Wednesday, September 6, 2017

Combat Radius

So many discussions about aircraft include mention and claims about range.  Unfortunately, range is a very imprecise concept and range numbers are highly variable.  There’s an old saying in statistics that you can make the numbers say anything you want.  The same is true in discussions of range - you can get any range number you want by playing with the conditions. 

Let’s look a bit closer at the concept of range by looking at the specific example of an F-18E/F Super Hornet (SH).  In a recent post, a SH range figure was quoted and I expressed doubt and stated that it was a very optimistic number.  Let’s see why.

As a general prelude to this discussion, we need to agree on some terms. 

Range is, technically, the distance from one point to another – in other words, a straight line, one-way travel.  Carrier aircraft don’t generally do that.  Instead, they fly out, execute a mission task, and return to the carrier.  So, their “range” is actually a radius.  Thus, their maximum radius is half their maximum range. 

Unfortunately, many people use “range” and “radius” interchangeably.  For the rest of this discussion, we’ll attempt to use “range” as meaning a one-way, straight line travel and radius to mean an out and back trip. 

Now, let’s plunge right in and check the range and radius for the F-18E/F.  From the F-18E/F NATOPS Performance Data Manual, Specific Range Chart Fig. 5-37, Alt = 15,000 ft, Wt = 50,000 lbs, we get the following data.


Using the Optimum Cruise line at the median Drag Index gives

Speed = 456 mph
Fuel Flow = 6500 pph
Specific Range = 0.058 nm per pound of fuel

So, for a SH with a full internal fuel load of 14,400 lbs, that gives a range of (14,400 lbs x 0.058 nm per lb = 835 nm), radius = 417 nm

Calculated alternatively,

Flight time = (14,400 lbs / 6500 lbs/hr = 2.2 hrs)
Flight range = (2.2 hrs x 456 mph = 1003 miles or 872 nm), radius = 501 miles or 436 nm



We see, then, that the combat radius of the SH is about 420 nm at a cruise altitude of 15,000 ft and a weight of 50,000 lbs and using optimum cruise speed.  As a reminder, the recent post quoted the SH range figure as 450 nm.  Well, that’s almost exactly the figure we just calculated so that seems like a reasonable and valid range number, right?  Why did ComNavOps express doubt and claim it was extremely optimistic?

Well, here’s where the discussion breaks down.  The calculated range is for straight line cruising at the specified altitude, speed, and weight but how did the aircraft get to that altitude?  It didn’t just appear there.  It launched from a carrier using maximum thrust which consumes huge amounts of fuel.  It had to climb to altitude which consumes additional fuel over and above that needed to simply cruise.  So, in the real (operational) world, the fuel required to launch and climb to altitude has to be subtracted from the available fuel in our calculations.  How much fuel is that?  I have no idea – 20%, maybe?  A pilot would have to tell us or I would have to dig even deeper into the NATOPS manual.  The point is that the calculation assumes the aircraft starts at altitude and with a full load of fuel which is impossible.  So, the calculated range/radius must be significantly reduced.  That 420 nm radius now becomes 350 nm, maybe?

But wait, there’s more confusion.

The 420 nm radius assumes a straight line, unwavering, constant speed flight.  On a combat mission, aircraft don’t generally fly straight, level, and constant speed.  Typically, a combat mission will involve changes in direction to weave around known dangers (radar sites, enemy bases, etc.) and/or to approach from a direction other than straight on.  So, even if you could fly 420 nm in a straight line, if you throw in several course changes that take you off that straight line, you’ll consume additional fuel which has the effect of shortening the apparent radius. 

Further, on a combat mission the aircraft don’t fly at a constant speed or altitude.  They increase speed, especially near the target when they use fuel gulping maximum power.  They fly at different altitudes.  For example, a mission might consist of a high altitude cruise to the target, a low altitude approach, and a high altitude return cruise.  The altitude changes not only consume additional fuel but change the flight efficiency – lower altitudes are generally less fuel efficient.

So, the actual combat mission flight profile is going to consume additional fuel.  That 350 nm radius now becomes 260 nm, maybe?

