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Archive for August, 2017

Why variable sweep wings or “swing wings” for fighter aircraft are not effective at air superiority

Posted by altandmain on August 19, 2017

Why not another variable sweep fighter?

There seems to be a lot of F-14 nostalgia around. While it may have had a great deal of impact on how the US Navy conducted fleet defense, we have to consider the effectiveness of the concept of variable sweep aircraft. It is human nature to always want to look up to the past.  The other reason may very well be that people find the F-14 to look visually attractive and want similar proposals.

The reason why we will not see future variable sweep fighters however is because there are very serious drawbacks compared to fixed wing aircraft.

Short Background

Variable sweep wings, known as “Swing wing” evolved as a solution for early jet engines. Experiments were being made as early as WW2 with wings that could change their sweep on the ground, such as the Messerschmitt P.1101.

Back then jet engines produced less thrust because they ran at lower inlet temperatures and were overall more primitive. Wings with a sharp sweep were desired for high top speed, but that left the aircraft vulnerable in dogfights, which as Vietnam revealed still happened, and also led to high take-off and landing speeds. High take off and landing speeds are less safe, which would result in increased number of crashes. They also led to long runways, limiting off  road mobility and making it easier to disable for enemy forces, as there would be a far larger airport to protect.

In Europe, there were two key projects, the Panavia Tornado, which entered service as a mult-role interceptor/bomber, and the Dassault Mirage G, which never entered production. The US would build the F-111, which was a very heavy variable sweep multi-role aircraft. The famous F-14 was derived from the F-111. The USSR made several variable sweep designs, most notably the  Mig-23 and the Su-24.

Bomber designs were also made by the US and USSR. The B1 Lancer from the US, along with the Tu-22 and Tu-160 from the USSR. All 3 bombers remain in service.

What do swing wing aircraft bring?

Their main advantage is that they can use that variable sweep wing to find the optimal wing swing angle (within their sweep limits) for a given airspeed.  This can allow for fuel savings on the climb and landing during a fighter sortie.

On aircraft carriers, they have the advantage of having very low sweep on take-off and very high sweep when bursting with full afterburner. Variable sweep wings can also be folded for compact storage without compromising wing’s structural integrity (as is the case with folding wings like on F-18E).

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On an aircraft carrier, deck-space is always going to be a bottleneck. While a carrier may look very large to an untrained eye, deck space is always at a very big premium.

So why not on fighter aircraft?

To achieve variable sweep aircraft, that requires a large gearbox in the fuselage of the aircraft. This gearbox adds a great deal of mass and makes the fuselage larger, causing drag. This means that fuel fraction on such aircraft is lowered a great deal.

In a dogfight, this heavy gearbox would mean that compared to a fixed wing, it would result in an unfavorable thrust to drag, even if the pilot could switch to what they felt was the optimal sweep right before combat. Switching the wing sweep during a dogfight would be risky, as it could cause a loss of energy.

This would mean:

  1. Higher wing loading due to mass of gearbox
  2. Faster fuel consumption due to gearbox
  3. Lower transient performance (very important in a dogfight)

This gearbox would also lead to lower G limits as well. On the F-14D, the symmetric limit at 50,000 lbs was 6.5G. The F-16  and F-15 were both capable of 9G. Navalized versions of the F-18 were capable of 7.5G, while certain land based variants of the F-18 could also perform 9G. For a comparison, Dassault Rafale can do 11G, with an ultimate limit of 16.5G.

The gearbox lowered the aircraft’s fuel fraction. An empty F-14D has a mass of 43,735 lb ( or about 19,838 kg) and can take on 16.200 lb of fuel. This results in a fuel fraction of 0,27, which is below 0,30 fuel fraction required for sufficient combat persistence.

Jet engines have become far more powerful than their 1960s and 1970s counterparts, allowing for much higher thrust to weight ratios. As such, they can achieve lower take distances, even more so on an aircraft carrier with a catapult. This fact somewhat negates swing-wing’s main advantage of high low-speed efficiency.

