One of the programs that’s causing excitement among military aircraft observers is the adaptive engine (AE) effort which is intended to be applied to the F-35 and the next generation aircraft.
What kinds of benefits are being sought? From Wikipedia,
The AETP [Adaptive Engine Transition Program] goal is to demonstrate 25% improved fuel efficiency, 10% additional thrust, and significantly better thermal management.[1]
From Wiki, here’s a brief description of the technology and hoped for benefits:
The XA100 is a three-stream adaptive cycle engine that can adjust the bypass ratio and fan pressure to increase fuel efficiency or thrust, depending on the scenario. It does this by employing an adaptive fan that can direct air into a third bypass stream in order to increase fuel economy and act as a heat sink for cooling; in particular, this would enable greater use of the high speed, low altitude part of the F-35 envelope. The increased cooling and power generation also enables the potential employment of directed energy weapons in the future. When additional thrust is needed, the air from the third stream can be directed to the core and fan streams. In addition to three-stream adaptive cycle configuration, the engine also uses new heat-resistant materials such as ceramic matrix composites (CMC) to enable higher turbine temperatures and improved performance. According to GE, the engine can offer up to 35% increased range and 25% reduction in fuel burn over current low-bypass turbofans.[1]
Currently, the F-35A has an unrefueled range in the region of 1,350 miles, which would be increased to around 1,800 miles with the new engine. [ed. 33% increase][2]
So, to sum up, what are the benefits? From the above description, we see claims of :
- 25% fuel efficiency
- 35% increased range
- 10% additional thrust
- Better thermal signature management
On the other hand, what do we know about developmental programs? Well, with 100% historical certainty, we know that developmental programs always overpromise and underdeliver. Thus,
- Costs always increase
- Schedules always slip
- Claimed capabilities are never met
- The new technology will be vastly more complex and less reliable then the preceding technology
In addition, the claimed benefits are obtained only under perfect conditions. For example, the claimed increase in range is only if the engine is used under ideal conditions for the entire distance. In reality, no aircraft is going to cruise under perfect, maximum economy conditions for an entire mission. Therefore, the increase will be significantly less than claimed.
So, combining the three factors of claims, historical reality, and realistic operating conditions, what would more realistic benefits be?
- 15% fuel efficiency
- 20% increased range
- 5% additional thrust
- Slightly better thermal signature management
Even those are likely on the optimistic side!
We don’t know the costs but, like any cutting edge technology, they’ll be eye-watering. Now, let’s combine the more realistic benefits with the massive costs, greater complexity, and lower reliability that goes hand-in-hand with greater complexity and ask ourselves, are the benefits worth the cost, complexity, and lower reliability (reduced aircraft readiness/availability)?
Given that aircraft readiness rates are already in the toilet, is introducing an even more complex and less reliable engine really a step in the right direction?
Are we sure this isn’t a case of pursing a technology for its own sake rather than for any actual gain in combat effectiveness? In fact, let’s think about combat effectiveness.
Fuel efficiency is a cost savings but is not a direct improvement to combat effectiveness. Similarly, increased range may offer some improvements in flexibility of operational planning or loiter time but is not really a direct improvement to combat effectiveness. Thrust, on the other hand, can enhance combat effectiveness but not significantly in the small amount we’re talking about. Thermal signature reduction also offers a direct improvement to combat effectiveness but the degree of improvement is unquantified and will likely be minor.
Without a doubt, gains in thrust (even small gains), fuel efficiency, and range are all nice to have. No one would argue with them or turn them down … if they were free. However, as with any new, cutting edge technology, they most certainly will not be free in terms of dollars, time, or reliability. There will be staggering prices to be paid.
Consider the examples of the LCS, Zumwalt, F-35, and Ford. All promised huge gains but the reality is that the gains have been non-existent to minimal and, in some respects, have resulted in decreases in combat effectiveness while incurring horrific costs and massive schedule delays. Do we really think that never before done adaptive engines will be the breakthrough technology that will achieve all its goals and do so affordably? Only a fool would believe that.