Of course, if the aircraft expends ordnance at the target, the aircraft’s weight decreases which improves the fuel efficiency on the return leg.  Also, as fuel is burned, the aircraft becomes lighter, further improving fuel efficiency and that 260 nm radius becomes 290 nm, maybe?

So, we see that combat radius is totally dependent on the specific conditions of the combat mission.  The point is that the published range/radius is generally significantly unrealistic.  Nowhere is this more evident than in discussing the much-hyped and much-lied about F-35.  You know those ranges are works of fiction!

So, is that the end of the discussion?  No, not by a long shot!

The problem is further compounded by actual carrier aircraft operating procedures.  Aircraft don’t actually launch with a full load of fuel, go out, execute their mission, and return, all on one load of fuel.  Instead, the aircraft usually launch with a partial fuel load and top off over the carrier, after launch.  Additionally, they are often partially refueled during the return leg and/or at the carrier for recovery.  Making the issue more complicated is that fact that aircraft don’t usually take off and immediately begin flying straight to the target – they take off and marshal at some point waiting for the rest of the strike package to launch and assemble.  This waiting burns more fuel.  The assembly point may also include a partial refueling. 

So, what does combat radius refer to?  Is it the radius after having launched and refueled and factoring in a return refueling or two?  If so, then the combat radius can be any distance you want just by adding in more refuelings!  When the Navy cites a combat radius of xxx nm, do they mean the radius with the benefit of multiple refuelings because that’s what a typical mission consists of?

Carrier aircraft rarely fly “unrefueled” missions so citing an unrefueled radius is a combination of unrealistic, pointless, meaningless, and confusing.  Yikes!

So how do we usefully compare the combat radius of one aircraft to another?  We intuitively know that aircraft differ in their inherent “range” but how do we compare the differences?  Well, for practical purposes, we can’t.  About the best we can do is get our hands on flight manuals and extract specific range numbers (nm miles per pound of fuel) under a specific set of conditions.  This will give us directly comparable fuel efficiency numbers which will reveal which aircraft is more fuel efficient and from that we can infer, and calculate, actual combat radii.  But, even that isn’t the end of the story.

Different aircraft fly different types of missions.  An air superiority fighter flies a different mission and flight profile than a strike aircraft so trying to compare combat radius at a single, arbitrary set of conditions is pointless and unrealistic. 

Further, different aircraft have different fuel efficiencies under different conditions.  Some aircraft are optimized for lower level flight while others are optimized for higher level flight.  How do we compare those?  Again, we really can’t.  The best we can do is try to compare apples and apples.  We can’t meaningfully compare the combat radius of an A-10 low level close air support plane to the combat radius of a high altitude F-22 air superiority fighter.  We can, however, compare the F-35C to the F-18E if we specify the mission, weapons load, and flight profile – assuming we can get our hands on NATOPS flight data.

What’s the overall conclusion from this discussion aside from the realization that published range/radius values are virtually meaningless?  The conclusion is to assume the published range/radius numbers are maximum and unrealistic values that would only be obtained under unrealistic, non-operational conditions.  If you want an “actual” operational combat radius, take 60% of the published figure and you’ll be somewhere in the realm of an actual combat mission radius.

So, did that clear things up?  Yeah, I didn’t think so but it’s the best we can do.  Hopefully, it will at least allow you to more intelligently discuss combat “range” in the future and more realistically assess published values.

On a related note, this discussion makes the published range/radius values for the SH and F-35 all the more disappointing when compared to the actual Pacific theater requirements.  It also emphasizes the need for an operationally effective tanker.  Above all, though, it clearly points out the need to build aircraft that are inherently longer ranged.  When we're talking about thousand mile A2/AD zones, it quickly becomes obvious that the F-18 and F-35 are both woefully short on their useful combat radii.

38 comments:

  1. One of the most important and powerful ideas I first learned in Acquisition back in 1984 was the idea of an OMP - Operational Mission Profile.

    This forced the user to define what the OMP would be for whatever period of time was pertinent. For Marines we used a 30 day deployment. It forced the user to say I expect to be moving for 10 days, I expect to fight for 5 days and hold a position for the last 10 days.

    This concept forced all of the stakeholders to use the same measure for figuring MBTF, Logistics requirements, manning, etc.

