More delays for the F-35
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If this is true one can only hope that the design team that did the jet pipe, lift fan and fan doors on the B model can think their way around a slightly longer hook; made perhaps of purest Unobtainium?
Again if true, it's slightly disappointing that they are going to have to. One would have thought that wheel to hook distance etc would have been a fairly fundemental design driver.
This reminds me of a trip to Warton where an ex-Gp Capt berated me for my cynicism when I suggested that I didn't trust computer modelling etc to the degree everyone else seemed to. At the time I was arguing that 'A400M - carries more weight' was a slight overstatement given that it was still just a picture (He thought it was accurate and balanced slogan). I was reliably, and somewhat forcefully, told that design flaws were now a thing of the past.
Maybe we could try a different height of wire? (Wanders well off beaten track and calls it a day..)
Again if true, it's slightly disappointing that they are going to have to. One would have thought that wheel to hook distance etc would have been a fairly fundemental design driver.
This reminds me of a trip to Warton where an ex-Gp Capt berated me for my cynicism when I suggested that I didn't trust computer modelling etc to the degree everyone else seemed to. At the time I was arguing that 'A400M - carries more weight' was a slight overstatement given that it was still just a picture (He thought it was accurate and balanced slogan). I was reliably, and somewhat forcefully, told that design flaws were now a thing of the past.
Maybe we could try a different height of wire? (Wanders well off beaten track and calls it a day..)
Last edited by orca; 16th Jan 2012 at 22:19. Reason: Managed to miss out a whole word.
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Its not the hook length, nor the wire height.
The hook reaches the deck in normal landing operations... the problem is that the hook is so close to the wheels that, after the wheels run over the wire and press it down, the wire does not have time to lift up before the hook arrives.
This is compounded by the hook sometimes bouncing back off the deck after it touches.
The first things they are trying are to change the shape of the hook so that it will slip under the wire even if the wire is still touching the deck*, and to strengthen the bounce dampers to reduce or eliminate hook bounce-back.
* The hook point is the same as used successfully on all F/A-18 models... its just that those aircraft have more wheel-hook distance, so the wire lifts up off the deck before the hook arrives.
The new shape is more likely to damage the wire over time, leading to the wire being replaced after fewer arrestments... they had re-used the Hornet/Super Hornet hook point because it was a low-wear design.
http://i98.photobucket.com/albums/l2...iewGraphic.gif
The hook reaches the deck in normal landing operations... the problem is that the hook is so close to the wheels that, after the wheels run over the wire and press it down, the wire does not have time to lift up before the hook arrives.
This is compounded by the hook sometimes bouncing back off the deck after it touches.
The first things they are trying are to change the shape of the hook so that it will slip under the wire even if the wire is still touching the deck*, and to strengthen the bounce dampers to reduce or eliminate hook bounce-back.
* The hook point is the same as used successfully on all F/A-18 models... its just that those aircraft have more wheel-hook distance, so the wire lifts up off the deck before the hook arrives.
The new shape is more likely to damage the wire over time, leading to the wire being replaced after fewer arrestments... they had re-used the Hornet/Super Hornet hook point because it was a low-wear design.
http://i98.photobucket.com/albums/l2...iewGraphic.gif
Last edited by GreenKnight121; 17th Jan 2012 at 01:17.
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What you say makes perfect sense. If (big and insurmountable if in all probability) one were to lengthen one's hook (either permanently or by using an extendable one), would this not increase the hypotenuse of the triangle which would increase the wheel-hook distance thereby increasing the time available for the wire to elevate? Or does the angle of dangle have to be fairly precise? Equally could you make the wire more taut therefore reducing the time required to spring back up? This would, in a given time frame, be tantamount to raising it.
(You may be able to spot that I don't work for LM but I'm interested in the answers nonetheless!)
(You may be able to spot that I don't work for LM but I'm interested in the answers nonetheless!)
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Right, here comes the civilian with an opinion and questions. I now some of you Steely-Eyed-Missile-Men don't like that sort of thing on here, but it's still a public forum and perhaps a few more civilians with some level of interest in your chosen profession might not be a bad thing, so here goes:
What would be the downside of this scenario?
