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WholeHawg
07-29-2005, 11:14 AM
I was watching the Military Channel (I love that channel!!) the other day and they had a special on about the BoB. In this special, they spent a great deal of time comparing the 109 and the Spit.

One of the key points they brought up was the fact that the Spits engine would cut out in positive G manuvers due to its carburator.

I have experienced this in several of the aircraft modeled in FB/AEP, but never in any of the Spits. I have to assume that this is because all the Spits in the game are based on fuel injected variants.

Do any of you Spit experts know when they switced to fuel injection?

Taylortony
07-29-2005, 11:21 AM
They used to cut in Negative G as the fuel flowed back from the carb, this allowed the 109 to escape.. A woman called Mrs Shilling at RAE Farnbourgh solved the problem by putting in effect a penny washer in the supply feed pipe to the Carb, this worked like a baffle and prevented fuel from flowing back from the carb and maintained power until normal G was restored.

It was nicknamed in service as

"Mrs Shillings Orifice"


Prior to that they used to have to roll em inverted then pull through and roll out in the dive to maintain a positive G in the chase...

WholeHawg
07-29-2005, 11:33 AM
So the end result was what? The engine would still cut out it just not quit all together?

Lucius_Esox
07-29-2005, 11:45 AM
No, it would work as it does in the game, although we don't have tha variants that were in the battle.

WholeHawg
07-29-2005, 11:58 AM
To my way of understanding simply placing a baffel to stop reverse fuel flow would only do just that. i.e. it would not keep fuel flowing into the carburator.
You would need a fuel pump as well, right? I am assuming that the fuel system myst have been 100% gravity feed?

I did a little more research and I found an account that stated this continued to be a problem to a lesser degree up to the Mk IX(No variant stated in the article).

Taylortony
07-29-2005, 12:39 PM
yes but it kept a supply at the carb that the engine could still draw and maintain power, it was the fuel running back from the carb that left an airlock and no fuel for the engine to use, so it cut. You do have a fuel pump yes, but the engine itself also works as a big pump and creates an updraft through the carb drawing the fuel in........... think pushbike tyre pump in a bucket of water, pull it out and it sucks water out of the bucket http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif same principal just a lot more money thrown at it http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

VW-IceFire
07-29-2005, 12:40 PM
One of the great problems as discerned by pilots was the tendency for the carburetted engine to cut out under negative 'g'. Luftwaffe pilots learned to escape by simply pushing the nose of their aircraft down into a dive, as their fuel- injected engines did not cut out under these circumstances. Many authors have criticised this aspect of the Merlin design. In reality, like most engineering, it resulted from a design compromise- the drop in temperature developed in a carburetor results in an increase in the density of the fuel-air mixture when compared to that of a fuel injection system. As a consequence the Merlin produced a higher specific power output (horse power per pound) that the equivalent German engine. It was felt that this gave a higher power to weight ratio for the fighter and (rightly or wrongly) that this outweighed the disadvantages. By 1941 Miss Tilly Shilling in Farnborough had developed a partial cure for the problem. A diaphragm across the float chambers with a calibrated hole (the infamous "Miss Shilling's orifice"!) allowed negative 'g' manouvres, and was fitted as standard from March 1941. Sustained zero 'g' manouvres were not sorted out until somewhat later. In 1942 an anti-g version of the SU carburetor was fitted to single and two-stage Merlins. 1943 saw the introduction of the Bendix-Stromburg carburetor which injected fuel at 5psi through a nozzle direct into the supercharger and was fitted to the Merlins 66, 70, 76, 77, and 85. The final development was the SU injection carburetor which injected fuel into the supercharger using a fuel pump driven as a fuction of crankshaft speed and engine pressures, which was fitted to the 100 series Merlins.
http://www.spitfiresociety.demon.co.uk/engines.htm

There's your answer.

The earliest Spitfire we have is the Spitfire Mark Vb which arrived on the scene a full year after the Battle of Britain and the variant that we have is infact a 1942 (its erroneously indicated as 1941 in game) version of the Mark Vb which presumably means that it has the "Miss Shilling's orifice" fix. The Bendix-Stromburg on the Merlin 60 and 70 series is what would be fitted on the Mark IX and VIII series that we have in the game.

As you can see, this negative G cutout is a non-issue for any of the Spitfires modeled in the game.

Too many TV productions give the false impression that the Spitfire and 109 series end at Mark I and E-4 (respectively) and that these two planes only met in combat during the Battle of Britain.

WholeHawg
07-29-2005, 01:10 PM
Thanks for the link Ice!!!

It's just amazing the amount of knowledge and research Oleg and his team have put in to this simulation to make it as accurate as possible. And we get reap the benefits of all that dedication for the low low price of ...... well about 20 bucks these days!!

jugent
07-29-2005, 02:59 PM
There are lots of other things that by some peculiar reasons aren€t modelled in the spitfire.



