Perfectos was a radio device used by

Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...

night fighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War) is a fighter aircraft adapted for use at night or in other times of bad visibility. Night fighters began to be used i ...

s during the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

to detect German aircraft. It worked by triggering '' Luftwaffe's''

FuG 25a Erstling FuG 25a ''Erstling'' (German: ''"Firstborn"'', ''"Debut"'', sometimes FuGe) was an identification friend or foe (IFF) transponder installed in ''Luftwaffe'' aircraft starting in 1941 in order to allow German Freya radar stations to identify them ...

identification friend or foe Identification, friend or foe (IFF) is an identification system designed for command and control. It uses a transponder that listens for an ''interrogation'' signal and then sends a ''response'' that identifies the broadcaster. IFF systems usual ...

(IFF) system and then using the response signal to determine the enemy aircraft's direction and range. This allowed RAF

interceptors An interceptor aircraft, or simply interceptor, is a type of fighter aircraft designed specifically for the defensive interception role against an attacking enemy aircraft, particularly bombers and reconnaissance aircraft. Aircraft that are c ...

to track the Germans without the need for a radar system of their own, in contrast to the earlier

Serrate radar detector Serrate was a World War II Allied radar detection and homing device used by night fighters to track Luftwaffe night fighters equipped with the earlier UHF-band ''BC'' and ''C-1'' versions of the Lichtenstein radar. It allowed RAF night fighters to ...

that lacked range information and thus required a radar of their own for the final approach. The resulting rapid ramp-up of night fighter losses in late 1944 alerted the Germans that the RAF was deploying a system to track them, and suspicion immediately fell on the Erstling. Pilots were told to leave their Erstling units turned off until they approached friendly airbases, where it was needed in order for their

flak Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...

units to avoid firing on them. This resulted in further chaos as crews often forgot to turn them back on, and flak units became increasingly paralyzed as

friendly fire In military terminology, friendly fire or fratricide is an attack by belligerent or neutral forces on friendly troops while attempting to attack enemy/hostile targets. Examples include misidentifying the target as hostile, cross-fire while eng ...

incidents mounted.

References

* {{mil-stub World War II British electronics Electronic countermeasures British military radio