chuchoteur
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F35C Unable To Catch The Wire?

Sun Jan 15, 2012 5:53 pm

http://www.dailymail.co.uk/news/arti...r-jets-land-aircraft-carriers.html

Apparently there may be an issue with the arrestor hook not being able to catch the wire...
That's embarassing if it's true...
 
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Dreadnought
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RE: F35C Unable To Catch The Wire?

Sun Jan 15, 2012 6:14 pm

Oh God...

This is why I wish Grumman was still around. They were called the Grumman Ironworks, because they understood that carrier aircraft had to be over-built to the fare-thee-well, and had a long history of building exceptional carrier-based aircraft.
Forget dogs and cats - Spay and neuter your liberals.
 
ThePointblank
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RE: F35C Unable To Catch The Wire?

Sun Jan 15, 2012 8:27 pm

A lot of older naval aircraft struggled with the arrestor hook not being able to catch the wire; for example, the Vought F7U Cutlass struggled initially to catch the wire, and they had 12 wires available to snag when that fighter came out.

The hook design for the F-35C was approved by NAVAIR engineering and flying specialists before it was approved for manufacture. Lockheed Martin can't be blamed on something that NAVAIR approved and it doesn't work.

The lesson here 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.

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. Designing a naval aircraft to do carrier landings is very difficult because of all the variables involved. Even then, you still have bolters; many navy pilots still have trouble catching the wire because practically, every landing is unique in terms of how the wire will behave when landing.

A redesigned hook is in the works with a modified profile; the issue is not a show stopper as some in the media would suggest, just a source of annoyance.
 
rfields5421
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RE: F35C Unable To Catch The Wire?

Sun Jan 15, 2012 8:41 pm

Well, they have at least four years, probably six, to work out the problem before the new aircraft carriers will come into service - assuming there are no delays in construction.
 
spudh
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RE: F35C Unable To Catch The Wire?

Sun Jan 15, 2012 9:13 pm

That Daily Mail article is drivel. The issue could be very serious if it has genuine problems with landing gear geometry, but I doubt you can read a huge amount into just 8 failed landings. From everything I've read about carrier landings and testing aircraft this is not a new occurance. I'm racking my brains but I can't remember exactly which aircraft before had a hard time with hook bounce but just about every navy fighter takes a lot of testing and tweaking before they sign off on a whole range of variables.

Anyone got a side shot of the F-35C with hook down?

The geometry can't be that far off something like an A-7 Corsair

You'd think that a change of AoA on approach might go a long way to dealing with the issue. The one thing the F-35C seem to have in spades is visibility over the nose so I'd guess they'll have a whole range of AoA's to choose from. The F-14 was specified to land at 125kts but crew were not happy with visibility over the nose on final approach. A relaxation in requirements led to an approach speed of 134kts at a lower AoA. Flew (and crashed  ) like that for the next 30 odd years. Remember the F4 Corsair which was designed for the marines in WW2 but USN couldn't land on a carrier due to visibilty issues until the RN decided to fly a curved approach and the rest is history. If the navy want it, they'll get it aboard.

Mind you, the last white elephant of commonality, The F-111B, failed on carrier landings too but the Navy were just looking for an excuse to kill that programme, you can bet they'll get the F-35 catching wires all right.
 
L-188
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RE: F35C Unable To Catch The Wire?

Sun Jan 15, 2012 11:03 pm

Well the corsair also had issues with being bouncy on landing until the navy figured out the correct oil/gas mixture for the struts.

This may be just a training issue, they almost lost the U2 prototype bouncing it on touchdown because he guy flying it tried to land it like a normal tail dragged and didn't listen to the advice of some of he b-47 guys on how to land a tandem gear aircraft.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
Arniepie
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RE: F35C Unable To Catch The Wire?

Sun Jan 15, 2012 11:05 pm

Of all things/problems that need to be tested, changed and adjusted, I somehow doubt that this whole, granted
somewhat embarrassing, tailhook mishap is anything more than an engineering challenge.
The JSF won't be stopped in its tracks because of this.

Also this wasn't found out while trying actual arrestor landings but was already identified when the testplanes did the
first high speed-cable catch tests.

[Edited 2012-01-15 15:05:57]
[edit post]
 
fvtu134
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 8:38 am

Maybe lease some Harrier GR.7/9's from the USMC? I heard they picked up a few for a bargain price  
Sorry.. couldn't resist that one.

Just another episode in the F-35 saga... Unfortunately to many bureaucrats running these programs these days... It really amazes me that nobody could have thought about this up front...

FVTu134
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chuchoteur
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 12:28 pm

The F-35 Concurrency Quick Look Review is available on the link below.
It makes for interesting reading...

http://pogoblog.typepad.com/pogo/201...trike-fighter-problems.html#report
 
XT6Wagon
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 12:41 pm

Quoting ThePointblank (Reply 2):
A redesigned hook is in the works with a modified profile; the issue is not a show stopper as some in the media would suggest, just a source of annoyance.

A source of "annoyance"

I don't find redesigning the primary structure of a $150M Fighter "annoying". I find it horribly lax in the engineering. Also quite short forethought.

