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DIRTY-MAC
09-21-2008, 06:21 AM
Found this on J-aircraft

Given that earlier I posted a comparison of combat results by both the P-40's of the 49th FG and the Spitfire Mk.V's of No.1 Wing; I thought it might be of interest to all to post a comparison of an actual test conducted by the RAAF between the two aircraft.

The tests were conducted over 3rd to 5th of November 1942, at the No.2 Operational Training Unit in Mildura - a very hot dry open locale in western Victoria. Oversighting the tests was Wing Cmdr. Peter Jeffrey; the actual test pilots beng:
Flying the P-40E - Flt. Lt. Arthur and Flt.Lt. Jackson.
Flying the Spitfire Mk.Vc - Flt. Lt. Foster and Flt Lt. Wawn.
All pilots involved were experienced combat pilots, with Arthur, Jeffrey, Foster and Jackson all being aces - Foster (9) flying Spitfires over Europe, Arthur (8) and Jeffrey's (6) flying P-40's in the Western Desert and Jackson (5) flying the P-40 against the Japanese over Port Moresby, New Guinea.

The results of the tests were as follows:

1. The Spitfire was fitted with a Volkes Filter

2. As the Spitfire was fitted with VHF, and the P-40 with HF, no R/T between them could be used.

3. The Spitfire tested suffered from negitive 'G' cutout, a typical Spitfire trait.

4. The Tests were carried out at heights between ground level and 20,000ft.

5. Results:
a) Spitfire had the greater rate of climb at all heights - the difference becoming greater as height increased above 13,000ft.
b) Spitfire is far more manoeuvrable at all heights.
c) Kittyhawk is faster in level speed from 0 to 16,000ft. Above 16,000ft Spitfire is faster and again the difference becomes greater as height increases. Estimated speed advantage of Kittyhawk up to 16,000ft: 0ft - 15mph; 12,000ft - 20 to 25mph; 16,000ft - 5 to 10mph.
d) Kittyhawk accelerates, both in dive and on increase of throttle on the level, far more quickly than the Spitfire.

6) Combat 1 - commenced at 13,000ft (equal height) and lasted for 5 to 7 minutes, in which time the fight was practically a stalemate. At the end of this period height was reduced to 4,000ft when the Kittyhawk pilots decided he had nothing to gain by staying and so broke off by diving away. Thus, in combat up to 16,000ft, the Kittyhawk has the distinct advantage in that the pilot can commence the fight and discontinue it at will. In such a combat the Kittyhawks tactics are to hit and run, and then come again.

7) Combat 2 - commenced at 20,000ft (equal height) and lasted less than 2 minutes. Spitfire quickly gained dominate position on the tail of the Kittyhawk and couldn't be shaken. Kittyhawk pilot broke off by diving away.

8) Combat 3 - Commenced at 16,000ft (height advantage to Kittyhawk) an lasted 14 minutes. Kittyhawk made repeated dive and zoom attacks with the Spitfire alternatively breaking hard to avoid and climbing for advantage where possible. Fight reduced to 9,000ft with neither pilot gaining a decisive advantage.

9) Combat 4 - Commence at 16,000ft (height advantage to Spitfire) and lasted 11 minutes. Spitfire pounced on Kittyhawk and attempted to gain a position on tail. Kittyhawk used speed advantage in first level flight and then shallow dive to gain separation and then climb for advantage. Spitfire countered by climbing hard. Gaining advantage Spitfire used climb and dive tactics to force the Kittyhawk to make repeated diving breaks to avoid. At 7,000ft Kittyhawk used superior roll rate to scissor behind the Spitfire, who countered with steep climb. Kittyhawk then used speed advantage to again gain separation and fight was broken off.

10) Visions - the vision in the Spitfire with the hood closed is better than the Kittyhawk, but it is a definte disadvantage that the hood cannot be opened at speeds above 160mph particulary when searching up-sun.

11) The flying characteristics of the Spitfire make it more suitable for Operations:
a) it is easier to fly.
b) Take-off run is much shorter and so could be operated from smaller landing grounds. Note - ithe Spitfire does not handle hard dirt strips as well as the Kittyhawk.
c) Mixture and boost are automatically controlled.
d) It is not necessary, as it is in the Kittyhawk, to alter rudder and elevator trims over great speed changes.

All these facts greatly reduce the pilot's problems and so increase his fighting efficiency.

