Hi again chaps.

A conversation I was having with a friend threw up an interesting point. Many pilots offer anecdotal comments on having to half roll to avoid negative G carb cutout, but what is roughly the point the cut out takes place? Most of the documentation I’ve been looking at seems to point to early Merlin’s suffering Carb cutout at around a half-gee negative, is that accurate?

And how much of an impact did Shilling’s orifice really have on the phenomena?

Having read the wiki entry on this topic, it is much the same overview that I understood.

http://en.wikipedia.org/wiki/Miss_Shilling’s_orifice

The restrictor provided an effective short term solution for a duration adequate for a dogfight, when sharp negative manoeuvres were usually short lived, by limiting the fuel flow rate from the pump.

The power loss came in two phases; a lean cut on entering neg-g when the fuel was at the top of the float chamber, followed by a longer duration (1-1/2 sec) rich cutout because the chamber became flooded with fuel.

None (or only a handful) of engines were modified with the restrictor by the BoB. It was widely implemented in 1941, with an anti-g carb design solution implemented in 1943.

As regards at what acceleration the unmodified engine suffers the onset of engine failure; I do not recall reading any details. I would assume it would begin at low-g conditions when the float was unable to overcome the fuel pressure from the pump.

DAI