    Heaven forbid that an old Mil-STD concept find use today in defining a Navy Carrier Aircraft mission profile so that everyone can use the same framework to compute: range, radius, cycle time, etc.

    An OMP would solve all of this apples to oranges obfuscation. But that Obfuscation is what allows the money to keep flowing for systems that will not meet our operational requirements.

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    1. You couldn't be more right. This is why I keep harping on Concept of Operations (CONOPS). You have to know how you're going to use something before you can intelligently spec, design, build, and buy it. Tragically, our current system jumps straight into the last step, purchasing, and skips all the vital, preceding steps. This is how we wind up with all the failures we have today.

      You're the voice of experience and wisdom. Great comment.

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  2. "So how do we usefully compare the combat radius of one aircraft to another? We intuitively know that aircraft differ in their inherent “range” but how do we compare the differences? Well, for practical purposes, we can’t. About the best we can do is get our hands on flight manuals and extract specific range numbers (nm miles per pound of fuel) under a specific set of conditions. This will give us directly comparable fuel efficiency numbers which will reveal which aircraft is more fuel efficient and from that we can infer, and calculate, actual combat radii."

    In my experience, "thrust specific fuel consumption" (TSFC) numbers are more readily available than "specific range numbers" because they can be used across a wide range of airspeeds, and thus thrust levels, to compare dissimilar aircraft. For those unfamiliar with TSFC, it is the mass fuel per product of unit of fuel times unit of thrust (i.e., mass fuel / (unit of fuel * unit of thrust)). To complicate things further, you need to make sure the TSFC is the installed TSFC in the airframe and not the TSFC of the motor on the test stand because the inlet design can have a large affect on the thrust produced per unit fuel. In combination with the airspeed(s), thrust at respective airspeed(s), and available fuel, it's possible to begin comparing ranges between aircraft.

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    1. I'm unfamiliar with this particular measurement so correct me if I'm misunderstanding it. It appears to be a measure of an engine's fuel efficiency, in simplest terms. However, our discussion, our focus, and our practical interest is in combat radius. Engine fuel efficiency certainly plays a major role in that but the same engine installed in a lighter aircraft will produce a greater radius than if the same engine is installed in a heavier aircraft. The TSFC seems not to take into account the aircraft design (weight, weapons load, drag, etc.). Perhaps this is why you noted the need to be sure the TSFC came from the installed engine?

      Where does one find TSFC-installed values for military aircraft? I've never seen them or, If I did, I skipped right over them and didn't notice.

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    2. "The TSFC seems not to take into account the aircraft design (weight, weapons load, drag, etc.)."

      Correct. This is on purpose. Because fuel is usually the limiting factor in an aircraft's range, most comparisons BETWEEN aircraft and between aircraft configurations compare the range at the same fuel flow-rate by calculating the thrust produced at that flow-rate to estimate a ground speed and multiply the ground speed by the endurance to determine the range. Differences in aircraft/armament are accounted for in that air speed/ground speed achieved for a given amount of thrust will vary (e.g., adding drop tanks increases both endurance and drag index). The TSFC values cited in literature are usually based on fuel flow rate at maximum dry and wet thrust so these values are only a rough approximation. Actual TSFC changes with speed and altitude, which also affect thrust.

      Examples can be found here:

      https://www.aircraftenginedesign.com/TableB2.html

      While the link notes the aircraft in which the engines are installed, the values for each engine do not appear to be values as installed in each aircraft.

      More info here:

      https://www.grc.nasa.gov/www/k-12/airplane/sfc.html

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  3. This comment has been removed by the author.

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    1. Aye, "retire without replacement" would have been best. The F-35B and the USMC rejection of SuperHornet led to this fiasco..

      The entire design by LM is built around that centerbox for VSTOL and has subsequently doomed all variants to less "performance"...

      What real combat value did the Harrier itself give this nation over the past 40 years?.. Sure it is a big crowd pleaser at airshows but the answer is "Not Much" and it IS the Widow-maker to this day. As Reagan would say.... "here you go again". The F-35B just continues the buffoonery with an even more expensive toy for the Marines to screw up with... But who is going to take on that Mafia- Mattis, Kelly, Dunford..Who wants to take on that group of infantry Marines...They know best, right? LOL.

      b2

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    2. "Re: F-35C. The Navy didn't determine the aircraft that it got, the Marines did. As it stands the Navy eked out more range with its C variant in comparison to the A/B variants. And more range than Super Hornet for that matter."

