Monica Tail Warning Radar

Monica tail warning radar, or ARI 5664, was an aircraft radar used by the RAF during the Second World War. It was mounted in the tail of bombers from 1942. The Monica functioned at frequencies of around 300 MHz. It was developed at the Bomber Support Development Unit in Worcestershire. Nevertheless, the Germans designed and manufactured a passive radar detector, known as the Flensburg (FuG 227), which was used by Luftwaffe nightfighters from Spring 1944 onward to home in on bombers using Monica. However, Monica-equipped aircraft did not suffer an increased casualty rate overall. The Monica tail warning radar was also used by the US Army Air Corps as the AN/APS-13, where it was also used as the radar altimeter for the Little Boy atomic bomb.