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Pratt & Whitney F135

Pratt & Whitney · Aircraft Engine · USA · Digital Age (2010–present)

Pratt & Whitney F135 — Aircraft Engine
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The Pratt & Whitney F135 is an afterburning low-bypass turbofan developed for the Lockheed Martin F-35 Lightning II family. It is the most powerful fighter engine in service, producing 43,000 lbf with afterburner and 28,000 lbf dry. The F135 was derived directly from the Pratt & Whitney F119 that powers the F-22 Raptor, scaling the F119 core up by roughly 22% in thrust class and adding the lift-fan-driving STOVL architecture for the F-35B variant. First production deliveries began in 2009 and the engine entered front-line service with the U.S. Marine Corps F-35B in 2015.

Architecture follows the F119 template: a 3-stage fan, a 6-stage high-pressure compressor, an annular combustor, a 1-stage high-pressure turbine, a 2-stage low-pressure turbine, and a full-authority digital electronic control. The F-35A and F-35C use a conventional convergent-divergent exhaust nozzle. The F-35B STOVL variant adds a clutch-engaged shaft drive to the Rolls-Royce LiftSystem lift fan in the forward fuselage and a 3-bearing swivel nozzle on the main engine, generating around 40,000 lbf of vertical thrust split between the lift fan, the swivel nozzle, and roll-control nozzles in the wings.

The F135 has been produced in three main dash-numbers: the F135-PW-100 for the U.S. Air Force F-35A and most international F-35A operators, the F135-PW-400 for the U.S. Navy and U.S. Marine Corps F-35C carrier variant with marinised seals and bearings, and the F135-PW-600 for the F-35B STOVL with the lift-fan drive shaft and swivel nozzle. By 2026 more than 1,200 F135 engines had been delivered across roughly 1,000 F-35 airframes (one engine per aircraft).

The General Electric F136, a competing engine developed jointly with Rolls-Royce under the F-35 alternative-engine program, was cancelled in 2011 after the Pentagon and Congress concluded the second source was not worth the cost. That left Pratt & Whitney as the sole F-35 engine supplier, which the Government Accountability Office has criticised as a long-term sustainment risk.

To address the F-35's growing thermal-management problem — the airframe demands more cooling than the original engine bleed and bypass air provide — the Air Force selected the Engine Core Upgrade (ECU) program in 2023 over the more ambitious Adaptive Engine Transition Program (XA100/XA101). The ECU adds around 10% more thrust, 6-7% better fuel burn, and 50% more thermal-management headroom by replacing core hot-section components rather than swapping in a new adaptive engine. First fielding is targeted for 2029. The longer-term replacement for sixth-generation fighters is being developed under the Next-Generation Adaptive Propulsion (NGAP) program.

For Kids — a shorter, friendlier version

The Pratt & Whitney F135 is a jet engine. It powers the F-35 Lightning II fighter jet. It is the most powerful fighter engine flying today. Over 1,200 of these engines have been built and delivered.

The F135 makes 43,000 pounds of pushing force with its afterburner on. That is faster than almost any other fighter engine in the world. The afterburner burns extra fuel to give the jet a big boost of speed and power.

The engine comes in different versions for different F-35 models. One special version helps the F-35B take off in a very short distance and land straight down like a helicopter. It does this using a lift fan and a nozzle that can swivel to point down. Together they make about 40,000 pounds of upward push.

The F135 grew out of an older engine called the F119. Engineers made it about 22 percent more powerful than the F119. The F119 engine powers the F-22 Raptor fighter jet. The F135 first entered front-line service in 2015.

Fun Facts

  • The F135 is the most powerful fighter jet engine in service in the world today.
  • It can push with 43,000 pounds of force — heavier than three full-grown elephants combined!
  • The F-35B version can land straight down like a helicopter thanks to a special swiveling nozzle.
  • The engine traces its roots to the F119, but is about 22 percent more powerful.
  • A special lift fan sits in the nose section of the F-35B and helps it hover during landing.
  • More than 1,200 F135 engines have been built and delivered since 2009.
  • A computer called a full-authority digital electronic control runs the engine automatically.
  • The F135 powers all three versions of the F-35: the A, the B, and the C.

Kids’ Questions

What makes the F135 engine so special?

The F135 is the most powerful fighter engine flying today. It can push with 43,000 pounds of force when the afterburner is on. That is an enormous amount of power for a single engine!

How does the F-35B land like a helicopter?

The F-35B has a special lift fan in its nose and a nozzle that can swivel to point straight down. Together they create a huge upward push of around 40,000 pounds. This lets the jet hover and land on very short runways or even on ships.

Where did the F135 engine come from?

Engineers based the F135 on an older engine called the F119. The F119 powers the F-22 Raptor fighter jet. They made the new engine about 22 percent more powerful than the original.

