Production of Pratt & Whitney’s F135 engines that power Lockheed Martin’s F-35 fighter is set to peak this year at 50 units before flattening out in the coming years as the U.S. defers deliveries of the new aircraft. According to Pratt & Whitney Military Engines president Bennett Croswell, the engine maker won’t have to substantially reduce its production rates in response to the slowdown, it will defer plans it had hatched to ramp up output that would have compensated for reduced rates of production for the F117 and F100 turbofans.

U.S. budget cuts apart, some F35 partner nations have reduced their commitment to the program, such as Italy, which will now take 90 aircraft instead of the planned 135. But Croswell said this has been compensated for by sales to new foreign military sales clients such as Israel and Japan.

“It [F135 production] will come down further in the next couple of years so the way for us to maintain momentum is to bring down the cost for the engine,” Croswell told AIN. “We’re making great progress in what we call ‘the war on cost’ and we have dropped the cost [of each engine] by about 40 percent since 2009.”

Cost-containment efforts are largely focused on making sure that a higher percentage of engine assemblies and components are made correctly the first time to avoid reworking. “We are working with the supply base to get new ideas for leveraging increased volumes and improving quality to make sure that scrap rates are as low as possible.”

Looking beyond the F135, Pratt & Whitney’s engineers are already working on early U.S. Air Force and Navy propulsion wish lists for sixth-generation fighters. Croswell explained that his includes work on variable cycle engines, such as those need for short takeoff and vertical landing capability. Efforts are also being concentrated on finding ways to significantly improve fuel efficiency for fighters and helicopters.

In a collaborative effort with Honeywell, Pratt & Whitney is pushing to deliver a 25-percent reduction in fuel burn with the HPW3000 turboshaft being developed for new versions of the Black Hawk and Apache helicopters. This will involve delivering a 60-percent increase in the ratio of horsepower to weight.

So far the Pratt & Whitney team has run about 24 component rigs for the HPW3000 and Honeywell has already run a core engine, as well as power turbine and low-pressure rigs. “We have a clear path to the goals of the program and the next step is to run the full engine, which will happen some time in the middle of 2013,” said Croswell. The U.S. Army is now working on a formal request for proposal for the new powerplant.

Meanwhile, Pratt & Whitney is working on the software modifications that will adjust the commercial airliner PW4062 turbofans to power the KC-46 tanker that Boeing will provide for the U.S. military. The first engines are due to be delivered to the airframer in the fourth quarter of 2013.