Perfectos was a radio device used by

Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...

night fighter A night fighter (later known as all-weather fighter or all-weather interceptor post-Second World War) is a largely historical term for a fighter aircraft, fighter or interceptor aircraft adapted or designed for effective use at night, during pe ...

s during the

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

to detect German aircraft. It worked by triggering '' Luftwaffe's'' FuG 25a Erstling

identification friend or foe Identification, friend or foe (IFF) is a combat 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 syst ...

(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 cap ...

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 that was 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 Royal Air Fo ...

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 (AAW) is the counter to aerial warfare and includes "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It encompasses surface-based, subsurface ( submarine-launched), and air-bas ...

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 or hostile targets. Examples include misidentifying the target as hostile, cross-fire while ...

incidents mounted.

References

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