Modern computer control surfaces too have played a role in rendering variable wing sweep obsolete as they can adjust wing shape and size very rapidly, without the weight penalty.

Complexity and reliability problems

The more complex a system is, the more risk there is for failure.

When the US Navy opted to retire the F-14 in favor of the F-18, a big reason that was given was the appalling flight to maintenance ratio.

The decision to incorporate the Super Hornet and decommission the F-14 is mainly due to high amount of maintenance required to keep the Tomcats operational. On average, an F-14 requires nearly 50 maintenance hours for every flight hour, while the Super Hornet requires five to 10 maintenance hours for every flight hour.

I’ve been told that a newer F-14 would likely require 40 to 1 and on average, the F-18 requires 8 to 1, which is in line with the USN’s claims of 5-10 to 1. So in that regard, the F-18 would be able to generate much higher sortie rates. Keep in mind that the 50 to 1 is with after  the General Electric F110 engines were put on the F-14. Early F-14s suffered from an unreliable TF-30 engine that was prone to flame-outs.

Compounding the problem, the  high flight to maintenance ratios mean that there’s a good chance you will not have enough F-14s available when you need them the most (ex: if an enemy launches a surprise attack on your carrier battle group, you may need to scramble the aircraft very quickly).

There were other points of failure. Sometimes when one side of the gearbox worked properly and the other did not, it could lead to an “asymmetric wing sweep”.

f-14-asymmetricWhile the aircraft could fly in such a situation and land with some difficulty, this leaves a point of failure. This could also be a weakness in combat, as the hydraulics could be damaged.

Much like this F-14, under Australian service, the F-111 did encounter a similar incident, and the B1 did once as well. I suspect that under Warsaw Pact service, Soviet variable sweep designs may have too.

Conclusions

The cons simply outweigh the pros when it comes to variable wing sweep. There are very significant penalties in terms of mass, cost, and complexity for variable sweep wings. While they may bring some advantages in the take-off and can have the “optimal” sweep for each scenario, the drawbacks outweigh these to the point where we are not seeing variable wing sweep aircraft on modern aircraft.

They are simply a dead end as far as aircraft design goes. While they may have seemed like a good idea on paper, when implemented in combat aircraft, they carried significant drawbacks that outweighed any advantages they brought.

 

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Posted in technology, weapons | Tagged: , , , , | 15 Comments »

Opposing Views: Debating The F-35’s Strengths And Weaknesses

Posted by Picard578 on August 17, 2017

Aug 8, 2017Aviation Week & Space Technology

F-35, in Black and White

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Podcast: F-35 in the Crossfire, Part 1

It is hard to find a more divisive topic in the aerospace world than the Lockheed Martin F-35. Aviation Week Pentagon Editor Lara Seligman sat down with two industry veterans who hold opposite views on the fighter: Marine Corps Lt. Col. (ret.) Dave Berke, a former Top Gun instructor, has flown the F-35, F-22F-16 and F-18; and Pierre Sprey, of “Fighter Mafia” fame, helped conceptualize designs for the A-10 and F-16. Excerpts follow. Listen to their debate in full at AviationWeek.com/check6

Seligman: Lockheed Martin and U.S. Air Force pilots contend that the maneuvers we saw at the Paris Air Show laid to rest the rumors that the F-35 can’t dogfight. Pierre, do you think that’s true?

Sprey: That was nonsense, just marketing hype. The demo was as phony as all the other [air show] demos are. They had a super-light F-35, and the performance wasn’t all that impressive. I talked to a guy who prepped an A-10 for the air show, and they did the same thing—they [made] it so light it actually looked super maneuverable, which it’s not, except at low speed. The F-35’s turn rate was not impressive. It was [much] slower than a 30-year-old F-16. An engineer friend of mine clocked it at 17 deg. per second. Any old F-16 can do 22 [deg. per second].

