A solicitation to modernize the power plant of the Lockheed Martin [LMT] F-35 fighter may come before the end of the year.

Raytheon Technologies‘ [RTX] Pratt & Whitney F135 equips the F-35, but the F-35 program has said that the fighter will need a new or significantly upgraded engine with improved electrical power and cooling capacity to accommodate the 53 new capabilities slated for Block 4.

Technology Refresh 3 (TR3)–spurred by the L3Harris [LHX] integrated core processor–is the computer backbone for Block 4, which is to have 88 unique features and to integrate 16 new weapons on the F-35.

Pratt & Whitney has said that its F135 Enhanced Engine Package (EEP) has “ample design margin” to allow for the envisioned Block 4 upgrades for the fighter and that EEP will save $40 billion in lifecycle costs.

General Electric [GE] has favored a new engine and said this week that it has tested out the company’s second XA100 adaptive cycle engine at the U.S. Air Force’s Arnold Engineering Development Complex in Tullahoma, Tenn., for the Air Force’s Adaptive Engine Transition Program (AETP) (Defense Daily, Sept. 13).

The completion of the testing of the second XA100 comes a year after such testing on that engine began in August last year, General Electric said. The company has said that the XA100 would give the F-35 30 percent more range, more than a 20 percent increase in acceleration, and significant mission systems growth for Block 4.

Block 4 may cost $15 billion, while the Air Force has pegged the development cost of AETP for the F-35 at $6.7 billion (Defense Daily, June 30).

Since 2016, the Air Force has funded the AETP, but thus far it appears that an AETP engine will fit on the F-35A and possibly the Navy F-35C, not on the Marine Corps’ F-35B short takeoff and vertical landing variant, as the latter requires an engine that drives the lift-fan system, provides bleed air to the roll-posts, and uses a swivel exhaust duct.

The Air Force plans to field full Block 4 on the service’s F-35As in 2028 when Lockheed Martin delivers F-35 Lot 20. The service may end up fielding some Block 4 functionality on unmanned Collaborative Combat Aircraft, especially if the Air Force decides to forego developing a new F-35 engine.

In addition to the possible release of an F-35 engine modernization solicitation, the F-35 program is also to submit to OSD a life cycle sustainment plan this year and is gearing up for first flights of an F-35 with TR3 and the Raytheon Next Generation-Distributed Aperture System (Next Gen- DAS) in the coming months.

Next Gen-DAS is to replace the F-35’s current Northrop Grumman [NOC] AN/AAQ-37 DAS, which consists of six electro-optical sensors to provide the pilot with 360-degree situational awareness for missile and aircraft threat warnings, launch point detection, targeting, and day/night navigation. The DAS sensors send high resolution real-time images to the pilot’s helmet, allowing the pilot to see the ground through the bottom of the aircraft.

In 2018, Lockheed Martin selected Raytheon to supply Next Gen-DAS, which is to be integrated onto F-35s starting with Lot 15 (Defense Daily, June 13, 2018).

Through July 31, Lockheed Martin had delivered 830 operational F-35s for international customers and DoD, including more than 300 Air Force F-35As, 100 U.S. Marine Corps F-35Bs, and 50 U.S. Navy F-35Cs.