So, again, is it worth it?
I would suggest, no.
Conclusion
An adaptive engine will, without a doubt, result in staggering costs, increased complexity, decreased aircraft readiness and minor improvements mainly financial and logistic in nature. Are the improvements worth the cost and problems? K.I.S.S. rules the battlefield. Is a more complex and less reliable engine the way to follow the K.I.S.S. mandate?
We also need to consider the implication for war. When the war with China comes, we’ll need lots of engines. The more complex the engine, the fewer we’ll be able to produce and the longer they’ll take to make. During war, it’s better to have a simpler engine that meets 80% of the performance needs and can be quickly and easily produced than to have complex engines that are difficult to make and cannot be produced in the required quantities.
China is coming for us and we need to reorient our thinking to wartime production requirements instead of long, drawn out, unaffordable, complex peacetime requirements. The adaptive engine appears to be more of a business case than a combat case.
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[1]Wikipedia, “General Electric XA100”, 14-Apr-2022,
[2]The Drive website, “F-35s Could Get New Engines As Soon As 2027”,Thomas Newdick & Joseph Trevithick, 11-Dec-2021,
https://www.thedrive.com/the-war-zone/43456/f-35s-could-get-new-engines-as-soon-as-2027
I think if you have accomplished the goal of the development of a system (e.g. a naval attack plane with a given range) is a nice addition to have greater advantages that you don't need urgently and will be let fail if there are cost overruns.
ReplyDeleteIf you have a system lacking in a given characteristic like range in F35 you are tied to that development and it will another endless money sink "too important to fail".
JM
"a nice addition to have"
DeleteWho pays for 'nice to have'?
As noted in the post,
"Without a doubt, gains in thrust (even small gains), fuel efficiency, and range are all nice to have. No one would argue with them or turn them down … if they were free."
Unfortunately, nothing is free. Who's going to pay for 'nice to have'?
My limited understanding is the F-35 P&W F135 was the F-22 engine the P&W F119 pushed to its limit for more power, which reflected in its history as being one of the main contributions, if the not the main one, to the low operational availability of the F-35 due to its engine operating at its limit and requiring additional spares over and above forecast, which P&W have been unable to meet demand.
ReplyDeleteRaytheon who now own P&W advocating large R&D funding to upgrade of the F135 (not as large as the new adaptive engine!) think the GE XA100 favortite over the P&W XA101.
Think for above reason why Air Force strong advocate for the adaptive engine for their new NGAD along with its better sfc with one of its primary requirements with long range to operate over the Pacific.
Have not seen any articles but would not be surprised if GE claim the new engine could be built in fewer hours than the F135, GE have invested heavily in 3D printing etc
"would not be surprised if GE claim the new engine could be built in fewer hours than the F135"
DeleteOf course, claims are largely fantasy and anyone can claim anything. I assume I don't need to list all the claims about LCS, Zumwalt, Ford, F-35, etc. that all proved false?
You always need to push the science, BUT only put it into production when it is mature enough to be reliable enough for practical use. I think AE may get developed for commercial engines (power take off, economy for range) unless small light batteries get developed first.
ReplyDelete"You always need to push the science, BUT only put it into production when it is mature enough to be reliable enough for practical use."
DeleteI agree 100%. Too many development programs outright collapsed because the managers demanded immature technology be used, for no reason other than bragging rights- not only in the military, but in the civilian world, e.g., the Lockheed Martin X-33, which was designed around unproven composite fuel tanks.
VCE don't have much use in the commercial space unless SST make a return. The primary advantage of VCE is the ability to adapt to the flight regime. Effectively the technologies allow high specific thrust turbojets to increase their bypass ratios when said specific thrust levels aren't required. That's really only a benefit for a plane that needs to have super sonic performance but spends significant times in sub/trans-sonic speeds. aka military fighter jets...