The report concluded by recommending that as the large Volkes air filter on the Spitfire cost 20-30mph in top speed, it should be removed inoperational service - or at least an alternative found. Also mentioned was the effect of the Spitfires rough paint finish on performance but the general feeling of the report was that the Spitfire was perahps the better fighter, especially at altitude.

The report also mentioned being surprised at just how well the Kittyhawk managed to hold it's own against the Spitfire in combat, concluding that in combat against an opponet it highlights the importance of using one's aircraft strengths to advantage.

M_Gunz
09-21-2008, 06:56 AM
Interesting in many ways.
Thanks for that D-M!

Xiolablu3
09-21-2008, 07:00 AM
Excellent, thanks http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

I wonder why the information about the Shilling Orifice wasnt posted off the Aussies sooner?

The RAF had been using it for over a year at this time.

There WAS an alternative at that time to the bulky Volkes filter which was used a lot in MAlta I believe. Began with 'K' and was arab sounding. Something like 'Kabur' filter, which hardly took any extra speed off.

It was fitted to many Malta Spitfire V's during 1941/42 and the Volkes was removed.

luftluuver
09-21-2008, 07:36 AM
Must be an early production Mk V as FC had the Shilling Orifice installed in all their a/c by March 1941.

M_Gunz
09-21-2008, 07:40 AM
Was the Orifice 100% effective?

Aaron_GT
09-21-2008, 09:47 AM
but it is a definte disadvantage that the hood cannot be opened at speeds above 160mph particulary when searching up-sun.

I presume this means the Spitfire couldn't open the canopy above 160mph not the Kittyhawk? It's not entirely clear!

Xiolablu3
09-21-2008, 02:46 PM
Originally posted by M_Gunz:
Was the Orifice 100% effective?

I dont think so Max, but it would be effective enough to stop the neg G effect for a few seconds.

I think it certainly stopped the total cut out of the engine.

There was still a slight effect I think, and possibly if it was a prolonged Neg G manouvre then it had a noticable effect on the engine power even with the orifice.

I think its pretty likely that the Aussie report is talking about a Spit V with no orifice. Spitfires/aircraft overseas often got new developments much slower than ones based near/in Britain.

I dont think the orifice was an 'offical' part of the SPitfire until later. In the beginning Miss Shilling travelled around Britain putting them in Spitfires with her small team in 1941. SO how long it was before it was an 'official Spitfire part' and built into new models, I dont know.

Did the Aussies build SPitfire V's over there? I am sure, from one of the docs you sent me that Mosquitos were built down under? Or am I thinking of Canada?

Xiolablu3
09-21-2008, 02:49 PM
Originally posted by Aaron_GT:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">but it is a definte disadvantage that the hood cannot be opened at speeds above 160mph particulary when searching up-sun.

I presume this means the Spitfire couldn't open the canopy above 160mph not the Kittyhawk? It's not entirely clear! </div></BLOCKQUOTE>

Yeah I think you are right.

M_Gunz
09-21-2008, 03:58 PM
Originally posted by Xiolablu3:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Was the Orifice 100% effective?

I dont think so Max, but it would be effective enough to stop the neg G effect for a few seconds.

I think it certainly stopped the total cut out of the engine.

There was still a slight effect I think, and possibly if it was a prolonged Neg G manouvre then it had a noticable effect on the engine power even with the orifice.

I think its pretty likely that the Aussie report is talking about a Spit V with no orifice. Spitfires/aircraft overseas often got new developments much slower than ones based near/in Britain. </div></BLOCKQUOTE>

"The Spitfire tested suffered from negitive 'G' cutout, a typical Spitfire trait."

If even with the Orifice you got some loss of power rather than near total loss, the meaning
may have changed without the words changing since anyone who flew them would know what was
being referred to, wouldn't they?


I dont think the orifice was an 'offical' part of the SPitfire until later. In the beginning Miss Shilling travelled around Britain putting them in Spitfires with her small team in 1941. SO how long it was before it was an 'official Spitfire part' and built into new models, I dont know.

That was the field mods. If it was as effective as some histories say then I would have
thought that Supermarine and all would have adopted it in about 2 seconds flat!

Didn't those buttons go into the late production Spit II's? IIRC the Orifice was from before
the Spit V.

We have a Spit V from mid-42 that's labeled as 1941 (an admitted by Oleg error) in IL2.
Drop the nose smartly on that and see what happens.

