The extreme weight constraint established by the Turin Agreement was among factors that drove trade-off studies leading up to the Eurofighter configuration freeze

Had history turned out a little differently, then consolidation of Europe's fighter manufacturers might today be a reality - or an impossibility. At various points, the programme now known as Eurofighter has involved as many as five and as few as two of the region's combat aircraft producers.

Although the heads of the Panavia partners first called for development of a three-nation air-superiority fighter in 1979, the design has its origins in escort-fighter studies begun by MBB (now DaimlerChrysler Aerospace) in 1974. The resulting TKF concept had much in common with today's Typhoon - a highly agile, single seat, twin engined, delta/canard fighter.

But there were to be many twists and turns before Germany, Italy, Spain and the UK were able to agree the operational requirement and sign the development contract for what was to become the Eurofighter.

Initially, the Panavia company heads wanted to use as many Tornado systems as possible in a follow-on air-superiority fighter. "But all the studies showed it would be a big aircraft," says Martin Friemer, Eurofighter development phase director. "It took time to convince management we had to go the way of a new aircraft if we wanted a small, highly agile fighter."

The first tri-national joint project team was formed in September 1979 by Aeritalia (now Alenia), British Aerospace and MBB. The result was the European Combat Fighter concept, a delta/canard drawing on the TKF design. In 1980-1, an attempt was made to bring Dassault into the project, resulting in the European Combat Aircraft concept, again a delta/canard.

The barriers to participation proved insurmountable for the French, however, and in 1982 the three Tornado partners formed the joint venture Agile Combat Aircraft (ACA) programme. When Germany pulled out in 1983, forcing MBB to withdraw from the project, BAe and Aeritalia continued on their own, building the Experimental Aircraft Programme (EAP) technology demonstrator.

The ACA design featured a cranked delta wing, long-coupled foreplane, chin intake and twin fins. After MBB withdrew, the rear fuselage from the Tornado had to be used, producing the single-fin EAP. The demonstrator flew in 1986, "and proved very worthwhile for development of the Eurofighter," Friemer says.

Meanwhile, in 1983, the air forces of France, Germany, Italy, Spain and the UK had agreed an outline European staff target for a future fighter. Industrial studies were completed in 1985, with four of the nations supporting one configuration, the forerunner to the European Fighter Aircraft (EFA).

In August 1985, Germany, Italy and the UK signed the Turin Agreement, committing the three nations to a project definition phase for an air-superiority fighter with 10,000kg (22,000lb) empty weight, 50m2 (540ft2) wing area and two 20,000lb thrust (90kN) engines. Spain joined a few weeks later.

France elected not to join and instead pursued development of the ACX, which became the Dassault Rafale - ending the chances of bringing Europe's fighter manufacturers together on one project. Interestingly, work on the five-nation study had benefits for the Eurofighter design team. "Work with Dassault on the Rafale ended in 1985, but had led to a lot of technology exchange," Friemer says.

The characteristics enshrined in the Turin Agreement were largely a result of Germany's insistence that the new fighter weigh less than 10t. "Germany had a cost versus mass plot and they wanted a 10t aircraft. That led to the Turin Agreement on a 10t aircraft with 50m2 wing and 90kN engines - the basics that defined the Eurofighter," he says.

The configuration which had emerged from all the studies was a highly agile delta/canard optimised for air combat, both beyond visual range (BVR) and close range, with low wing loading and high thrust-to-weight ratio. The weight limit forced some changes, the switch to a single fin saving 132kg (290lb), Friemer says.

All the European manufacturers were agreed that an unstable delta/canard was the most efficient design for BVR combat, providing the highest supersonic agility in the smallest airframe. Where the Eurofighter and Rafale concepts diverged was in location of the foreplane and intake, Dassault favouring a short-coupled delta/canard with side inlets.

A chin intake was one of the key configuration features of the Eurofighter (and the TKF before it), selected because it offered performance advantages at high angles of attack and sideslip. As a foreplane located close to the wing produced too much supersonic drag when combined with a chin inlet, designers selected a long-coupled delta/canard configuration.

The extreme weight constraint established by the Turin Agreement was among factors that drove trade-off studies leading up to the Euro-fighter configuration freeze in early 1988. The original cranked delta planform, seen on the EAP, was replaced by a simpler plain delta when supersonic agility requirements were relaxed. Foreplane size, determined by the degree of pitch instability needed to provide the agility required, was reduced. Meanwhile, the change from an elliptical- to a circular-section forward fuselage, to increase radar antenna size, resulted in the "smile" shape of the chin intake.

Meanwhile, the four air forces continued to refine their requirements, leading to signature of the European Staff Requirement - Development (ESR-D) in September 1987. Go-ahead for the programme was given in January 1988, and development contracts were signed the following November. First flight was then scheduled for 1991 and entry into service for 1997.

The fall of the Berlin Wall in 1989 plunged the programme into turmoil, however, and Germany, burdened by the costs of re-unification, came close to withdrawing in 1992 - a move which could have been fatal to the programme, and to European collaboration. "The specification had been written, and contracts signed, before the fall of the Berlin Wall, and this caused problems," says Friemer.

The Eurofighter had been designed to meet the "unidirectional" threat posed by the Warsaw Pact; now the threat was seen to be omni-directional, unpredictable and out-of-area - characteristics which placed a high premium on the Eurofighter's mix of capabilities. "We had to adapt to the new threat, but the old and the new threats were very similar," says NETMA's Christian Biener.

A revised ESR-D was signed in January 1994, but the requirements were essentially unchanged, except to increase the emphasis on air-to-ground capability. The programme had slipped, however, with the first development aircraft flying in March 1994 and first production deliveries now scheduled for June 2002.

Known first as the EFA, then the EF2000, the aircraft was officially christened the Typhoon in September 1998, but Eurofighter continues to be used by the partners. Not surprisingly, given the industrial and political investment they have made in getting the programme this far.

From TKF, through EAP to Typhoon, the delta/canard configuration has been a constant.

Source: Flight International