The fuel system is among Typhoon's technological innovationsEurofighter says it "pushed technology on several fronts" to package the required capability in an aircraft as small as the Typhoon. The task was made more challenging by customer demands that the Eurofighter be capable of autonomous operation and require minimum support in the field.

Additionally, the aircraft is required to enter service with substantial built-in growth potential. Targets include 10% spare avionics volume, 25% extra electrical and environmental control system capacity and 100% growth capability in computer processing, memory and databus load. This has necessitated the redesign of several systems during the transition from development to production standard to provide the required capacity.

"Productionising" the aircraft also has included increasing basic empty weight by 1t, to 11t, and maximum take-off weight by 2t, to 23t, to increase multirole capability. Airframe structure and landing gear have been strengthened accordingly, says Eurofighter.

The Typhoon is also designed to require the minimum of ground support equipment. The electrical system is configured for autonomous operation of the aircraft, allowing engines to be started, systems tested and avionics activated without external power. ADC battery is used to start the auxiliary power unit (APU), which provides electrical power until the two engine-driven AC generators come on line. The original integrated drive generators are being replaced by constant frequency generators in development and production aircraft.

The secondary power system, of which the APU is part, drives the electrical and hydraulic systems on the ground and provides emergency back-up power in the air. An air turbine motor on each of the engine-driven gearboxes is powered by the APU for engine start. In the event of an engine failure, the affected gearbox is driven by the associated air turbine motor using bleed air from the live engine.

In normal operation, each engine-driven gearbox will power one of the aircraft's two 276bar (4,000lb/in2) hydraulic systems, but the crossbleed capability allows either gearbox to drive both systems. The hydraulic systems power the flight controls, inlet cowl flaps, spine-mounted airbrake, refuelling probe, gun and canopy, as well as the landing gear, nosewheel steering and wheel brakes.

Anti-skid braking and nosewheel steering are digitally controlled, with steering linked to the flight control system. The aircraft has an arrester hook for emergency use and an optional braking parachute.

Fuel is contained in centre fuselage and wing tanks, and acts as a heat sink for the hydraulic and electrical systems and engine-driven gearboxes. Fuel transfer is by two boost pumps per engine. In the two seater, the forward transfer tank is removed to accommodate the second cockpit, but the reduction in fuel capacity is offset by installing an auxiliary tank in the enlarged dorsal spine.

The hydraulically actuated retractable in-flight refuelling probe is housed in the right side of the forward fuselage, below the windscreen. Flight testing has resulted in the change to a dual door arrangement enclosing the internally mounted probe.

Liquid cooling for the radar, forward-looking infrared sensor and pilot's garments is provided by the environmental control system. This also supplies air for avionics cooling, cockpit conditioning and pilot anti-g protection. A molecular-sieve oxygen generation system produces breathing air from engine bleed air and eliminates the need for oxygen bottles.

Onboard oxygen generation is integrated with the Martin Baker Mk16Aejection seat. This features a lightweight structure, narrow head box for improved rearward vision and digital sequencing control.

Aircraft general services are integrated by the utilities control system, which provides continuous monitoring and fault detection, as well as an interface with the cockpit, avionics and engine controls. Elements include fuel, secondary power and landing gear computers, linked by digital databus to a front computer located near the cockpit and a maintenance data panel under the wing.

The maintenance panel provides access to data from the integrated monitoring and recording system. This monitors the airframe, engines and systems for status, damage and exceedences.

Other functions include mission data loading/recording and cockpit video/voice recording. Data are loaded on to a portable data store plugged in by the pilot, as well as a bulk storage device and crash-survivable memory unit mounted in the aircraft.

Source: Flight International