F-15X: the story of the USAF’s new Eagle

The US Air Force looks set to purchase its first new F-15 Eagles since 2001 — so what has spurred this move?

US Air Force Secretary Heather Wilson told senators on March 13 that the service’s $165-billion budget for fiscal year 2020 is designed to make the force larger and better able to confront global threats. The USAF is working hard to address critical shortfalls in what it calls readiness — a metric that can be defined and measured in several ways, but Wilson says ‘it’s about the readiness of our squadrons to fly and fight that matters to us.’

Recapitalizing aging fleets of fighters, tankers, trainers and transport aircraft is critical, but problematic. Large fleets of legacy platforms are being replaced by more advanced, more expensive, new aircraft, but the spiraling cost of the new equipment puts the brakes on the ability to trade in old models for new on a one-for-one basis. The USAF also needs to expand in order to meet its relentless deployment schedule, which is burning out its people, spurring them to leave and thereby having triggered a manning crisis.

The equipment solution to date has been either to stretch out recapitalization initiatives to avoid burning budgets and to concurrently engage in upgrades for old aircraft to stretch out their usefulness. Moreover, in 2018, Wilson set out a plan to expand the USAF by 74 squadrons, with seven of these additions being fighter units.

A source familiar with the discussions told Combat Aircraft that as early as March 2016, various fighter aircraft manufacturers were being called to the Pentagon for quiet conversations about possible solutions regarding new-build fourth-generation fighters. The Pentagon was apparently concerned that relying entirely upon the F-35 wasn’t an optimal or sufficiently versatile solution. Operation and maintenance costs of the F-35 were running far higher than expected and the air force needed to be able to quickly transition squadrons to new fighters. The conversation was geared to what was readily available off the production line, what was low risk and what wouldn’t require a protracted development project.

Boeing was part of these early conversations, looking at an Advanced F-15 that could roll straight off the active production line in St Louis, Missouri, with a few of the USAF F-15E’s latest modernization elements sprinkled in. The exercise was about cost avoidance, not just in platform acquisition, but also via exploring savings from leveraging existing spares chains and support equipment. It was also about ease of transition, not taking a squadron offline for an 18-30 month re-equipping and training phase. For the F-15, it became a more appealing proposition.

The final push for new F-15s in the USAF came from former Defense Secretary Jim Mattis. Boeing offered the USAF two variants of what it calls the F-15X, the single-seat F-15CX and the two-seat F-15EX, which are billed as being identical except for a rear seat in the latter. The F-15X is essentially the two-seat F-15QA, with a few US-specific systems such as the new Eagle Passive Active Warning and Survivability System (EPAWSS) and its accompanying Operational Flight Program (OFP) 9.1 (the same OFP as in the F-15E EPAWSS upgrade).

Both the CX and EX would both be air-to-air and air-to-ground capable — and officially the only difference is that the CX has ‘Bay 5’ behind the pilot instead of a second seat, however, clearly the single-seat Eagle has traditionally featured a different cockpit canopy profile. Both variants will feature the large area display and digital Joint Helmet Mounted Cueing System (JHMCS) and because part of the foreign investment in the new displays and management of the systems, everything can be run from the front seat of the EX — the missionized rear cockpit can be optionally occupied by a Weapons Systems Officer. This is significant because the first jets (although destined for F-15C squadrons) will be two-seat F-15EXs. It’s not certain if the USAF will acquire the F-15CX at all — any talk to date has centered on the two-seat EX. In fact, the USAF has said that F-15C units receiving F-15EXs will operate them with the rear seat unoccupied. Porting the Advanced F-15 into a single-seat CX will clearly require some sort of re-certification of the complex fly-by-wire system, and despite the two aircraft retaining the same overall dimensions, any risk incurred from new testing may prove unacceptable.

A full feature on the F-15X appears here https://www.key.aero/article/f-15ex-usaf