hopsalotGood question. IIRC the first tests of an AESA radar in Typhoon (2007? 2008? I forget) used the existing back end & a fixed array, & that could have been developed into a drop-in upgrade. But it was decided to go for something better, & simple retrofit to Tranche 1 seems to have got lost along the way.
BTW, I think one could ask the same question about the APG-79 not fitting the early F-18Es.
This is a problem across all modern fighter programs. The programs take so long to reach IOC that it is almost inevitable that new technology will emerge during the course of development. Not only that, but in the interest of actually getting something into production/service most fighters have IOCed with only limited capabilities.
The F-35 has taken a somewhat different approach than most others wherein upgrading the early production planes was built into the program from the start. This at least was good planning and it allowed the program to get production rolling earlier than it otherwise would have… but the delays in the program have meant that there are more of these early airframes needing “concurrency” fixes than was originally anticipated.
At this point currency is essentially a solved problem. An F-35 ordered today wouldn’t come off the production line until 2018-2019 and currency costs would be negligible. Of course sometime around 2021-2022 we will be talking about Block 4 upgrades …. and it never stops. At some point presumably the earliest F-35s will be left behind.
hopsalotAirshow over the airfield ?
I am not sure what your interest is. Yes, a hypothetical engine failure at a relatively high altitude and in close proximity to an airfield would be the only scenario where a pilot might have the ability to attempt a landing but it is unlikely ever to happen. Modern fighters just don’t glide well and the sort of failure that destroys an engine often causes other damage.
99% of the time the pilot would be wisest to point the plane away from anything valuable on the ground and eject at a safe speed/altitude.
hopsalotNo hope to bring it to the airfield in tact in any situation?
It may not be completely impossible, but it would only happen under the rarest of circumstances.
hopsalotSo it seems they are moving forward with “finding an A-10 replacement” — does this mean they have scrapped the plans of replacing A-10 with F-35?
No, not at this point. This could hypothetically lead down that path, but it is a very early step.
First they will define the requirements of a hypothetical A-X. Then they will presumably conduct an analysis of alternatives to determine whether an existing system or systems (including the F-35) could meet the requirements and what that would cost relative to a new design.
A new A-X design could have lower operating costs than an F-35, it could even have lower acquisition costs, but if a clean-slate design costs $13 billion to develop (Gripen level costs) then you could buy 150 F-35As (at $85 mil each) for the development cost alone… before you buy a single A-X or set up a separate maintenance and training pipeline.
On the other hand… if something like the Textron Scorpion can meet the requirement and has negligible development costs and very low acquisition and maintenance costs you could potentially make an argument for it.
hopsalotDoes anyone know if F-35 can be deadsticked ? What kinda glideratio does it have ?
The F-35 has an APU that would provide power to the flight control system in the event of a total engine failure. This combined with the F-35’s good handling properties at low speed should allow the pilot to stay with the jet long enough to ensure a safe ejection.
hopsalotIt’s nonetheless far from being insignificant up to LRIP5 and still noticable up to LRIP8. The LRIP quantities already exceed the annual production of 4th gens by a fair margin and hundreds of aircraft will have been produced and as it seems a few billions being spent to compensate the concurrency. That puts Hopsalot’s statement…
…a bit into a different perspective!
I disagree completely. The first few LRIP batches were quite small, 2, 12, and 17 aircraft for LRIP 1, 2, and 3 respectively. As you can see from the table already posted the concurrency cost per plane fell rapidly after those first few batches and is now well under $5 million/plane. In the context of a program the size of the F-35 these costs aren’t significant and it ensures that every plane is brought up to the full production standard specified by the project with no orphan planes.
Consider for comparison that the Eurofighter program produced ~150 Tranche 1 Eurofighters out of a total production run of around 600 jets…
hopsalotYour missing the bit about flying them less ~300hrs to ~250hrs… 17% less flying per year stretches out the planned maintenance and should reduce costs including a 17% reduction in fuel. your looking at an increase of 11% in flight hours (Source page 92 SAR 2016), you should see a net saving, see down below for reasoning.