When did the F135 start flying with real fighter pilots?

The first F135 engines were delivered in 2009. The engine entered front-line service with American Marine Corps F-35B jets in 2015. Since then, more than 1,200 engines have been built.

Variants

F135-PW-100
Conventional take-off and landing variant for the F-35A. 43,000 lbf afterburning, 28,000 lbf dry. The most-produced dash-number, used by every F-35A operator including the U.S. Air Force and most international customers.
F135-PW-400
Carrier variant for the U.S. Navy F-35C, with marinised seals, salt-water-resistant coatings, and modified bearings for catapult launches and arrested landings.
F135-PW-600
STOVL variant for the F-35B, driving the Rolls-Royce LiftSystem lift fan via a clutch-engaged shaft and using a 3-bearing swivel nozzle on the main exhaust. Used by the U.S. Marine Corps, U.K. Royal Air Force/Royal Navy, Italian Navy, and Japan Maritime Self-Defense Force.
F135 Engine Core Upgrade (ECU)
2023-selected mid-life upgrade adding around 10% thrust, 6-7% lower fuel burn, and 50% more thermal-management capacity. Fields starting 2029 across all three F-35 variants.

Notable Operators

F-35A (CTOL, 2015-present)
Conventional F-35 variant operated by the U.S. Air Force and most international customers (Australia, Belgium, Denmark, Finland, Germany, Israel, Italy, Japan, Netherlands, Norway, Poland, South Korea, Switzerland, etc.). One F135-PW-100 per airframe.
F-35B (STOVL, 2015-present)
Short-take-off-vertical-landing variant for the U.S. Marine Corps, U.K. Royal Air Force/Royal Navy, Italian Navy, and Japan Maritime Self-Defense Force. Uses the F135-PW-600 with the shaft-driven LiftSystem and 3-bearing swivel nozzle.
F-35C (carrier, 2019-present)
U.S. Navy and U.S. Marine Corps carrier variant with marinised F135-PW-400. Designed for catapult launches and arrested landings from Nimitz- and Ford-class aircraft carriers.

Frequently Asked Questions

How much thrust does the F135 produce?

43,000 lbf with afterburner and 28,000 lbf dry, making it the most powerful fighter engine in service (Pratt & Whitney F135 page). For comparison, the F-22's F119 produces around 35,000 lbf and the F-15E's F100-PW-229 produces 29,160 lbf. The Engine Core Upgrade scheduled for 2029 will add roughly another 4,000 lbf.

What aircraft use the Pratt & Whitney F135?

Only the Lockheed Martin F-35 Lightning II, in all three variants: the F-35A conventional fighter, the F-35B short-take-off-vertical-landing variant, and the F-35C carrier variant. One engine per airframe. By 2026 more than 1,000 F-35s had been delivered across 18 partner and customer air forces, all flying the F135.

How does the F135 differ from the F119?

The F135 is a scaled-up F119 with a larger core. Both engines share the 3-stage fan and 6-stage high-pressure compressor layout, but the F135 grows the flow path to deliver 43,000 lbf versus the F119's 35,000 lbf. The F-22's F119 has 2D thrust-vectoring nozzles; the F-35's F135 uses a fixed convergent-divergent nozzle on the F-35A/C and a swivel nozzle on the STOVL F-35B. The F135 also adds the shaft-drive option for the F-35B's lift fan, which the F119 does not have.

What happened to the GE F136 alternative engine?

The GE/Rolls-Royce F136 was cancelled in 2011 after the Department of Defense and Congress agreed a second engine source was not worth the development and sustainment cost. The decision left Pratt & Whitney as the sole F-35 engine supplier, which the Government Accountability Office has periodically flagged as a long-term sustainment and pricing risk.

Why was the Engine Core Upgrade chosen over a new adaptive engine?

In 2023 the U.S. Air Force selected the Pratt & Whitney Engine Core Upgrade (ECU) over the more ambitious GE XA100 and Pratt XA101 adaptive three-stream engines developed under the Adaptive Engine Transition Program (USAF release). The ECU costs roughly half as much, can be fitted to all three F-35 variants (the adaptive engines would have only fit the F-35A), and re-uses existing logistics. The trade-off is smaller performance gain.

How does the F-35B's lift system work?

For vertical landing, a clutch in the F135-PW-600's front section engages a drive shaft running forward to the Rolls-Royce LiftSystem lift fan in the airframe's mid-fuselage. The lift fan produces roughly 20,000 lbf of cold vertical thrust. At the same time the engine's 3-bearing swivel nozzle rotates 95 degrees downward to direct the main exhaust vertically, and roll-control nozzles in the wing roots stabilise the aircraft in hover. Total vertical thrust is around 40,000 lbf.

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