JMR (Joint Multi-Role) & FVL (Future Vertical Lift) Programs

[yasotay]

I would love to see some pictures of Valor next to a Blackhawk.

LOL - A photo that neither vendor is too keen on having done. Have to wait till ~2026.

 

[TomcatViP]

I think they should take the opportunity of re-engining to have the mass restricted UH-60 cabin increased in volume through a deep upgrade.

Since range and speed are now de-facto decoupled from UH-60 family mission (doesn't mean they can't be fitted with large EFT), a deep upgrade will focus on what Valor can't do better.

 

[yasotay]

I think they should take the opportunity of re-engining to have the mass restricted UH-60 cabin increased in volume through a deep upgrade.

Since range and speed are now de-facto decoupled from UH-60 family mission (doesn't mean they can't be fitted with large EFT), a deep upgrade will focus on what Valor can't do better.

Seems a sensible approach since the US Army has indicated several decades of continued operations.

 

[TomS]

I think they should take the opportunity of re-engining to have the mass restricted UH-60 cabin increased in volume through a deep upgrade.

Since range and speed are now de-facto decoupled from UH-60 family mission (doesn't mean they can't be fitted with large EFT), a deep upgrade will focus on what Valor can't do better.

Not a terrible idea. It would also probably align to the Navy's future needs for an SH-60 replacement. They need cabin volume far more than they need increased speed. As long as they can stuff the result into DDG hangars., it will be an improvement.

 

[Moose]

I think they should take the opportunity of re-engining to have the mass restricted UH-60 cabin increased in volume through a deep upgrade.

Since range and speed are now de-facto decoupled from UH-60 family mission (doesn't mean they can't be fitted with large EFT), a deep upgrade will focus on what Valor can't do better.

There's only so much volume you can add to that cabin, though. Any taller and you run into air transport issues, for example. Unless we're talking about hanging a nearly clean-sheet composite cabin under the turbines, I don't know if they can add enough to be worth the cost of the effort.

 

[Spyclip]

CT Senator Murphy is not letting go with regards to FLRAA costs. He seems firmly in the camp of believers with the flawed mentality that V-22 is tiltrotor incarnate, ignoring all the myriad lessons learned in the last quarter century that were baked into the V-280 design from day one.

The irony is that there isn't even a baseline for a production rigid rotor compound coaxial at any scale, only a long line of essentially failed demonstrator aircraft. So the logic that an unproven, high-risk, new-paradigm platform will exceed all cost estimates puts the 20th century V-22 on precisely the plane as the contemporary SB1. At least the Osprey was preceded by the immensely successful XV-15.

MURPHY: “Thank you very much, Mr. Chairman. Thank you both for being here today. Mr. Chairman, I wanted to take my time to ask a few questions about the Future Vertical Lift Program. First of all, this is the first opportunity to talk about this in this subcommittee. Mr. Chairman, as you know, I made, along with Senator Blumenthal, a series of requests of the Army to get a briefing on a FLRAA award and was denied that briefing by the Army multiple times.

“I think this subcommittee, and more broadly the Appropriations [Committee], has to pretty rigorously guard our equities when it comes to getting information from the Army and from the administration when it comes to contract awards. In fact, the regulations governing the awarding of contracts carves out a very specific role for Congress to be briefed on these matters even while the award is pending. And I hope this committee will continue to work on what I think is a misaligned equilibrium right now between the administration, the Department of Defense, and this committee when it comes to how much information is shared.

“Ms. Wormuth, I wanted to talk to you about this specific award. I understand I have parochial interests, right. This was a contest between Bell Textron and Sikorsky and the award went to the Bell program. But I guess I want to talk to you a little bit about my concerns regarding tiltrotor aircraft. My understanding is that past performance did not factor into the contract award, and this committee is going to be charged with picking up the full cost of this new program. Tiltrotor aircraft, like the V-22 Osprey, have a pretty miserable performance, reliability, and safety record over the last 30 years. The V-22 is supposed to have a mission readiness of 82%, but over the last five years, the Osprey has been at 56%. The procurement cost went from 33 million to almost 100 million [per aircraft]. Today, the cost per flight of the V-22 is $10,000 an hour, which is double the initial estimate.