KEY QUESTIONS ABOUT THE JOINT STRIKE FIGHTER
Can the F-35 dogfight?

How does the F-35’s ability to communicate in flight change warfare

What are the difficulties of producing F-35—a program that remains in development?

What are the impacts of the F-35’s $406 billion price tag?

Berke: I would not disagree. Air show demos are exactly that, a demonstration. I think part of the reason this demo got so much publicity is there has been a long-held misunderstanding of what the airplane can do in the visual arena. People have made claims that it’s incapable of dogfighting and things like that. It is a highly capable, highly maneuverable airplane, like everybody who has ever flown it understands.

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Pierre Sprey helped to conceive the design of the F-16 and A-10 fighters. Credit: James Stevenson

Sprey: The airplane that flew at Paris was totally incapable of combat. And that’s not just me talking; that’s the operational testers of the Air Force, Navy and the Marines. In their assessment, the configuration that was flying in Paris, to go to war, would need an escort to protect it against enemy fighters. It would need extra help to find targets, particularly air-to-ground threats.

How does the F-35’s networking capability change the game for warfare?

Berke: I can’t think of any airplane that we’re flying today that would want to get into a dogfight. I would avoid that in any platform. F-22 pilots don’t fly around looking for dogfights. Part of the reason why the F-35 and the F-22 have such a massive advantage over legacy platforms is their ability to make really intelligent decisions. You’re getting information presented to you on a much larger scale, and it’s fused more intelligently.

All my career, I’ve flown fighters, and flown them in combat, and I was a forward air controller. It’s all about making an intelligent decision as soon as you can. It is really difficult for me to overstate what a massive advantage you have in decision-making in the F-35. I don’t know a single pilot—and I know a lot of F-35 pilots—that would even consider taking a legacy platform into combat. The F-35 advantage over these platforms is infinitely greater.

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When he was an active duty Marine, Lt. Col. (ret.) David Berke flew the F-35B, F-22, F-18 and F-16. Credit: U.S. Marine Corps

Sprey: The original marketing hype, both out of the services and Lockheed Martin, was always “It’s a great dogfighter; it’s a great close-support platform.” In truth it can’t do any of those missions very well because, like all multimission airplanes it’s highly flawed, and the technical execution of this airplane is unusually bad by historical standards. I agree with [Lt.] Col. Berke that no airplane looks for a dogfight. On the other hand, in serious wars sometimes you can’t avoid it. The F-35 is a horrible target if it has to get into a dogfight. It’s got an enormously high wing load. It’s almost as unmaneuverable as the infamous F-104. 

All that networking stuff, if it worked, would make the pilot smarter and more situationally aware. But right now it is an impediment, and it might be a permanent impediment given the cyber [threat], which is horrible for this airplane. All that reliance on networking is giving inferior, less well-funded, less equipped enemies a tremendous opportunity, because the airplane is so vulnerable to all kinds of cybermeddling. The people we might face—Chinese, Russians, Yugoslavs, whomever—are all pretty clever with computers. We’ve given them a tremendous opportunity to wreck our airpower for almost no money.

Berke: I would disagree with virtually all of that. The idea that there are things wrong with the airplane is 100% true, but the idea [that] does not work is 100% not true. To fuse broadband multispectral information, [radio frequency], electro-optical infrared, laser infrared and laser energies among several cockpits, ground users and sea-based platforms is really complicated stuff. And so there are things wrong with the airplane. I don’t know a single [F-35] pilot that would deny that. But the idea that you would read some sort of report on the airplane’s performance and then draw the conclusion that it is broken forever is a leap. We inside the community haven’t done a good job of explaining how amazing the airplane is.

You could bring 100 people into this room and ask what warfare is going to look like in 30 years, and you’re going to get 100 different answers. If I hear somebody talking about dogfighting, that person is not thinking about the future. And if I hear somebody say “wing loading,” that’s a red flag that you are thinking about the wrong things. Among every Marine, Air Force and Navy [F-35] pilot I know who came from a legacy aircraft—Hornets, F-15s, F-16s—there is no debate about what is the most capable aircraft they’ve ever flown and what they would take into combat tomorrow.

