JSF Hoping for a Brighter New Year



After seven months of flighttestus interruptus caused first by an electrical problem and then by the failure and subsequent requalification of the F135 engine, the first Joint Strike Fighter -- aircraft AA-1 -- is back in the air.

Next week will see another milestone as BF-1, the first short take-off, vertical landing (STOVL) F-35B, rolls out in preparation for hover-pit tests -- where the powered-lift system is run up as the aircraft stands on a grating over a deep trench.

BF-1 will be much more important than AA-1 next year. AA-1 itself was built to the pre-2004, overweight JSF design and is not fully representative of the production JSF; and the STOVL version is the long pole in the tent, because it needs more flight testing than either the F-35A or the Navy F-35C, and is supposed to enter service first, achieving IOC in early 2012.

BF-1 is due to fly in May 2008 and is expected to be flying in STOVL mode by the end of the year. Program vice-president Tom Burbage, talking at a conference in Oslo last week, says that the customer wants a test program in which the jet "backs in" to STOVL -- slowing down from conventional flight to progressively lower speeds in each sortie, finally reaching the hover -- rather than performing "push-up" tests from the hover pit as the X-35B test aircraft did in 2000.

Everyone in the JSF program will be watching the hover-pit tests, though. A key issue: as reported here and here, the jet (to say the least) has no thrust to spare in vertical-flight mode. So far, says Burbage, recent rig tests of the F135 and its lift fan are showing that thrust is higher than expected. (That was the experience in the X-plane program, where the jet popped up to 30 feet on the first push-up, to the consternation of the engineers.)

The team is not taking credit for the lift bump, but it will be a big relief if it's still there on the hover pit. At the same time, work is underway on a redesigned second stage for the lift fan, which optimizes the work split between the two counter-rotating stages and provides another vertical thrust boost.

What Burbage calls "constipation" in the production system is also a concern, because the front-loaded test program needs to get assets on time. The problem centers on the big main frames or bulkheads that hold the wings and body together: early frames were late and the effect is rippling through the line.

On the sales side, Burbage is in constant motion, still trying to set up a deal between multiple non-US customers and the US government to reduce early-aircraft prices. The issue is that export customers -- particularly Australia and the European F-16 founder nations -- need early deliveries from the low-rate initial production (LRIP) batches, but that these come with a scary price tag.

That's a cost of doing business for the US government, which plans to buy many, many more aircraft once production stabilizes, and buys year-by-year by law; but export customers who are ready to sign multi-year contracts see it as a raw deal.

Read more Av Week predictions about the JSF's 2008 fortunes at Military.com.

-- Christian

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