The Pratt & Whitney F135 is the propulsion engine for all three versions of the Lockheed Martin F-35 Lightning II. The programme combines a common engine lineage with different installation requirements for conventional operations, aircraft-carrier operations, and short take-off and vertical landing. Pratt & Whitney describes it as an engine in the more-than-40,000 lbf thrust class.[1]
Development lineage
The F135 evolved from the F119 engine used in the F-22 Raptor. The U.S. Air Force describes an F119-derived core, including a six-stage compressor and single-stage turbine, combined with a new low-pressure spool. The relationship is a development lineage, rather than a claim that an F119 can be installed directly in an F-35 or that the two aircraft have identical propulsion requirements.[2]
Altitude qualification testing at the Arnold Engineering Development Center examined performance and operability before flight release. Tests also addressed failure detection and accommodation, structural behaviour and the internal operating environment. Separate facilities supported development testing and accelerated mission testing, evaluating how the engine performed across simulated operating conditions.[2]
Aircraft roles
The F-35A uses conventional take-off and landing, the F-35C is the carrier version, and the F-35B adds short take-off and vertical-landing capability. Pratt & Whitney produces the main engine. Rolls-Royce supplies the specialised lift equipment used with the F-35B configuration.[1][3]
Vertical-lift system
The Rolls-Royce LiftSystem includes a forward LiftFan, driveshaft and clutch, swivelling rear exhaust module and roll posts. Power from the main engine is transmitted through the driveshaft to the LiftFan. The swivelling module redirects rear thrust, while the roll posts provide control forces. This distributes lift around the aircraft rather than relying on one downward-pointing exhaust alone.[3]
The lift fan is therefore mechanically powered by the main propulsion engine; it is not a separate fuel-burning lift jet. Rolls-Royce lists up to 29,000 shaft horsepower transmitted to the fan. That shaft-power figure and the F135's thrust rating measure different things and should not be added together as though both were thrust.[3]
Integrated functions
The F135 programme also encompasses engine controls and thermal management. Pratt & Whitney describes these functions alongside thrust and signature requirements, reflecting the integration of propulsion with the wider aircraft. Engine capability therefore involves more than the maximum force available for acceleration: it also includes managing the machinery and supporting the operating environment of an advanced combat aircraft.[1]