      How so? The mold-line of the fuselage is quite different between the A/C and B versions. While the alarmist anti-JSF crowd like to point to the weapons-bay placement of the F-35 as evidence that the B-version compromised the design, it's clear that the weapons bays are at the corners because of the engine placement and not because of the lift fan. There simply isn't enough longitudinal length between the inlets and the engine face to accommodate weapons bays that are long enough, wide enough, and deep enough to swallow two Mk 84s and two AMRAAMs. Moving the engine rearward would reduce the moment that the stabilators can provide. Note that the F-35's SUPERB pitch instability characteristics are due to the same boom-mounted stabilators and unstable wing/engine arrangement employed on the F-22. The C version ekes out more range due to the larger wings that also significantly increase wave drag and thus increase acceleration times. If the navy cared about the acceleration performance, they probably could have used a boundary layer control system instead of going to a large wing, but their experience with them on the F-4 soured their view on such systems, despite their advantages as evidenced by the Blackburn Buccaneer.

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    3. "it's clear that the weapons bays are at the corners because of the engine placement and not because of the lift fan."

      No, that's not at all clear. Your statement may or many not be true. For sake of discussion, let's say it is true. It's still not clear that it's true. At a casual glance, I see no instant, compelling visual evidence to support your contention. Of course, it's quite likely that I simply haven't looked closely and/or don't know what to look for.

      Someone should do a post on this, with drawings and photos, and demonstrate that the contention is true. I'd read that post!

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  4. The new U.S. Air Force Secretary Heather Wilson commentating on her August trip to Afghanistan and importance of tanker fleet. Stated how dependent fighter a/c were on tankers, refueling four or five times per mission, requiring ~ 65 tanker sorties per day.

    Emphasizes the importance of internal fuel capacity for fighter/attack a/c, CNO mentioned on numerous posts:)

    From

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  5. I understand the rationale for limiting a discussion of mission radius to performance utilizing internal fuel only, but how often does a Super Hornet actually perform a mission without external fuel tanks? And if carrying external tanks is standard (presumably more likely to be the case when the Navy is unable to rely upon air-force tanking assets) shouldn't these be taken into account when discussing Super Hornet radius?

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    1. Well, that's an interesting point. If an aircraft launched 100% of the time with x number of external fuel tanks then, yes, for all practical purposes those tanks would be part of the internal fuel load and their impact, presumably positive, on the radius would, logically, be included.

      However, that is not the case. The number of external tanks, if any, depends on the range to the target, availability of tankers, and, perhaps most importantly, the desired weapons load since every hardpoint devoted to a fuel tank takes away from the weapons load. It becomes almost a vicious circle of reasoning. Do we want to get to the target but have insufficient weapons to accomplish the mission or do we want to carry sufficient weapons but be unable to get to the target? Hence, the need for tankers.

      So, to answer your posed question. Unless operational practice dictates 100% use of external tanks then, no, I wouldn't include them in any combat radius discussion. I would also note that your observation that a Hornet generally launches with tanks is a peacetime observation where we can afford to launch with small weapons loads. Come high end combat, that is likely to change!

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  6. Is it even possible to build a carrier bourne aircraft that has a long enough range to penatrate a 1000 mile A2/AD zone of an advanced enemy?
    Missiles seem to have all the advantages, no pilots with all there asotiated systems, easier launching, better stealth, and no need for that range halving return journey. Air defence being the exception, we might be better off concentrating on missiles for strike missions.
    Even if a long range carrier strike aircraft is developed, how much cheaper is it for the enemy to design even longer range missiles?
    MA

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    1. I've stated that long range, penetrating strike should not be a carrier aircraft mission and is not even viable/survivable. Cruise missiles are the preferred long range, penetrating, strike weapon.

