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As of late, there have been attempts to question the value of stealth

Posted by altandmain on November 27, 2019

An article was recently posted that was quite an improvement over the typical articles that we see in the mainstream media. Although I may not agree with all of the assertions here, the article was well written.

https://nationalinterest.org/blog/buzz/how-good-stealth-f-22-and-f-35-anyway-82791

Let’s go through some of the key points in greater detail.

While virtually any plane can be equipped to fire long-range missiles, stealth airframes are built using radar-absorbent materials and engineered precisely to minimize reflection of radar waves. This constrains their load-carrying abilities, as external weapons or drop tanks could increase their visibility on radar. The United States fields two stealth fighters, the F-22 Raptor and the F-35 Lightning II.

There seems to be an attempt here to make a serious discussion about the trade-offs of stealth technology.

 

Stealth aircraft are optimized to be difficult to observe on the precise X-Band radars used on modern fighters: while some radars have better resolutions than others, most will only be able to track a stealth fighter at shorter distances. An F-22 is claimed to have the radar cross section of 0.0001 square meters in certain aspect—the same as that of a marble.

Low-bandwidth radars are more effective at detecting stealth aircraft. These are typically used by ground installations and ships, but also found on specialized aerial platforms such as the E-2D. However, they come with a major limitation: they can reveal only the general location of a stealth fighter and are too imprecise to be used to target missiles—though they can indicate to an X-Band radar where to look.

Infra-Red Search-and Track (IRST) systems offer another means of detecting stealth aircraft, but their range is generally limited. The latest IRST system on the SU-35 has extended the range up to 50 kilometers, whereas its radar has detection range of up to 200 kilometers. Just like low-band radar, IRST doesn’t give a precise track and can’t be used to lock on weapons. Stealth fighters include features designed to minimize heat signature, but they are far from completely effective.

Of course, a stealth fighter can be seen within visual range, and is vulnerable to heat-seeking missiles.

 

I’m glad to be seeing a serious discussion about how stealth can be possibly defeated.

One factor that is difficult to calculate is how likely long-range missiles are to hit. Extrapolating from past usage of radar-guided missiles is problematic, both because missile technology has advanced considerably since its inception (early radar-guided Sparrow missiles had a less than 10 percent kill probability in the Vietnam War), and the conflicts in which radar-guided missiles have been more successful (Arab-Israeli conflicts, the Gulf War) involved poorly trained opponents lacking effective countermeasures.

It’s safe to say that long-range missiles will have lower hit rates than short-range missiles like the AIM-9 Sidewinder and the Russian R-73—modern versions of which have chalked up a roughly seventy percent probability of kill.

One of the recurring themes that Picard has always emphasized is that BVR radar guided air missiles are not going to have the kill ratios that they had in simulations.

This is also why shorter range IR missiles and guns are going to remain relevant today.

 

But referring back to the Battle of Britain can reveal a limitation of this strategy. The British hit-and-run attacks succeeded in inflicting deadly attrition on German bombers over time until they were forced to call off the air offensive. But they rarely prevented the German formations from hitting their targets. The German simply had too many aircraft.

At first, this was a problem: the Germans relentlessly pounded British airfields, degrading the Royal Air Force’s ability to fight in the air. But then the Germans switched to bombing civilian targets in London. While this inflicted many civilian casualties, the raids did not degrade the RAF’s ability to fight back. The British fighters could sustain their advantageous rate of attrition versus the German Luftwaffe until the latter was forced to tap out.

 

One thing I do like is that the author of this article is very well versed in aviation history.

 

Let’s consider what would happen when American fighters encounter a much larger force of fighters based on the coast. The American fighters could fire their long-range AIM-120D missiles from more than one hundred kilometers away—four from each F-35 and six on the F-22. Soaring at Mach 4—twice the maximum speed of the aircraft that launched it—an AIM-120 can traverse eighty kilometers in one minute.

The radar-warning receivers on their targets would light up as they detect the incoming attack. The further away the target, the more time it has to evade the missile. Therefore, BVR missiles may be fired at well below their maximum range to ensure a higher probability of a kill, particularly when engaging maneuverable fighter aircraft.

 

Presumably in this case, the author is referring to China.

One thing the author does not discuss is that a stealth heavy fleet means lower numbers. It means higher acquisition costs per plane, higher costs per hour of flight, and higher flight to maintenance ratios, which means less aircraft for a given amount of money.

