Forum: Program and politics

arkadyrenko said: "spazsinbad - do you just make a habit of throwing out military spec graphs to "prove a point"? ..."

Earlier (until corrected/clarified) arkadyrenko said: "..."...because this amount of weight and hook length haven't been seen before for a carrier airplane...." Whilst arkadyrenko expanded on his original comment in a later post I went away to get the WEIGHT TABLES. Oooh - so there was no mention of the hook length. I did not think to mention at that time - 'how was that relevant'?

However you later expanded on your point and I have not replied. So what is the big deal? I am not psychic. I responded to the weight component. Get a grip.
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And to be clear I am not suggesting the QLR people are liars. If you read the hook design MILSPEC you will see that NavAir and LM have been co-operating from the beginning about the F-35C hook design. If there is fault to be found then it can be found in this co-operation. What I am suggesting, as the QLR suggests, is that due to this detailed analysis (that did not work in the case of the eight failled roll-in arrests - don't forget there were three unspecified successful [probably fly-in?] arrests at some point) that the fix has been identified - with the more dire possibility only if that first fix does not work. Your mind goes straight to the worst case that has not been reached yet. So be it. Catastrophism rools man.

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Ah, ok, sorry about that. I read the QLR too. The key question is about the new hook geometry's margins, especially compared to the hook for the current aircraft. Eh, we'll see about that. They were going to test it this December, if I recall correctly?

Fair enough. I don't claim to know the answers however I do claim that LM and NavAir are not foolish. If a mistake is made then a mistake is made, however it seems a fix is easily possible given all the prior knowledge gleaned during the co-operative process of designing the hook that does not quite work yet. Sometimes Pprune is just full of .... but there are people there with some knowledge (mostly UK-centric) but perhaps relevant to this discussion. Some of it (what I think are relevant bits) are below:

Off Topic

If anyone can find a downloadable for free "NAVAIR Aircraft Carrier Reference Data Manual" that info would be nice to know. Thanks.

On Topic

Two thread pages on Pprune about HOOK F-35C issues [Crusader pic below is referenced in the thread - I have added an UnHappyHornet pic of 'F/A?18C Strike Fighter Squadron 94 (VFA?94)'. It is always easy to do a bad carrier landing, although this Hornet is not in bad shape really (compared to the Crudmaster). Twisted Evil

More delays for the F-35:

http://www.pprune.org/military-aircrew/ ... 5-a-4.html

11th Jan 2012, 'Engines ' "Guys,
Further to my last on 17 Dec (Thanks Courtney!),
Having quickly looked at the arresting gear Mil Spec, I can't find a specific gear/hook distance requirement. There are a zillion other parameters there for various angles, clearances, etc., and the F-35C hook, as far as I remember, meets those.

I can confirm that the team designing the hook (which is LO - it retracts under a complex set of covers) were certainly fully aware of all the various specs. They had a couple of goes at getting a hook that did that, and one of the redesigns addressed a problem you can see on the Crusader picture (nice pic) which shows an effect called 'wheelbarrowing', where the hook is too low down on the aircraft. When it engages the wire, the effect is to pull up on the fuselage, lifting the mains off the deck, and leaving the aircraft sitting unstably on its front leg. The first hook design sat it too low, so a redesigned mounting yoke system was then used.

The hook system design was also exhaustively checked by the US Navy NAVAIR engineering and flying specialists before it was approved for manufacture.

THe USN specs are largely empirical and actually reflect the experience gained on aircraft like the F-7U and F-8U. By the way, the Cutlass landings were on a straight deck, and they had up to 12 wires at one stage to make sure they caught a wire - the options weren't too good if they didn't. [I think 'Engines' has read the very old MILSPEC rather than most recent.]

The lesson here (sorry if I sound a bit schoolmasterish) is that getting 'cat and trap' to work with large high performance combat aircraft is really, really difficult. The USN make it look easy because they are damned good at it. It's also risky and takes a high degree of skill to do even when you get the kit right. I wonder whether our lords and masters really understood all that when they went for the C. (John Farley would have plenty to say on this, I'm sure). I'm not saying it's a wrong decision, we just need to get our heads around the reality of it. This thread is really helping to do that.

