Fly Past

20 FLYPAST November 2018

BOYS

MOONSHINE

A

s Arthur Harris took over

at Bomber Command in

February 1942, his arrival

signalled a major change in the

fortunes of the ‘Bomber Boys’.

Believing that aerial bombardment

at an uncompromising level could

win the war, Harris sought to prove

his theory had merit with showpiece

raids involving more than a

thousand aircraft a time.

Apart from the massive

organisational and logistical

challenges, there was a problem with

putting so many bombers in the air;

they could be tracked easily by

enemy radar. With the increased

onslaught from Bomber Command,

the Germans had established a

defence infrastructure par excellence,

with corridors of searchlights and

heavy flak batteries to meet

incoming waves. They had also

fielded squadrons of night fighters,

guided to their quarry by

sophisticated ground and air radar.

At the core of the German defences

was ‘Freya’ – a network of early

warning radars capable of detecting

an approaching aircraft from a range

of up to 100 miles (160km).

This system represented a threat to

all RAF operations, including

Fighter Command.

Fighter sweeps fell within the remit

of 11 Group, then under the

command of Trafford Leigh-

Mallory. He wrote to his immediate

superior, Air Marshal Sholto

Douglas – the commander-in-chief

of Fighter Command – in April

1942 about the increasing losses his

forces were suffering. Leigh-Mallory

made specific mention that the

enemy’s radar defence: “...has

1918 2018

BOYS

MOONSHINE

THEY FOOLED GERMAN DEFENCES BY ‘SPOOFING’

A SOPHISTICATED ENEMY RADAR SYSTEM – BUT

IT WAS PERILOUS WORK FOR THOSE FLYING THE

BOULTON PAUL DEFIANTS, AS BOULTON PAUL DEFIANTS, AS SEAN FEASTSEAN FEAST REVEALS REVEALS REVEALS

TR.1427). It worked by receiving

pulses from the Freya installations,

amplifying them and sending them

back, creating the illusion of a much

larger force flying in formation.

For Moonshine to work effectively,

a small number of aircraft equipped

with the device would fly in

formation in daylight until the spoof

prompted a response. At that point

they could break formation and fly

home independently.

For the screen, the scientists

created ‘Mandrel’, a noise jammer

that overwhelmed the signals from

Freya. Echoing Moonshine, this was

a radio transmitter that could be

carried in the air.

The tactic for Mandrel required

the jamming aircraft to fly out into

the night until they reached a

specific patrol area, approximately

50 miles off the enemy coast. Here

they would orbit, sometimes for an

hour or more, until the weather,

shortage of fuel or the unwelcome

improved so much in the last few

months that it is very difficult to get

a formation into France without it

being detected and reported with

great accuracy.”

SPOOF AND SCREEN

There were several ways that the

potentially devastating impact

of Freya could be minimalised.

One involved creating a ‘spoof ’,

deceiving the German radar into

thinking that there were many

more aircraft in the sky than were

actually present. Another comprised

a ‘screen’, jamming the radar to the

extent that a large formation could

pass effectively ‘unseen’.

The task was given to scientists at

the Telecommunications Research

Establishment (TRE) in Malvern,

Worcestershire. For the spoof,

codenamed ‘Moonshine’, they

developed what was known as the

Airborne Radio Installation

Transmitter Receiver (ARI

Right

Personnel of 515

Squadron assembled for

a formal photograph.

ALL VIA AUTHOR

UNLESS NOTED