“What was interesting about this particular contract award is that the bid that came in from Textron was twice, twice the amount of the bid that came in from Sikorsky. Layer on top of that, this history suggesting that a tiltrotor is going to end up costing our taxpayers inordinately more than even the initial bids. And I worry that we're going to have a hard time being able to fund the full cost of this award.

“So I guess my question is, do you have any information as to why the Army did not take past performance of tiltrotor aircraft into account when awarding the FLRAA contract? And what do you say about my concerns that if the cost curve on this new helicopter, which is obviously a foundational program for the Army, is anything like what we saw for the Osprey that, then we're in for some pretty big, unexpected costs that we're going to have to bear on this subcommittee?”

WORMUTH: “Senator Murphy, first of all, I want to say, you know, of course, I completely support and value the important oversight role of Congress in these matters. So we want to be good partners with you in terms of being transparent. And if you have not already received a detailed briefing now that the GAO has issued its decision, if you will, on the competition, I certainly will make sure that Mr. Doug Bush and their team get up to talk with you about that.

“My understanding is that the things that were valued or emphasized, if you will, in the selection process did include looking at lower technical risk, precisely because of the fact that in the past if the technical risk is higher, a lot of times that means the costs in the out years are higher. The sustainment costs can be higher because they're not appropriately baked into the competitive process. So one of the reasons, as I understand it, that we selected the Bell Textron aircraft was because it was assessed to have lower technical risk, even though the bid that came in from Sikorsky from an overall dollar amount was lower. You know, it was a best value competition. It wasn't strictly based on price. And we in the Army had some considerable concerns about our visibility into the design process that came from Sikorsky. So I can get back to you in more detail in terms of how exactly we incorporated past performance of the Osprey into the calculations. But we absolutely emphasize the importance of having lower technical risk in the program.

MURPHY: “Mr. Chairman, I will just note that our subcommittee has a GAO report on this very specific question of whether risk is being properly calculated when awarding programs within the Future Vertical Lift aircraft process. And what this GAO report comes to the conclusion is that right now, the Army is not properly identifying long term risk on these programs. And so look forward to being in a dialogue about some of the recommendations in this GAO report and getting a better, holistic sense of how much this is going to cost the taxpayer in the long run. Thank you very much.”

I do wonder why Army representatives maintain such an opaque public stance on the technical failings of the Sikorsky team. Surely it has to do with the ongoing FARA tender.

 

[TomS]

Unless we're talking about hanging a nearly clean-sheet composite cabin under the turbines, I don't know if they can add enough to be worth the cost of the effort.

That's more or less what I expect for FVL-Maritime. It's vaguely possible that they'll be interested in a V-280 derivative, but it seem unlikely, since the main roles for combatant ship helos involve a lot of hovering and not a lot of flying really fast. Seahawk already does pretty well, and the temptation to just find a way to get some more cabin volume with the same dynamics and footprint has to be real. It has the benefit that NAVAIR is already familiar with the process thank to the King Stallion -- keep the nameplate and some bits of the dynamic systems, then build a new helo that fits inside the same box.

I could see, if budget permits, a mix of MH-60X manned helos to replace the MH-60R/S and "MQ-247" tiltrotor drones to replace the Firescouts. But that's a lot of budget.

 

[yasotay]

I am not surprised that the honorable Senator from Connecticut is continuing to bang the drum, since his seat is heavily dependent on union votes. One must keep up appearances. Unless there was anyone else on the committee who spoke up I think it is more noise for the masses. Is there any similar verbiage from the HASC? Also, as was highlighted in the transcript above, the Secretary of the Army intimated that Sikorsky's platform "ain't the bomb" and their numbers were considered BS. I really would like to be in the room when the Honorable Mr. Bush does the deskside briefing.

 

[yasotay]

Posturing has begun.

US Army says open system requirements clear for next-gen helicopter

Lockheed's future assault aircraft proposal lacked detail needed to validate its design had an open architecture at sub-system levels, the GAO found.

www.defensenews.com

 

[Spyclip]

Posturing has begun.

US Army says open system requirements clear for next-gen helicopter

Lockheed's future assault aircraft proposal lacked detail needed to validate its design had an open architecture at sub-system levels, the GAO found.

www.defensenews.com

Last year, at the same event, his directorate put together a video using a fifth grader to explain MOSA, playing it during a panel discussion. We intentionally made it to where a fifth grader could understand it… to try to help people understand it’s not nearly as complicated as it sounds, which is really just existing standards, not somebody’s special mouse trap [where] they are the only people in the world that understand how that mouse trap works,” Langhout said. “It’s really that simple, but yet it’s amazing how unbelievably complicated some folks try to make it.”