DeleteThe only benefit to the commercial sector is the materials works but that's largely flowing the other way, advanced in materials used for high efficiency commercial engines finally finding their way back to military engine designs. Those materials are what give longer life and thermal headroom.
Thanks
Delete'China is coming for us' in SE Asia the same way Russia was coming for us in E Europe.
ReplyDeleteEither one can beat us militarily, and one has already beaten us economically, diplomatically, and scientifically.
How about we beat some of those swords into ploughshares before it's too late?
"Either canbeat us militarily" - Thats possibly half right.
Delete"...economically..."- theyve built everything they have off of our economy. Our capital.
"...diplomatically..."- If you consider bullying their neighbors and throwing international norms to the wind diplomacy, then sure.
"...scientifically..."- I dont think intellectual theft counts...
Now isnt the time to roll over, its time to stand, rebuild, and deal with the threat, as we've historically done before.
"intellectual theft counts"
DeleteThat absolutely counts!
It might not be "fair", but it's extremely effective.
True... But in the vein of rebutting some kind of overall superiority, having to steal it, rather than being able to develop it, was my point. But yeah...theft still "gets it done"...
Delete"but it's extremely effective."
DeleteTo a limited point. While you may steal the blueprints and be able to build the item, you won't really understand why particular shapes were used or particular materials were chosen. That limits your ability to innovate, improve, repair, and continue developments in the future. You become dependent on theft and it leaves you vulnerable. If we were smart, we'd leave tons of fake documents in our computers and make the Chinese spend time and money figuring out which are real and which are not.
or even how the materials were made. China certainly has both blueprints and actual engines to inspect and tear down, but their ability to actually make reliable engines hasn't materialized primarily because they can't recreate the manufacturing processes for the materials.
DeleteSo is the plan to re-engine the entire fleet or just the next block? If the former, I suppose the cost will be even more enormous, but if the latter we’ll have to deal with all the complications of maintaining two completely different power plants. Will we keep an open supply chain and spares etc. for the original engines? Sounds very problematic either way, as we can barely keep these things flying as it is.
ReplyDeletethe plan is to use VCE engines in NGAD/PCA, the idea to re-engine the F35 is basically a nice to have after thought.
DeleteFrom a 31-Jan-2022 Janes article,
Delete"The F-35 Adaptive Engine Replacement (FAER) RFI seeks information on a complete propulsion system to be integrated into the F-35A variant aircraft, with a contract to be awarded in fiscal year (FY) 2024 and deliveries starting from FY 2028."
I suppose this relates only to the USAF’s F35s, or do our allies and procurement partners get a say?
DeleteWell, US DoD loves concurrency so we see the price to pay in now having to retrofit 100s of "old" F35s....or keep 2 different engines in service. My guess is USAF will take a page from USN playbook and just decided to retrofit Block 3 jets and toss everything before that as too expensive and not worth it to upgrade.
ReplyDeleteThis sounds like great tech...
ReplyDeleteFor the NEXT fighter, or maybe the one after that!! Good grief, leave stuff off of our combat assets til its proven in the lab, proven in testing, and beaten to death in prototype testing. Maybe THEN, issue in a govt part number and install it!!
Believe this is the set of engines going in the next Navy and US AF fighter jet. But if they were to be smart, and it indeed is better than the current engine, you then have your scale across three platforms.
Deletethat's always been the plan of record. NGAD/PCA are linked to availability of viable variable cycle engines. Its part of the core set of technologies.
Delete" Are the improvements worth the cost and problems?"
ReplyDeleteUnfortunately, no choice, as other nations, especially China, have advanced their technologies, outdated weapons simply are not useful.
Key problem is current military R&D is a mess. Pentagon should do something to make them deliver.
"Key problem is current military R&D is a mess. Pentagon should do something to make them deliver."
DeleteThe Pentagon- specifically, the Secretary of Defense, who leads the Pentagon, is usually the problem, forcing the services to adopt "All New, All Different" concepts and systems that don't work out. Congress is the government organ with the power AND the ability to make the Pentagon fix its messes with military R & D- asking the Pentagon itself to fix these messes, is literally having inmates run the asylum.
