Pratt & Whitney has reached an informal agreement with government officials to slash 16% off the total price of the next batch of 37 engines to be ordered for the Lockheed Martin F-35 Joint Strike Fighter.

At the same time, the company acknowledges the cost of the overall F135 engine development programme will grow by about $1 billion to support a three-year extension of flight tests and to improve the engine's performance and durability.

Company officials also confirm a debate exists within the programme over slightly boosting the thrust of the F-35B short take-off and vertical landing variant in order to meet a key performance target.

The pending contract award for the fourth lot of low-rate initial production (LRIP) shows the company is making progress, says Warren Boley, president of Pratt & Whitney's military engines business.

Getting to a "handshake agreement" with the government on an LRIP price tag, however, took months longer than expected.

"I turned in my proposal on Sept 15, 2009, and I said it should be a 5min negotiation," Boley says. "It took 16 months."

In the extended discussions, P&W increased the cost savings by about 2-3% compared to its original proposal, Boley says. P&W has committed to lowering the F135's price tag to $10 million per engine with the 250th unit, he says, although he declined to identify the F135's current unit recurring flyaway cost.

If P&W reaches its goal, the 250th F135 engine will cost the same as the F119 that powers the Lockheed F-22A Raptor, although the former weighs 680kg (1,500lb) more and produces 20% more thrust, Boley says.

Continuing to reduce the recurring cost of the F135 will not be affected by recent decisions that will increase the non-recurring cost of the engine's development.

The cost of the development programme has already increased by 50% to $7.5 billion, Boley says, adding that two-thirds of the cost increase was driven by requirements changes out of the company's control.

On 6 January, the F-35 flight test programme was extended by three more years to 2016, and the number of flight tests jumped from about 5,000 to 7,500.

The new delay will add about $600 million to the cost of the F135 development programme, Boley says.

Meanwhile, several performance improvements for the lift-fan system will increase the cost of development by another $400 million, he says. Those upgrades include increasing the temperature and performance margins in the design of the lift fan, clutch and roll-posts actuators, he says.

In addition to those improvements, P&W has offered to boost the overall thrust provided by the STOVL propulsion system by about 400lbf, or roughly 1%, Boley says.

"There are those who debate whether the STOVL has sufficient margin to always come back and land fully loaded," Boley says.

According to Boley, Larry Lawson, Lockheed's executive vice president leading the F-35 programme, told him last week that the STOVL variant currently has enough thrust to meet the "bring-back" requirement established by the US Marine Corps.

"He said, 'I have sufficient margin. If I need more thrust I will let you know'," Boley says.

Source: Flight International