Air-Minded: A Different Shade of Gray (Updated)

I’ve updated this Air-Minded post twice now, first on 7/21/20 and now on 7/23/20. The first update included comments from readers who claimed to have inside knowledge. The most recent update is a 3/27/19 article from the Aviation Week, the source document I’ve been searching for, addressing the single-seat versus two-seat Eagle replacement question, along with my questions on WSO manning. Both updates appear at the end of the post, below.
— Paul


If you follow defense and military air news, you probably know the US Air Force took my advice and decided to start replacing its older F-15 Eagles with new F-15 Eagles.

The USAF doesn’t have enough F-22 Raptors to perform its air-to-air and air defense missions, so it has kept a small number of older single-seat Eagles in the air to supplement and back up the Raptor fleet. These older Eagles, built in the mid-1980s, are well past their retirement dates. There’s no money to reopen the F-22 production line, let alone quickly procure a new air-to-air fighter, but hey, they still make F-15s in St. Louis — why not buy some new ones?

USAF F-15C Eagle (Wikimedia Commons)
USAF F-15C Eagle (Wikimedia Commons)
USAF F-15E Strike Eagle (Wikimedia Commons)
USAF F-15E Strike Eagle (Wikimedia Commons)

See, the F-15 Eagle is still in production, albeit since the early 2000s only for foreign customers. The latest version, the F-15QA, built for Qatar, is a two-seater derived from the F-15E Strike Eagle built for the USAF from 1989-2001. The F-15EX, the first eight of which have just been funded for the USAF, is also a two-seater, similar to the Qatari jet but capable of carrying more air-to-air missiles.

Qatari F-15QA (photo: Chase Kohler Aviation)
Qatari F-15QA (photo: Chase Kohler Aviation)

In 2018, when the USAF saw the wisdom of my proposal and announced its intention to buy new production F-15s, it said the new jet, designated F-15X, would be a single-seater. The older Eagles it was to replace are single-seat C models like the ones I flew during my career, which were optimized for single pilot operation and did not require a second crewmember to operate avionics and weapons. The idea of a single-seat F-15X, in that context, made a lot of sense.

USAF F-15X concept (Boeing)
USAF F-15X concept (Boeing)

The original air-to-air Eagles, the F-15A and F-15C models I flew, were single-seaters, though some two-seat versions were made. Every tenth Eagle came off the production line as a two-seater, and every squadron had a couple of “family models” on hand for checkrides and incentive flights. There are no important differences between single-seat and two-seat models. The single-seaters had a large bay behind the pilot’s seat that was easily converted to a second cockpit in the two-seat versions. The later F-15E Strike Eagle, a version of the F-15 optimized for air-to-ground employment, was always a two-seater with a dedicated weapon system officer (WSO) in the rear cockpit to operate and manage avionics, weapons, and defensive systems.

To bring us up to today: the USAF’s FY2020 budget includes funding for the first eight replacement Eagles, which will be two-seat F-15EX models, not the single-seat F-15X announced in 2018. What happened to the F-15X? Is it gone forever? The impression I get from current reporting is that all the new jets, an eventual buy of around 200 aircraft, will be two-seat F-15EX models, flown by pilots and WSOs.

If you suspect single-seat fighter pilots make distinctions between themselves and pilots who crew with WSOs in two-seat fighter-bombers, you are to be congratulated on your powers of perception. You can understand then why I was so excited, two years ago, to hear they were going to build single-seat Eagles again. So yes, I’m disappointed.

Beyond my own elitist prejudices, it seems odd to me the USAF would decide to replace 200-some single-seat Eagles with crewed two-seaters. What functions will WSOs perform in the new air-to-air F-15 jets, which up to now have been more than adequately handled by F-15 pilots alone? Surely the new cockpits, avionics, and weapons controls will be at least as well optimized for single-pilot operation as those in older Eagles. And what about the personnel and training costs of adding new WSO positions to the air-to-air F-15 fleet? That’s nothing to blink at, and I can only imagine there must have been spirited debates over it in the Pentagon. Granted, the factory hasn’t built a single-seat Eagle since 1985, but how hard can it be to do? They didn’t keep the jig and molds for the original canopy?

