The Lancaster was usually fitted with three turrets, although some had a fourth or mid-lower turret, positioned underneath the aircraft to the rear of the bomb doors. This would carry two Browning 0.303in guns with 1,000 rounds of ammunition. Each turret had its own hydraulic system, to enable the others to function should one be hit in action; this comprised a hydraulic pump, reservoir and recuperator. The BBMF Lancaster is fitted with the following turrets, although the hydraulic systems have been disabled and the turrets can only rotate when manually operated.
The FN5 nose turret was fitted with two Browning 0.303in machine guns, which held 1,000 rounds of ammunition per gun. Once the air gunner was in situ he was able to rotate through 190° by the use of two control handles. The handles also contained the triggers for the firing mechanism.
The FN50 mid-upper turret was also fitted with two Browning 0.303in machine guns which each held 1,000 rounds of ammunition. To gain access to the turret a step was stowed on the inside of the fuselage, which swung into position when undipped. Once the gunner was inside the turret the hammock-type seat was then clipped into position. The turret could rotate through 360°. In order to protect the tail unit from damage during firing there was a failsafe mechanism comprising 'taboo arms' that ran on a track fitted to the fairing around the turret. This enabled the air gunner to concentrate on firing without worrying about shooting his own tail off.
The FN121 rear turret was fitted with four Browning 0.303in machine guns, which were fed ammunition from stainless steel tracks that ran from two ammunition boxes attached to the floor at formers 20-22. The tracks ran either side of the fuselage and together could supply 2,500 rounds for each of the four guns. The turret could rotate through 190° and was operated in the same manner as the other turrets. Once inside the turret the air gunner closed two doors behind him, which prevented him from falling out when the turret was rotated.
Bomb bay and loads
The Lancaster's bomb bay could hold a variety of bomb loads depending on the operation to be carried out. The BBMF Lancaster has a 4,0001b bomb carrier and several 5001b bomb carriers fitted.
Before loading bombs, the bomb cell doors were opened by pushing down the lever on the left-hand side of the pilot's seat. If the inboard engines were running the doors would open automatically, but if they weren't it was necessary to operate the emergency hand pump on the port wall of the fuselage just aft of spar 4. Safety brackets were then fitted to the four hydraulic jacks to prevent inadvertent closure of the doors whilst bomb-loading operations were in progress.
Standard bomb-loading winches were required, two 2,0001b winches being used to hoist the 4,0001b bomb. The adjustable crutches for the 4,0001b bomb were removed when other bomb loads were to be carried. A step-ladder was necessary in order to remove the bomb carriers, to make final adjustments, and to check that the bombs were in position.
Order of loading
Heavy bombs had to be loaded in the correct sequence. For this purpose each of the bomb gear housings (the arrangement of which depended on the type of bombs being carried) was numbered above and below the floor for ease of identification. Typical load options were:
• 14 x 250lb, 500lb or 1,000lb bombs (other than 500lb Marks I, II, III or IV AS bombs)
• 6 x mines or heavy bombs, plus smaller bombs
• 6 x 500lb AS bombs (Marks I, II and III only), plus smaller bombs
• 1 x 4,000lb bomb, plus smaller bombs
Note that in options В, С and D several smaller bombs were carried in addition to the main load, eg option D might comprise six 1,0001b and two 2501b bombs in addition to the 4,0001b bomb. The 14 bombs of option A, however, represent a maximum load, with only ABOVE Close-up of the central bomb housing not being used. The bomb slip.
250lb or 500lb bombs or containers could be of the following types:
500lb GP bombs 500lb SAP bombs 250lb GP bombs 250lb SAP bombs 250lb LC bombs 250lb В bombs 250lb AS bombs Small-bomb containers
Although not important, it was more convenient to load the small bomb containers, the 500lb bombs and the 250lb bombs in that order. If the number of bombs to be fitted was less than 14, the centre housings would be used.
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