      To answer your question, yes it is possible to build a very long range carrier aircraft. We already did it! The A-3 Skywarrior had a 1000+ mile combat radius, if I recall correctly. The F-14 and A-6 had radii of several hundred miles, depending on mission specifics. We tend to think this stuff is impossible because it's been so long since we've done it. The bar has been lowered and we've forgotten that it used to be higher.

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    2. Yes the A-3 had amazing capability even on the thirsty engines of the day. The original design had 3 crew, a tail turret and gross weight of 70,000lbs ( later it went to 82K on bigger carriers). The max weight of the F-35 is around 60K lbs.
      The numbers Ive seen give A-3 radius at 1000+ nm, not just miles!
      eg Strike from the Sea, Tommy Thomason

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  7. From everything I've read, it seems like "more internal fuel" = Better. I'm not saying their arent drawbacks. But both the USAF and the USN both seem to be well short of the optimal spot in terms of fuel fraction.

    Not only are we limiting internal range, and flexibility, but having to tank all the time is insanely expensive. This would seem to skyrocket the operating costs of the aircraft (and I'm not sure if that's taken into account).

    A gallon of tanker gas is far more expensive, from what I've read, than a gallon of gas loaded on the ground. This is due to the extra infrastructure needed as well as the amount of gas you have to burn to get the refueling gas in the air.

    I'm not sure why we've erred on the side of short legs.

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  8. The F-35 news is depressing. It does have a large fuel fraction but doesn't seem to be as efficient as it might be.

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    1. I wouldn't get too depressed. The anti-JSF crowd abuses range/acceleration/g-limit data as much as, or more than, the pro-JSF crowd. In the case of the anti-JSF crowd, it's usually to inflate the performance of the F-16.

      If you want evidence of this, just look at the case of the conformal fuel-tanks (CFTs) for the F-16. Anti-JSFers will loudly proclaim that an F-16 with CFTs and a center-line drop tank with an anti-air loadout begins to rival or surpass the F-35 with a similar load-out in the anti-air role, you know except for the whole stealth thing. There is some truth to that, but why? Maybe because adding CFTs significantly increases volume for fuel by using a volume of increased fineness and decreased wetted area (i.e., skin friction) compared to a drop tank and pylon. Now what if we applied the same concept to weapons and sensors? You get something close to the weight, shape, and volume of an F-35. Is the F-35A ever going to be as "efficient" as an F-16A with nothing but internal fuel, two sidewinders, and John Boyd at the stick wearing nothing but an oxygen mask and a speedo, of course not, but no one flies an F-16 in that configuration in a real-world scenario. The drag index of an F-16, block 60, with EMPTY CFTs, 2 AIM-120Bs on wing tips, and 2 AIm-120Bs on pylons, a full load of 20mm, and full internal fuel is 24 (only the AIM-120s on pylons and CFTs contribute to drag index). Drag index only goes up from there....

      http://elementsofpower.blogspot.com/2015/04/f-35-transonic-acceleration-vs-f-16.html

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  9. Nice post CNOPs. Trying to provide some rationality to the madness, eh? LOL.

    At best people can get their info from here:

    http://www.navy.mil/navydata/fact_display.asp?cid=1100&tid=1200&ct=1

    NATOPS, btw while unclassified is considered FOUO although one can see pirated manuals on the internet....

    NATOPS is derived from actual DT/OT testing and constantly revised through an aircrafts service life. That original data, some from interpolation also has an engineering factor on it on top...

    Basically pilots fly "max range" (most efficient power settings altitudes, etc) to get from Pt. A to Pt.... or they fly "max endurance" (minimum fuel to stay airborne as long as possible) around a fixed point.. And of course, they also fly power settings in between for training purposes and to win in combat as the mission dictates! ....Simple enough, eh? LOL.

    Now NATOPS performance is used for planning purposes only and has charts that call out fuel burned/nm, altitudes to fly, time to climb, enroute descents, etc, etc, all with a specific drag count for different fuel/ weapons loadout. The possible combos/permutations are endless as they should be. That is why NATOPS is called the "big blue sleeping pill" by pilots.