Aaron_GT
09-21-2008, 04:57 PM
SO how long it was before it was an 'official Spitfire part' and built into new models, I dont know.

Standard in 50 series engines, kit on earlier. First test December 1941. Unless the orifice is something other than what I have in my sources.

Xiolablu3
09-21-2008, 05:37 PM
I think the orifice is from mid 1941.

From what I remember it was just after the BOB that she started fitting them.

Once it was developed it was very quickly fitted to most of the Merlin engines. Miss Shilling used to travel around the airfields fitting them, with the frontlines first, so it was done very quickly.

M_Gunz
09-21-2008, 05:48 PM
I thought it was spring of 41 so I had to check and it took a bit of searching (not on the
first page, lol)

By March 1941 the device had been installed throughout Fighter Command as a stop-gap until an improved carburettor became available in 1943. (http://en.wikipedia.org/wiki/Beatrice_Shilling)

There was the disc and a change to a needle valve. I see a real chance of it not getting
done super quick down under but I also see how it should have been possible to as well.
It's not like technical descriptions and drawings had to travel by sailboat to get there,
it's not like they didn't have machine shops in Australia.

luftluuver
09-21-2008, 05:52 PM
Originally posted by M_Gunz:
I thought it was spring of 41 so I had to check and it took a bit of searching (not on the
first page, lol)

By March 1941 the device had been installed throughout Fighter Command as a stop-gap until an improved carburettor became available in 1943. (http://en.wikipedia.org/wiki/Beatrice_Shilling)
I see ppl don't read all the posts.
I stated this already.


Must be an early production Mk V as FC had the Shilling Orifice installed in all their a/c by March 1941.

M_Gunz
09-21-2008, 05:54 PM
Right. Forgot.

ElAurens
09-21-2008, 06:02 PM
I'm rather surprised that the P40E out accelerated the Spit. The P40 is significantly heavier.

Skoshi Tiger
09-21-2008, 08:04 PM
I've read that comparison before, Most pilots thought the Spitfire was a better aircraft, but numerically the P40 was out most important fighter for basically one reason. The Spitfire lacked the range that most pacific operations required.

When Australia was deciding upon which aircraft to build locally, we chose the Mustang for its range and ease of manufacture.

WTE_Galway
09-21-2008, 08:43 PM
Originally posted by Xiolablu3:
I think the orifice is from mid 1941.

From what I remember it was just after the BOB that she started fitting them.

Once it was developed it was very quickly fitted to most of the Merlin engines. Miss Shilling used to travel around the airfields fitting them, with the frontlines first, so it was done very quickly.

There was more to it than just the restrictor but overall it was apparently a relatively simple install..

The source of the cutout was that under negative G the float moved forcing the needle valve wide open filling the float chamber resulting in an over-rich mixture which stops the engine.

The orifice itself was a diaphragm with a hole in it across the float chamber. The diaphragm came in two sizes depending on the boost used in the engine. There was also some modification of the needle valve itself.

Clearly the Shilling orifice could only negate negative G for short periods and could not conceivably have allowed sustained inverted flight. The style of carburetor to which the orifice was fitted relied on a float chamber and no carb with a float chamber can possibly function inverted for more than a few seconds.

This issue was overcome mid to late war with the introduction of the new Bendix carburetors which did not have a float chamber.

struth
09-21-2008, 10:57 PM
Originally posted by ElAurens:
I'm rather surprised that the P40E out accelerated the Spit. The P40 is significantly heavier.

Perhaps the electric prop of the P-40 outperformed the hydraulic prop of the Spit in the acceleration envelope.

The P-40E was about 1525kg heavier gross weight than the Spit V.
The P-40E had 1150hp Allison
The Spit V had 1230hp Merlin

Given these it might be that having momentum with a heavier weight the P-40 accelerated better under added power. Certainly it could not have slowed down as fast as the Spitfire but it could certainly outdive it and this was an attribute which was the saviour of many a RAAF P-40 pilot when a Messeschmitt or a Zero was on their tail.

The P-40 was no slouch down low or at medium altitude. It was good for about 366mph at 15000ft while the Spit VA got to 375mph at 19500 ft. The Spit VB was slower than the VA while the VC was faster.

So it seems the Spit was improving in performance with altitude and this would have been aided by its automatic control systems.