Unrelated news: vaguely remember this exercise so nice to see some conclusions from it. Wish USN would hold a no hold bar anything goes training exercise like this, bet we would learn a few things, not that some inside USN don't already know what's right or wrong but too scared or it's too hard to change what's going on inside USN...sure looks like fast and furious and major loses are still a thing in naval warfare!
ReplyDeletehttps://www.navalnews.com/naval-news/2022/05/feedback-on-french-navy-high-intensity-exercise-polaris/
With the way the current F35 engines are not lasting as long as was thought (just like a Russian engine, gasp), it probably makes sense to look hard at these. I thought the thrust angle was higher than 10%, there seem to be various things published out there depending on whom writes it, but at times thought it was a 20-30% more, which makes more sense. The f135 upgrade program talks 10% itself, which one would think the adaptive engine would outperform it. At least engines for Jets seem to have less issues than say US Navy Corvettes or boats built without a purpose, so this has a much higher potential outlook.
ReplyDelete"With the way the current F35 engines are not lasting as long as was thought (just like a Russian engine, gasp), it probably makes sense to look hard at these."
DeleteThis is some serious wishful thinking. Stop and ask yourself why the F35 engines aren't lasing as long as anticipated? The answer is because they're so complex and so pushing the edge of technology. With that in mind, your solution is to go down the path of an even more complex, more advanced engine? And you think that, somehow, that engine will be more reliable instead of less?
That's no logical.
"thrust ...thought it was a 20-30% "
You're not only ignoring the published figures, you're ignoring the historical reality, as noted in the post, which assures us that the thrust will be a fraction of that claimed. Again, that's some serious wishful thinking! If you have published data to back up your wished for thrust, please share it. Otherwise, you need to accept the published figures and modify them downward to account for historical reality.
You would have a point, but the F35 engines were modeled after what the f22's were using, and they don't seem to have the same issues, at least known to the public. It may be that the services are asking the current engine to do too much rather than its poorly designed. This is not a Tomcat or a Hornet, the jet itself is one massive computer and nobody 20+ years ago would have any idea of the computation in jump that occurred. I think the reality is these programs today take too dang long to come to fruition and drawing boards 10+ years earlier make the first batch of airframes almost outdated when they first come out, and engines not exactly excluded. Regardless, they can't use the same engines they have now and they can't go to older, less powerful ones. It's a dilemma, perhaps we can agree on that...
DeleteHere is some press on it, choose to believe or not, but it's promising. https://www.sandboxx.us/blog/ges-new-fighter-engine-just-blew-away-existing-jet-technology/
DeleteRemember, unlike ship engines and shipbuilding in general, jet engine makers have done a pretty good job in their craft. If they can make a 110k lb. thrust engine for the 777 airliner, that makes the 777 a better aircraft in nearly all facets than the venerable 747, I think they can lend some credence to this engine too. But if they hit 20% better thrust as this states, perhaps they can do the 10% and get much better efficiencies. Can it really be worse? Today's are not cutting it long term for the f35, which is going to need more power and better fuel sipping ability.
"believe or not"
DeleteDecidedly not! All the information was from a single source, the head of the GE engine group! What else is he going to say but that it's the greatest thing ever developed? He's literally paid to say that! Now, that doesn't necessarily mean he's wrong but it does mean he's not credible. I hope he's right but history says, with 100% certainty, that his claims are vastly overstated.
" jet engine makers have done a pretty good job in their craft."
No, they're been like everyone else. They overstate and underdeliver followed by a period of slow improvements to try to eventually get somewhere near the original claims (though they never do). The F-35 engine you cite as a problem was initially hyped as a miracle of engineering that would offer performance beyond our wildest imaginings. How'd that work out? Every engine ever made was initially promised as a miracle ... none were.
"that makes the 777 a better aircraft in nearly all facets than the venerable 747"
You may not be understanding aircraft performance. For example, the 747 is a four engine aircraft versus the two engine 777. That means that the 747 engines are less stressed which, generally, means better life and better reliability.
