(propellers whirring)
German troops were poised to invade Britain.
In the skies above England RAF Hurricanes and Spitfires
fought desperately to stop them.
As the battle intensified a fatal flaw was exposed
at the heart of the legendary Merlin engine.
Piston engines like the Merlin required a very
precise amount of fuel.
Too little and it would not generate enough power,
too much and it'll flood and stall.
Very simply a carburetor is a device to control
the flow of fuel.
Fuel comes into the carburetor lifting a floating valve.
When a certain level is reached, the valve closes
feeding the combustion chamber
with the right amount of fuel.
This system works well in level flight
but when the plane goes into a steep dive
the fuel is forced to the top of the float chamber,
and the engine loses power.
Worse still fuel continues to flow into the carburetor.
When the plane levels out this fuel floods into
the combustion chamber, causing the engine to stall.
Luftwaffe pilots were quick to exploit this weakness,
knowing that RAF planes couldn't follow them
in a steep dive.
The advantage was critical.
The obvious solution was to design and fit
an improved carburetor but this would have taken months,
time that the RAF and the country didn't have.
As the battle continued this flaw was costing lives,
the very future of Britain hung in the balance.
The nation needed a hero.
Step forward Beatrice Shilling, engineer,
motorbike champion and trailblazer.
She worked out that by restricting the flow of fuel
she could overcome the carburetor problem.
She make a small brass collar with a hole in it,
and welded it to the fuel inlet.
The brilliance of this idea is in it's simplicity,
it took only a few minutes to fit the device
and cost only pennies.
(plane engine whirring)
The modified RAF planes returned to the fight,
but the German pilots going into a deep dive
found the Spitfires were following them with guns blazing.
Beatrice Shilling didn't fly a plane or fire a gun,
but her innovation was arguably the greatest
single contribution to the defeat of the Luftwaffe
and the survival of Britain.
