The two X-35 concept demonstrators taking shape at the Skunk Works in Palmdale, California, are very similar in appearance to the aircraft Lockheed Martin will offer in the Joint Strike Fighter (JSF) competition - and that is a trump card in the company's battle against Boeing to win the 3,000-aircraft US/UK programme.
The latest version of the aircraft Lockheed Martin will enter in the JSF competition, called the Preferred Weapon System Concept (PWSC), met 99% of the requirements, the company says, against a target of 90%.
That means fewer iterations will be needed to arrive at the final PWSC design that will be submitted late next year.
Lockheed Martin has had to switch the roles of its two X-35 concept demonstrator aircraft (CDAs), however, because of cost overrruns on the programme.
Originally, the first X-35, CDA 1, was to fly in the US Air Force's conventional take-off and landing (CTOL) configuration then be converted to demonstrate the US Navy's carrier-based (CV) variant.
Meanwhile the second X-35, CDA 2, was to fly as the US Marine Corps/Royal Navy short take-off and vertical landing (STOVL) version.
To save money and time, Lockheed Martin is now building CDA 1 as the STOVL version, but will fly it initially in CTOL form, with all the lift system hardware installed but disconnected. CDA 2 will now be built and flown as the CV variant.
Converting CDA 1 from CTOL to STOVL will be quicker and cheaper than converting it from CTOL to CV, the company says, arguing that the new approach still demonstrates the required commonality between the three variants.
After lengthy ground tests in STOVL mode, including hanging the aircraft over a pit so that the lift system can be fully tested, CDA 1 will make its first flights in CTOL form.
After about two months, the aircraft will be grounded, the lift system reconnected and flights resumed in STOVL form.
Conversion will only take about a month, says Lockheed Martin. This is much less than the time it would have taken for the CTOL to CV conversion, it says, which would have involved fitting a larger wing and tail. CDA 2 is now expected to fly about the time that CDA 1 is being grounded for conversion,
Both demonstrators will have the hole behind the cockpit for the Rolls-Royce Allison shaft-driven lift fan, allowing the CV demonstrator to be converted to STOVL if the first aircraft is lost in an accident, Lockheed Martin says.
Both X-35s are scheduled to fly early in 2000, initially at Palmdale, then at the US Air Force's Edwards AFB test centre in California and later at the US Navy's NAS Patuxent River test site in Maryland.
Source: Flight Daily News