Best Regards as ever to all those on land and sea and air who are doing the job for real,
Engines "

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http://www.pprune.org/military-aircrew/ ... 5-a-5.html
'kbrockman': About the pictures;

That's not a Cutlass but a Skyray in photo number 2.

The Cutlass had also some tailhook problems but because it had a massively high frontgear and a high AoA when landing combined with a redesigned hook that was considerably further away from the rear LG compared with the F35C it eventually was able to land on the Carriers.

The F35C's hook is indeed too close to the rear gear, even closer than the unmanned X-47, but it is not a showstopper in the longrun, a redesigned hook (the actual catching part) is already being manufactured giving it a higher probability of trapping the wire, also a hook that pivots the other way around is possible giving automatically a much greater distance without needing a major strenghtening of the frame while making it possible to make it fully covered by RAM plating better integrating it into the plane improving its Stealth characteristics also...."
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'Engines ': Kbrock,

You are spot on that the Cutlass had severe problems - the extended nose gear was added to achieve reliable launch, the cockpit then had to be raised, and its controllability on approach was always marginal at best. I understand it was called the 'Ensign Killer' due to its poor safety record.

Your comments on the F-35C hook are spot on too - they will fix this, but they are running risks until the optimised hook shape and damper setup are proved...."
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F-35 Cancelled, then what ?
http://www.pprune.org/military-aircrew/ ... at-12.html

18 Dec 2011 - 'Engines': Glo,
Fortunately, the UK made bit of the fuselage does not include the Arresting Hook System (AHS) or the supporting structure, which is massive with a big M.

The issue reported is serious but should be solvable with some clever engineering - but if the hook has to be moved aft that is going to be a very serious design change indeed.

The source of the issue is the well aft location of the main wheels - driven in part by the requirement for long weapon bays and also by the structural layout that hangs a number of big loads (aft spars, verticals, thrust mounts, main gears) on or around a big frame located well aft. In addition, with a single engined aircraft, there isn't much structure at the end of the fuselage to hang the hook system on, mostly just jetpipe. That moved the hook system forward. The report contains a huge amount of interesting detail.

My bet is that they will try a hook point and damper redesign, and if that doesn't work, they could go for a more complex (but sadly heavier) translating or extending hook mechanism to get the point further aft. If that's not possible, it's a hook system move aft - potential nightmare.

This is a complex one to fix and test, as the time between the main wheels hitting the wires and the hook engaging them is not fixed and the dynamic behaviour of the wire is complex, depending whether you engage in mid span or off centre. You also have to do a number of traps on land and more importantly at sea on a pitching and heaving deck to really test it out.

Remember, this cat and trap stuff is complicated and difficult. The USN make it look easy. It ain't.

Best Regards as ever to all those actually doing the dangerous stuff on land or sea,
Engines"

Based on the Powerpoint slide on the new and original hook points the redesigned one will be significantly better. Note how apex of the hook point is below the centerline of the cable when it's on the deck. That's the worst case senario. If the cable is any distance above the deck it should ride up the hook point. The only question I have is how reliable will the cable engagement by the hook be at worst case scenario? You have two similar surfaces mating almost normally. Would prefer a little offset or a smaller radii on the hook point.

The key to making it work will be the strength of and the response time of the damper. Need to drag the hook point on the deck.

For the same scenario the original hook point apex was more bulbous and it's centerline was above the cable. Additionally the shoe-like geometry below the apex of the hook point aids in causing the hook to skate above the cable.

marksengineer wrote:

...the shoe-like geometry below the apex of the hook point aids in causing the hook to skate above the cable.

"wire-jumper?".

With the conventional "tail-hook" training and the JPALS feedback to the "auto-land" algorithm, the hook placement/ engagement "Should" be easier for the "Sea" aviator. This would be certainly predicated on a successfully designed tailhook.

The man-in-the-loop and computer controls to "finesse" the hook to CDP engagement, is percentage wise unsuccesful todate, as related by vAdm. V.

We will see the test of the improvements in first quarter 2012.