USAF F-15EX concept (Boeing)
USAF F-15EX concept (Boeing)

The F-15EX will start with the Qatari F-15QA platform, an advanced multi-role version of the primarily air-to-ground F-15E Strike Eagle. The F-15EX will retain those air-to-ground capabilities, and can eventually be used to replace the USAF’s F-15E Strike Eagle fleet, though no such plans have been announced. You can see a strong hint of that possibility in the above artist’s concept of an F-15EX loaded with air-to-air and air-to-ground weapons.

In the USAF, single-seat air-to-air F-15C Eagles are called “light grays”; two-seat air-to-ground F-15E Strike Eagles are called “dark grays.” Though externally similar, the USAF and the aviators who fly them consider them quite different aircraft, performing quite different roles. Pilots who fly light grays can’t just transfer to a dark gray squadron and start flying missions — they have to go through an entirely different training program first, and such transfers aren’t all that common.

Will F-15C pilots assigned to fly the F-15EX, with the addition of a second crewmember sitting behind them to operate systems they used to operate by themselves, look on the new jets as dark grays masquerading as light grays? How long will the USAF be able to resist adding dark gray mission requirements to light gray units, diverting some of the new replacement aircraft into Strike Eagle squadrons, or giving all F-15 units a multi-role mission?

I can’t answer any of these questions and hesitate to speculate. I could also be wrong; maybe the single-seat F-15X concept is still operational (and if so I’ll be delighted to delete this post). For now I’m content to wait and see. At least we’re finally buying new Eagles to replace the ones my mates and I over-G’d repeatedly in the 1980s and 1990s, even if they aren’t the single-seaters the USAF initially proposed.


Update (7/21/20):

— From a aeronautical engineer at Wright-Patterson AFB:

From what i’ve read, they’re planning to fly with the back seat empty. I think it’s a wise move in that it leaves open the possibility of adding new missions and capabilities to the plane in the future. With a fatigue life of 20,000 hours, they’re going to last long enough to still be around when the next gen air superiority platform comes online. The F-15E currently has no replacement, so if these planes are still in good enough shape when the next gen fighter is ready, i imagine they could repurpose these airframes to become an F-15E replacement. Or perhaps they could decide to have the second crewmember could manage a swarm of unmanned “loyal wingmen” that are currently under development. In summary it sounds like they just want the extra flexibility that comes with a rear cockpit available.

— From a Boeing employee at the St. Louis plant:

As of now, EX is two seater. Supposedly there will be a single seater. The airplane is just as advanced avionics wise as the 5th gen. Some instances more advanced. The old planes hydraulics moved everything, new planes fly by wire. My source. I’m setting next to the production line. 30 plus years building the F-15.

— Counterpoint from another reader (who didn’t cite any sources):

There won’t be a single seat variant. Only reason the USAF is getting these is because the Strike Eagle line was still open. Saudi and Qatar paid for all the R&D because it’s the same setup as the QA and SA.

— Counter-counterpoint from the Boeing employee quoted above:

They are discussing building a single seat variant. I work in the main production building. They initially wanted both. Single and Two seater. The discussions according to our vice president Prat. We were going to take a two seater. Gut it , make a single seater. The work was to be done in Bldg 102 (same area where they modified 2 Saudi jets into the fly by wire config ). Or across the street.

— My response, FWIW:

I’ve heard from a couple of people that F-15C units receiving new F-15EX aircraft plan to fly them with the rear seat empty. I can’t find any source documents for that, but I’m looking. To say “we’ll fly them with the back seat empty” would be the natural reaction of the F-15C community, and may or may not be the position of the Air Force. Two of the commenters I quoted above suggest only the initial purchases will be two-seat EX models, since that’s what Boeing is making now and it’s a quicker way to get the jet into service, and claim there’ll be single-seat F-15X jets down the line. Again, I’m looking for sources … and so far coming up dry.


Update (7/23/20):

— My Wright-Patterson AFB aeronautical engineer friend has found a source, Aviation Week no less. Short version: the USAF will purchase only the two-seat F-15EX version, and existing F-15C units will fly them with empty back seats.

