GENERAL BACKGROUND
The Hydraulics constitutes the lifeblood and muscle of Concorde. Without the Chevron M2V coursing through the network of pumps, pipes and valves, the lights would be on, but nothing would stir
There are three separate independent hydraulic systems. There are two main systems identified as Green and Blue and a standby system called yellow, which is available at any time for back-up purposes. Each of these systems is powered by two engine driven-pumps.
Green Hydraulic System
This system supplies power for normal operation of the following services:-
Landing gear including the doors
Nose wheel steering
Engines 1 and 2 air in-take ramps and spill doors
Nose and Visor
Main landing gear brakes with anti-skid
Tail skid actuator
Four motors for the engine air-intake ramps and the dump doors
One motor for the fuel trim tank 11 transfer pumps
On ram of each power flight control
One ram of each relay jack
Artificial feel
(The Green system also supplies the Emergency Generator hydraulic motor)
Blue Hydraulic System
This system supplies power for normal operation of the following services:-
Engine 3 and 4 air in-take ramps and spill doors
One Artificial feel jack on each flight axis
One tank 11 fuel pump
The second cylinder of each flying control actuator and of each flying control booster jack
Yellow hydraulic system
This system supplies power for standby operation of the following services:-
Engine 1m2, 3, and 4 air in-take ramps and spill doors
Flight controls
Nose and visor lowering
Landing gear lowering
Main landing gear brakes with anti-skid
Emergency and parking brakes without anti-skid
Nose landing gear wheel steering.
Normal and standby generation is provided by six engine-driven pumps that are mounted on the airframe accessory gearboxes on the engines: The two Green system pumps are driven by engines 1 and 2, the Blue system pumps by engines 3 and 4. The two yellow system pumps are driven by engines 2 and 4. These pumps pressurize the hydraulic system to 4000 psi (pounds per square inch), and in case of overpressure a pressure limiter allows a maximum pressure of 4500 psi. To prevent cavitation of the engine-driven hydraulic pumps, the three reservoirs must be pressurized. An auxiliary air compressor is provided to ensure that the three reservoirs are pressurized before engine start.
The systems are designed to work at temperatures between -40C and + 120C and the fluid used could withstand temperatures between -606 and +220C. To keep weight down and to obtain the required response rate at the controls the operating pressure was designed to be very high, hence the 4000 psi (pounds per square inch). During the flight between take off and landing, the yellow pumps are depressurized automatically (by means of a micro-switch operated by the landing gear) but they can be switched on from the flight deck.
These pumps are connected in such a way that each system has two pumps driven by a different engines and it will always be possible to use two systems if any two engines fail (see diagram1). Even after total engine failure the aircraft could be controlled in a glide descent by using the RAT (See below for further details concerning the R.A.T.)
All three systems are similar in design. From the reservoir, a line to each pump passes through a fuel-cooled heat exchanger and isolate valve. Pumps themselves have a solenoid operated off-load control and a cooling case drain flow routed through a case drain filter back to return. It is vital to keep a close check on these filters; any restriction in flow can lead to raised case pressure and pump-case separation, with the consequent system loss. Downstream, each pump output passes through an HP filter and non-return-valve before communing-up with its partner to supply aircraft services. All return flows combine to pass through an LP filter before returning to the reservoir.
Fluid must be supplied to pumps at a positive pressure. The Concorde method is to fashion the fluid contained as a stainless steel bellows, then surround with an airtight container, pressurized to 60psi using engine bleed air. A small electrically driven compressor is available to top-up the air pressure during ground servicing activities.
The reservoirs and charging points are located in the lower fuselage hydraulic equipment bay between frames 72 and 74 – frame 72 is the elevon attachment point. A special hand-pump charging gun is required; there is no gravity fill facility, thus no opportunity to top-up in flight
GROUND GENERATION
Ground generation is provided by two electrical Ground Hydraulic Check Out pumps that can be selected to pressurize the main and standby systems while the aircraft is on the ground. The maximum delivery pressure and flow of the electrical pumps is less than that of the engine-driven pumps.
AUTOMATIC PROTECTION FOLLOWING SYSTEM FAILURE
In the event of low pressure or tank low level in Green or Blue systems, a detection system automatically on-loads the Yellow system engine driven pumps and changes the hydraulic power supply for the appropriate ramp and spill door-actuators from Blue or Green system to Yellow.
In the event of a low level in the Yellow system reservoir, the first low level detection automatically inhibits the Yellow supply to:
(A) Nose wheel steering
(B) Flying controls
(C) In the case of a Yellow/Green selection the Yellow supply to main wheel brakes with anti-skid is cut off.
At a second low level, the Yellow supply to the in-take spill doors is cut off but this is overridden during manual inching on Yellow.
If a first low level cut off of the selected Yellow supply to flying controls occurs and a low pressure exists in the other side of the flying controls, there is an automatic change to Yellow supply to power the second failed flying control system.
If a GREEN ONLY or BLUE ONLY selection by the PFCU servo selector has been made and low pressure occurs in the selected system there is an automatic change to power the selected system with Yellow system.
If the flying controls are being powered by a single main hydraulic system after Yellow tanks low pressure cut-off and transfer of fluid from the operating system to Yellow tank causes both a low pressure in the operating system and Yellow tanks contents to rise above the low level cut-off, it is a design feature that Yellow system pressure will be supplied to both sides of the PFCUs.
THE FLIGHT ENGINEER’S HYDRAULIC MANAGEMENT PANEL