1. The MOD/BAES/Etc keep their stake in the F-35, but with a reduced number of F-35C (say 60-80) to enter service from 2022-24ish when the type is hopefully getting the bugs ironed out and the GR.4 is sorely needing replacement in the strike role. Eventually the F-35C may still equip the carrier(s), but until the 2018-2025+ timeframe that need is met by:
2. A lease of a small number (12-18?) of F-18F immediately...say within 6-12 months. This squadron-sized force trains with the USN, to include CV ops. If political needs dictate then the RAF/RN Hornet Sqn is UK based with exchange postings ongoing. As the RN Carrier(s) come closer to becoming operational, deliveries of a 48-60+ airframe order begin, ideally with Growlers as part of the package. Could this purchase along with the deferred costs of F-35 allow for cuts elsewhere to be moderated?
3. Naval variants of Taranis and/or its offspring begin to equip the carriers for "Day One" operations in the 2020-23 timeframe to supplement the F-18E/F/G. Depending on how the stealth vs sensor competition works out this may even end up negating the need for the F-35C on the carriers in the longer term, leaving the eventual F-35C purchase to fill the RAF manned strike role, and possibly with a 2-seat variant, serve as a 'mothership' for unmanned platforms in the longer term as evolved Typhoons start showing their age.
I'm not a Walt or a Wannabee, just a guy who wanted to go the military route but couldn't because of eyesight. S o instead I went the civilian way and have managed to accumulate 7,000ish hours in largish flying things, but always kept an interest in military aviation and its role in global affairs. Honest answers appreciated...
What would be the downside of this scenario?
1. The MOD/BAES/Etc keep their stake in the F-35, but with a reduced number of F-35C (say 60-80) to enter service from 2022-24ish when the type is hopefully getting the bugs ironed out and the GR.4 is sorely needing replacement in the strike role. Eventually the F-35C may still equip the carrier(s), but until the 2018-2025+ timeframe that need is met by:
2. A lease of a small number (12-18?) of F-18F immediately...say within 6-12 months. This squadron-sized force trains with the USN, to include CV ops. If political needs dictate then the RAF/RN Hornet Sqn is UK based with exchange postings ongoing. As the RN Carrier(s) come closer to becoming operational, deliveries of a 48-60+ airframe order begin, ideally with Growlers as part of the package. Could this purchase along with the deferred costs of F-35 allow for cuts elsewhere to be moderated?
3. Naval variants of Taranis and/or its offspring begin to equip the carriers for "Day One" operations in the 2020-23 timeframe to supplement the F-18E/F/G. Depending on how the stealth vs sensor competition works out this may even end up negating the need for the F-35C on the carriers in the longer term, leaving the eventual F-35C purchase to fill the RAF manned strike role, and possibly with a 2-seat variant, serve as a 'mothership' for unmanned platforms in the longer term as evolved Typhoons start showing their age.
I'm not a Walt or a Wannabee, just a guy who wanted to go the military route but couldn't because of eyesight. S o instead I went the civilian way and have managed to accumulate 7,000ish hours in largish flying things, but always kept an interest in military aviation and its role in global affairs. Honest answers appreciated...
Perhaps if they made the decks of the ships with slight longitudinal corrugations at and before the wire, the wire would sit higher and the hook would stand a better chance of catching it?
I bet the person who chose to get rid of the arrester runway at Farnborough is unpopular with the MOD...
I bet the person who chose to get rid of the arrester runway at Farnborough is unpopular with the MOD...
The wire (deck pendant) sits proud of the deck in current systems.
As GK says, what is happening at / near mid-span of the cable is that the wheels running over the wire depress it close/onto the deck. Because the jet is doing something like 120kts relative (~60m/s) at that point, the time between the wheels depressing the wire and the hook point passing it is (2.5/60) or 0.04 secs. This is insufficient time for the cable to spring back up.
The trough-type arrangement you're describing would have to be very narrow (driven by the wheel track on both F18 and F35) and of the order of 1-2m in width at best, to avoid the same problem. However, by doing that you're automatically constraining the aircraft to recover within 0.5 to 1m laterally of the deck CL, which will increase the pilot burden / reduce operating envelope and also putting an osbtruction in the deck which in addition to being a corrosion / FOD trap would also be a hazard to tyres during a landing. The current safe parking lining allows for a 3m deviation off CL for the E2. It's a lot of trouble to go to before trying to sort the hook itself.
A new hookpoint is the obvious first thing and if that doesn't work, some sort of hook extension needs looking at, but that will be much trickier. If that doesn't work then they are in trouble. One thing is for certain, whoever in the project was responsible for it getting this far without the basic check on geometry for carrier landings, needs a shoeing of biblical proportions.