IMHO, when both aircraft types were tested Down Under they were in different conditions to where they were designed and flight tested and modified. In Australia in summer - more often than not - there can be excellent upswellings and great flying conditions such that ballooning and soaring fare well. The performance envelope could then be expected to be different and noting that the P-40 excelled in another hot dry climate - that of the western desert campaign, perhaps this environmental factor levelled the field to some extent between the P-40 and its adversaries in the earler part of the war.

When a P-40 rolls into an inverted dive you sometimes see stall trails under the inner wing rather than at the tips. This is not soley limited to the P-40 and I can't say if this is common to aircraft with a great roll rate but it is common pilot opinion that the P-40 outrolled both the Spitfire and the Mustang. RAAF fighter pilots claim it turned with the Spitfire if flown properly.

ImpStarDuece
09-22-2008, 12:05 AM
Remember though, that not only did the Volkes filter cost the Spitfire speed, due to the extra drag, but it also restricted the airflow to the engine, causing a reduction in power.

RAAF testing of four different Spitfires in 1942-1943 showed they lost between 55 and 70 hp due to the Volkes filter, depending on each fighter. This is at sea level nominal power. The engine could actually be expected to lose more power as it went higher; the Merlin 45 in the Spitfire Vc gave full power at about 14,500 feet.

Speed in the RAF tests dropped to as low as 346 mph, while others were able to do about 360 mph. This means that the Volkes cost Spitfires between about 10-25 mph, against the nominal top speed of a Mk V. The top speed height also dropped from about 20,000 feet to about 17,000 feet, which also attributed to the loss of speed.

RickRuski
09-22-2008, 02:06 AM
I have been reading "Wings over the Pacific" by Alex Horn an account of RNZAF units in the Pacific in WW2. here is a quote from page 63: -

Incidentally, the Spitfires were no more capable of mixing it in tight dog-fighting with the Zeros than the Kittyhawk was. In the early days of the war with Japan, a squadron of Spitfires with combat experienced pilots arrived in Burma full of confidence, but almost a whole formation of Spits was destroyed in the first engagement.

Aaron_GT
09-22-2008, 11:18 AM
Given these it might be that having momentum with a heavier weight the P-40 accelerated better under added power.

F=ma, and so for a heavier m with the same F a is lower. So in level acceleration the greater weight would hamper the P-40 so that points to either much lower drag (not that likely) or better gearing and higher prop efficiency (much more likely given the good US electric prop design as noted above)

The only time more m helps is going down as F=ma downwards too and m is roughly proportional to the cube of the linear dimensions, but drag depends on surface area which is roughly proportional to the square. I.e. when diving the force due to gravity minus drag is higher for larger objects.

M_Gunz
09-22-2008, 11:44 AM
The filter on the Spit really throws the results.

Frequent_Flyer
09-22-2008, 06:52 PM
Most all pilots from any of the combatants put the highest value on " speed and range " . Turning with your advesary was an obsolete tatic.The P-40 was a very under appreciated fighter. As was the P-39.

WTE_Galway
09-22-2008, 07:47 PM
Originally posted by Frequent_Flyer:
Most all pilots from any of the combatants put the highest value on " speed and range " . Turning with your advesary was an obsolete tatic.The P-40 was a very under appreciated fighter. As was the P-39.

Ironically about the time the RAAF got its first Spitfires Douglas Macarthur in all his wisdom as Supreme Commander SWP decided the RAAF was best suited to low level ground attack mopping up operations against isolated but well defended remote islands. A task far more suited to the P40. Higher RAAF brass went along with this stupidity.

This idiotic use of experienced combat pilots (Caldwell for example had 28 kills) in Spitfires against strategically unimportant ground targets resulted in the famous "Moratai Rebellion" where the RAAF pilots refused to fly. There was an investigation and they were exonerated at the time and several higher "brass" removed form their positions.

I often wonder if the subsequent scandal where the same pilots were later charged with using their Spitfires to smuggle whisky to USMC officers (a practice that had been previously ignored) was an unofficial punishment for the rebellion.

Frequent_Flyer
09-22-2008, 08:20 PM
Originally posted by WTE_Galway:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Frequent_Flyer:
Most all pilots from any of the combatants put the highest value on " speed and range " . Turning with your advesary was an obsolete tatic.The P-40 was a very under appreciated fighter. As was the P-39.

Ironically about the time the RAAF got its first Spitfires Douglas Macarthur in all his wisdom as Supreme Commander SWP decided the RAAF was best suited to low level ground attack mopping up operations against isolated but well defended remote islands. A task far more suited to the P40. Higher RAAF brass went along with this stupidity.

