Have you tried turning it off and then back on again?

BY RICHARD MADDOX

THE NIGHT OF 2/3 DECEMBER 1942 and the RAF is using ‘TINSEL’ for the first time.

As you might expect, this is not a way of making their aircraft pretty or of sharing festive greetings with the German people.

In this context TINSEL was a communications jammer – a microphone fitted inside one of the four engine nacelles or ‘pods’ on a ‘heavy’ RAF bomber like the Avro Lancasters on display at IWM Duxford, the RAF Museum and IWM London where the forward fuselage section of Lancaster DV732 in on display.

Both this aircraft and the RAF Museum’s example (R5868, PO-S ‘Sugar’ credited with 137 operational sorties) flew with No. 467 Squadron Royal Australian Air Force.

Image: The forward fuselage section of IWM London’s Avro Lancaster BIII. The aircraft flew with No. 467 Squadron RAAF as PO-F ‘Freddie the Fox’ and completed 45 operations over Europe. Dominant to the left is the radio operator’s position with the 1154/1155 radio transmitter/reciever equipment. © R Maddox 2017.

When the bomber’s radio operator heard German speech he – and literally hundreds of other radio operators on the other aircraft in the bomber stream – could transmit the sound of one of the 12 cylinder, 27-litre Rolls-Royce Merlin engine directly to the Luftwaffe Night Fighter Control station on the ground.

The resulting noise could interfere with that German controller’s instructions to the fighters he and his team were guiding to attack the RAF aircraft.

It didn’t always completely drown out the conversation – the Germans just increased the power of their signal to reduce the interference.

Image: A close-up of the radio transmitter in the IWM Lancaster. The painted legend referring to ‘Tinsel’ below the red switch can just be seen. © R Maddox 2017.

But often, as each of up to a thousand wireless operators were doing the same thing the process masked bits of it – making it very frustrating for both the Luftwaffe fighter crews and their ground controllers.

And of course this frustration could lead to mistakes that could benefit the RAF crew…

But like all things in the technological battleground, one side’s advantage doesn’t last for long.

Late-war translations of Luftwaffe records of RAF prisoner interrogations (held at the UK National Archives in Kew, England) show that the Germans knew what TINSEL was.

20170530_152616A

Selective image from an RAF SIB (Special Investigations Branch of the RAF Police) report of a translated German interrogation of a captured RAF aircrew member. The Sergeant’s identity has been removed from this image by me to protect his identity. Image from a document at the National Archives UK.

 

From a practical point of view, German aircrew soon realised that if they switched off their communications and then switched them on again (similar to a computer reboot) there was often a gap of a few seconds before the RAF radio operators found them again and the jamming resumed.

And sometimes in those few seconds there was enough information from their controllers for the hunters to find their prey.

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