I cannot imagine being a member of that Sikorsky / Boeing proposal team over the past 3 weeks.

 

[Tuna]

Posturing has begun.

This is also important for FARA. Basically the Army putting it's foot down and saying: "We'd really like to buy your stuff, but you do have to bid a system with MOSA."

I think at this point it is extremely likely that Sikorsky will win that one, because of simple industrial policy concerns, but if they do lose, it will be for the exact same reason why their bid for FLRAA was disqualified. Very clear public signalling helps prevent that outcome.

 

[yasotay]

@Spyclip - It is a pretty brutal beat down.

@Tuna - I agree with you, regardless of what the US Army says, Industrial Base will be much more of a consideration in the FARA decision.

 

[jsport]

Industry devises plans to keep helicopter fleet capable for decades

The UH-60, AH-64 and CH-47 may need to fly for decades more, even as the Army brings future aircraft into its fleet.

www.defensenews.com

 

[VTOLicious]

Posturing has begun.

US Army says open system requirements clear for next-gen helicopter

Lockheed's future assault aircraft proposal lacked detail needed to validate its design had an open architecture at sub-system levels, the GAO found.

www.defensenews.com

Last year, at the same event, his directorate put together a video using a fifth grader to explain MOSA, playing it during a panel discussion. We intentionally made it to where a fifth grader could understand it… to try to help people understand it’s not nearly as complicated as it sounds, which is really just existing standards, not somebody’s special mouse trap [where] they are the only people in the world that understand how that mouse trap works,” Langhout said. “It’s really that simple, but yet it’s amazing how unbelievably complicated some folks try to make it.”

I cannot imagine being a member of that Sikorsky / Boeing proposal team over the past 3 weeks.

Speaking of Boeing. What was their part? How was work shared on this proposal? ...or did they just watch the bus driving off the cliff?

 

[Colonial-Marine]

It would seem Boeing has had a lot of experience driving busses off cliffs in recent memory so I'm not certain it would had helped if they had a more active role.

 

[yasotay]

I believe Boeing was in it financially and working the software side of the effort. More a guess really. I suspect there was a bit of hubris as well in that both Boeing and Sikorsky believed that they "owned" US Army Aviation. Ironically this sort of hubris affected Bell when the UH-1 and attack helicopter requirements were released in the 1970's.

 

[yasotay]

This week's FVL update.

While their prototypes wait for engines, FARA competitors touting their technology
(Inside Defense, May 5, Dan Schere)

