Merlin negative G cutout too quick?

[Osprey]

Originally Posted by Crumpp

It was a positive G maneuver most likely and certainly did not have a float carboretor. AFAIK, Spitfires were not outfitted for inverted flight.

Float type carburetor's are not capable of inverted flight as fitted to the Merlin.



http://www.airspacemag.com/how-things-work/upside.html

Did you watch the video? I was referring to the video.

[41Sqn_Banks]

Originally Posted by Osprey

Did you watch the video? I was referring to the video.

Indeed. Positive G maneuver? No way ...

[Osprey]

That's what I thought. And it had power applied too otherwise there's no way it could retain height.

All I would like to know is if this was an injected engine or Ms Schillings Orifice

[klem]

Originally Posted by Osprey

That's what I thought. And it had power applied too otherwise there's no way it could retain height.

All I would like to know is if this was an injected engine or Ms Schillings Orifice

Looking at the video again the engine was not supplying power when inverted, it was windmilling with the occasional detonation. When he was inverted he was almost certainly bleeding airspeed as he went until he rolled right way up and the engine picked up - quite quickly too. Pretty sure its a carburettor not an injector.

[JtD]

The Mk.Va came with a float type carburettor. The Tilly orifice would only have an effect when flying at 12lb boost and 3000 rpm, if you did not do that, it was pretty much meaningless. If you did, however, the engine would continue to work under negative g just fine.

To me it sounds as if combustions stops during the inverted flight and the engine spools back up thereafter, which indicates the behaviour to be typical for a Merlin with a standard float type carburettor.

On the other hand the engine spools up quite nicely (though on a very rich mixture) immediately after returning to positive g's, so maybe a fuel flow restrictor (i.e. Tilly orifice) was in place. The Merlin handbook states up to 10 seconds of recovery after a neg g situation, which clearly isn't there.

[41Sqn_Banks]

Originally Posted by JtD

The Mk.Va came with a float type carburettor. The Tilly orifice would only have an effect when flying at 12lb boost and 3000 rpm, if you did not do that, it was pretty much meaningless. If you did, however, the engine would continue to work under negative g just fine.

To me it sounds as if combustions stops during the inverted flight and the engine spools back up thereafter, which indicates the behaviour to be typical for a Merlin with a standard float type carburettor.

On the other hand the engine spools up quite nicely (though on a very rich mixture) immediately after returning to positive g's, so maybe a fuel flow restrictor (i.e. Tilly orifice) was in place. The Merlin handbook states up to 10 seconds of recovery after a neg g situation, which clearly isn't there.

Which Merlin handbook are you referring to? Don't you mean Pilot's Notes General? Standard procedure for inverted flying was close the throttle to allow a smooth recovery.

[JtD]

Not a plane handbook / pilot notes, but a Merlin document, which I can't seem to find at the moment. Sorry.

Good point about closing the throttle, slipped my mind and it would indeed limit the problem, but the fuel pump would still flood the engine to some extend.