Ok heres the snippet for ya frenchy: its from 'warbirdtech series: Republic P-47 Thunderbolt: volume 23' by frederick A Johnsen ISBN 1-58007-018-3
'check 6:
the classic fighter pilots warning " check six" means look to the rear, to the six oclock position, for a possible threat. During 1943 a P47 participated in tests of a 20 pound AN/APS-13 radar set that did just that.Visible as three quarter inch metal rods piercing the vertical fin, and extending out for about five and a quarter inches on either side, the radar provided warning of the approach of aircraft behind the equipped thunderbolts.Within a cone of space behind the P47, any aircraft approaching closer than 800 yards was announced.The cone radiated through about 60 degrees horizintally and 90 degrees vertically behind the thunderbolt.The cone of coverage was slightly skewed upward, to enhance detection of diving aircraft.Given limitations on radar technology the system was useless at altitudes below 800 yards, an AAF test sumary explained, "since it is practically impossible to prevent spurious radiation from returning from the earth's surface".
Upon detection of an aircraft in the rear cone of space, a brilliant red jeweled light in a sheild beside the P47's gunsight illuminated letting the pilot know instantly of the presence of an aircraft which might pose a threat.The tail-warning radar was tested initially mounted in a twin-engined Beech AT-11 followed by installation in a P47.
Following encouraging tests with one P47, six follow-on AN/APS-13 tail warning radars were installed at Orlando, Florida, in thunderbolts of squadron F of the 904th AAF base unit stationed at Kissimmee Army Air Base Florida. An AAF paper explained " The position and arrangement of the antenna on the stabiliser determines the tilt of the cone with respect to the airplane".The six sets installed in Orlando also featured an alarm bell that sounded when the warning light was illuminated.
A staple of cold war jet fighters, tail warning radar proved its utility on a handfull of P-47s during world war two."
now that sounds usefull doesnt it!