This idiotic use of experienced combat pilots (Caldwell for example had 28 kills) in Spitfires against strategically unimportant ground targets resulted in the famous "Moratai Rebellion" where the RAAF pilots refused to fly. There was an investigation and they were exonerated at the time and several higher "brass" removed form their positions.

I often wonder if the subsequent scandal where the same pilots were later charged with using their Spitfires to smuggle whisky to USMC officers (a practice that had been previously ignored) was an unofficial punishment for the rebellion. </div></BLOCKQUOTE>

[/QUOTE]

At Darwin P-40's actually gave a better showing against the Japanese then did the Spitfire. The lack of range and other mechanical problems cost the RAAF quite a few planes. The Japanese attacked at higher altitudes which consumed a good quanity of fuel just attaining intercept.
If the spits attempted to engage as the enemy regressed many of them ran out of fuel and could not return.There was quite a bit made of the spit's inadequate range. It received some persistant bad press,some at Douglas Macarthur instgation.

M_Gunz
09-22-2008, 08:39 PM
That's what happens when ground commanders get too fine a handle on air assets.
Same Old Thing happened in the early part of Africa and that ended up with the formation of
USAAF Fighter Command. Things really changed with that. Planes didn't change nor the pilots
except for losses and experience being outnumbered, but the doctrine and missions turned the
situation right around.

Men whose lives are on the line should have enough lattitude to be listened to seriously.
Not saying VOTE. Just heard.

coolinoz
09-22-2008, 11:04 PM
There was a magazine article in an aussie aerplane magazine last year about this subject, ill try and dig it out..from what i can remember the testing pilots came out in favour of the P-40

Xiolablu3
09-23-2008, 07:41 AM
I guess this is why most of the Spitfire VIII's built (over 1600) were sent overseas.

They had a 650 mile combat range on internal fuel and over 1000miles with drop tanks.

The SPitfires range was increased significantly in this model and as its the 3rd most numerous, it can be said that the SPitfires inadequate range in the pacific was addressed with tis model, which served from 1943 to the end of the war.

Was the range of the Spitfire VIII better than the P40's?

Aaron_GT
09-23-2008, 09:47 AM
Was the range of the Spitfire VIII better than the P40's?

It's the same as the P-40E (1941, Spitfire contemporary) but less than the P-40N's (1943 contemporary) 750 miles on internal fuel (1100 with drop tanks). But the difference is a lot less.

Viper2005_
09-23-2008, 11:01 AM
Originally posted by Xiolablu3:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Was the Orifice 100% effective?

I dont think so Max, but it would be effective enough to stop the neg G effect for a few seconds.

I think it certainly stopped the total cut out of the engine.
</div></BLOCKQUOTE>

The orifice prevented a rich cut.

The negative g cut was a two-stage phenomenon.

The initial problem was a lean cut. However, sustained negative g would result in a rich cut which could stop the engine. It was this rich cut that the orifice prevented. You would still get an initial loss of power as the engine ran lean; but instead of a total rich cut, the orifice was sized to deliver sufficient power for full power operation. Therefore sustained negative g would result in full power fuel flow. However at less than full power the engine would run rich and could still cut.

I suspect that this would have been a potential problem at high altitudes substantially above FTH. The other potentially nasty case would be getting bounced whilst at cruising power. Shoving the stick into a far corner at cruising power would probably result in negative g cut. Opening the throttle and increasing rpm to prevent this seems like a good idea, but it's quite easy to envisage this causing vicious backfiring. Thankfully AFAIK Merlins were fitted with flame traps in the induction system, so you'd be unlikely to grenade the engine...

Anyway, these sort of problems clearly illustrate why metered injection directly into the eye of the supercharger was really the only sensible long-term solution.

Why into the supercharger eye rather than the cylinders? Because evaporation of the fuel was worth about a 25 K reduction in supercharger delivery temperature. This both reduced supercharger power requirement (because it effectively increased its isentropic efficiency) but also increased charge density, thereby allowing a higher mass flow of charge to be delivered to the cylinders at constant volumetric efficiency, thereby increasing power.

Obviously the down-side of this approach is that the mixture distribution could never be as good as is possible with direct injection into the cylinders. But then again you only have to buy one injector and it doesn't need to be such a high pressure device, so you take some load off the accessory gearbox.

