Aviation Week & Space Technology
F-35 In-Service Dates Slide
By Robert Wall
06/13/2004 08:29:39 PM
STRETCHED-OUT
Top Pentagon officials are about to consider a new course for the F-35 Joint Strike Fighter that includes delaying the fielding by two years.
The adjustments are merely the latest ripple stemming from the Pentagon's realization last year that the fighter is overweight. Managers have opted to spend more time and money early in the development program to tackle the weight problem which is impacting, in particular, the short takeoff and vertical landing (Stovl) version. Program officials had already delayed design reviews and indicated first flights of the various models would incur schedule slips.
The move will further complicate deliberations for British military planners at a time when they are reviewing which version of the multirole fighter to buy. If the U.K. bows out of the Stovl version, it would buy the carrier-based configuration instead.
The Pentagon's top acquisition panel is to convene as early as this week to discuss whether the new schedule is acceptable. The revised plan calls for the U.S. Marine Corps to remain the first to field the F-35. However, the in-service date is now projected to be 2012, rather than 2010. The U.S. Air Force's initial operational capability with the conventional takeoff and landing version (CTOL) has been delayed to 2013 from 2011.
The U.S. Navy's carrier-based model would reach service in 2013, a one-year delay rather than two. The original Navy schedule was not as aggressive as those of its sister services, so the effect of the delay is least on its version. Navy officials aren't overly concerned by the development. Since the F/A-18E/F production line is hot, the Navy can easily avoid operational shortfalls, notes Capt. David Philman, who oversees strike aircraft requirements for the Navy.
The British in-service date is still undefined, although it is likely to be in 2013 or later, according to a U.S. government schedule. The U.K. wanted to take delivery of JSFs as early as 2010, with an initial operational capability in 2012 concurrent with the fielding of the first of two new aircraft carriers.
First flight of the CTOL will now take place in late 2006, while the first Stovl model will fly in mid-2007, says John C. McKeown, JSF's technical director. Both of those aircraft will be in the original configuration and not feature some of the weight reduction measures being implemented for later models. The carrier version would fly in 2008, also a year later than planned.
Critical design review for the CTOL aircraft, the first to take place, is set for November 2005. The Stovl review will follow in mid-2006 and the carrier version in 2007. The start of low-rate production so far is holding steady and is slated for mid-2006.
McKeown told the American Helicopter Society that the government and Lockheed Martin have made great strides in recent months to reduce the F-35's weight to achieve range performance goals. However, he suggested that for the Stovl version--which last year was still 2,400 lb. overweight--more needs to be done since managers are taking a very conservative view as to weight savings. In fact, he indicated weight reductions alone won't achieve the desired results and that the services will likely have to trade off some JSF performance parameters.
Top level performance goals--such as a 450-naut.-mi. combat radius for the Marines with the ability to land on a ship while carrying two 1,000-lb. bombs and two AIM-120 missiles--are unlikely to be affected. However, smaller requirements could be adjusted. For instance, the wave-off flight pattern the U.K. uses is smaller than for U.S. carrier operations. Adhering to the U.K. standard would reduce fuel requirements when returning to the ship and save weight.
McKeown noted that managers are looking to performance trades because they want to avoid being overly aggressive in their on-aircraft weight reduction initiatives. There is concern that cutting too much weight could jeopardize the airframe's durability and drastically boost life-cycle costs. Similarly, the government so far is steering clear of pressuring engine makers Pratt & Whitney and General Electric to boost thrust to offset the higher weight, because such efforts curtail the life of the F135 and F136 powerplants. Engineers hope that installed engine weight will generate about 500 lb. of additional savings in areas such as the inlet.
Deciding on what weight savings to pursue hasn't always been easy. Some suggestions could have led to negative results in other areas, so managers are closely scrutinizing every measure before proceeding.
In terms of range performance, Mc- Keown said USAF and Navy aircraft pretty much meet their requirement. Developers also have brought the carrier version's maximum on-ship landing speed near the target of 145 kt. with more work being done. The Navy official notes that the projected approach speed is adequate and that the improvements being sought are intended to reduce strain on the airframe during landing.
The Stovl aircraft also can meet its range requirements, even with the added weight, but it can't do so when landing vertically, in zero wind and with the required "bring back"--weapons and fuel.
Although weight has received lots of attention, there are some long-term challenges managers are grappling with. For instance, McKeown said development of JSF's extensive prognostics and health management system could become a challenge to complete in time. Moreover, software is likely to be a hurdle, with 5-6 million lines of code on the aircraft and another 6-8 million lines for mission planning and other ground equipment directly related to the fighter. Coding of the initial aircraft flight software is ongoing, and first results should become available next year.
JSF program director USAF Maj. Gen. John Hudson also noted that there are continuing problems working international aspects of the program, such as sharing information on datalinks, logistics, and in the long-term software support arena.
In the coming months, designers also hope to set interoperability demands. Interoperability, the ability to share information with other systems, is one of JSF's key performance parameters. But there is a potentially large pitfall because not all the interoperability demands have been set, since some systems that will interface with JSF aren't fully defined. The challenge to developers is to devise a configuration that can accommodate those later, McKeown notes.