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“If you bought F-16s at the same budget, you’d be able to buy five times more airplanes.” —Pierre Sprey. Credit: Lockheed Martin Photos

What are the difficulties posed by what is known as concurrency—the process of producing F-35s and testing them before system development is complete?

Sprey: The testing that has taken place so far is very benign. It’s engineering testing—there has not been any rough testing yet—and the airplane has performed very badly on a whole score of issuesThey’re not flying against any stressful scenarios for the simple reason that the Joint Program Office is sabotaging the operational tests, and this is very deliberate. Because if you fail, the [program] might be canceled. 

I have mixed feelings about pilots being so enthusiastic about their airplanes. It is very common now, because the services are so wound up with procurement, and people critical of their equipment tend to have shorter careers. I think you want to be skeptical about everything you work with. You don’t want to be a true believer going into combat and wind up hanging from a parachute, or dead.

Berke: The idea that any professional uniformed officer, let alone a fighter pilot, would somehow find themselves unprepared for the horrors of combat because they were illusively in love with their equipment is preposterous. I’ve [been] a Top Gun instructor, and we would spend 8 hr. debriefing a flight. All you do is talk about things you did wrong, your strengths, your weaknesses, how to mitigate one and play to the others. If you are going to ask a fighter pilot who has done operational testing what their opinion is, the idea that even one shred of what they say is a party-line answer would be offensive. I’ve spent 23 years as a U.S. Marine, and never once did I get the implication that I shouldn’t be completely honest with my evaluation.

The F-35 has good and bad things about it. In the operational test world, we are focused on making the airplanes better. We spend our time on a laundry list of things that need to be improved. When every single pilot that has taken the airplanes into highly complex [exercises] at Red Flag and at places like Nellis [AFB, Nevada,] comes back with overwhelming dominance, it’s difficult not to be really supportive. So if you hear pilots saying the F-35 is awesome, it’s not a sales pitch. It’s steeped in a long history of flying several different airplanes in different environments.

F-35 procurement costs have come down in the last couple of years, but this year they ticked up slightly to $406 billion from about $380 billion.

Sprey: Cost is part of what force you can bring to bear. To create airpower, you have to be able to put a bunch of airplanes in the sky over the enemy. You can’t do it with a tiny handful, even if they are unbelievably good. You send six airplanes to China, they could care less about what they are. F-22 deployments are now six airplanes, and that’s because of the cost. Force is a function of cost and how reliable the airplane is, how often it flies per day.

If you bought F-16s at the same budget, $400 billion, instead of F-35s, you’d be able to buy five times more airplanes. It is five times as expensive and flies at best half as often. My feeling is it will fly less often than an F-22—it is a good deal more complicated than an F-22, and it’s showing that right now. If that’s the case, it may fly once every five days, in which case if will fly one-fifth as often as the F-16.

Berke: I don’t care how cheap the airplane is; if you can’t fly it in combat, it is useless. We are inventing technology that didn’t exist before, and it’s all driven toward the idea of being relevant in a highly complex, 3D battlespace that we have a hard time predicting even for the next 15 years. I don’t want to buy a car that’s cheaper and then have that car not be drivable in three years. The fact is the Chinese [are developing] fifth-generation airplanes. They are building and buying [them] right now, and that’s going to make air warfare complicated. [The F-35 is] too expensive? That’s easy to say. Compared to what? Losing a war in 15 years? Or compared to an F-16 in 1977? Make sure you get that frame of reference right, because it is really important.


NOTES: F-35 is unmaneuverable POS, and it is true that often, you simply cannot avoid a dogfight. It is also true that air show demos are done with only light fuel load. As for F-35s vaunted networking abilities, it is a complex system, and complex systems in a war are prone to failure. You simply have to have a backup, which means dogfighting capability. Even F-22 was designed to be able to dogfight. F-35 was not designed for dogfight because it is a ground attack platform, it was only pushed into air-to-air role after F-22 couldn’t be procured in large enough numbers. And networking is a danger as much as an opportunity.