    Problem here is that you don't believe what they tell you.. and rightfully so.. The manufacturer always puts their products in the best light w/unreasonable claims and of course the testers "become the product" and we can't believe everything they say. However despite that, it is when those that lead the folks who must fight with this stuff, stretch the performance numbers or obsfuscate, from ignorance or on purpose, we are all screwed. Well CNOPS that's where it at..

    Yes, pilots do fly by the NATOPS and that is the key.

    b2

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  10. All this involves tactics too. Combat maneuvers really burns up fuel. So you want the enemy to venture out to your bases so you can engage them when they really don't have much fuel to fight, so they must break off and run or risk ditching. And if tankers are involved you want to attack while their near empty fighters are trying to tank up with a big lumbering tankers. So for a China scenario for example, it will be much better to wait and lure them out to the east far from home, and not take the fight to their shores using tankers, where the fuel advantage is theirs.

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    1. In any reasonable scenario, why would the Chinese be lured east? Everything they want (Taiwan, the South/East China Seas, neighboring countries and seas, etc.) all lie to the west. They don't need to fight to the east! We're the ones who will have to go to them if we want to stop/reverse their gains.

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    2. The most likely scenario is war between Japan/USA and China about some petty island dispute, while South Korea and Taiwan stay neutral. Whatever happens, everything is about sea lanes through Indonesia. The Chinese need a path and its easy for us to block it, so they'll have push out to secure that. That means clearing out Guam and maybe N. Australia (unless they declare neutral too)

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    3. China only needs sea lanes during peacetime. During war, they will rely on alternate routes (overland - their new silk road, for example, or through Russia). All they have to do is make their initial gains and then hold on until the US tires of combat and negotiates and gives China what they want. China will seize a few extra "things" that they don't really want to use as bargaining chips that can be magnanimously returned at the negotiating table.

      In any war, Taiwan will be the first thing to be seized regardless of whether it is the focus of the war or not. For many reasons, political, strategic, and cultural, China cannot allow Taiwan to stand in a war. Taiwan won't have an option to stay neutral! SKorea may or may not attempt to remain neutral. China has no need to push out beyond the first island chain to achieve their goals.

      Many years from now, after they have solidified their hold on the first island chain, annexed (peacefully) the Philippines, subjugated Vietnam, and built up their islands around Japan, they will push out to the second island chain and beyond but not until the first, local war is fought and concluded.

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  11. “Above all, though, it clearly points out the need to build aircraft that are inherently longer ranged. When we're talking about thousand mile A2/AD zones, it quickly becomes obvious that the F-18 and F-35 are both woefully short on their useful combat radii.”

    Maybe. Maybe not. How many aircraft of A-3, F-111B size can a Nimitz/Ford accommodate? Is it enough to constitute a useful strike package? In cooperation with how many other carriers? Are the aircraft stealthy? If not, how many air-superiority, SEAD/DEAD, and EW escorts are required to execute a successful strike? If using standoff munitions, how many more aircraft are required to put sufficient ordinance on target?

    At some point, you start making an argument for land-based aircraft, whether in whole or in part, that are not constrained by the requirement that they operate from a carrier. Adaptive-cycle engines may change the calculus slightly, but I think we still have an issue of fitting a sufficient number of large aircraft on the carrier(s).

    Personally, I think you had right idea as most recently stated in your “Carriers and Tankers” post.

    https://navy-matters.blogspot.com/search?updated-max=2017-08-12T09:55:00-07:00&max-results=7&start=7&by-date=false

    “Increasingly, long range, penetrating strike is a mission given to cruise missiles. That being the case, what role does the carrier serve? Well, the cruise missiles (Tomahawks, at the moment) are mounted on Burkes and submarines. Burkes need to get within several hundred miles of their targets. Depending on how close the targets are to an enemy’s shoreline and how straight a course the missile will fly, the Burkes may need to penetrate hundreds of miles into an A2/AD zone to reach their launch point. They’ll need protection to do that. Some of that protection can be provided by their own Aegis/Standard defense systems, of course, but that alone will not be sufficient especially if we want to heavily load the VLS cells with cruise missiles rather than surface to air missiles. Thus, the ideal escort for the cruise missile shooting Burkes is a carrier.”