Take this reasoning to its logical conclusion… if you flew the plane 0 hours it would be free, right?
No… many costs are fixed. You have to maintain depots, trained maintainers, etc etc, if you want to have the capability to fly your jets.
In the real world it is cheaper to fly your jets like crazy, at least on a cost per flight hour basis.
hopsalotPlease note that when comparing the cost of Eurocanards to the F-35.
The F-35 has a rather larger proportion of its cost bundled up in maintenance and logistics than the Eurocanards.
I’m sure it’s due to the enormous cost pressures on the F-35 program to lower its “flyaway” costs, where a large chunk of costs are shifted to the right where they can be accounted for in maintenancesustainment.
Rather like buying a luxury car for $10 but having to pay the $150,000 first service fee before delivery.
Source? :rolleyes:
The commonality between F-35 is small ~30%, your in effect getting 3 fleets of dissimilar aircraft so don’t go counting all those F-35 in one.
That is referring only to the structure of the aircraft. Most of the complexity is in the avionics/software and that is essentially completely common. Even the structure, while not necessarily identical, is very similar with most parts being produced using the same tooling, etc, just as all three F-35 variants move down the same production line.
While Concurrency issues will plague (cost) the F-35 for the next decade, its the maintenance cost that have risen that is a concern.
The concurrency costs are proving to be a non-issue. All you are seeing is that the F-35 learned from the Eurocanards and built upgrades for the early airframes into the program’s planning and budget. That is why there are no Tranch 1 F-35 equivalents or Rafale F1s that need to be overhauled at great cost or relegated to reduced roles.
The projected rise in maintenance costs is because they are projecting flying the planes longer. This isn’t rocket science and we are talking about a lifetime from today.
hopsalotSure, you can bet on that.. all this nationalistic jingo aside, we are still aircraft enthusiasts, right? 🙂
Yes, in general I wish the board was more reasonable. There is no one single right answer as clearly evidenced by the contrasting approaches taken by design teams around the world. Certainly there are shared principals, but their relative weighting varies depending on philosophy/doctrine and other factors. Too many people here seek to simply define one aircraft as the “best,” generally because it is the one their country developed or operates.
Thanks for your time and effort you’ve put into this.. It’s been a valuable lesson for me.
To make long story short, all the imposed g-limits are for instantaneous turn rates, in order to prevent structural damage on the airframe.. Sustained turn rates simply have to be tested and depend on the aircraft weight (fuel), as well as drag resulting from stores.. Logically, they can never exceed the imposed g-limits and usually are much lower.. And that is what makes Picard’s claim unreasonable.. Got it.. Sorry for the drivel I’ve written before..
You are welcome, and I am not sure he even understands why his claims are ridiculous.
I still fail to see importance of the sustained turn rates as I think that nobody fights this way, yet for us they still are an useful parameter to judge the dynamic performance of a design vs its peers.
If there was anything wrong, feel free to correct me.. Thanks
Sustained turning performance is important in a few ways.
It speaks to an aircraft’s ability to maintain energy while maneuvering in a general sense. (here we might be talking about a heavily laden aircraft) Just because plane X can take off with load Y doesn’t tell you much about how it flies with such a load. Carrying an equivalent load an F-15 will offer far higher sustained turn performance than an F-16 as it is simply a much larger aircraft with twice the thrust, etc. If you load a fighter up to where it can barely turn/maneuver the aircraft will be pretty limited in terms of its ability to respond to threats, etc. (one reason why aircraft so rarely operate near their maximum weights)
In a dogfighting scenario sustained turning performance speaks to an aircraft’s ability to maintain energy (or lose it more slowly anyway). The F-16 was designed with a huge emphasis on its sustained turning performance and it is still an outstanding aircraft in that regard. Its designers believed that its energy superiority would allow it to dictate the terms of an engagement (either engaging or disengaging at will) and ultimately win.