Berke is talking about the future, but how can you know the future if you don’t know the past? That future they are talking about is based on the performance of BVR missiles against Iraqis and Yugoslavs, first of whom were incompetent fools all across the board, and latter who were also undertrained and flying literal flying bricks (aircraft had no radar, no MAWS, no RWR, no ECM… real representative of peer threats). Sensor fusion is important, but wing loading is also important… even in BVR combat, you need to be able to maneuver. Wing loading matters for turn rate, for climb rate, and both are still quite important. And F-35 may be more capable than “teens”, but those are not its competitors.

Equipment is important, and equipment that doesn’t work is useless. And in war, you have to have reliable equipment. What is more important is that complex equipment often leaves more avenues open for it to be countered. Berke talks about F-35s performance in air combat, but does not mention its survivability on the ground. And that is possibly F-35s biggest Achilles heel.

Posted in weapons | Tagged: , , , | 10 Comments »

ISIS fighters given houses and jobs as part of “hug a jihadi” campaign

Posted by Picard578 on August 13, 2017

Police in the city of Aarhus, Denmark, has introduced the scheme in which ISIS fighters returning from Syria are being offered apartments, education and jobs to reintegrate the radicalised back into society. Scheme was introduced after 19 youths had returned home, out of 36 who had travelled to Syria to fight for ISIS. proponents of the police-run scheme in Aarhus say that jihadists are “isolated” and struggling to integrate, and claim that offering them kindness and forgiveness will deter them from their murderous ideology. Superintendent Allan Aarslev claimed that “From my point of view it would be much more safe for the local community here to help these young men to have a normal life after they have returned than to leave them alone.”, and “If we did not integrate them into the local community again they would be a safety hazard for us.” He failed to explain why should they be allowed to return in the first place.

The program however was criticized for de facto rewarding jihadists for their activities. Naser Khadeer, a Muslim member of the Conservative People’s party, called for a hardline approach to foreign fighters. Speaking on the Australian news programme Dateline, he said: “What I have criticised when it comes to the Aarhus model is when you have been in Syria and you come back, it is wrong in my opinion to reward whoever has been in Syria by giving them an apartment, jobs, education. We should prosecute them not reward them.”. Jihadis are much more likely to see the program for what it is – a sign of weakness – than to appreciate it as a goodwill gesture. Dr. James Mitchell had called a program extremely naive. “I want you to imagine Rob O’Neill, the guy who shot bin Laden, kicking open the door in his compound, and he’s armed with warm cookies and a ‘Let’s Cuddle’ t-shirt. And he goes, ‘Get on over here, you rascal. I got lots of hugs for you,'” Mitchell said on “Fox & Friends” this morning. “It’s a ridiculous idea.”

At the same time, a Danish student, Joanna Palani, was shunned for fighting against ISIS after she returned to Denmark. Since returning to Denmark she said she had been forced into hiding and claimed she was “seen as a terrorist”. Ms Palani told MailOnline: “I was willing to give up my life and my freedom to stop ISIS advancing, so that everyone in Europe can be safe. This was my choice.” “But I am seen as a terrorist by my own country.” She added: “I live in one of the best countries in the world but I am hungry and homeless and freezing cold in bed at night, even though I am working full time.” “I don’t trust anyone.” Joanna Palani was handed a 12-month travel ban to prevent her from travelling back to the conflict zone in September 2015 and was threatened with jail when she flew to Qatar. Other Danes who had gone to fight against ISIS had been threatened with jail on their return from Syria.

Posted in news, security | Tagged: , , , , | 9 Comments »

Israel: The World’s Most Moral Army

Posted by Picard578 on August 1, 2017

Posted in politics, security | Tagged: , , , , , | 8 Comments »

 
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