I've posted this elsewhere but worth reposting here:
As introduced -- the Lancaster had:
Pilot
28 lb (4 mm) seat back
27 lb (9 mm) head piece
Flight Engineer
?? lb (2.5 in) armoured glass
W/T Op and Navigator position
160 lb (7 mm)
*another source has 6 mm*
W/T Op seat back
13 lb (4 mm)
Mid-upper turret (FN50)
26 lb (6 mm)
38 lb (10 ga dural)
Rear turret (FN20)
45 lb (9 mm)
8 lb (6 mm)
Engine coverings
144 lb (10 swg)
Engines + ancillary
100 lb (8 mm)
Unsure, but I think the above 100 lb of armour consisted of:
- crescent-shaped plate which protects the oil tank sump
- vertical piece of plating behind the header tank leg
- vertical plate at the side of the radiator at outboard engines