Since power was generally more important than brake thermal efficiency, and emissions weren't even on the page, I think that direct injection into the eye of the supercharger was the correct pragmatic decision.

Xiolablu3
09-23-2008, 11:58 AM
How was this problem solved on the merlin 60 series Viper? (Spit VII/VIII/IX)

Viper2005_
09-23-2008, 01:16 PM
Direct fuel injection into the eye of the supercharger.

No traditional carb = no float = no reliance upon gravity.

http://en.wikipedia.org/wiki/Pressure_carburetor

There was an SU direct injection system as well as the Bendix.

struth
09-23-2008, 06:33 PM
Originally posted by Aaron_GT:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Given these it might be that having momentum with a heavier weight the P-40 accelerated better under added power.

F=ma, and so for a heavier m with the same F a is lower. So in level acceleration the greater weight would hamper the P-40 so that points to either much lower drag (not that likely) or better gearing and higher prop efficiency (much more likely given the good US electric prop design as noted above)
</div></BLOCKQUOTE>

Yes...if the filter on the Spit is not the vital difference (drag) then thrust seems to be the key if the P-40 accelerated better than the tropicalised Spit V. Therefore, I wonder if it's possible to get some figures for the tramsposed formula? => a=F/m

F (thrust) would seem to be the harder historical figure to obtain.

Viper2005_
09-23-2008, 06:53 PM
"Acceleration" as recorded in flight tests is an interesting thing.

These guys were flying without r/t, and the general impression given is that they were trying to formate at some fixed level speed and then drag-race each other.

That's not exactly easy...

How do you think they signalled the start of the race? Which of them did it?

I imagine that they would have tried to set up a fairly close line-abreast and then the leader would have made an appropriate hand signal.

The chances are that he would have used his left hand because his right hand would have needed to be on the stick for reasonably close formation work.

To signal, he needs his hand at head level.

The other guy has his left hand on the throttle.

Additionally, whoever is signalling has probably tightened up his throttle friction nut so that he can signal without risk of the throttle running away.

It's easy to see how this arrangement could lead to inaccurate results.

This doesn't mean that I think that the Spitfire was necessarily capable of more than the report suggests. I just don't think that the way in which this test was carried out naturally lends itself towards accuracy.

IMO, this is one of the few situations in which the mock combats give a better indication of reality than the apparently controlled tests...

struth
09-23-2008, 07:54 PM
yes...I don't know how they tested acceleration.

I guess there is always the lab possibility of measuring (average) maximum velocity over a fixed ground distance at a certain height; then testing acceleration over the same ground distance at the same height.

Kettenhunde
09-23-2008, 08:51 PM
Direct fuel injection into the eye of the supercharger.


That is not direct fuel injection and does not have the benefits of direct fuel injection.

This is closer to single point injection or TBI.

It does not precisely meter fuel to the cylinders but is the same as any other carburetor in regards to metering.

http://www.minimania.com/ArticleV.cfm?DisplayID=1458

http://en.wikipedia.org/wiki/SU_carburetor

All the best,

Crumpp

Saburo_0
09-30-2008, 01:31 PM
Originally posted by Viper2005_:
"Acceleration" as recorded in flight tests is an interesting thing.

These guys were flying without r/t, and the general impression given is that they were trying to formate at some fixed level speed and then drag-race each other.

That's not exactly easy...

How do you think they signalled the start of the race? Which of them did it?

I imagine that they would have tried to set up a fairly close line-abreast and then the leader would have made an appropriate hand signal.

The chances are that he would have used his left hand because his right hand would have needed to be on the stick for reasonably close formation work.

To signal, he needs his hand at head level.

The other guy has his left hand on the throttle.

Additionally, whoever is signalling has probably tightened up his throttle friction nut so that he can signal without risk of the throttle running away.

It's easy to see how this arrangement could lead to inaccurate results.

This doesn't mean that I think that the Spitfire was necessarily capable of more than the report suggests. I just don't think that the way in which this test was carried out naturally lends itself towards accuracy.

IMO, this is one of the few situations in which the mock combats give a better indication of reality than the apparently controlled tests...
& tests I've seen showed a marked difference depending upon what speed they started from. So 1 a/c could accelerate from a given speed better, but if the starting speed was changed then the other would best it.
1 thing IL2 can misrepresent in many flight tests & in game (IMHO) is combat cruise & acceleration to fighting speed. This was very important IRL, but I'm not sure our sim represents this so well.