HYDRAULIC SYSTEMS

The hydraulic systems are effectively the life blood of the aircraft, driving all control surfaces, undercarriage and braking systems on the aircraft. The system is split into 3 separate circuits as outlined below, each operating its respective service. The power supply to the flying control units is completely duplicated to obviate loss of control should one engine or hydraulic system fail.  Each hydraulic circuit also has a limited emergency back up operation in the event of complete pump failure. This is achieved by the use of Nitrogen accumulators which in effect 'store' potential hydraulic energy, allowing for limited or gentle operation of control surfaces in the event of failure. Each circuit encompasses its associated services, which either operate at the overall circuit pressure, or through reduction valves operate at lower pressures. All circuits are integral closed systems with pressure, return and suction lines. All 3 hydraulic circuits are supplied by a separate central reservoir, which is in turn pressurised through an auxiliary air supply. 

The hydraulic installation comprises three separate circuits

  • Services circuit

  • No 1 controls circuit

  • No 2 controls circuit

The systems provide power for the hydraulically-operated services detailed below

SERVICES

No. 1 CONTROLS

No. 2 CONTROLS

Undercarriage

Aileron PFCU (outboard)

Aileron PFCU (inboard)

Wheel brakes

Tail plane PFCU (starboard motor)

Tail plane PFCU (port motor)

Nose wheel centering

Rudder PFCU

Rudder PFCU

Flaps

Brake parachute compartment doors

 

Airbrakes

Undercarriage emergency lowering

 

Canopy

 

 

Feel system

 

 

Auto-stab actuators

 

 

GW pack or rocket launchers

 

 

 

Hydraulic Pumps

Power is provided by four engine-driven pumps, two mounted on each engine wheel case. The forward pumps on each engine jointly power the services system; the aft pump on No 1 engine powers the No 1 controls system and the aft pump on No 2 engine the No 2 controls system.

A hand-pump for ground operation  of the services system is behind an access panel on the port side of the fuselage. A quick access panel in the rear ventral tank is opened to allow a pump handle, stowed in the port wheel-well, to be fitted to the pump.