As seen in this A4G + Brazilian photos often the wire will be caught onboard whilst wheels airborne, however ashore it seems at least there is the 'roll-in' problem. The hook has to work in all reasonable situations ashore and afloat. Probably where error became evident was 'roll-in'?

marksengineer wrote:

Based on the Powerpoint slide on the new and original hook points the redesigned one will be significantly better. Note how apex of the hook point is below the centerline of the cable when it's on the deck. That's the worst case senario. If the cable is any distance above the deck it should ride up the hook point. The only question I have is how reliable will the cable engagement by the hook be at worst case scenario? You have two similar surfaces mating almost normally. Would prefer a little offset or a smaller radii on the hook point.

The key to making it work will be the strength of and the response time of the damper. Need to drag the hook point on the deck.

For the same scenario the original hook point apex was more bulbous and it's centerline was above the cable. Additionally the shoe-like geometry below the apex of the hook point aids in causing the hook to skate above the cable.

I had many of the same thoughts when I read the QLR. The original shoe design assumes the cable will be off the deck. But the current short tail length means the cable is still flush with the deck when the hook meets it, and that big rounded shoe nose is sliding right over the cable. Giving the shoe more of a wedge shape to help it get under the cable MAY fix the problem.

It seems like another solution might be to make a folding tailhook, essentially doubling its length. That will give the cable more time to recover from being pushed flush to the deck by the mains.

Only the nose was lengthened by 12 inches to make the Trainer Version of the Skyhawk, so the hook point to main wheel distance is the same in two seat / single seat versions (see the QLR graph for distance in feet).

MLG (main landing gear) to tailhook distance 9.4 feet (F-35C 7.1 feet) - see the Brazilian AF-1 (formerly A-4KU) above.

AF-1 pic below shows the effect of trample on the arrestor wire - with ZOOM to follow...

Last edited by spazsinbad on Jan 13, 2012 - 01:03 PM; edited 3 times in total

A-4K - RNZAF Skyhawk Hook with ZOOM:

http://www.aircraftresourcecenter.com/A ... vin/03.jpg

2nd Zoom from slightly forward angle from:

http://www.aircraftresourcecenter.com/A ... vin/02.jpg

[Found the SkyHooks!] Last 2 Pics...

Close Up Russian Hook Action in this recent video. Screenshot from video.

Airwing Kuznetsov training in the Mediterranean

http://nosint.blogspot.com/2012/01/airw ... ng-in.html

Mediterranean_flights.avi

http://www.youtube.com/watch?feature=pl ... SyDa_J0XaM

"December 30, 2011. TV Zvezda. Mediterranean Sea. Training flights carrier-based aircraft AC Admiral Kuznetsov."
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"Jet fighter pilots on Russia’s aircraft carrier “Admiral Kuznetsov” have been conducting take-off and landing drills in the Mediterranean.

A vessel group led by Russia’s only aircraft carrier, the Northern Fleet’s “Admiral Kuznetsov” is currently on a mission in the Mediterranean Sea.

Besides port visits to Syria, Lebanon and Cyprus, the vessels will be conducting drills in the area. The Greek Joint Staff has given green light to flights in western Greek air territory."

duplex wrote:

The UK should immediately start working on a navalized Typhoon or simply buy the French Rafale . The third best alternative would be the Super Hornet.
Otherwise, these two new QE class carriers which cost UK taxpayers a fortune , won't have any aircraft on their deck at the time they are launced .

Navalized Typhoon would cost a fortune.

Vipernice wrote:

duplex wrote:

The UK should immediately start working on a navalized Typhoon or simply buy the French Rafale . The third best alternative would be the Super Hornet.
Otherwise, these two new QE class carriers which cost UK taxpayers a fortune , won't have any aircraft on their deck at the time they are launced .

Additionally Saab opened up a Sea Gripen design centre in London to complete work on a carrier version based on the NG being built for Sweden/Switzerland.

It's interesting because it's compact and has drop down engine (good for tight spaced carriers) yet quite powerful. High UK content including the AESA front-end.

http://i.imgur.com/YSaNs.jpg
http://i.imgur.com/n74Te.jpg

More: http://www.flightglobal.com/news/articl ... uk-357137/

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Too small. Sea Gripen would be for something the size of the old french Clemenceau class.