1. The overpressure mix of fuel and air in the pipes that goes from compressor / carburator to cylinder, is very dangerous.
On hit and a little spark turn the engine into a torch.

2. The radiator(s) is (are) large and placed under the wing (s).
One hole in a radiator will make the engine overheat and stop unless you land first.

3. The spit got a large torque. This didn€t matter when the used grass fields without runways.
They took of against the wind.

4. The aircraft was more than a match for an inexperienced pilot.
They said that the Hurricane is like a beer-delivery horse, stabile and reliable.
The spit is like an Arabic thoroughbred. Nice to ride but if you loose control it runs wild.

Perhaps many costumer dont want to buy this game if the legendary and mythic spitfire also got this behaviour.

The following is told to me by an Israeli flight-mechanic during an airshow in 1978 in Tel Aviv, where the spitfire and some other old planes where involved. Unfortunately I wasn€t so interested in the other planes

" The spit got four chambers for fuel to feed the carburator.
This didn€t work well but it worked. It needed a lot of maintenance.
When a spit rolled the feeding of the carburator automatically is switched from chamber to chamber and in some positions it was feed from two chambers and got to much fuel. You can see that in some positions it will come out black smoke from the exhaust, like a car that runs with the choke on."

WTE_Target
07-29-2005, 09:19 PM
Originally posted by jugent:
There are lots of other things that by some peculiar reasons aren€t modelled in the spitfire.



1. The overpressure mix of fuel and air in the pipes that goes from compressor / carburator to cylinder, is very dangerous.
On hit and a little spark turn the engine into a torch.

2. The radiator(s) is (are) large and placed under the wing (s).
One hole in a radiator will make the engine overheat and stop unless you land first.

3. The spit got a large torque. This didn€t matter when the used grass fields without runways.
They took of against the wind.

4. The aircraft was more than a match for an inexperienced pilot.
They said that the Hurricane is like a beer-delivery horse, stabile and reliable.
The spit is like an Arabic thoroughbred. Nice to ride but if you loose control it runs wild.

Perhaps many costumer dont want to buy this game if the legendary and mythic spitfire also got this behaviour.

The following is told to me by an Israeli flight-mechanic during an airshow in 1978 in Tel Aviv, where the spitfire and some other old planes where involved. Unfortunately I wasn€t so interested in the other planes

" The spit got four chambers for fuel to feed the carburator.
This didn€t work well but it worked. It needed a lot of maintenance.
When a spit rolled the feeding of the carburator automatically is switched from chamber to chamber and in some positions it was feed from two chambers and got to much fuel. You can see that in some positions it will come out black smoke from the exhaust, like a car that runs with the choke on."

It amazes me with all these "Defects" none of the pilots like Johnson,Bader and many many others both pilots and historian writers like Dere and Deiton make mention of these terrible defects.
Infact I am sure all I have read is that on the ground the poor vis and prop torque were a handfull for the novice but as soon as the Spit was airborne it became "an extension of you mind and body,you only had to think it and the Spit would react" -DBader-
I only quote Bader because I remember his quote of the top of my head.
Now I understand that some people are uncoordinated but I fail to see how the quote of mind/body extensions can be seen as anything else than praise for the plane.
Why O why do I let myself continuously get dragged into this rubbish http://forums.ubi.com/images/smilies/35.gif

Cajun76
07-29-2005, 10:20 PM
Originally posted by jugent:
There are lots of other things that by some peculiar reasons aren€t modelled in the spitfire.


Probably the same peculiar reasons the 109 isn't modeled with thick black smoke pouring from the exhaust at full power, to name one. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

ClnlSandersLite
07-30-2005, 05:40 AM
For such defects you tend to have to stick with pilot accounts. For example, did you know that IRL the p-38's turbo superchargers kicked in at slightly different altitudes? To paraphrase the account (since I don't have it handy):

As you're climbing, you know when you're about to hit the mark where the turbo's kick in. You don't know EXACTLY when, but you got a pretty good idea. You sit ready not knowing which engine is going to kick up first. When it happens you must Suddenly apply rudder to keep the aircraft straight or you'll slam into the aircraft next to you (and he's having the same problems). Then, as soon as you get it corrected for, the other engine kicks up. Forcing you to make a dramatic correction once again. In tight formation, this was most problematic.

Also, how many here know that the lightning should be singificantly quieter than most other aircraft due to the exhaust driven turbo suber chargers acting as mufflers?

GerritJ9
07-30-2005, 09:39 AM
The Hurricane Mk. 1 (used in the BoB in parallel with the Spitfire Mk. 1 and Mk. 2) also has the G cutout, as do I-153, I-16 to name a few others.