    “Of course, the Air Force’s long range bombers can also launch cruise missiles, if they can survive to reach their launch points. Again, the carrier air wing can provide the local air superiority needed to clear transit lanes and safe launch points for bombers.”

    “Understanding what the role of the carrier is, we see that the carrier does not, and indeed should not, have the role of deep penetrating, land attack strike against a peer enemy. The job of the carrier and its aircraft is to secure local (though a very large “local”) air control for the purpose of escort. Tankers are needed to facilitate that but not long range, stealthy, penetrating, high capacity tankers. All we need is a medium capability and capacity tanker to support the far flung air superiority aircraft.”

    If this is our CONOPS, it seems to me like the F-35 might be a decent aircraft for the follow-on phases of the conflict where the A2/AD zone has been reduced and degraded but would still pose an unacceptable risk to legacy aircraft. In my opinion, its range, kinematics, and size are a reasonable compromise if a radius of 400-500 nm or so is adequate for relatively "self-sufficient" strike platform.

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    1. You need to understand that I write in two different realms. One is the world as it ought to be (according to me, of course!) and the other is the world as it is, which is flawed. I believe, as I've stated repeatedly, that the air wing should not be conducting long range, penetrating strike - that mission is best left to cruise missiles. For this post, however, I'm discussing the world that is, however badly flawed. The Navy wants to conduct aviation strike warfare. To do that, they need a long range, penetrating tanker and inherently longer range aircraft.

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    2. Along the lines of this post, this is interesting:

      https://www.govconwire.com/2017/09/ge-secures-92m-contract-option-for-navy-fa-18ef-aircraft-engines/

      GE is selling the Navy 24 new 414 engines, which give greater thrust and efficiency:

      "F414-GE-400 engines are designed to increase thrust capacity of Boeing-built (NYSE: BA) F/A-18E/F Super Hornets by approximately 35 percent and help manage the aircraft’s fuel consumption."

      I know. It's the vendor. But still, even a 15-20% increase would help.

      As to the F-35; in CNO's CONOPS I don't see that the F-35 has a place; it's still expensive, and has other issues that do seem to not yet be fixed (The heat issues in the weapons bay; still some issues with the helmet visuals, payload size in A2A mode, code *still* not done. ALIS *still* not done).

      I'd rather that the Navy started over with a more potent A2A fighter or interceptor with a big fuel fraction and lessons learned from the F-35. The Fuel fraction and stealth of the F-35 are nice. But the sensor fusion has been problematic, and ALIS looks like a nightmare.

      If we could ditch some of the complexity so we could buy in numbers that would help a lot.

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    3. "If we could ditch some of the complexity"

      Now that's a fascinating idea. If ALIS could be stripped out of the code, we'd be miles ahead. I'm not sure how mission planning and weapon's management would occur but still ...

      Great thought!

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    4. Complexity leads to high cost; leads to fewer units purchased. High number of maintenance hours per flight hour leads to less hours hours of flight time; leads to less experience and skill of the pilots. I'd prefer more aircraft flown by more experienced pilots even if they aren't super advanced f-35 type.

      MM-13B

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    5. "F414-GE-400 engines are designed to increase thrust capacity of Boeing-built (NYSE: BA) F/A-18E/F Super Hornets by approximately 35 percent and help manage the aircraft’s fuel consumption."

      Read the quote carefully. It says the engines will increase thrust. It does NOT say that they will improve fuel efficiency. It says they will "help manage the aircraft’s fuel consumption". They could be less efficient but just easier to see and document the decrease - that would be "managing" the fuel efficiency.

      The manufacturer and the Navy put ridiculously positive spins (lies) on every bit of news. The fact that they didn't make any explicit claim of increased fuel efficiency makes me wonder if the engines aren't less efficient!

      Why don't you do some more research and see if you can find out anything else about the anticipated fuel efficiency and let us know?

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    6. Karnac speaking- When it comes to re-engine-ing a carrier jet there ain't no such thing as Form, Fit, Function (FFF) replacement. It will take years and years of DT testing up to and including carrier suitability. many hundreds of millions and 5-10 years...wanta bet?

      Re fuel efficiency- When you add more hp/pounds of thrust it doesn't mean you are going to get a better product. There ain't no "money for nothing and your chicks for free" in carrier aviation power/propilsion. Leastways, not on planet earth yet... Also, add more power and you will pull more G's, that ain't good for a jet that has life issues.

