Propulsion – Pratt & Whitney F135
¶ 2. Propulsion – Pratt & Whitney F135
Note on cost basis: All USD amounts from US government sources (GAO, CBO, DoD) in this article are expressed in Base Year 2012 Dollars (BY2012$). Adjusted for inflation to 2026, actual values are approximately 40–50% higher.
The Pratt & Whitney F135 is the most powerful fighter jet engine ever to enter series production. It exists in three sub-variants [6]:
- F135-PW-100: Standard variant for F-35A and basis for F-35C (the version Switzerland is procuring)
- F135-PW-400: Marinized variant for the carrier-based F-35C
- F135-PW-600: STOVL variant with coupling to the Rolls-Royce LiftFan for the F-35B
¶ Performance Data
| Parameter | Value |
|---|---|
| Dry thrust | approx. 128 kN (28,000 lbf) |
| Afterburner thrust | approx. 191 kN (43,000 lbf) |
| Engine length | approx. 5.59 m (220 in) |
| Inlet diameter | approx. 1.09 m (43 in) |
| Architecture | Three-stage fan, six-stage high-pressure compressor, annular combustor |
| Maintenance concept | 6 hand tools for all Line Replaceable Components |
Sources: P&W F135 Fast Facts [7], P&W F135 Characteristics [8]
¶ Fleet Status
Over 1,300 engines have been delivered and have collectively accumulated more than 1 million flight hours [6].
¶ Engine Core Upgrade (ECU)
The ECU modernizes the engine core and provides [9]:
- +25% more electrical power and cooling capacity
- Double the thermal management capacity (critical for Block 4 avionics)
- Full retrofittability for all three F-35 variants
- Critical Design Review (CDR): mid-2025
- First test run: 2026, planned entry into service: 2029
The ECU contract amounts to 1.31 billion USD [10].
¶ AETP and NGAP
The Adaptive Engine Transition Program (AETP), with the XA100 (GE) and XA101 (P&W) demonstrators, was not pursued for the F-35 because the adaptive engines only fit in the F-35A, not in the B and C variants [11]. Instead, AETP technology is flowing into the Next Generation Advanced Propulsion (NGAP) program for the F-47 (NGAD), with a total volume of 7 billion USD [12].
¶ References
[6] RTX / Pratt & Whitney: F135 Engine – Powering the F-35 Lightning II
[7] RTX / Pratt & Whitney: F135 Fast Facts 2025 (PDF)
[8] Pratt & Whitney: F135 Engine Characteristics
[9] Pratt & Whitney: F135 Engine Core Upgrade
[10] Air & Space Forces Magazine: Engine Core Upgrade for F-35 Passes PDR. 2024
[11] Air & Space Forces Magazine: Air Force Skips AETP Engines for F-35, Presses on with NGAP. 2024
[12] Air & Space Forces Magazine: Pentagon Hands Out $7 Billion for NGAP Engine. 2025