference if both would have the same aditional armour.


In CLOD now only biritish fighters have huge performacne error but German ones too - 109 is also too slow plane according to RL data.

Kudos on your post, Talisman.

The objective is to have performance modelled accurately in ALL aircraft - Allies and Axis, fighters and bombers. Hopefully this thread can stay the course.

Just wait till the FM is addressed with one of the upcoming patches. Spit I doesn't match the performance of 87 octane nor of 100 octane so there is no way to determine what fuel so supposed to be modeled.

Until then just fly Spit IA vs. Bf 109, both don't match the historical performance but against each other they are a good match for entertaining dogfights.

Precisely my point.

But this thread was started after the release of v1.05.15950, and I hope that what's happening in picture number one didn't cease until they got it right.

http://forum.1cpublishing.eu/showthread.php?t=27926

If 1C couldn't make accurate and realistic performance of well known BoB fighters i dont want to know what they could do with russian planes performance in BOM :P

Il2 deja vu?

:eek:I'm under the impression that there was a "rush job" done on all the fighters (RAF and LW) re flight modelling. The Spitfire in particular seemed to have been pushed out the door too quickly. Aside from the hugely flawed flight model, other glaring indicators of hasty work are:

1) incorrect external sound. Spits & Hurries sound like diesel semi trucks. The 109's also sounded lame until corrected in later patch.
2) Spitfire mixture control animation reversed. Causes many an unnecessary blown Merlin to the unwary Hurricane pilot transitioning over to Spits.
3) Spit trim control animations (both rudder and elevator) non-functioning; although fortunately the actual trimming can be done by keyboard command.

The devil is in the detail, as they say, and it's significant that the three above dysfunctional features have not been corrected after 9 months of a series of patches. These would be simple fixes, I'm not confident that more complex flight modelling adjustments will be made in the much-anticipated upcoming patch.

I'm hoping threads such as this will be given enough serious consideration by the devs that these flaws will indeed be addressed in a straightforward, non-obfuscating, manner.

I know Snapper mate, I know! ;)

My point is that whatever work resulted from them 'poring over Spit perf data' as in the link, hasn't been released yet. Nothing's been released since v1.05.15950.

Let's hope 'The Patch' sorts all this stuff out.

If it doesn't, well there'll be a bit of a 'stuffstorm'!

Unfortunately, this thread's already been 'pilot's lounged' so not likely the devs will look either!:(

Klem my friend, we agree to disagree :)

The SpitII is the second most accurately modelled TIE fighter!
(The first one being the infamous LA5-FN Oleg gave us after a patch - which could perform continous loopings until it ran out of fuel).

Easy check: With a SpitII (Immelmann manouver): Full speed level, switch to vertical (3-5g), climb 200-400 meters, switch to level (3-5g) and roll back (head up). Check your speed.

Repeat this with a SpitI


~S~

The good news for the devs ought to be that having a number of tests with different weights and engine outputs, but the same airframe ought to make the fms more accurate.

When in steady state flight like a speed test, the drag cancels the thrust and the lift cancels the weight. Obvious I know, but it makes it hard for the devs to know which bits are right, or whether errors are canceling.

If they match all the tests, they know they have a good model.

Sadly, I don't reckon this will happen in the next patch. Ilya mentioned something about FUTURE fm development as if the staff had left or were working on other things.

@Grathos - as Talisman says, we want accurate fms, not improvements for one side, and- yes- the 109s are too slow.

56RAF_phoenix

I'm not sure where we're going with this Kwiatek.

The conclusion says that there is a drop in max speed with the Rotol vs 2-pitch. I think thats what A2A are saying.

In Tests 18th Aug - December 12th 1938 K.9787 MerlinII, DH5-20 returned 361mph at 18,000 feet, boost +6.4.

That report you linked says that Merlin III engined MkI N.1371 with Rotol achieved 353.5 (~354)mph TAS at 20,000 feet/3,000 rpm/Boost dropped off to 5.25. Actually thats the top speed at altitude A2A are claiming for their Ia.

This seems to be what the devs should be looking at:
http://www.spitfireperformance.com/spit1vrs109e.html

Anyway, we could go round and round for ever.....

There is a slight problem with k9787 ( 1st production Spitfire ) as a reference for mk 1a's. It was much lighter than a mk 1 in BoB trim. All up weight of k9787 was only 5819 lb, mk 1 in BoB trim 6155 lb ( source Alfred Price Spitfire in combat). It didn't have the bullet proof windscreen, which cost 6 mph, the IFF aerials cost about 2 mph, no armour plate.. Etc.