 

What if the U.S. fighters close to short range after expending their long-range armaments, rather than prudently disengaging? If both sides are closing upon each other at maximum speed at high altitude, the distance between them would diminish at a rate of 60-80 kilometers a minute. Even if the AIM-120s were fired at maximum range, the opposing aircraft could close that distance in one or two minutes.

In short-range engagements, surprise, pilot training and flight performance will determine the victor.

The F-22 is a superb dogfighter. The F-35…not so much, though ithas its defenders. Both aircraft can carry two Sidewinder missiles and fire shells from their onboard cannons.

 

While I question the F-22’s value as a dogfighter, the author does have a very important point. Training, surprise, and flight performance will be decisive factors. One problem with stealth fighters in that regard is that pilots will have to spend more time in simulators rather than real world aircraft.  The higher costs per flight hour force this.

 

Why? The hostile aircraft didn’t have trouble detecting the tankers supporting the U.S. forces. Unlike the F-22s and F-35s, tankers have neither the speed nor stealth to evade a determined attack.

If the tankers get shot down, it doesn’t just force the U.S. fighters to abandon the fight. It could force them to crash into the ocean, without enough fuel to make it back to base. In effect, a tanker would be a high-value target that U.S. air-superiority fighters would need to defend to the last.

A similar problem exists while defending an aircraft carrier from attack. Unlike the resilient city of London in the Battle of Britain, a carrier is a vulnerable and militarily consequential target that must be defended at all costs. A lost carrier consigns its fighters to the ocean as well.

A final consideration is that opponents may field limited number of their own stealth fighters, such as the J-20 or the Sukhoi T-50. Even a small number of stealth fighters would be effective at sneaking into the range of the tankers and AWACs aircraft and taking them out before the U.S. aircraft could evade or retaliate. Very long-range missiles such as the R-37 and the PL-13 could also assist in the anti-tanker mission.

 

First, one concern is that there is a trade-off between stealth and aerodynamics. The second is that the tankers and AWACs are themselves not stealthy. Making tankers stealth would be costly and mean less money for fighter aircraft.

AWACs simply cannot be made stealthy. It will remain vulnerable to anti-radiation missiles.

 

Already, many theorists believe that carriers would be forced to remain far away from hostile shores. The survivability of airbases in the event of a mass surface-to-surface missile attack is also open to question. One possibility is that no large-scale air battles would materialize.

The two key limitations are logistical: lack of internal fuel to operate without support, and insufficient missiles to tackle superior numbers. For the time being, there is no obvious fix to the fuel problem: the latest U.S. fighters, the F-22 and F-35, are simply going to depend on tankers. Some suggest that the Navy should deploy light-weight low-observable drones from carriers that could potentially operate further afield.

 

In the case of aircraft carriers,  submarines might also prove to be a threat. So might land fired anti-shipping missiles.

Another issue is that rough field operation is a big deal for modern war – fixed airbases provide fixed targets for enemy forces.

 

The U.S. military is a big proponent of networked warfare. In theory, if one airplane detects an enemy, it could pass on that data to friendly ships and aircraft—and through Cooperative Engagement Ability, even potentially allow those friendlies to shoot at that target from far away. One potential tactic is to use a vanguard of stealthy fighters to identify incoming enemy aircraft and send targeting data to ships or non-stealth fighters, which can carry heavier weapons loads. The F-35’s excellent sensors and datalinks could make it effective in this role.

There is even an idea being kicked around to mount large numbers of missiles on a B-1 or B-52, which would be fired off hundreds of kilometers away from the battle. Of course, such an “arsenal plane” would be vulnerable if enemy fighters broke through the accompanying line of F-22s and F-35s. The tactic would likely require even longer-range missiles than the U.S. currently employs.

 

I’m not at all convinced this would work – keep in mind that an aircraft that is stealthy would have to transmit to the friendly aircraft information. That may be detected and it may be possible to reveal the locations of enemy aircraft.

Longer range missiles are likely to have an even lower probability of kill ratio, except against targets that don’t have the agility to defeat them.

 

Concluding thoughts

While I may not agree with all of the points in this article, I am happy to see someone who is asking questions about the limitations of stealth.

It is certainly an improvement over the fawning, and often uncritical coverage that stealth aircraft have received.

