Innominate;9862898]
ISTR that early Lancasters (and possibly the other types) had a ventral turret, and the H2S scanner was mounted in the hole provided for the turret.
Yes the FN64 was the original ventral turret ,but was deemed unsuitable for night use.
The Preston-Green design was later deemed more suitable for series production but as more H2S units became available - the space for fitment disappeared.
As I posted earlier though - the canadians had already fitted 'scare guns' under many of their heavies.
Preston Green under defence mounting Mk.II
On 29th February 1944, a Halifax III, (LW650), took off from Boscombe Down. It appeared to be just another Halifax, with the bulging blister of H2S radar beneath the fuselage, but close inspection would have revealed a 0.5in. Browning protruding through the rear of the blister. The aircraft was being used for trials of the Preston Green under-defence turret.
Preston Green began with an American mounting used by USAAF bombers. It gave free movement of the gun whilst providing a firm anchorage. Work had begun 18 months earlier, when it was suspected that enemy night fighters were attacking from below. At this time, the H2S sets were looked on as an essential aid, but production of bombers was outstripping the supply of radars, and it was decided to install Preston Green mountings in all Halifax IIIs.
The adapter was fixed across the base of a bowl-shaped enclosure immediately behind the bomb bay. The gunner had an aft-facing bucket seat within the blister, with a tilting back rest. The gun could be swung clear of its aperture when searching, but could rapidly locked in the firing position if needed.
Had more Bomber Command aircraft been fitted with the Preston Green turret, this previously non-existent protection from attack from below would have cut down the toll taken by Luftwaffe night fighters using upwards firing cannon.. Unfortunately, when H2S production increased, the turrets were taken out, much to the annoyance of bomber crews.