Graham Warwick/WASHINGTON DC
Lockheed Martin says it is on schedule to fly the X-35 Joint Strike Fighter (JSF) concept demonstrator aircraft (CDA) in 2000, despite a late change to the fly-by-wire flight control computer. An advanced computer under development by Lockheed Martin Controls will now be used instead of the original Honeywell unit.
The last-minute change means that an "aggressive" ground test programme will be required to ensure that the flight control software is validated before the X-35's first flight, says Rick Baker, CDA product manager at Lockheed Martin Skunk Works, where the aircraft is being assembled.
The manufacturer planned to use the computer developed by Honeywell for the Boeing 777, but ran into throughput problems as flight control software grew.
"The 777 computer was the best available when we selected it in 1995, but, one month ago, we decided to go to a much faster computer to eliminate throughput problems," Baker says.
The biggest task facing the team is validating the integrated flight and propulsion control software for the short take-off and vertical landing (STOVL) variant of the X-35, the second CDA to fly. Baker says software will be provided to Pratt &Whitney for ground tests of the JSF119 STOVL engine, to begin later this year.
The engine and shaft-driven lift fan will then be installed in the second X-35 for ground tests at the Skunk Works. About a year of ground tests will precede the eight-months of flight tests
The first X-35 will be flight tested at Edwards AFB, California, to validate the "up-and-away" flying characteristics of the conventional take-off and landing variant of the JSF design. The aircraft will then be grounded for two months for conversion to the carrier-capable JSF configuration, for approach handling tests at NAS Patuxent River, Maryland.
The second X-35 will begin STOVL build-up tests at Edwards to evaluate hover performance, according to Baker, before it is ferried to Patuxent River later in 2000 for the formal vertical-flight demonstration phase.
Source: Flight International
