11.01.2011, 00:59
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Zitat:Why The F-35B Is In Trouble
Three big issues to be dealt with this week: F-35B, J-20 and bombers. Here goes on the first:
Defense Secretary Gates announced last week that the F-35B short take-off, vertical landing fighter was "on probation". Coupled with the release of a short summary of actions that follow new program manager VAdm Dave Venlet's review of the program, it points to a challenging couple of years.
The change to the F-35B plan is major. All but three of the FY11/Lot 5 B-models are cancelled, and another 27 aircraft in FY12 and FY13. Production is being drawn down to the minimum level necessary to preserve a restart option.
Gates said that solving the unspecified technical issues now afflicting the aircraft "could" add cost and weight; the program office says that it "will", and that it will take two years to "engineer solutions ... and assess their impact."
This action has been in the works for some time, foreshadowed by comments in September from Lockheed Martin CEO Robert Stevens.
Gates hit the issue on the nose when he stated that changes could "add yet more weight and more cost to an aircraft that has little capacity to absorb more of either." The current situation has been in the making since the start of the systems development and demonstration program and has to do directly with the basics of a STOVL aircraft.
Vertical landing is a nonvariable requirement. The required airspeed is zero and can't be adjusted by a few knots to compensate for extra weight. The JSF key performance parameter for bring-back load - corresponding to two 1,000-pound JDAMs and two Amraams - was set early on at a minimal level.
One reason that Lockheed Martin's shaft-driven lift fan (SDLF) concept was a winner in 1996 and 2001 was that it seemed to offer thrust margin for vertical landing. At the start of SDD, the F-35B was projected to have an empty weight of 29,700 pounds - not a bad place to be in with (then) almost 40,000 pounds of vertical thrust. But, in the weight crisis of 2004, engineers found that the jet had ballooned to a far higher figure (never actually published) at which it could not land vertically with normal fuel reserves, let alone weapons...........