 

Posted in technology | Tagged: , | 2 Comments »

The F-35 will not be flying on aircraft carriers in the near future, which is a major blow to the program

Posted by altandmain on June 8, 2019

Recently, an article was published with the site “War is Boring”, about how the F-35 may be many years away from serious carrier operations.

It could be another decade before Ford-class carriers are able to launch F-35C jets

This is a very significant blow to the program. The whole justification of the F-35 program was inter-service platform sharing and the resulting cost savings that this would result in. Without this aircraft having a functional naval variant, one of the big justifications for the program is in serious jeopardy.

This comes on top of the Ford class of aircraft carriers, which has been experiencing issues with its  Electromagnetic Launch System (EMALS) and  Advanced Arresting Gear (AAG) systems, which means that the aircraft carrier cannot do the basic functions of launching and recovering aircraft. These are not, by the way the only problems the carrier is facing. It is also facing issues with its elevators. In addition, the nuclear propulsion system is also facing difficulties. These appear to be significantly worse than what problems are “normally” expected in a first of class vessel.

On top of these issues are the other ongoing issues with the F-35, which the Ford class is going to carry. These have resulted in a very poor rate of combat readiness for the aircraft and the General Accountability Office has raised concerns about the situation. Here as well is an older DOT&E report. If you go through the report, there are a number of problems that it uncovered worthy of an article it and of itself.

It  should be noted that the F-35C, the naval version is not the only aircraft with problems. The GAO and DOT&E reports cover some of this, but to put things into perspective, it is believed that the F-35B may only have a service lifetime of a little more than 2000 hours due to structural problems.

While it is very possible to have an aircraft that can serve both on land and for naval applications (indeed Picard here has proposals for that involved navalized versions of all of his aircraft), the F-35 is unlikely to realize any cost savings from the approach they have taken, which actually don’t share that many parts between the aircraft.

Going back to the original story, this problem with the F-35C simply not being able to function on aircraft carriers puts into question the whole (increasingly shaky) justification for the program.  It may very well be the proverbial straw that breaks the camel’s back, so to speak. Not only are the aircraft and the aircraft carrier deeply flawed, but the F-35C simply may not be able to work on aircraft carriers anytime soon.

If these different versions of the F-35 cannot deliver their promised capabilities, then the whole justification for the F-35 program begins to fall apart. I think that it is time to evaluate whether or not the program is truly worth and if not, well in a situation like this, the sunk cost fallacy comes into play. Committing additional resources for a failing program like this is totally counterproductive.

Posted in Uncategorized | Leave a Comment »

Another consequence of very high flight to maintenance ratios in aircraft – vulnerability to disasters

Posted by altandmain on October 15, 2018

This article discusses how flight to maintenance ratios can leave air forces exposed to the unexpected, including natural disasters.

A high flight to maintenance ratio is one of the big issues in fighter aircraft that are complex. It is often an issue that does not go acknowledged during the procurement stage of military spending, but has immense consequences. Lower is better in this case, because it means less maintenance is needed per hour of flight.

Flight to maintenance ratio, roughly means that for every hour of flight, how many man maintenance hours does one need on average to keep the aircraft operational? A high flight to maintenance ratio means that more man hours are needed for every hour of flight.

The B2 stealth bomber, for example has the worst flight to maintenance ratio, and as a result seldom flies.

Hurricanes and other losses

Recently, a hurricane struck the United States. What occurred is that the hurricane, Hurricane Michael, took a sudden turn that was not expected and changed course towards the Florida Panhandle, where Tyndall Air Base is located. Tyndall Air Force Base is a major US Air Force base, where many F-22 stealth fighters are stationed.

There were 55 F-22 aircraft stationed there, but only 33 were moved out and the status of the remaining 22 are not known. It would seem that some were destroyed by the hurricane.

It is likely based on the comments that the USAF could simply not evacuate them quickly enough.

Air Force officials have not disclosed the whereabouts of the remaining 22 planes, other than to say that a number of aircraft were left at the base because of maintenance or safety reasons.

An Air Force spokeswoman, Maj. Malinda Singleton, would not confirm that any of the aircraft left behind were F-22s.

But photos and video from the wreckage of the base showed the distinctive contours of the F-22’s squared tail fins and angled vertical stabilizers amid a jumble of rubble in the base’s largest building, Hangar 5. Another photo shows the distinctive jet in a smaller hangar that had its doors and a wall ripped off by wind.

