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Kwiatos
09-27-2004, 06:41 AM
I wonder if some version of Spitfire MK V and Hurricane should have cut engine at negative G. In FB only Hurricane MK I 1938r have it.
I read some books and test about problem with cut engine in dive and i found that these problem was resolved in 1941 year in UK. In december 1941 first tested SPitfire MK VB nb. W3228 recived special "negative carburettor" which prevent cut engine in dive. These system was implemented in serial production in Spitfire with engine Merlin 50 and above. So Spitfire MK V and eariler model until engine Merlin 50 had cut engine at negative "G".
So in Fb Spitfire MKV wih egine Merlin 45 and 46 should have cut engine at negative "G", which haven't now.
See these for example:
"The only difference between a Merlin 45 and 50 is the fitting of a "negative g" carburettor and a fuel de-aerator on the latter
engine, and these are unlikely to have a marked effect on performance"
http://www.fourthfightergroup.com/eagles/w3228.html

Probably the same situation should be with Hurricane MK II which have Merlin 20. In FB only Hurricane MK I have engine cuting.

Kwiatos
09-27-2004, 06:41 AM
I wonder if some version of Spitfire MK V and Hurricane should have cut engine at negative G. In FB only Hurricane MK I 1938r have it.
I read some books and test about problem with cut engine in dive and i found that these problem was resolved in 1941 year in UK. In december 1941 first tested SPitfire MK VB nb. W3228 recived special "negative carburettor" which prevent cut engine in dive. These system was implemented in serial production in Spitfire with engine Merlin 50 and above. So Spitfire MK V and eariler model until engine Merlin 50 had cut engine at negative "G".
So in Fb Spitfire MKV wih egine Merlin 45 and 46 should have cut engine at negative "G", which haven't now.
See these for example:
"The only difference between a Merlin 45 and 50 is the fitting of a "negative g" carburettor and a fuel de-aerator on the latter
engine, and these are unlikely to have a marked effect on performance"
http://www.fourthfightergroup.com/eagles/w3228.html

Probably the same situation should be with Hurricane MK II which have Merlin 20. In FB only Hurricane MK I have engine cuting.

p1ngu666
09-27-2004, 07:32 AM
iirec there was a less effecient fix put in fairly early

Kwiatos
09-27-2004, 02:23 PM
what you mean?

JG53Frankyboy
09-27-2004, 03:42 PM
"Carburettor design
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."

btw, dont forget the A6M2 , its Sakae12 engine should also cut at negative G http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

XyZspineZyX
09-27-2004, 04:44 PM
Only the Spit I should have carburetor problems. This was fixed by the Spit II, I believe. But certainly by the time the V made its appearance.

Nexus2005
09-28-2004, 04:02 AM
Just because proper neg G carburettors weren't fittted until Merlin 50 doesn't mean that they still had severe negative G problems in earlier models. As Frankyboy said, Miss Shilling's orifice was fitted before then, although that was only a partial solution so maybe some Spit Vs should cut out in "sustained zero 'g' manouvres." But it should not be nearly as bad as the Hurricane I.

Kwiatos
09-28-2004, 04:36 AM
Ok thx for help so until Merlin 50 Spitfires and Hurricanes couldn't do sustained zero G manouvres but ben able to do short negative G manouvers.

p1ngu666
09-28-2004, 07:05 AM
not much should be able todo sustaind 0/- g manouvers
gravity was used in the oil system for most/all planes

VW-IceFire
09-28-2004, 03:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Kwiatos:
Ok thx for help so until Merlin 50 Spitfires and Hurricanes couldn't do sustained zero G manouvres but ben able to do short negative G manouvers. <HR></BLOCKQUOTE>
Yes...the retrofit meant that the engine wouldn't cut right away because of a negative-G manuver. Through a prolonged manuver it would cause problems like the ones without the retrofit but a few seconds of negative G is better than almost none at all.

I think the game as it is now only does instant G cut out.

In the training video for the P-38 its even recommended with that aircraft that you not fly in severe negative G situations or fly upside down for prolonged periods of time because of the oil not reaching the engine. So I think ultimately negative G for sustained time is bad for any engine...unless the Germans had a radically different system.

I'd expect with a Spitfire Mark I we'd have neg G cut out fairly quickly. We don't have one so thats that...

This advantage by German aircraft is generally mentioned during the time period of the Battle of Britain (Summer 1940). Later its never mentioned...by either side.