As GK says, what is happening at / near mid-span of the cable is that the wheels running over the wire depress it close/onto the deck. Because the jet is doing something like 120kts relative (~60m/s) at that point, the time between the wheels depressing the wire and the hook point passing it is (2.5/60) or 0.04 secs. This is insufficient time for the cable to spring back up.
The trough-type arrangement you're describing would have to be very narrow (driven by the wheel track on both F18 and F35) and of the order of 1-2m in width at best, to avoid the same problem. However, by doing that you're automatically constraining the aircraft to recover within 0.5 to 1m laterally of the deck CL, which will increase the pilot burden / reduce operating envelope and also putting an osbtruction in the deck which in addition to being a corrosion / FOD trap would also be a hazard to tyres during a landing. The current safe parking lining allows for a 3m deviation off CL for the E2. It's a lot of trouble to go to before trying to sort the hook itself.
A new hookpoint is the obvious first thing and if that doesn't work, some sort of hook extension needs looking at, but that will be much trickier. If that doesn't work then they are in trouble. One thing is for certain, whoever in the project was responsible for it getting this far without the basic check on geometry for carrier landings, needs a shoeing of biblical proportions.
2. A lease of a small number (12-18?) of F-18F immediately...say within 6-12 months
if Boeing(?) think that by shoving the RN a knocked off 12 aircraft fleet of F/A-18F's - that will, realisticly, mean that that the F-35 programme gets cancelled and the the F/A-18E/F/G will stay in production for the next 15 years and take a good slice of would have been the sales going to F-35, then they'll find a way of making it affordable.
coz thats whats on the table - if the RN/RAF decide that actually, FA-18E/F/G with some stand-off weapons can do 90% of what JSF can do for 75% of the money and do it before their shiney new carriers turn to rust/the GR4 fleet starts falling out of the sky, then the export market for F-35, and the USN's already lukewarm interest in the programme will evaporate.
continuing the JSF programme as F-35A only probably isn't credible - and Boeing know that as well as the subsequent F/A-18E/F/G sales they'd make if JSF was cancelled, they'd be flogging new-build F-15's like hot cakes.
its called a 'loss-leader' at Tesco, and Boeing aren't stupid...
coz thats whats on the table - if the RN/RAF decide that actually, FA-18E/F/G with some stand-off weapons can do 90% of what JSF can do for 75% of the money and do it before their shiney new carriers turn to rust/the GR4 fleet starts falling out of the sky, then the export market for F-35, and the USN's already lukewarm interest in the programme will evaporate.
continuing the JSF programme as F-35A only probably isn't credible - and Boeing know that as well as the subsequent F/A-18E/F/G sales they'd make if JSF was cancelled, they'd be flogging new-build F-15's like hot cakes.
its called a 'loss-leader' at Tesco, and Boeing aren't stupid...
In terms of who pays for it, it depends on the required "ramp-up" and payment schedule for F35. As I don't believe we've committed to a purchase schedule yet (?), no expenditure on actual F35 squadron a/c will be due until the mid-to-late teens and will be predicated on IOC of the first squadron of JFDave (any takers?).
One might argue that a UK buy or lease of SuperBug in say 2018, would allow a squadron to get IOC broadly when whichever of QEC/PoW commissions and is ready for sea trials (although you could do it with an IFTU, rather than a full squadron for that date.
That would provide CS until the late 20s, at which point funding for F35C (which is off the current spending horizon) could be programmed in.
As for the Boeing's revenge option, while it may look palatable to some (and it'll take a lot more than 12 frames!), for the USN aviation community it probably spells institutional death. After the A12 debacle and an F35C cancellation they will not get another shot at a manned aircraft, ever. SuperBug will not do everything in the requirement and UCAVs are further away (in a non-permissive environment) than you might think.
BTW if the UK does go the Joint Force Dave route, I'd just like to suggest that all assigned aircrew are renamed Dave (even the ladies) and callsigns assigned on a Dave-One, Dave-two, Dave-leader basis. Might even buy some political clout in number 10 atm........
One might argue that a UK buy or lease of SuperBug in say 2018, would allow a squadron to get IOC broadly when whichever of QEC/PoW commissions and is ready for sea trials (although you could do it with an IFTU, rather than a full squadron for that date.
That would provide CS until the late 20s, at which point funding for F35C (which is off the current spending horizon) could be programmed in.
