The F-35 joint programme office (JPO) has revealed the first details of a three-year, block-buy proposal for the Pratt & Whitney engine that powers the Lockheed Martin fighter.

The programme could sign contracts for 477 F135 engines over a three-year period beginning in FY2017, according to a JPO notice posted online on 25 March.

A JPO spokesman clarifies that the 477 number excludes spares, so it could be matched with an equivalent number of airframes.

The details of the block-buy proposal were not revealed previously as the US Congress has not yet authorised the approach, and some of the international partners have not made formal commitments to acquire the aircraft. Acquisition rules require the JPO to notify the industry of potential sole-source contracts.

USMC F-35B - AirTeamImages


The US Department of Defense typically buys aircraft and engines in annual lots through the end of low-rate initial production. Once production costs have stabilised during full-rate production, programmes sometimes shift to multi-year procurement, but only if the contractor agrees to deliver a minimum discount of 10%.

The timing of the three-year block buy, however, begins in the final year of low-rate initial production in FY2017, so the JPO needs specific authorisation from Congress to move forward with the deal.

The JPO is currently authorised to negotiate a block buy of nearly 150 F-35s that are expected to be ordered between FY2015 and FY2016.

F-35 programme officials have committed to reducing the flyaway cost of the F-35 by more than 25% over the next five years.

Four-fifths of that cost reduction is expected to come from increasing the production rate more than five-fold from 35 aircraft in 2014. The remainder would be the result of a cost reduction initiative by Lockheed and a “war on cost” initiated by P&W.