Aircraft like the Mirage 2000 and F-18 were designed with a different vision of WVR combat, one where they could drive the fight to lower speeds and win with superior nose pointing ability. These aircraft bleed energy rapidly in a dogfight, but if they are successful the fight simply won’t last that long…
Here are a few good anecdotes comparing the F-16 to other fighters: http://theaviationist.com/2012/12/10/viper-dogfight/
In general newer designs have found ways to offer more favorable combinations of both philosophies, but there are still relative differences in emphasis. (The Typhoon should sustain turns better than a Rafale, while a Rafale will generally have better very slow speed handling.) Neither of these approaches is strictly right or wrong and successfully employing these aircraft requires the pilot to understand the relative strengths and weaknesses of his aircraft. As Ozair has already commented, HOBS missiles likely favor aircraft with good slow speed nose pointing as it better enables them to end a fight quickly.
Based on pilot accounts so far the F-35 is clearly more in the F-18/Mirage 2000 camp as far as dogfighting philosophy goes. It will bleed energy very quickly, but will have very good low-speed high AoA maneuverability.
I hope we can turn over a new leaf and focus on discussing aircraft rather than just bickering. I think everyone would benefit.
hopsalotInstantaneous turn?
One additional note… it is possible for a jet to “sustain” an instantaneous turn. That is to say that if a pilot is willing to trade speed and/or altitude away a plane could maintain a 9g turn for some seconds so in a sense it is “sustaining” a 9g turn, but that doesn’t make it a sustained turn in the sense of the endlessly discussed F-35 requirement that was relaxed.
hopsalotInstantaneous turn?
I will take this at face value and assume you are actually trying here.
A max instantaneous turn is the maximum g turn that an aircraft can achieve (typically limited by lift/mass) or that is allowable (structural or flight control limited). An aircraft performing a max instantaneous turn will typically be bleeding energy, either losing speed or altitude, but there are some specific cases, typically when the limiting factor is structural that the aircraft might not be losing energy.
A “doghouse plot” is an expression of a fighter’s instantaneous turn performance. The peak of the plot represents the fighter’s maximum achievable turn rate under the conditions of the plot, it is the lowest speed where the fighter is capable of achieving its structural load limit. To the right of the peak (faster) the limiting factor is loads, and to the left (slower) the limiting factor is lift.
Just because a fighter is hypothetically capable of achieving 9gs at a certain altitude does not mean it can do so at all speeds, only if it is at or above its corner speed.
[ATTACH=CONFIG]245045[/ATTACH]
Here you can see a pair of overlaid doghouse plots, one for an aircraft with slightly higher maximum speed and G-load performance and another for an aircraft with a lower g-limit, but a lower corner velocity as well, which allows a greater peak turn rate despite its lower g limit. (the blue aircraft here would be the more F-16-like, the multi-colored aircraft would be more F-18-like) This is why if you look at the corner velocity requirement for the F-35 the threshold was listed as F-16, and the objective was listed as F-18… all else held equal a lower corner velocity is an advantage.
The F-35 and Rafale have the same structural max-G, 9gs. Both aircraft can presumably exceed that structural limit under certain circumstances without encountering a catastrophic failure (the Rafale has demonstrated this in air show routines, and the F-35 has been tested to at least 9.9g) but in normal operation 9gs is the limit.
If the Rafale is carrying heavy air to ground stores, it is limited to .9 mach and 5.5gs, but the limit could actually be lower depending on the aircraft’s weight, etc. (as illustrated in the article where the FCS limited the reporter to 4gs.)
The F-35 also presumable has limits when heavily loaded but they aren’t public so far as I know.
Now, shifting gears completely…
A sustained turn is a turn during which an aircraft either retains or gains energy (speed/altitude). A maximum sustained turn is the hardest turn a fighter can maintain without losing energy. This is a totally different metric than a max instantaneous turn in almost all cases. Like an instantaneous turn, it is dependent on speed, altitude, and the aircraft’s load.