Some RAFALE JuJu - I wonder what the specs are re hook / main wheels and whatnot?

http://www.globalsecurity.org/military/ ... /cdg28.jpg

maus92 wrote:

hb_pencil wrote:

That's not quite true, and your comments reflect the success the Navy had in demonizing the fighter.

Everything I said was was true. The history of military aviation development programs is littered with underperforming aircraft that were cancelled both for technical reasons and changing requirements. That is the way it works. And it turned out that it was the correct decision.

Okay for the last time, the F-111 was not a seriously underperforming aircraft, at least if you make an honest comparison to other aircraft. It met most of the Navy's specifications as they were laid out. They then changed the specifications. Much of the F-111 history has to be understood from the prism of bureaucratic politics. The Navy did not want the fighter and played political games to get it killed.

Neither was the plane dangerous to fly; the F-14A was significantly more risky. The tomcat's the wide spacing of its engines, which made extremely difficult to gly when one of the TF-30 had a "malfunction." With equivalent bring back (ie same amount of fuel and weapons), the F-111 actually was easier to land.

The F-111 received a lot of bad press at the time, which wasn't really deserved. Noted aviation historian Tommy Thomason made this blog post that details some of the inaccuracies perpetuated about the F-111B. His book goes through it pretty comprehensively.

maus92 wrote:

What exactly is untrue? Just because the program is run through NAVAIR and the current PEO is a naval aviator doesn't mean the F-35 basic design was weighted towards naval specifications.

Okay, you say that but then you say...

maus92 wrote:

Quite the contrary. The basic F-35 design is inadequate for CATOBAR (and incidentally is also at the root of the current tailhook issue.) Major structural modifications had to be incorporated to make it work: larger wings and tails, more robust landing gear, a tailhook strong enough for routine use, a keel to withstand the unique forces and fatigue generated by repeatedly slamming onto the deck, etc. All this makes the aircraft considerably heavier than the other models, while using the same powerplant - patently not good.

So first you say that the fighter "was not weighted to navy specifications," then you proceed to list off five things they did to make it acceptable to the Navy. And this isn't really at all unique situation. Almost all Navy fighters had inferior performance to their AF counterparts due to the extra carrier equipment. (the only exception was the F-4.)

maus92 wrote:

As far as the corrosion specs go, if the were Navy driven, than it's a good thing considering the corrosion problems the air force is currently experiencing with its fleet of stealth aircraft, and I don't see how that has anything to do with my statement.

No, maybe you don't get what I'm saying. The JSF wasn't an AF project made to meet Navy specifications. It was a joint project right from the start of its CDP. The CV variant meant that the aircraft had to meet Navy specifications and metrics for almost everything, of which corrosion was one of thousands. There was no "weighting." It met their specifications or it didn't. In this very thread you had an account about the tailhook design had to meet stringent navy standards. In many ways the navy's requirements represented the lowest common denominator for common areas. For several parts of the F-35A's design has redundancies that go beyond AF specifications because they needed to meet Navy standards. In places where the design could not meet both specifications, you had the different variant.

I just wanted to go back to one post you made earlier....

maus92 wrote:

Hence we are in the situation we find ourselves today - trying to adapt what is an essentially land based design into something that can withstand the harsh operational environment inherent in carrier aviation. .

You know what's the irony of this comment? Basically all of the same changes were made to the YF-17 to create the F/A-18, yet you're here on a daily basis lauding the latter's performance.

Here is a good thread to warm the cockles of any F-111 Defender of the Fleet:

Arresting F-35s & Brake Testing Yump Forwards/Backwards as youse wish....

http://www.f-16.net/f-16_forum_viewtopi ... rt-30.html

spazsinbad wrote:

Here is a good thread to warm the cockles of any F-111 Defender of the Fleet:

Arresting F-35s & Brake Testing Yump Forwards/Backwards as youse wish....

http://www.f-16.net/f-16_forum_viewtopi ... rt-30.html

Yeah I posted the direct link to Thomason's article in my post above. I think he wrote that post when he was able to receive detailed info about the B's specifications, because he didn't have them in his book.

Forum: Program and politics

U.S. Navy and U.K. Royal Navy F-35 unable to get aboard ship