Eurofighter Typhoon IPA4

IPA4 was the fourth of the Eurofighter Typhoon programme's Instrumented Production Aircraft and the one allocated to Spain in the four-nation division of flight-test tasks. Unlike the three earlier IPAs, all of them twin-seaters, it was the first single-seat production aircraft to roll off a final assembly line: the EADS-CASA line at Getafe, to which Eurofighter GmbH announced in March 2003 the delivery of the first major components of the airframe then known by its production number, PS001. In Spanish Air Force service it carried the serial C.16-04. Immediately before its first flight the aircraft was weighed to establish its mass and centre of gravity; the result confirmed that the mass prediction for the single-seat production aircraft was well in line with the contracted requirement, with a basic mass empty of 11 tonnes, and allowed the partners to conclude that all Tranche 1 aircraft should fall within the contracted limits.

The maiden flight took place at Getafe on 27 February 2004 with test pilot Alfonso de Castro at the controls. The date slipped against the consortium's original plan, which at the end of 2003 still expected the first flight before the year was out. At that moment IPA4 was the most advanced Typhoon yet flown, offering the highest standard of hardware and software integration of the weapon system, and it also flew with an enhanced-standard EJ200 engine that was tested in the air for the first time on that flight. Its main role was to continue the certification of the design and of system functionality towards the customer nations, with a test plan directed at verifying new audio and MIDS communications functions.

Its best-known campaign was the cold-weather one. On 9 December 2004 the aircraft arrived at Vidsel Air Base in Sweden for three months of Cold Environmental Trials, intended to verify the operational behaviour of the airframe and its systems at temperatures consistently between -25 and -31 °C. During the trials IPA4 provided more than 45 proofs of performance, both on the ground and during the 17 flights it made, and demonstrated fault-free operation of the whole aircraft and its on-board systems, including refuelling and the loading and off-loading of various external stores up to a maximum landing weight of just under 19 tonnes. Because the weather was initially not cold enough for the planned conditions, the team used the time for unscheduled trials such as taxiing on icy and snow-packed runways. The trials were completed on 8 March 2005 and the aircraft returned to Getafe on 10 March, stopping en route at the German air base of Laage, home of JG 73.

In July 2005 EADS-CASA began long-term tests under operational conditions at the Spanish Air Force base of Morón, near Seville, transferring IPA4 and the mobile telemetry station there for hot-weather trials in temperatures of 40 °C or above, with flight corridors over the Atlantic that also allowed low-level supersonic flying. The Spanish Air Force supported the 41-flight programme by locating its MIDS ground station at Morón and flying one or two operational Eurofighters in joint missions with the test aircraft, while EADS-CASA operated a second station from Talavera Air Base. For this work the aircraft was upgraded to Block 2B standard, which added the PIRATE forward-looking infrared sensor and the DASS defensive aids subsystem.

Within the air-to-surface weapons work-share, IPA4 concentrated on the GBU-16 laser-guided bomb: having concluded electromagnetic compatibility tests with the weapon, it was used in 2006 for flutter and vibration testing, pit drops and actual separations, together with basic handling tests throughout the summer. On 4 and 5 May 2006 it carried out the first releases of air-to-surface weapons in the history of the programme, with Alfonso de Castro taking off from Morón accompanied by a Spanish Air Force F-18. On 19 March 2007 the Typhoon test fleet reached 5,000 flying hours on an IPA4 sortie flown by Carlos Esteban Pinilla and devoted to environmental data gathering with a Meteor air-to-air missile; the same year the aircraft also flew laser-guided bomb jettison trials at Morón.

On 31 March 2009 IPA4 fired an AMRAAM at a Mirach target drone over southern Spain using the MIDS data link: the target data were transmitted by IPA5, which had flown to Morón on 12 March for the trial. In mid-2009 the aircraft was upgraded to Tranche 2 standard and continued to be used for environmental and communications systems tests, MIDS work and Meteor trials. Since late 2012 it has been used for software evaluation; together with IPA7 it completed the Phase 1 Enhancement test flights on 28 October 2013. As of January 2014 it was counted among the 41 Eurofighters delivered to Spain, listed separately from the 18 Tranche 1 series aircraft.