As Bell and Sikorsky await the delivery of the Improved Turbine Engines for their respective prototypes in the Future Attack Reconnaissance Aircraft competition, each company is making its best case to the Army for why its technology is preferred.
Doug Bush, the Army’s top acquisition official, said FARA is currently eight months behind schedule, due in part to quality-control-related delays with the engines at the sub-vendor level.
Bell, owned by Textron, is offering its 360 Invictus, which features a fly-by-wire flight-control system, single main rotor system, low-drag tandem cockpit fuselage, lift-sharing wing and 20mm gun.
Sikorsky, owned by Lockheed Martin, is offering the Raider X, which features two main rotors on the top of the aircraft and a pusher propeller in the back. It uses the company’s coaxial rotor technology (X2) and also has fly-by-wire controls.
Chris Gehler, Bell’s vice president and program director for FARA, outlined the steps for testing their FARA prototype during an interview last week at the annual Army Aviation Association of America conference in Nashville, TN.
“We’ll take the engine. We’ll instrument it since this is a prototype flight test aircraft. That’ll take a little while. Then we’ll integrate the engine. We’ll do more functional tests. Then early 2025 in the springtime we’ll be ready to ground run,” he said.
Sikorsky, while it waits for the ITEP, has been flying its S-97 Raider at Sikorsky’s flight development facility in West Palm Beach, FL to help inform the development of the Raider X and ensure risk reduction, Jay Macklin, the business development director for future vertical lift at Sikorsky told Inside Defense in an interview on March 23.
“It’s all about reducing risk on this aircraft. So, all of our sill work, our demonstrations, making sure that we’re able to seamlessly move these systems on and off the aircraft, the supportability approach,” he said.
To date, Raider X is 96% complete and S-97 has flown at over 200 knots, Macklin said.
“What the Army ends up saying what it wants RAIDER to fly will have to be when the RFP comes out and they say, 'We want you to fly this speed,'” Macklin said.
“We’re eagerly awaiting the [engine], and as soon as we get it, we’ll fully go about integrating the aircraft,” Macklin said.
While its prototype FARA aircraft also sits nearly complete, Bell has been focusing on the design and development of Increment 1-- the aircraft that will eventually be deployed to Soldiers in the field. Gehler said the work has been ongoing to integrate weapons, sensors and other elements of the system into the aircraft.
“We are progressing with the baseline design and development of that now. And so it’s a concurrent development. We’ve learned a lot in building the prototype, so we have a very good baseline understanding of the weight. All the engineering that we’ve done in the competitive prototype is the baseline for what we do in the Increment 1 weapon system,” he said.
Macklin explained the compound coaxial rotor system that Raider X uses has two rotors spinning in opposite directions. This eliminates the need for a tail rotor because the two rotors provide stabilization.
“What we did is we put a prop on the back. Now this prop accelerates. So, you have level body acceleration. And then you pull back and decelerate,” he said.
Gehler said last week that he does not think Sikorsky’s design is efficient, insisting Bell’s offering uses “validated technology” in which a wing is used to offload the rotor system.
“We don’t have any exquisite new technology, exquisite blades and exquisite drive systems, much as our competitor does. We have taken technology and used the lowest-risk approach to make it the most efficient platform for speed and range,” he said.
Representatives from both companies say they are excited about FARA’s utilization of a Modular Open Systems Architecture (MOSA).
“If you think about today, on an enduring fleet aircraft, if you want to change something on a display or you want to change a box out, or you want to add a new system, it’s going to be a laborious process. With future vertical lift, MOSA is really the underpinning of how you’re going to do all of that,” Macklin said.
Ultimately, Macklin believes MOSA will make it possible to do more predictive maintenance on future aircraft.
“You’re going to have maintenance-free operating periods on these aircraft where you can fly out a platoon in these aircraft and land, and a platoon sergeant is out there. There’s a high degree of reliability in these aircraft, and the aircraft is talking to you, so you’re able to understand and be proactive in what maintenance is done and when it’s done,” he said.

 

[Spyclip]

I think at this point it is extremely likely that Sikorsky will win that one, because of simple industrial policy concerns, but if they do lose, it will be for the exact same reason why their bid for FLRAA was disqualified. Very clear public signalling helps prevent that outcome.

History suggests that RaiderX will suffer the exact same performance issues as all other rigid rotor coaxial designs. Its hard to imagine a situation where the Army would select a fundamentally flawed platform, especially in this case where the aircraft will be given to the Army to do the test flying. Think about how Sikorsky has, to date, still never let an Army XP be PIC on the S-97. And also how there were no Army XP on Defiant until the absolute last minute on a single sortie before it went radio silent and likely retired.

There'll be no place to hide the weenie this time.

With the competitive prototype aircraft both designed around a single engine, RaiderX will be objectively outperformed by Invictus in flight test. If the Army pivots, as expected, to a twin with a larger footprint allowable then it negates the entire CP aircraft exercise and all the losing bidders for the demo will have a field day in court. Combined with the ongoing schedule slips of T901, I do not see how this entire SNAFU does not get canceled before EOY 2023.

 

[yasotay]

Sadly, I have to agree with your assessment of program termination.

 

[aim9xray]

This week's FVL update.

What the Captain meant to say was : "We now return you to our soap opera, "As the Stomach Churns" sometimes titled "As the Dollars Burn", already in progress."

 

[Spyclip]

A very interesting article with some hints at the Italian Military leadership's unusual interest in X2 despite Leonardo's reservations.

Some LM greased skids perhaps?

Industry eyes Ukraine war to sharpen proposals for NATO helo fleet

Industry officials and military leaders have studied tactics as they craft their designs for a new generation of rotorcraft supporting alliance forces.

www.defensenews.com

 

[yasotay]

A very interesting article with some hints at the Italian Military leadership's unusual interest in X2 despite Leonardo's reservations.