Top speed according to price of a fully equipped mk 1 in the summer of 1940 was nearer 350 mph. It's a minefield! :)

Just chewing the cud now...

Yes and I actually made a mistake over the K9787 prop - it was a fixed pitch wooden prop, quite light. 5819lbs all up, Merlin II, +6.25lbs, 361mph at 18,000 (360.5 @20k).

K9793 with the MerlinII and the 2-pitch metal prop and weighing only 5935lbs put up 366mph at 20,000 feet.

N.3171 weighed 6050lbs during its tests (231lbs heavier than K9787), Merlin III (same power as II) same boost +6.25, heavier Rotol prop, blown canopy and bulletproof windscreen, 354mph at 20,000. I don't think Alfred Price would argue with that. The ~6mph loss was attributed to the bullet proof screen but I can't help feeling that weight had something to do with it and perhaps the canopy too. Just to keep the Spit/109E comparisons in order, here's that level speed chart again:-
http://www.spitfireperformance.com/spit1vrs109e.html

One final point on N.3171, the speed tests were made at 3,000 rpm but they also reported:
"The results show that the maximum level speed is reached with the airscrew controlling at 2800 engine r.p.m. On increasing the r.p.m. to 3000 the speed was reduced, on the average by 4 m.p.h." So perhaps we could add 4mph to that 354mph result.

And again this shows the danger of just reading off max speeds as gospel. All three aircraft had different weights, different props plus a couple of other bits on N.3171.

well the bigger the better is not true check this wiki on octanes:

Octane" is colloquially used as a short form of "octane rating" (named for the ability of octane's branched-chain isomers, especially isooctane, to reduce engine knock), particularly in the expression "high octane". However, components of gasoline other than isomers of octane can also contribute to a high octane rating, while some isomers of octane can lower it, and n-octane itself has a negative octane rating

edit:

for what i know the antiknokcing charachteristic dpened on what kind of engine

so the fuel is syn with engine, normally revolutions

i just learnt it can even be negative

edit:

imagine i fuel creates a flame tongue in 0.1 seconds
the sync so the fuel doesnt expand while the piston contract and knoks depends on the speed of it

the antiknocking chararacthericstics of fuel that is the octanes determines how much does it take to burn

Good thread Talisman its about time we got the mk ia fixed. I do appreciate that the 109 is under powered when it comes to top speed as i do like to fly them now and again but a hurricane faster than a spit is just not on.

You're just trying to confuse me aren't you :D

I admit defeat! :D

well i understood this in my classes but most of the time i was daydreaming so maybe im mixing things :)

Good point Raaid.

There is nothing in the 100 Octane fuel that produces extra Horse Power, but it does allows the engine to run in the conditions where the motor can produce more HP. (if that makes sense????)

For example, my valiant with it's 10:1 compression needs 98 octane petrol to run smoothly in all conditions. if I run it on standard unleaded (91 octane) it will ping and knock at even low RPM and is unpleasant to drive at any speed. Using 95 octane I can drive at regular city road conditions, but will get pinging only when I try to flog it!

For true motoring bliss I need the 98 octane fuel to use the entire range of RPM and power in my engine.

AFAICMO, the modifications performed to the Merlin to realise the benefits of 100 octane fuel were in the delivery system to allow the engine to run at the higher boost. The changes to the actual engine were minimal and more for reliability rather than increased power.

Cheers!

The advantages of the massive stockpile of 100 Octane the British built up before and through the war should not be underestimated.

As an example, the DB605 in Luftwaffe service produced 1450 hp with B4 (87 Octane) and needed Mw50 to achieve more power. The same DB605 running 100 Octane with the Swedish air force produced 1700 hp without needing MW50.

Of course with 100 Octane MW50 would not have have had near as much effect as it is basically an anti-knock agent.

Yep. I've been running some 'time to climb' tests and comparing with Alfred Price's Data, a much better test IMO.

The results with the Ia compared to the IIa are 'illuminating', and they show the CSP Ia performing no better than the DH metal 2-speed prop.

See here if you're interested. :)

http://theairtacticalassaultgroup.co...=8095#post8095

From Price The Spitfire Story (Haynes, 2010, p. 106) - Spitfire I N3171 with the CSP was tested in March 1940, and wasn't fitted with armour plating, and IFF; the CSP was heavier than the two-pitch, by about 115 lb, so this and the other added weight would have pulled back climb performance, as described by ATAG_Dutch

The main benefits of the CSP were a greatly improved take-off distance (Two pitch: T/O 320yds, 490 yds to clear 50 ft screen versus 225 yds, and 370 yds respectively). It also meant the pilot didn't have to remember to change the pitch settings, and there was less strain on the engine.