As for the Boeing's revenge option, while it may look palatable to some (and it'll take a lot more than 12 frames!), for the USN aviation community it probably spells institutional death. After the A12 debacle and an F35C cancellation they will not get another shot at a manned aircraft, ever. SuperBug will not do everything in the requirement and UCAVs are further away (in a non-permissive environment) than you might think.
BTW if the UK does go the Joint Force Dave route, I'd just like to suggest that all assigned aircrew are renamed Dave (even the ladies) and callsigns assigned on a Dave-One, Dave-two, Dave-leader basis. Might even buy some political clout in number 10 atm........
Last edited by Not_a_boffin; 17th Jan 2012 at 18:00. Reason: compliance with Equal Opps policies
Not_a_ Boffin wrote:
Not_A_Boffin, What you are describing is a single trough. What I had in mind was a series of shallow undulations with a maximum depth, of, say, one wire diameter and a wavelength of, say, a metre. The next wire would have its dips half a wavelength out of sequence with the first, so if the hook did hit a highpoint on the deck at the first wire it would be more likely to find a low point at the next one.
As for being a FOD trap, with a 1 metre wavelength and a 1 wire diameter depth it should be easy enough to keep clean. The 20 to 42 foot pitch between the arrester wires means that the slope of the longitudinal wavelength will be small.
Some useful info and drawings on arrester hook design and carrier decks here:
http://www.f-16.net/index.php?name=P...topic&p=212174
Given the loads the arrester hook has to take, and its importance, Making it telescopic sounds like a lot of weight and potential unreliability to be incorporating into an already 'weight challenged' aircraft.
Is there any precedent of telescopic arrester hooks for carrier use and what is their track record?
The trough-type arrangement you're describing would have to be very narrow (driven by the wheel track on both F18 and F35) and of the order of 1-2m in width at best, to avoid the same problem. However, by doing that you're automatically constraining the aircraft to recover within 0.5 to 1m laterally of the deck CL, which will increase the pilot burden / reduce operating envelope and also putting an osbtruction in the deck which in addition to being a corrosion / FOD trap would also be a hazard to tyres during a landing. The current safe parking lining allows for a 3m deviation off CL for the E2. It's a lot of trouble to go to before trying to sort the hook itself.
As for being a FOD trap, with a 1 metre wavelength and a 1 wire diameter depth it should be easy enough to keep clean. The 20 to 42 foot pitch between the arrester wires means that the slope of the longitudinal wavelength will be small.
Some useful info and drawings on arrester hook design and carrier decks here:
http://www.f-16.net/index.php?name=P...topic&p=212174
Given the loads the arrester hook has to take, and its importance, Making it telescopic sounds like a lot of weight and potential unreliability to be incorporating into an already 'weight challenged' aircraft.
Is there any precedent of telescopic arrester hooks for carrier use and what is their track record?
OK, see what you're saying. Could be fabricated, but still a lot of trouble to go to for a single bird without trying to fix the hook.
No idea re telescopic hooks in the jet age, but wouldn't expect to see many (any?) prior successes. Might just need to reach for the unobtanium catalogue.......
No idea re telescopic hooks in the jet age, but wouldn't expect to see many (any?) prior successes. Might just need to reach for the unobtanium catalogue.......
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Grumman Panther/Cougar had tail hook that extended aft below the jet pipe before dropping down:
I do think it wasn't dealing with such heavy aircraft as F-35 though and it may be a maintenance issue.
I do think it wasn't dealing with such heavy aircraft as F-35 though and it may be a maintenance issue.
Last edited by Kitbag; 17th Jan 2012 at 19:33. Reason: Trying to get a working link to pic
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A-4 Hook Shoe for F-35C?
Another link for the intended hook shoe redesign which closely resembles the A-4 hook shoe here: CLICK graphic for larger version TAH.
http://www.f-16.net/f-16_forum_viewt...start-105.html
http://www.f-16.net/f-16_forum_viewt...start-105.html
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http://upload.wikimedia.org/wikipedi...ier_3-wire.jpg
good picture here of what happens when a wheel passes over the wire....
good picture here of what happens when a wheel passes over the wire....
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Rather than a telescopic hook, has anyone ever tried a forward facing pantograph rather than a straight hook and bar?
A two -section pantograph, with a short rear facing upper arm, single rear-facing joint, and a longer lower section facing forward could put the hook in front of the wheels.
There would be some pretty extreme forces on the joint between the two arms as it was allowed to straighten out after capture, but it would put the hook in a better place.
A two -section pantograph, with a short rear facing upper arm, single rear-facing joint, and a longer lower section facing forward could put the hook in front of the wheels.
