* Problem could cause engine stall
*"Minor" tweaks for fuel-pump software planned
*Impact on flight testing schedule uncertain
(Recasts with Pentagon statement)
By Jim Wolf
WASHINGTON, Oct 1 Flight testing of Lockheed
Martin's (LMT.N) F-35 fighter jet, the costliest U.S. arms
purchase, has been suspended after discovery of a fuel pump
sequencing problem that could have caused engine stall, the
Defense Department said on Friday.
All three F-35 models have been grounded as a precaution
pending "minor" modification of software that controls signal
timing, Cheryl Irwin, a Pentagon spokeswoman, said in a
statement emailed after the close of markets.
The radar-evading F-35, also known as the Joint Strike
Fighter, is the Pentagon's costliest acquisition at a projected
total of up to $382 billion for 2,457 planes over the next two
A software fix has been developed and is due to be
installed in test aircraft starting Oct. 5, Irwin said. The
faulty sequencing was discovered during laboratory testing.
"It could possibly trigger a shutdown of all three boost
pumps, potentially further causing engine stall," the
But she said a simultaneous shutdown of the United
Technologies Corp's (UTX.N) Pratt & Whitney F135 engine's
three fuel "boost pumps" was unlikely.
The grounding was the latest hitch in a high-profile
multinational program revamped by Defense Secretary Robert
Gates this year to deal with cost overruns and schedule slips.
"The aviation development process discovers technical
challenges that force programs to pause, reassess, resolve, and
continue," Vice Admiral David Venlet, executive officer for the
Pentagon program, said in the statement.
The grounding's impact on the flight test schedule is
unknown, John Kent, a Lockheed Martin spokesman, said in a
separate emailed statement.
Lockheed, the Pentagon's No. 1 supplier by sales, said it
had never experienced the fuel pump sequencing anomaly in any
Lockheed and BAE Systems Plc (BAES.L), the fuel system
software developer, have identified a fix and begun testing
that software in their labs, Kent said.
BAE and Northrop Grumman Corp (NOC.N) are Lockheed's chief
F-35 subcontractors. An alternate, interchangeable engine is
being developed by a joint venture of General Electric Co
(GE.N) and Britain's Rolls-Royce Group Plc (RR.L).
The United States is co-developing the F-35 with eight
foreign partners -- Britain, Italy, the Netherlands, Turkey,
Canada, Australia, Denmark and Norway. Together, the partners
are projected to buy about 730 planes.
(Reporting by Jim Wolf; editing by Carol Bishopric)
(additional reporting by Andrea Shalal-Esa)