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engines and did not suffer from this problem as injection pumps kept fuel at constant pressure. German pilots could exploit this by pitching steeply forward while opening the throttle, a manoeuvre that pursuing
British aircraft would be unable to emulate. The British countermeasure, a half roll so
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manoeuvre (pitching the nose hard down), fuel was forced up to the top of the carburettor's float chamber rather than down into the engine, leading to loss of power. If the negative G continued, fuel collecting in the float chamber would force the float to the floor of the chamber. Since this float
132:, invented a simple device which could be fitted without taking the aircraft out of service. She designed a thimble-shaped brass flow restrictor with precisely calculated dimensions to allow just enough fuel flow for maximum engine power. It came in two versions, one for 12
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inverted V12 powerplant had utilised fuel injection since 1937. During early 1941, Shilling travelled with a small team to fit the restrictors in one RAF base after another, giving priority to front-line units. By March 1941 the device had been installed throughout
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While not completely solving the problem, the restrictor, along with modifications to the needle valve, permitted pilots to perform quick negative G manoeuvres without loss of engine power. This improvement solved the drawback of the RAF's
157:. Officially named the 'R.A.E. restrictor', the device was immensely popular with pilots, adopting the affectionate nickname 'Miss Shilling's orifice' (or simply the 'Tilly orifice'), given to the restrictor by
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manifold pressure and another for the 15 psi achieved by supercharged units. The design of the thimble-shaped flow restrictor was later refined to a simplified flat brass washer.
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This simple measure was only a stopgap: it did not allow inverted flight for any length of time. The problems were not finally overcome until introduction of the
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the aircraft would only be subjected to positive G as it followed German aircraft into a dive, could take enough time to let the enemy escape.
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The Rolls-Royce Merlin engine originally came with a direct carburettor, prone to cut-out due to fuel flooding in negative G.
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was a very simple technical device created to counter engine cut-outs experienced during negative G manoeuvres in early
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with an over-rich mixture. The consequent rich mixture cut-out would shut down the engine completely.
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controlled the needle valve that regulated fuel intake, the carburettor would flood and drown the
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Cracking the Zero
Mystery: How the U.S. Learned to Beat Japan's Vaunted WWII Fighter Plane
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286:(second ed.). Missoula, Montana: Pictorial Histories Publishing Company.
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Complaints from pilots over engine cut-out during dives and brief
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led to concentrated search for a solution. Engine manufacturer
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produced an improved carburettor, but this failed in testing.
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explaining the
Merlins carburettor and the Tilly orifice
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Fuel flow restrictor retro-fitted to Merlin engines
283:Koga's Zero: The Fighter That Changed World War II
51:, it was referred to under various names, such as
330:Negative Gravity, the Life of Beatrice Shilling
75:engine came equipped with dual-choke updraught
246:. Marlborough, Wiltshire: Airlife Publishing.
214:Negative Gravity: A Life of Beatrice Shilling
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244:British Piston Engines and their Aircraft
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265:. London: Arms and Armour Press Ltd.
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144:-powered fighters versus the German
367:Rolls-Royce aircraft piston engines
263:The Spitfire Story: Second edition
216:. England: Charlton Publications.
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59:in reference to its inventor,
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212:Freudenberg, Matthew (2003).
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332:, by Matthew Freudenberg (
101:gasoline direct injection
61:Beatrice "Tilly" Shilling
300:Originally published as
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67:Engine cut-out problems
30:Miss Shilling's orifice
261:Price, Alfred (1986).
242:Lumsden, Alec (2003).
99:, German fighters had
71:Early versions of the
53:Miss Tilly's diaphragm
43:aeroplanes during the
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280:Rearden, Jim (1995).
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169:pressure carburettor
146:Messerschmitt Bf 109
130:Farnborough Airfield
155:RAF Fighter Command
150:Daimler-Benz DB 601
159:Sir Stanley Hooker
142:Rolls-Royce Merlin
108:The RAE restrictor
73:Rolls-Royce Merlin
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312:978-0-8117-2235-3
122:Beatrice Shilling
97:Battle of Britain
49:R.A.E. restrictor
45:Battle of Britain
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188:Price 1986
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235:Sources
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351:Video
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