Some LM greased skids perhaps?

Industry eyes Ukraine war to sharpen proposals for NATO helo fleet

Industry officials and military leaders have studied tactics as they craft their designs for a new generation of rotorcraft supporting alliance forces.

www.defensenews.com

As stated in another thread I think it was Leonardo hedging it's bet. It has tilt rotor technology. Had X2 won, then they would have had the European market for the other US high tech rotorcraft.

 

[yasotay]

https://www.defensenews.com/congress...on-helicopter/

With respect to Freddy - "Another one bites the dust."

Headline - Army shoots itself in the foot, again. Advises it will have to start shooting itself in the hands.

 

[donnage99]

Lockheed will lobby hard don't you worry. they need to tell investors why buying sikorsky is a genius move.

 

[Spyclip]

The tiltrotor currently has greater cruising speed and autonomy but greater size and less maneuverability.

If the priority is to transport passengers or material across greater distances in shorter times, its advantages are undoubted.

The choice made by the U.S. Army to purchase the Bell V-280 Valor is linked to the Indo-Pacific theater, where the U.S. envisages an increasing presence.
On the other hand the coaxial helicopter with propellers can perform sudden and fast maneuvers, albeit having less speed and autonomy than a tiltrotor in the same category.

In the future, both these platforms will enter service with NATO armed forces since both show, at least on paper or in preliminary trials, good performance. However, I would also say that no country can do without, at least for now, a fleet of reliable, traditional helicopters. The new technologies will increase performance but have not yet reached the maturity to be game changers for at least another 10 years.

Italy’s Army aviation chief talks helicopter advancements

Out with the old, in with the new, right? Not so fast, says Italy's chief of army aviation.

www.defensenews.com

Interesting interview with the commander of Italy’s Army aviation fleet, Maj. Gen. Andrea Di Stasio. He is still clinging to the unproven compound coaxial marketing points around agility and lack thereof for tiltrotors - despite the results of the entire JMR-TD exercise.

He even then goes on to say both platforms would be in service with NATO!

 

[H_K]

He even then goes on to say both platforms would be in service with NATO!

Sounds like his future (after retirement) is assured… helping Sikorsky-Boeing make that happen!

 

[yasotay]

Regardless of its potential viability at some point, if FARA is cancelled I cannot see Italy electing to pick up the full tab for X2.

 

[e-Graphite]

Regardless of its potential viability at some point, if FARA is cancelled I cannot see Italy electing to pick up the full tab for X2.

If FARA isn't canceled, it will go to Bell, and I can't see Italy picking up the tab to carry an X2 aircraft to production in that scenario, either.

 

[VTOLicious]

Regardless of its potential viability at some point, if FARA is cancelled I cannot see Italy electing to pick up the full tab for X2.

If FARA isn't canceled, it will go to Bell, and I can't see Italy picking up the tab to carry an X2 aircraft to production in that scenario, either.

How do you know it will go to Bell?

 

[e-Graphite]

Because Sikorsky's Raider-X is a rigid coaxial rotor configuration and those essentially don't work. There's no evidence the fundamental problems plaguing Raider and Defiant are fixed and there's no field history for this configuration. It's high risk without a substantial performance benefit over the Bell for the Army mission described. The weapons deployment scheme frankly looks ridiculous. There's no successful X-2 demonstrator that met all its engineering and performance goals to base a production model off of.

My money is on Raider-X being the last X-2 aircraft that flies for a few generations... and it'll end up as a dusty hulk in a museum somewhere.

If FARA survives Congress and Boeing, we'll get a new attack/recon helicopter with a single main rotor and a lift sharing wing.

 

[VTOLicious]

I totally accept your personal opinion. However, it is just that. "rigid coaxial configurations essentially don't work" is a bit of a bold statement btw.

 

[e-Graphite]

Or... it's a deeply informed opinion utilizing all available evidence and theoretical knowledge.

 

[sferrin]

Or... it's a deeply informed opinion utilizing all available evidence and theoretical knowledge.

You know more than Sikorsky and Lockheed? Really?

 

[zevets]

Or... it's a deeply informed opinion utilizing all available evidence and theoretical knowledge.

You know more than Sikorsky and Lockheed? Really?

judging by the brain drain at Sikorsky, he may know exactly as much as them

 

[yasotay]

Or... it's a deeply informed opinion utilizing all available evidence and theoretical knowledge.