      But I am sure the vendor will claim the R&M costs (always B.S. upfront) will blow the socks off off the 404! Predictable.

      Believe me I hate being so cynical about anything "new" and improved in this environment.. but there it is...

      b2

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    7. I'm not going to launch into a huge post because turbine efficiency is a vast and complex topic, but a basic tenant is that increasing turbine inlet temperature (TIT) can increase both maximum thrust AND fuel efficiency across the operating envelope. If the only variable is TIT, increasing TIT generally gets you higher thrust at the same fuel flow rate and requires less fuel for the same thrust. There's nothing ground breaking about this other than the materials needed for acceptable operating life at those elevated temperatures. Reduced requirements for cooling air and refinements in compressor and turbine aerodynamics help too. Nevertheless, yeah, take that 35% number with a healthy grain of salt.

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    8. This looks like shoddy reporting more than a case of a manufacturer overstating the performance. GE claims a 35% increase in thrust over the F404, not previous F414 iterations. The C/D uses the 404, the E/F/G uses the 414.

      GE also markets an F414 Enhanced Engine for which they claim an 18% increase in thrust over the F414-GE-400, twice the the horsepower to the alternator, and a 2-3% decrease in specific fuel consumption (SFC or TSFC). The emphasis on aerodynamic improvements and increase in airflow from 170 lbs/sec to 187 lbs/sec but only a very modest 2-3% decrease in SFC suggests a modest increase in TIT, if any. It looks like the overall compression ratio has remained roughly constant at 30:1 as well. It's possible that an increase in bypass ratio accounts for most of the increase in thrust and a more efficient compressor (i.e., extracting less work from the combustion products to achieve the same pressure ratio and drive more air through the fan) explains the relatively low improvements in SFC with little or no increase in TIT and thus overall pressure ratio.

      https://www.geaviation.com/military/engines/f414-engine

      https://www.geaviation.com/sites/default/files/datasheet-F414-Enhanced.pdf

      http://www.mtu.de/fileadmin/EN/2_Engines/2_Military_Aircraft_Engines/1_Fighter_Aircraft/F414/Product_Leaflet_F414.pdf

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  12. I love these types of write ups. I do believe the air wing(s) accounts for this, but I certainly do not believe contractors do (or care). Beautiful analysis of the capabilities and limitations in normal vernacular. Keep it up!

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  13. Why would a F-18 cruise at 15,000 ft? That's VERY low, and burns too much gas.

    I think I'll choose to believe the Navy and Boeing's estimates of the range of the aircraft.

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    1. You didn't get the point of the post at all, did you? Oh well.

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    2. Yes, I think I did. Any you (very nicely) provided a clear summary: "The conclusion is to assume the published range/radius numbers are maximum and unrealistic values that would only be obtained under unrealistic, non-operational conditions. If you want an “actual” operational combat radius, take 60% of the published figure and you’ll be somewhere in the realm of an actual combat mission radius."

      Sure. But I don't see why I should trust your 60% number when you think F-18s cruise at 15,000 feet.

      I still trust Boeing/Navy over you. That's all.

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    3. I didn't pick 15,000 ft because I think that all F-18's cruise at 15,000 ft and only 15,000 ft. I picked it because I had to pick some number and given the multitude of mission profiles, and hence cruise altitudes, that seemed a reasonable average number. If you want to argue that 20,000 ft or 10,000 ft would be better, I wouldn't have any objection.

      I gave you the reference. Why don't you pick any altitude you think is "better" and run the numbers and tell me what you get and how it alters my conclusions, if at all? I'm pretty sure you'll find that it doesn't alter the conclusions at all. Let me know what you find.

      Finally, the point was that the published range/radii are totally unrealistic. You may disagree with the altitude I picked but my ultimate 60% number is based on at least an attempt to inject a note of realistic flight profiles, carrier practices, mission types, speed and altitude changes, etc. into a reported range/radius value.

      If you'd like to disagree with me, that's fine but do so with some actual data. Do your homework. Run the numbers and tell me what you get.

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