21AnkushIts a combination of several factors but the canads do help and enhance the AoA flow separation control created by the delta wing vortices.
exactly! its a combination of several factors, with avionics and EW systems being a very important part of the efficacy of a fighter in service.
so, just by looking at whether the LCA has fewer control surfaces than a J-10, you cannot judge which is better.
otherwise, I’d simply say the Su-30MKI really is the world’s finest fighter, judging by its triplex canard config and you’d have no other go but to simply agree, otherwise you’d contradict your own hypothesis. 😎
such simplistic analyses are hardly technically very sound.
21Ankushthe canarded Su-27 aka Su-35 is far far more agile than the Su-27.
so if canards are the definition of super agility, why did the new Su-35BM dump the canards ? going by your definitions, its not as agile as the Su-30MKI, so why is it being hyped up so much?
21AnkushMore control surfaces or at least more flow separation control devices assure more agility and tail planes and canards are prefered by other manufacturers rather than a simple delta with two leading edge swept angles, in fact see the Mirage 2000 and Rafale have canards, in the Mirage 2000 well strakes but the canarded Rafale is far far more agile than the Mirage 2000.
the canarded Su-27 aka Su-35 is far far more agile than the Su-27.
more likely due to higher T/W ratio, better FBW and better actuators than just adding canards.
21AnkushI remember watching a fighter-related programme on some channel a while back. Apperently when manuevering, many fighters which are only cleared for (say) +9G go well above this limit…yet only for fractions of second (literally). Of course such manuevers in excess will have an effect on the overall life span of a fighter, but its the human factor which is more important here (even with improving G suits). While an F-16 or F-15 might be able to do a manuever requiring 8 or 9G for a few seconds or so, I wonder how many pilots are out there who can sustain such a G force for more than a fraction of a second.
PS. Though FBW systems do put limitation on fighters, I think its more to do with sustained manuevering above certain G force/s rather than instantaneous ones.
very true..even during an accident in a car, say a headon collision, peak loads on the human can be as high as 20Gs, but for a very short duration (fraction of a second), which does’nt kill the human. however, its a different matter if the Gs are sustained for longer periods.
but high peak loads sustained even for short periods, but over several cycles will result in fatigue setting in for structures and then you may find that it may fail well below its ultimate load.
21AnkushNo,
every part of an aircraft has a design-load factor of 1,5 minimum.
Every part built into a fighter is a certificated one. It does take a long time to achieve that for all. By the way, why “better” parts have to wait or will never built in as replacements, because to expensive by that. A main reason, why weight savings seldom come true and aircraft get fatter over the years, when beefed-up in several areas.
that is added on during the calculations for loads to calculate the “ultimate Load”. but if every part that is there on the aircraft are to be given a margin of 1.5 on every single failure check, you’d have mega-heavy aircraft.
on the 787, Boeing made a conscious decision to go do Finite Element Methods instead of Classical composite plate theory based checks, because these classical methods were conservative and resulting in heavier structures. and like I said earlier, there are multiple failure criteria for parts and not all are high..some may be very high and some are just about 5%. and then, if the part is loaded as high as its max loading is, it may fail because that one failure criteria MoS was just about positive.
remember how the A-380s wing failed before it attained its max. load during static tests?
As is usual with static testing, “limit load” tests — approximating the maximum loads likely during normal service — had been completed, and the company was in the process of applying progressively greater loads to simulate more extreme conditions. The typical ”ultimate load“ condition is the load limit plus a factor of safety of 1.5.
max loads likely during normal service are taken at 1G cruise and 2.5G ultimate load for passenger aircraft for secondary structures and 9G ultimate for primary structures like beams, etc.
for fighters, normal service is not 9G, that is quite near to the ultimate load. so, the 1.5 times margin that you’re referring to is generally just about enough to sustain the fighter’s primary structure at 10-11Gs.
21AnkushBoth the early f-15s and the mig-29s were not FBW but were able to pull 9Gs. And while it is correct that the MoS is lower for the fighters, the same holds for all fighters and not just for the JF-17. In the case of JF-17, the FBW limits the plane to 8.5G to stay within operational limits.
whether a fighter is FBW or not DOES NOT DEFINE ITS DESIGN LIMITS. even if the JF-17 was not FBW, but designed to a max. structural load of 8.5Gs, then the pilot would be very clearly told that he was to stay below it.
the reason that early F-15s and MiG-29s were able to pull 9Gs was because they were designed from the word go to be able to do so. it has nothing to do with their having or not having FBW. its a different matter that in modern jets, the FCS would basically pull the aircraft back to safe G limits, if the pilot were to inadvertently enter a maneuver that exceeded safe G limits. MiG-29s are restricted to less than 4 Gs (as far as i can remember) when they had the centerline tank- and the reason had to be that the pylon used to attach the centerline tank to the aircraft would’nt be able to sustain higher loads without strengthening..so, this deficiency remained till now and the pilots would have to punch centerline drop tanks before entering combat.
and MoS are lower for all aircraft, not just fighters. extra weight is a big no-no for aircraft designers and stress analysts. for first time prototypes, it may be understandable if there is added weight due to the wish to stay on the safer side, but as an aircraft goes into production, major weight savings efforts are made and most of it centers around re-sizing from the MoS POV.