You know more than Sikorsky and Lockheed? Really?

judging by the brain drain at Sikorsky, he may know exactly as much as them

Not surprising, Bell has established a facility in Pennsylvania to look at advanced technologies and has advertised in Philadelphia and Connecticut.

 

[VTOLicious]

For the record:
There is not a single word in the GAO report that would indicate something in the likes of "rigid coaxial configurations essentially don't work".
It's all about the functional architecture, or rather the lack of detail of it:


It's puzzling how they could mess up so bad in this regard. Allocation and decomposition of functions is an elementary engineering discipline. I really don't get it.

 

[red admiral]

It's all about the functional architecture, or rather the lack of detail of it:
It's puzzling how they could mess up so bad in this regard. Allocation and decomposition of functions is an elementary engineering discipline. I really don't get it.

You've also got the OMS lead saying that they made it so simple that they got a tennyear to explain it. For me, it just points towards it not being a mistake and instead being a Sikorsky business decision to ignore OMS compliance (in order to secure vendor lock in and future income) which has bitten them. Its nothing to do with technical merits of one configuration or the other.

 

[MihoshiK]

It's all about the functional architecture, or rather the lack of detail of it:
It's puzzling how they could mess up so bad in this regard. Allocation and decomposition of functions is an elementary engineering discipline. I really don't get it.

You've also got the OMS lead saying that they made it so simple that they got a tennyear to explain it. For me, it just points towards it not being a mistake and instead being a Sikorsky business decision to ignore OMS compliance (in order to secure vendor lock in and future income) which has bitten them. Its nothing to do with technical merits of one configuration or the other.

Sounds to me like the Army carefully circumvented the whole mess of whether or not the rigid coaxial rotor actually worked, and found a ready made excuse in the non-compliance in other fields.
Which, to be fair, were apparently quite serious.

Mind you, this might be because if they'd said that the rigid coaxial rotor didn't work, they might also have instigated trouble with the FARA bids: Maybe the concept works on a smaller scale, but if they disqualified Sikorsky because of the failure of the RCR concept in the large unit, it could easily give Bell a nice reason to protest if they lose the FARA bid.
After all, RCR craft don't work, see the JMR results!

 

[yasotay]

There are a number of reasons that the U.S. Army would prefer not to question the viability of the coaxial compound concept at this point. First there is an active competition ongoing with the coaxial compound one of the competitors. Second, pointing out that one of the platforms is not tenable in an already contentious program is not good for maintaining the program. Third, the U.S. Army might really want coaxial compound as it is more technologically challenging, and Congress prefers to through money at fancy new aviation technology.
I would remind all that 50% of the coaxial compound that Sikorsky has flown, have had rotor intermeshing issues (fortunately while at a hover). All have shown excessive vibration at the higher speeds. High speed being the reason to do the unconventional rotor technology in the first place.

 

[e-Graphite]

There are a number of reasons that the U.S. Army would prefer not to question the viability of the coaxial compound concept at this point. First there is an active competition ongoing with the coaxial compound one of the competitors. Second, pointing out that one of the platforms is not tenable in an already contentious program is not good for maintaining the program. Third, the U.S. Army might really want coaxial compound as it is more technologically challenging, and Congress prefers to through money at fancy new aviation technology.
I would remind all that 50% of the coaxial compound that Sikorsky has flown, have had rotor intermeshing issues (fortunately while at a hover). All have shown excessive vibration at the higher speeds. High speed being the reason to do the unconventional rotor technology in the first place.

I can only think of one intermeshing incident while in the air. The S-97 Raider's control laws fumbled the transition between ground and air mode and had the wrong set of control laws active while in the air and intermeshed the rotors while in a hover while suffering massive roll oscillations. The XH-59A had a crash early in flight test due to running out of longitudinal pitch authority. There's a photo of it practically standing on its tail but the rotors don't appear intermeshed. Perhaps they did a few seconds later. The X-2 Technology Demonstrator didn't intermesh rotors and neither did the SB>1 Defiant. So I count 4 Sikorsky X-2 aircraft but only 1 intermesh incident. I'd call it 25%.

Fully agree on the high vibrations at high speed cruise... it's a subject of some hilarity in the industry. Shouldn't just be high speed cruise, either, according to theory.