All of the hangars at the base were damaged, Major Singleton said Friday. “We anticipate the aircraft parked inside may be damaged as well,” she said, “but we won’t know the extent until our crews can safely enter those hangars and make an assessment.”

It is likely based on the comments that the USAF could simply not evacuate them quickly enough. The extent of the damage, if you read the full article, is not yet known, but appears to be extremely extensive.

The reason why aircraft like the F-22 are going to be affected by this is because stealth aircraft have a set of unique characteristics that make them vulnerable:

  1. A very high flight to maintenance ratio means that they simply cannot take off quickly enough. They are down for maintenance when they need to move most urgently.
  2. There are fewer of them (since there are less than 200 F-22s due to the costs to manufacture them and because the program was terminated early), so any losses will be a larger percentage of total fleet losses.
  3. Where they can evacuate to is limited. Stealth aircraft like the F-22 or B2 need special climate controlled hangars and have a lengthy supply chain.
  4. The sheer complexity means that there will be unexpected downtown of these aircraft. From the article below:

The high-tech F-22 is notoriously finicky and not always flight-worthy. An Air Force report this year found that on average, only about 49 percent of F-22s were mission ready at any given time — the lowest rate of any fighter in the Air Force. The total value of the 22 fighters that may remain at Tyndall is about $7.5 billion.

This is inherently exposed in not just a war against a competent enemy, but also in peacetime against natural disasters.

A brutal reality of this world is that disasters that occur suddenly will happen. Whether they be hurricane/typhoons, tornadoes, earthquakes, fires, or any other disaster, a smaller fleet with a high flight to maintenance ratio means that the entire fleet of aircraft is far more vulnerable to being caught by surprise by these events.

The F-35 would also be affected

The F-35 JSF is significant in that it will be replacing the majority of aircraft in not just the USAF fleet, but also several NATO allies.

The F-35 also suffers from a high flight to maintenance ratio.

Four years into their operational career, F-35 fighters are expected to require between 41.75 and 50.1 maintenance man-hours (MMH) per flight hours, or about three times as many as most fighter aircraft currently operated by Western air forces.

Considering both the F-35 and F-22 are in this situation, this will leave the fleets of Western air forces far more vulnerable, not just to enemies in a war, but also to natural disasters and other unexpected events.

What would be the solution?

The solution is to procure cheaper aircraft (so that more aircraft can be procured and losses would be a small percentage of the fleet). These aircraft would be more widely dispersed, so that they are harder to destroy, either by an enemy, or in this case by a natural disaster.

Picard’s FLX proposals are a good step forward to protecting the Western air forces against losses like this one.

The existing aircraft would be retired. This is not without historical precedent. The F-14 was retired in part due to its unfavorable 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.

Not only does a more complex aircraft mean fewer aircraft due to the expensive unit costs, but it also means fewer sorties per aircraft because they will be down for maintenance. This is on top of the greater vulnerability to natural disasters.

A historical perspective

Natural disasters, in the history of war, have played a key role in swinging the outcomes of many wars in the past. It would be extremely inadvisable to think that modern armies are immune to the effects of unexpected natural disasters and other weather events.

Furthermore, if we consider the effects of a natural disaster on these aircraft, what could the effects of a surprise attack be from a competent enemy? With so few aircraft concentrated in a handful of bases, and with such a high flight to maintenance ratio, the losses could be quite bad indeed. These aircraft would be in known locations on the ground. Forget for a moment about being radar stealthy in the air and worry about being exposed on the ground. Prudence would demand that we reduce our vulnerability to such events.

In a way, the OODA loop is much slower with these aircraft. Since it takes so long to maintain each aircraft, the ability for an air for with a large percentage of its total aircraft with high flight to maintenance ratios to react to a changing battlefield. It would take more time for example, for intelligence to be relayed and then a sortie generated in response to that intelligence. There are fewer aircraft, concentrated in a handful of locations, and they need more time before going to a sortie to prepare.

Clearly the solution is to procure more aircraft that are less complex, cheaper, and easier to maintain. This will not only mean fewer losses due to unexpected events, but also a much faster OODA loop.

This is an extremely costly lesson to learn, but fortunately one that was learned in peacetime and not in a war.

On a final note, I wish the best of luck to everyone affected by Hurricane Michael.

 

Posted in weapons | Tagged: , , | 2 Comments »

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.

 

Posted in technology, weapons | Tagged: , , , , | 18 Comments »

 
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