There would be some pretty extreme forces on the joint between the two arms as it was allowed to straighten out after capture, but it would put the hook in a better place.
COCL2,
Wow. Seriously inovative thinking. I'm no engineer so can't really help. Maybe speak directly to Boeing and sell your idea!
Mechta,
Thank you for the link. Some fascinating material there. One of the quotes that stuck in my mind was "it can't be that difficult to design a hydraulic telescoping tail hook that will increase the distance from the mains."
No, it probably isn't, but two issues occur. First, running hydraulics in a hook that moves pretty violently would be a "hostile" environment and the weight issues would be significant. Second, it's a stealth jet and the design of the hook is always going to be a significant lim fac. I'd like to hear more thoughts on this.
Wow. Seriously inovative thinking. I'm no engineer so can't really help. Maybe speak directly to Boeing and sell your idea!
Mechta,
Thank you for the link. Some fascinating material there. One of the quotes that stuck in my mind was "it can't be that difficult to design a hydraulic telescoping tail hook that will increase the distance from the mains."
No, it probably isn't, but two issues occur. First, running hydraulics in a hook that moves pretty violently would be a "hostile" environment and the weight issues would be significant. Second, it's a stealth jet and the design of the hook is always going to be a significant lim fac. I'd like to hear more thoughts on this.
Kitbag referenced, before his edit, a very interesting article but as it was in a blog you can reach it, as I did, by typing "A Brief History of Tailhook Design" into Google.
As for a telescopic tail hook, anything involving sliding tubes or rods is going to be prone to trouble. The best and lightest solution I can currently think of for the F-35, is something which works on the same principle as the party whistles (below) in Kevlar with the metal shoe on the end ( provided it can be damped enough). It would at least be able to get the hook back far enough for a reliable hook up:
As for a telescopic tail hook, anything involving sliding tubes or rods is going to be prone to trouble. The best and lightest solution I can currently think of for the F-35, is something which works on the same principle as the party whistles (below) in Kevlar with the metal shoe on the end ( provided it can be damped enough). It would at least be able to get the hook back far enough for a reliable hook up:
Mechta,
And to think I was almost taking you seriously!
So, I've been watching a number of vids of this wonder jet raising and lowering it's gear and I can't help wondering if this isn't another modern a/c with systems that aren't quite man enough for the job (no sexism intended and there are other manufacturers of a/c/ systems).
Thus, second generation fast jets were brick built **** houses with massive generators, engines that could eat birds and launch a man into space and hydraulic pumps that could power a JCB. Third gen FJs had Skoda generators, turbo charged 1.6 litre engines (when they really needed a 6 litre V8) operating closer to the surge margine than was always healthy and that struggled to pick up the gearbox load if it's mate quit and hyd pumps that were bought on ebay.
It's been a long night, but try to stay with me.
Now we're looking at an a/c that doesn't seem to want to operate all three gear legs at the same time - somewhat reminds me of the a/c my father flew where the gear legs struggled up one at a time.
Can someone please tell me this is because of some sound aerodynamic/stealth/technical reason and not because the utility hyd system just can't move all three legs at the same time?
And to think I was almost taking you seriously!
So, I've been watching a number of vids of this wonder jet raising and lowering it's gear and I can't help wondering if this isn't another modern a/c with systems that aren't quite man enough for the job (no sexism intended and there are other manufacturers of a/c/ systems).
Thus, second generation fast jets were brick built **** houses with massive generators, engines that could eat birds and launch a man into space and hydraulic pumps that could power a JCB. Third gen FJs had Skoda generators, turbo charged 1.6 litre engines (when they really needed a 6 litre V8) operating closer to the surge margine than was always healthy and that struggled to pick up the gearbox load if it's mate quit and hyd pumps that were bought on ebay.
It's been a long night, but try to stay with me.
Now we're looking at an a/c that doesn't seem to want to operate all three gear legs at the same time - somewhat reminds me of the a/c my father flew where the gear legs struggled up one at a time.
Can someone please tell me this is because of some sound aerodynamic/stealth/technical reason and not because the utility hyd system just can't move all three legs at the same time?
http://upload.wikimedia.org/wikipedi...ier_3-wire.jpg
good picture here of what happens when a wheel passes over the wire....
good picture here of what happens when a wheel passes over the wire....
Hard to tell but isn't that the nose wheel? Wonder what it looks like when 2 spaced out main gears go over it?