I have pondered writing a reply, even though I am far from an unbiased observer. However, that bias is based on 25 years in the aerospace industry, with 16 years working propulsion systems, 9 years specifically on the F-35 propulsion system, the F135-PW-100/600. I worked on fuel systems, engine test, and flight test in the first decade of the program.
Looking at re-engining the aircraft is not too controversial., as CDR Salamander noted. The original engine, the JSF119, itself a derivative engine, first flew in late 2000 on the X-32 and X-35 aircraft. The F135, redesigned during the SDD (aka EMD) program, first flew in December 2006 on the CTOL AA-1 flight test aircraft. GE had a competing design funded through 2011, as the original concept was dual sourced engine, to revive the Great Engine War of the 1980s. Given that the JSF program was conceived in the 1990s and flew in the early 2000s, it is not surprising that propulsion, power, and thermal management requirements would change over 25-30 years of system development.
The first challenge for incorporating either AETP engine is the matter of security and exportability. The Joint Strike Fighter enterprise is an international effort, involving US DoD, services, multiple partner countries, and multiple FMS countries. The partner countries include United Kingdom, Netherlands, Australia, and Canada, nations with current or former interests in the Pacific. The FMS partner countries include Japan, South Korea, and Singapore, which are all located in the Pacific theater. These countries are operating F-35As and F-35Bs. The AETP engines, as designed today, can only work in the F-35As, and potentially F-35Cs. Due to the classification of the engine and US only clauses in contracts, the engine is only available to US services operating F-35As and possibly F-35Cs (if the Navy wants the complication). The security requirements will also have ripple effects across the aircraft as well as the maintenance and logistics for the aircraft.
This creates the second paired challenge of supportability and affordability (two of the original claims for the F-35, the other two being survivability and lethality). The security and physical construction leave both the USMC and multiple Allies out of the upgrade option and requires two separate engine production and sustainment efforts, which will increase propulsion production and sustainment costs for the enterprise.
The third constraint is likely time. While both GE and P&W were funded for technology development and engine demonstration programs, neither has been funded for a full EMD program. The engine designs must go through MIL-HDBK-516C for airworthiness (assuming no waivers from services, DOT&E, etc.), which will take time (years). New engine production lines must be created (years). New engine depots and procedures must be created (years). The program had a goal of no aircraft changes, but the classification requirements mentioned above will drive aircraft changes, at least software and procedures. This may limit the aircraft that can receive new engines further, slowing the creation and deployment of USAF squadrons with new engines.
P&W has a trivariant common upgrade for the F135 that increase range for all users, domestic and foreign. Changes to the power & thermal management architecture are available that could support growth in power generation and thermal management while reducing specific fuel consumption from any engine installed in the aircraft. GE could likely produce an upgraded version of the F136 to produce similar benefits, if dual sources for propulsion is desirable for the US and international user community.
Bottom line, if the USAF really wants AETP and funds it, industry will respond, but it will not be the right solution for the JSF enterprise.
I have pondered writing a reply, even though I am far from an unbiased observer. However, that bias is based on 25 years in the aerospace industry, with 16 years working propulsion systems, 9 years specifically on the F-35 propulsion system, the F135-PW-100/600. I worked on fuel systems, engine test, and flight test in the first decade of the program.
Looking at re-engining the aircraft is not too controversial., as CDR Salamander noted. The original engine, the JSF119, itself a derivative engine, first flew in late 2000 on the X-32 and X-35 aircraft. The F135, redesigned during the SDD (aka EMD) program, first flew in December 2006 on the CTOL AA-1 flight test aircraft. GE had a competing design funded through 2011, as the original concept was dual sourced engine, to revive the Great Engine War of the 1980s. Given that the JSF program was conceived in the 1990s and flew in the early 2000s, it is not surprising that propulsion, power, and thermal management requirements would change over 25-30 years of system development.
The first challenge for incorporating either AETP engine is the matter of security and exportability. The Joint Strike Fighter enterprise is an international effort, involving US DoD, services, multiple partner countries, and multiple FMS countries. The partner countries include United Kingdom, Netherlands, Australia, and Canada, nations with current or former interests in the Pacific. The FMS partner countries include Japan, South Korea, and Singapore, which are all located in the Pacific theater. These countries are operating F-35As and F-35Bs. The AETP engines, as designed today, can only work in the F-35As, and potentially F-35Cs. Due to the classification of the engine and US only clauses in contracts, the engine is only available to US services operating F-35As and possibly F-35Cs (if the Navy wants the complication). The security requirements will also have ripple effects across the aircraft as well as the maintenance and logistics for the aircraft.
This creates the second paired challenge of supportability and affordability (two of the original claims for the F-35, the other two being survivability and lethality). The security and physical construction leave both the USMC and multiple Allies out of the upgrade option and requires two separate engine production and sustainment efforts, which will increase propulsion production and sustainment costs for the enterprise.
The third constraint is likely time. While both GE and P&W were funded for technology development and engine demonstration programs, neither has been funded for a full EMD program. The engine designs must go through MIL-HDBK-516C for airworthiness (assuming no waivers from services, DOT&E, etc.), which will take time (years). New engine production lines must be created (years). New engine depots and procedures must be created (years). The program had a goal of no aircraft changes, but the classification requirements mentioned above will drive aircraft changes, at least software and procedures. This may limit the aircraft that can receive new engines further, slowing the creation and deployment of USAF squadrons with new engines.
P&W has a trivariant common upgrade for the F135 that increase range for all users, domestic and foreign. Changes to the power & thermal management architecture are available that could support growth in power generation and thermal management while reducing specific fuel consumption from any engine installed in the aircraft. GE could likely produce an upgraded version of the F136 to produce similar benefits, if dual sources for propulsion is desirable for the US and international user community.
Bottom line, if the USAF really wants AETP and funds it, industry will respond, but it will not be the right solution for the JSF enterprise.