As far as thrust, the 747's four engines generate a total of 174,000 lbf - 266,000 lbf, depending on specific model. In contrast, the 777 generates a total thrust of 154,500 lbf - 230,600 lbf, depending on the model. Thus, the 747 has more thrust.
Of course, what matters is thrust to weight ratio and I haven't bothered calculating those since the two aircraft seem to have roughly similar weights.
"Can it really be worse?"
Even setting aside performance specs, it most certainly can be worse and in the worst way: maintainability and reliability. More complex engines will, inherently, be less easily maintainable and less reliable.
With all that said, I hope this is the miracle technology that delivers more, costs less, weighs less, is easier to maintain, and is more reliable than anything that have ever been developed but history assures me that it won't be. History has shown that if you cut technology claims in half, double the cost, and double the schedule you'll be about right.
If the engines GE supplies to the airline don't meet their SFC, GE owes the airlines money. Unlike the Navy, if your stuff doesn't work, you will pay for it.
DeleteAnyway my favorite adaptive engine is the J58,
more power is more faster. Important fighter pilots,
of no interest to the Navy.
"Can it really be worse?"
DeleteUltimately, it's not about specifications; it's about maintenance, reliability, and availability. For example, the Navy's Aegis radar system is phenomenal (if you believe the claims) but, as the Navy has publicly stated and as I've documented in this blog, it is in a permanently degraded state because it can't be maintained by anyone other than a team of manufacturer's Ph.D engineers. What good is a phenomenal piece of equipment that can't be maintained and has poor availability? The F-35 is claimed to be a miracle machine but operationally is stuck at 25%-50% availability. What good is that? The Freedom class LCS is a miracle warfighting machine (according to the Navy) but it can't leave the dock for 24 hrs without breaking down. What good is that?
It's not the specs that are important, it's the maintainability and availability. It doesn't matter what the specs on the adaptive engine are if it can't be easily maintained and doesn't have a high availability. I don't hear anyone raving about that.
It's hard to say whether funding this engine in general would have been a good or bad decision in its previous guises thirty years ago (YF120) or ten/fifteen years ago (YF136); the prototypes reportedly performed comparatively well in testing and had about 40% fewer parts than their counterparts in the F-22 and F-35 programs, and funding a secondary engine choice for fighters from GE based on new technology to compete with an underperforming P&W product worked great the last time we tried it with the F101DFE/F110, which brought down cost and dramatically increased capability by giving the F100 (and TF30) a competitor. The Navy and Air Force saved more in purchase price reductions and reduced need for spares to pay for the development program several times over if memory serves, even if one doesn't attach any value to the increase in performance, tactical flexibility and reliability seen from both engine makers once there was competition.
ReplyDeleteThe problem, of course, is that we killed this project once already and the apparent restart *after* we already bought a boatload of engines from P&W means we're unlikely to recoup costs, even if things go better than they usually do for new procurements - by the time the new engines are ready to maybe be chosen to outfit the next block of purchases, the ratio of planes that have already been bought to planes still to be purchased will be unfavorable.
I think this is a lot more about maintainability than assumed. USAF sure seems to have a problem with current fleet of engines, my guess it's pilots using lot more thrust than assumed at start of project and spare parts supply cant keep up. The thrust increase isn't that significantly, 10% isn't much, cant get more because you can't modify the inlets, my guess is the increase will have little effect power wise BUT basically in most regimes, new engine will be running less hot than old engine for same thrust rating which should also help with fuel consumption.
ReplyDeleteThink of it as USAF putting more powerful engine in a car than required and just de-tuning for better reliability. I think that's really whats happening here.
A quick read suggests to me that adaptive engines are a promising technology definitely worth the R&D effort, but should not be installed on actual combat aircraft until a lot more testing and proving is done. Of course, if the cats can't launch them and the arresting gear can't trap them, does it really matter whether the engines work?
ReplyDelete