Bristol Turret hydraulic system.

Among my father’s papers I found the attached notes that he made on the Bristol Turret hydraulic system.

These notes would have been made either late 1940 or early 1941 and I am surmising that these notes would have been made at either 9 B&GS or 14 OTU. If at 9 B&GS they would pertain to the Whitley and if at 14 OTU to the Hampden. I would appreciate any clarification of this from board members.

Bristol Turret hydraulic system.

Tank is fitted on bulk head of engine, fluid contents 1 gallon air, 1 gallon oil. The filter is positioned so that the tank cannot be over filled and an air vent is fitted to the top of the tank.

Engine driver pump: – Mounted on the engine and generates 600 lbs per square inch normal. The pump supplies pressure to the undercart wing flaps and rear turret.

Hand pump:- Is located on the right hand side of the pilots seat, it may be used for operating turrets on the ground but is not of sufficient power to form a substitute for the EDP for normal operation.

Relief valve: – Bypasses oil to the return pipe if pressure rises above 600 lbs.

Selector valve: – Is a three way valve in the pilots cockpit, its positions are,
1. Central, returns fluid to the pump giving low pressure circulation.
2. Up, fluid passes to turret.
3. Down, fluid passes to undercarriage and flap controls.

Gun turret: – The main pressure and exhaust lines are led into the turret at the base and are provided with swivel joints to permit turret rotation. They are led to the multiple control valve which embodies 1 master valve, 2 elevation and depression valves, 3 turret rotation valves, 4 Gun rotation valve.

Master valve: – is controlled by a grip on the control handles.

Elevation and depression valve: – controlled by moving control handles above the vertical axis. This diverts pressure flow of oil to either side of jack position for elevation or depression.

Turret Rotation Valve: – controlled by movement of control handles about their axis. This controls pressure flow to either side of the rotation jack for rotation to left or right.

Gun Rotation Valve:- operated by levers and controls pressure flow to gun rotation jack for movement of guns to left or right.

Hydraulic lock :- since the seat is elevated and depressed with the gun, the gunners weight on the seat would cause the seat to gradually sink, due to creep leakage past the valve, to prevent this a hydraulic lock is fitted. It accomplishes its purpose by means of a valve which is held on its seating by the combined pressure of its spring and the weight of the gunner on the seat.
It is fitted with a float lever which is a manual means of breaking the hydraulic lock, should the gunner wish to lower the seat when power is not available.

Interrupter Gear: – is a mechanical device to limit the depression of the guns and thereby preventing damage to the aircraft, the gun arm carries a lever which is normally held away from the gun. When the lever comes over the fairing of the aircraft and the gun is depressed, the lever is forced upwards the lever being connected to the elevation valve control moves the control to the central position, there neutralizing the elevation valve.

Filling oil used: – here anti freezing oil (Intava?) since the circuit is an open one, the system is self bleeding.