GRAHAM WARWICK / WASHINGTON
Raptor trials programme is altered as USAF attempts to meet critical 2003 milestone
The first guided launch of a Raytheon AIM-120 AMRAAM medium-range air-to-air missile from a Lockheed Martin/BoeingF-22 Raptor is imminent. The firing will be a key test of the Northrop Grumman APG-77 active-array radar and Block 3.0 avionics software and a critical milestone in the F-22 flight test programme, which is running substantially behind schedule.
Although the pace of flying is accelerating, by mid-year the programme had lost 61 aircraft test months due to late deliveries and other problems, according to Congressional testimony by Lee Frame, acting director of the US Department of Defense Operational Test and Evaluation Office. As a result, the USAir Force has delayed the start of initial operational test and evaluation from August next year, with April 2003 as the objective and October 2003 as the threshold beyond which the December 2005 initial operational capability date would be in jeopardy.
Controversially, the USAF has also cut the amount of avionics flight testing planned, from 1,970h to 1,530h, by assuming more efficient testing and reducing the number of live missile firings - despite the fact avionics testing has been slower than planned. Programme details will be revealed when defence secretary Donald Rumsfeld formally notifies Congress of the DoD's decision to approve production of the F-22, expected next week.
Six flight-test aircraft have been delivered, with the remaining three scheduled to be flown, if not all delivered, by year-end. Five aircraft are at Edwards AFB, California, where flight testing had exceeded 1,320h by the end of August. The first F-22, aircraft 4001, has entered live-fire testing at Wright-PattersonAFB, Ohio, after completing its flying career.
The 22 August live-fire test, with the aircraft in simulated manoeuvring flight, assessed the survivability of the fuel-filled wing when hit by a high-explosive incendiary anti-aircraft artillery round. Earlier tests resulted in a wing redesign that replaced selected composite spars with titanium to reduce hydrodynamic ram damage caused when a round explodes in the fuel tank.
The USAF says a portion of wing skin deformed and ripped off, but the wing remained largely intact, with limited structural damage that would enable the aircraft to return home. Further tests will determine the remaining flight capability of the damaged wing.
Aircraft 4005, meanwhile, has received additional instrumentation and software stability fixes to support the first AIM-120 guided launch. Aircraft 4006 has been similarly modified, while aircraft 4004 is being updated with the Block 3.0 avionics software.
Source: Flight International