Just because an F-35 can sustain 5gs at some speed/altitude doesn’t mean it can’t also achieve 9gs in an instantaneous turn. (in almost all cases an aircraft can achieve higher loads in an instantaneous turn than a sustained turn)
At sea level and while lightly loaded most fighters can actually sustain a 9g turn… but that falls away as you climb. You can’t compare a sustained turn at one speed/altitude to an instantaneous or sustained turn at another speed/altitude.
2. Why is the F-35 limited to 4.6g sustained, even when clean?
It just depends on flight conditions. At high enough altitude a fighter’s sustained turn capability will drop to 0gs. (all lift needed to maintain altitude) This same fighter might sustain 9gs near sea level. Without knowing the specifics of what that 4.6 (actually more like ~5gs) refers to we really don’t know much. The F-35 won’t be a strong performer relative to other fighters in sustained turning performance as the F-16 was, but then neither was the F-18 or Mirage 2000 and nobody doubts that they are fighters.
hopsalotOK.. let us put it simply.. once, again, what is the g-limit [sea level] with such load, then? Do we know that or not?
I am not putting your knowledge in doubt but I can’t seem to get a clear answer here..
The Rafale’s G-limit at sea level with that load would be 5.5g, or less. We don’t know the exact limit with that load but we do know that with an air to ground load its max G-limit is 5.5.
The equivalent number for a clean F-35 is 9g, but like the Rafale above it could actually be lower depending on the aircraft’s weight.
OK.. If the F-35A is 9g rated, then why was it limited from 5.2g to 4.6g?
Because you still don’t understand the difference between an instantaneous turn and a sustained turn. :stupid:
The F-35’s structural design point is 9g. In normal operation a pilot and the aircraft’s FCS will seek to avoid exceeding 9gs. The second number is a sustained g performance requirement…. that means the aircraft could maintain a continuous 4.6g turn without losing speed or altitude. (as long as fuel remained)
These are two totally different things.
In order to get clear answers, I am limiting my response to these two paramount questions because otherwise we are obviously getting lost in the myriad of details..
Thanks for your time..
You have gotten clear answer after clear answer. The problem is between your keyboard and chair.
hopsalotif Rafale use the same JP-5 fuel as others NATO aircraft then 3*600 gallons bag would weight around 12240 lbs ( fuel weight) + 3000 lbs( empty shell of fuel tank ) = 15240 lbs
2 SCALP weight 5732 lbs
4 Mica weight 738 lbs
total weight is 21710 lbs
Rafale empy weight is 21,720 lb
So you can see that these amount of weapon almost double it’s weight , available G should be around 1/2 of 9G or 4.5G
sustain G at sea level is likely to be less because such load create significant drag
That isn’t how this works. For one thing your math suggests only a completely clean/empty Rafale can hit 9 Gs.
hopsalotCanada to withdraw from F-35 programme
Is this a joke or something?
Here is the article at the correct link… note the date:
hopsalotOK, let’s do it piece by piece..
1. what is the sustained g-limit for Rafale with the heavy config (2x SCALP, 3xbag, 4xMICA) at sea level?
The FCS will limit a Rafale to no more than .9 Mach and 5.5Gs while carrying that load, but we have no reason to think a Rafale could sustain a 5.5 G turn with that load at sea level.
2. What is the g-limit for the clean F-35A in such conditions?
The F-35’s “g-limit” is 9 Gs at sea level but there aren’t any numbers available on what its sustained turn performance would be like at sea level while clean.
Most modern fighters can maintain ~9Gs (unless their structural limit is lower) at sea level while clean and it would be reasonable to assume the F-35 would be in that vicinity.
Of course you are showing your ignorance once again in trying to frame things this way. A comparison would also require us to know the speed at which we were comparing and each aircraft’s weight. (A Rafale with three tanks carrying how much fuel? Similarly, a “clean” F-35 could be carrying as much as 18,000lbs of fuel and another almost 5,000lbs of internal weapons.)
Sign In