21AnkushPerhaps i was not clear in my original post. You are correct that excessive fatigue would cause stress on the airframe and shorten the lifespans. But this holds for ALL aircraft and not just for the JF-17. There is a safety margin in all designs. What i was refering to in your original post was your assertion that JF-17 would be any different then other planes operating at the edges of their G limits (whatever they may be).
what I was saying was that, even for aircraft like the Mirage-2000 that are stressed to withstand upto 13Gs before any catastrophic failure of primary structures, the nominal Gs are not higher than 9Gs, to preserve airframe life mostly..for a fighter that has been structurally designed for a max. 8.5G load, this nominal G limit will be even lower- around the 6 G-6.5G mark.
and fatigue is related to cycles- how many cycles (takeoff/fly/land) will define the fatigue limit and the airframe life. the more often the pilot takes the aircraft near or past the nominal G limits, the higher the airframe fatigue will be, but fatigue is also related to number of flights/landings (one of the reasons that PAF’s F-16 fleet at one time was restricted in terms of number of hours operated, to preserve the fleet).
as for the safety margin you’re referring to, believe me they’re not that high in aircraft design. I constantly have arguments with my Stress Lead over that because weight is a big headache and as long as margins are “sufficiently” positive, the design is passed. so, while certain failure criteria may have large margins, there may be others that are just about 5-7%.
21AnkushIt is very difficult to compare a plane like the LCA which is pretty much an open book (of which a lot is known from official sources as well as reliable and unreliable news sources) as compared to a plane like the J-10 which is a closed book and all that is known is based on pure speculation by the J-10 fan club. So to say one is superior to the other without relevant verifiable information is a total waste of time in my opinion. Even saying one is superior to the other just based on the existence of things like canards is ridiculous. (By the way canards were considered and modeled on the LCA and were discarded as they were deemed to not improve performance in any of the flight regimes)
yup, when there are no official reports or journalistic reports based on official reports, it ensures that most of the issues/problems with the program never really get known..all we hear are reports from fans of the program and bias will always ensure that the reports are favourable to the J-10. I’m not saying that its not good, but for analysts to compare it to F-16s and F-18s based on internet speculation and youtube videos is hardly believable.
21AnkushJust a reminder, Dassault had an estimation of 150 sales for the Rafale.
If they put all their efforts to win the Indian MRCA competition, they’d exceed that entire number in one win itself, since the IAF will definitely order more MRCA fighters after the initial 126.
21AnkushUnfortunately, the bright orange chute cap makes a great visual targetting cue. I believe at least the color will change, if not the chute being deleted all together.
In any case, that LSP-2 seems to have a slightly modified a$$… We’ll just have to wait to find out what the mod is.
some mods to accomodate the IN20 in place of the F2J3 maybe?
21AnkushAbhimanyu, a couple of corrections:
– JF-17 does have pitch FBW.
– Even non-FBW fighters can pull 9Gs. We are discussing limits on Gs and the FBW is used to limit the Gs to 8.5 ie FBW is used to stop the plane from going beyond 8.5Gs.
no, they need not be able to.. the reason is that the Margins of Safety for the structures (not just primary, but also secondary) are not that high in fighter aircraft (primarily to keep weight low) at the highest load conditions. and older generation non-FBW fighters NEED NOT have been designed to take 9Gs..if the stress engineer only sized it for 7Gs and the pilot does pull 9Gs, there will be a catestrophic structural failure.
actually, the MoS are not that high for civilian aircraft either..some MoS may be high, but there are critical ones which need not be high, otherwise the structure would be unacceptably heavy.
21AnkushAll fighter designs are a compromise. And for most modern ones, the FBW places the limit on what they are allowed to pull to preserve the plane as well as the pilot. The airframe times of the JF-17, and all other fighters take this limit into account. So it is incorrect to assume that the stresses on the JF-17 airframe would cause excessive fatigue if it crosses the 8.5G limit. The actual designed G limit would be greater then what the FBW allows the JF-17 to pull. Same holds true for all fighters.
But i think you are correct that in order to save weight, they may have limited the available Gs to 8.5 taking into account that in the real world, the fighters are not likely to cross that limit.
dude, there are European F-16s that had major cracks in their primary structures (spars mostly) due to having to lug heavy ordinance during most of their training missions. and these were F-16s that were still at their mid-life stage and are structurally able to withstand more than 9Gs. the reason is that fatigue does set in when the aircraft is made to lug around heavy payloads or if the pilot pull high Gs in maneuvers a lot..
even IAF Su-30MKI pilots are asked not to unnecessarily pull high Gs to preserve airframe life. what makes the JF-17 any different?
also, if the JF-17 is restricted to 8.5Gs then the structure may not be designed for much more than that, otherwise there would be no reason to restrict it to less than 9Gs which are the norm among 3rd generation fighters.
21AnkushEvery fighter can pull 9G, when not restricted by FBW to do so.
not true.
if the JF-17 has been designed to withstand 8.5G structurally, then in reality, pilots will be restricted to less to prevent some major structural failure. the Mirage-2000 for instance is structurally capable of withstanding 13Gs and yet the nominal max is 9G due to pilots being incapable of taking more. also, if the structure is designed for >9Gs, then even with maneuvers often taken at 5-6Gs, structural fatigue may not be a major issue. on the other hand, if the fighter is designed only for 8.5Gs and the pilot frequently flies the fighter at high Gs, the fatigue levels on the primary structure would be higher, reducing the overall airframe life. (makes me wonder how much the expected service life of the JF-17 is)
IMO, the JF-17 has been designed for 8.5Gs consciously to keep the weight to a level where the T/W ratio is respectable. being a BVR capable fighter, its designers may just feel that the number of times that the pilot needs to go past 8Gs in combat may be limited and its not worth adding approx. 200 kgs to the airframe to be able to take 1G more.
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