Here’s the text of the full Aviation Week article, dated 3/27/19 (link is subscription only):

Boeing’s two-seat F-15EX aircraft will be flown with an empty back seat by squadrons now flying single-seat F-15Cs, the U.S. Air Force confirms to Aerospace DAILY.

Although derived from an international version of the two-seat F-15E, the Air Force plans to acquire at least 144 F-15EX aircraft, including 80 over the next five years, to replace an aging fleet of mainly single-seat F-15Cs.

Boeing designed the F-15EX to operate in both the air superiority role of the single-seat F-15C and the fighter-bomber role of the F-15E. The latter includes a back-seat station for a weapon systems officer to manage the munitions and sensors for land attack while the pilot in the front seat concentrates on flying and air-to-air engagements.

The F-15EX comes with two functional cockpits, but the pilot can manage air-to-air and air-to-ground missions alone in the front seat, the Air Force says. F-15EX aircraft delivered to squadrons now flying single-seat F-15Cs will not be staffed with an expanded cadre of weapon system officers, which would leave the back seat of the two-seater empty.

“Fighter squadrons that receive the F-15EX are projected to retain their current mission and crew composition,” an Air Force spokeswoman says in response to questions by Aerospace DAILY.

Although the role of former F-15C pilots flying F-15EXs would expand under the current plan, the Air Force does not expect an increase in training costs during or after the transition.

“There should be no need to expand aircrew training requirements,” the spokeswoman says.

Boeing offered the Air Force a single-seat version of the F-15X for the F-15C replacement, which was designated as the F-15CX concept. The Air Force decided to buy only the two-seat F-15EX, which minimizes nonrecurring engineering costs.

The F-15EX is a straightforward derivative of the F-15QA ordered by the Qatari air force. It features a lightened wing, but still carries the same load of weapons and sensors as the F-15E. The F-15EX also includes other upgrades added since the Air Force last ordered the F-15E in 2001, including fly-by-wire flight controls, the Eagle Passive Active Warning Survivability System, the Advanced Display Core Processor II mission computer and a new cockpit with a large format display.

© 2020, Paul Woodford. All rights reserved.

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3 thoughts on “Air-Minded: A Different Shade of Gray (Updated)

  • I appreciate your words ” Woody”. And yes I inspected more than one jet that you put a few extra ” G’s ” on.
    Best times of my life.

  • Do not know where but another aviation sight confirmed that it was a design/cost convenience to just leave it a two seater for “future testing/upgrade purposes. Since the EX is now an offshoot version of 2 seat for QA and E model before that, easier than a retool/redesign back to a single. I do know it was always difficult with C models to fill flight needs like Check/IP/Incentive/Flight Doc rides with only 2 Dual seaters per squadron generally. Periodic/ unscheduled maintenance sometimes hindered that.

  • A friend sent this comment by DM:

    “From what i’ve read, they’re planning to fly with the back seat empty. I think it’s a wise move in that it leaves open the possibility of adding new missions and capabilities to the plane in the future. With a fatigue life of 20,000 hours, they’re going to last long enough to still be around when the next gen air superiority platform comes online. The F-15E currently has no replacement, so if these planes are still in good enough shape when the next gen fighter is ready, i imagine they could repurpose these airframes to become an F-15E replacement. Or perhaps they could decide to have the second crewmember could manage a swarm of unmanned “loyal wingmen” that are currently under development. In summary it sounds like they just want the extra flexibility that comes with a rear cockpit available.”

    I’ve heard from a couple of people that F-15C units receiving new F-15EX aircraft plan to fly them with the rear seat empty. I can’t find any source documents for that, but I’m looking. This would be the natural reaction of the F-15C community. One writer suggests only the initial purchases will be two-seat EX models, since that’s what Boeing is making now and it’s a quicker way to get the jet into service, which implies there’ll be single-seat F-15X jets down the line. Again, looking for sources.

    To me the big implication, if we’re switching over to a two-seat jet, is whether over time the F-15 mission will become a multi-role one. A return to the days of the F-4 Phantom II? Yes, in the F-4 days there were units with primary air-to-air missions and units with primary air-to-ground missions, but aircrews still had to maintain proficiency in both.

    If all the new F-15s wind up being two-seat EX models, I don’t see the USAF leaving those rear seats empty for long.

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