Mid Upper Turret

The Boulton Paul Type H Mid-upper Turret
The Type H turret Mk.II was a development of an early design project started in May 1939, to arm the Halifax and Stirling, with a twin-cannon armed dorsal turret, the BP Type H Mk.I, together with a proposed twin-cannon under defence turret, the BP Type O. These being cancelled before any metal was cut. The later Mk.II project was ordered in February 1942 as a Mid-upper turret for the Lancaster. It was to be armed by twin 20mm (0.78 in) Hispanos or 2 x 15mm (0.59 in) Cannon of a type developed by Vickers at Crayford. The Vickers Guns did not materialise, however, and the 1st prototype was a Test-Firing mock-up with 20mm (0.78 in) Hispano Guns.  By September 1942 the Company was ordered to give the project top priority, and 5 Prototypes were requested by the Air Ministry on 14th September. By 23 September this number had been increased to 6, together with a Lancaster mock-up.

By January 1943 the signs were that the Lancaster would soon be armed with a Type H Mid-upper Turret.  The production drawings were 55% compete, 2 Prototypes were nearly finished and ground Firing was scheduled for April.  On 27th February a Directive was received from the Air Ministry cancelling further development: the project was to be abandoned so that the Company could concentrate on 12.7mm (0.5 in) Type Ds, and an ‘ideal’ Lancaster Front Turret, the Type F, together with a remotely controlled Barbette Defensive system. Such were the frustrations of Wartime Design & Production.

The main structure of the Type H Turret comprised an upper section & skirt above the Turret Ring and a lower section below the Ring. The upper part of the Turret was divided into 3: a central compartment, into which the gunner’s head & shoulders projected, which had a central Perspex Sighting panel to the front, and a Gun Compartment to each side. This arrangement protected the Gunner from the considerable fumes given off when the Hispanos were fired.  The empty cartridges and links were collected in boxes under the Guns, after being deflected by side plates at the sides of the Turret.

As can be seen in the illustration, the Gunner sat well forward in the Turret, his feet supported by an extension platform fixed to the Turret base.  He entered the Turret from the front, by swinging the control table out horizontally.  The Turret had provision for emergency hand operation in rotation only, a feature which was meant for Emergency Escape.  Gun elevation & firing could not be carried out with the power off. The Mk.IC Gyro Sight was mounted on a Sight bar, connected by a parallel linkage system to the Turret elevation control.  The Gunner was provided with a socket for heated clothing, the standard intercom jack, and regulated oxygen supply. The Turret was heavy, with Guns & Ammunition it weighed 2,425kg (1,100lb). This would have been quite a penalty had it been accepted for use. The Gunner was protected by an armoured apron extending around the front of the Turret, the 12mm (0.48 in) plates protecting all except his head. The electro-hydraulic power unit was mounted behind the Gunner, giving a maximum rotation speed of 35°-sec; a minimum speed of 0.25°-sec could be achieved when adjusting Aim.  The Guns were limited in the traverse to 45° either side of aft, with elevation limits of 50° up and 9° below horizontal.

Details of the Type H Mk.II Turret:
Power system: Modified BP electro-hydraulic
Armament: 2 x 20 mm (0.78 in) Hispano Mk.II cannon
Ammunition: 300 rounds per gun
Ammunition feed assisters: Drive sprockets for the 2-Guns driven by separate electromagnetic clutches from a common electric motor. Clutches activated by belt tension.
Operating limits:
Traverse: 45°
Elevation: 50°
Depression: 9°
Power requirements:
Voltage: 24V
Current: Normal 50 amps; high speed 75 amps
Turrets speeds: Max: 35°sec; Min: Less than 0.25°sec
Gunfire interrupter: Electro-mechanical type providing separate control for each Gun
Turret weight: Empty: 227 kg (500 lb); Armed: 449 kg (1,100 lb)
Gun Sight: Gyro Gun Sight Mk.IC (proposed)
Turret Dome: Not detachable, consisting of Perspex & Metal panels mounted on frame members. The Sighting panel could be powered to slide upwards leaving a clear space for Night Sighting
Turret sizes:
Overall height: 176 cm (69.25 in)
Dome diameter: 112 cm (44 in)
Dome to skin line: 65 cm (25.25 in)
Fuselage opening: 94 cm (36.75 in)

The Boulton Paul Type H Mk.I Turret
Aircraft type: Handley Page Halifax, Short Stirling
Type & Mark: H.Mk.I
Position: Mid-upper
Guns: 2 x 20 mm (0.78 in) Hispano Mk.II
Traverse:
Elevation:
Depression:
Status: Cancelled before Production

The Boulton Paul Type O Mk.I Turret
Aircraft type: Handley Page Halifax, Short Stirling
Type & Mark: O Mk.I
Position: Mid-under
Guns: 2 x 20 mm (0.78 in) Hispano Mk.II
Traverse: 90°
Elevation: 0°
Depression: 70°
Status: Cancelled before Production

The following Aircraft were fitted with the Boulton Paul Type H Mk. II Turret
Aircraft: Avro Lancaster (Not allocated)

Type & Mark: H Mk.II
Position: Mid-upper
Guns: 2 x 20 mm Hispano Mk.II
Traverse: 90°
Elevation: 50°
Depression: 90°