Thats right, the program evaluation found out that they are going to have to redesign the primary structure to relocate the hook.

So, please don't describle being mauled by a bear as rough cuddling on a bear skin rug. While some of the, er, "facts" are true in theory, its not at all accurate of what really happened.
 
spudh
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 2:51 pm

I found this:

http://3.bp.blogspot.com/-VqEq1NKQMT...W26Nwx3-9U/s1600/hooklocationC.png

Ouch!! that looks bad. I assume the wire isn't bouncing up fast enough after the wheel goes over it. That'll take a bit of fixing!!
 
XT6Wagon
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 4:56 pm

Quoting spudh (Reply 10):
found this:

http://3.bp.blogspot.com/-VqEq1NKQMT...W26Nwx3-9U/s1600/hooklocationC.png

Ouch!! that looks bad. I assume the wire isn't bouncing up fast enough after the wheel goes over it. That'll take a bit of fixing!!

Thanks, I knew it was something stupid like that, but hadn't seen it in nice graphical form.

Seriously, its been what? Oh 100 years since this was invented?

"Arresting cable systems were first invented by Hugh Robinson and were utilized by Eugene Ely on his first landing on a ship - the armored cruiser USS Pennsylvania, on January 18, 1911"
http://en.wikipedia.org/wiki/Arresting_gear

olo
Its ok, cause its going to replace an A10, F16, F15, F14, F18, and your lawnmower. All better and cheaper. We just can't tell you when and the cheaper has a huge astrisk after it. You know, one the size of what the greek titan Atlas holds up.
 
dlednicer
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 5:25 pm

Quoting spudh (Reply 4):
Remember the F4 Corsair which was designed for the marines in WW2 but USN couldn't land on a carrier due to visibilty issues until the RN decided to fly a curved approach and the rest is history.

Its a little more complicated than that: the Vought F4U Corsair failed USN carrier qualification trials in September 1942 and March 1943 due to numerous shortcomings including poor stall characteristics, landing gear bounce, insufficient directional control at low-speed, high-power conditions and poor cockpit visibility on approach. After further development the F4U Corsair passed carrier qualification trials in April 1944. The bounce problems were really bad and led to changes in the oleo strut metering.
 
bennett123
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 8:41 pm

Also of course, the Corsair happened in war time.

Would war time attrition and corner cutting be acceptable in peace time.
 
spudh
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 9:34 pm

Quoting dlednicer (Reply 12):
Its a little more complicated than that: the Vought F4U Corsair failed USN carrier qualification trials in September 1942 and March 1943 due to numerous shortcomings including poor stall characteristics, landing gear bounce, insufficient directional control at low-speed, high-power conditions and poor cockpit visibility on approach. After further development the F4U Corsair passed carrier qualification trials in April 1944. The bounce problems were really bad and led to changes in the oleo strut metering.

Thanks for that, didn't have the full story but it goes to show what can be achieved, the F4U being arguably the most successful WW2 fighter in terms of service longevity, definitely from carriers but I think it outlasted even the P-51 in US service. And that from a really bad start.

Quoting bennett123 (Reply 13):
Also of course, the Corsair happened in war time.

Would war time attrition and corner cutting be acceptable in peace time.

But that just goes to shows how bad the problems with the F4 were, it took 18 months to sort it out even during full war conditions with pressing needs, I don't know how long it took to develop the F4 in the first place but the Mustang only took 5 months. But the F4 proved well worth the effort.

Its going to be difficult for the F-35C engineers. If it's fundamentally a geometric problem and not a damping issue they don't have much room to work with if they are going to preserve the stealth characteristics. The 9'4" figure for the A-4 will give hope, shifting the mounting point back 2' might be in the realms of what is possible. At least then they're operating in proven ground. But any change of that magnitude is going to add a lot of weight so it'll be interesting.

I can't help thinking of any pilots coming in to land on a heaving deck at night. Any book I've read by Navy pilots describes night traps in marginal weather as the scariest thing imaginable for a pilot even compared to combat. A bolter prone fighter won't instill the confidence necessary to take that on.

I was starting to come off the fence in favour of the F-35 programme but that was based on believing that the C model was the most critical model from the point of view of security of funding. It really needs to be 'good at the back of the boat', the Navy can't afford anything less.
 
chuchoteur
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RE: F35C Unable To Catch The Wire?

Mon Jan 16, 2012 9:48 pm

Quoting spudh (Reply 14):
I can't help thinking of any pilots coming in to land on a heaving deck at night. Any book I've read by Navy pilots describes night traps in marginal weather as the scariest thing imaginable for a pilot even compared to combat. A bolter prone fighter won't instill the confidence necessary to take that on.

A really good series on the subject of pitching deck qualifications:

http://www.youtube.com/watch?v=4Ki8Ji4HQVU
 
AirRyan
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RE: F35C Unable To Catch The Wire?

Tue Jan 17, 2012 2:34 am

Quoting dlednicer (Reply 12):
Its a little more complicated than that: the Vought F4U Corsair failed USN carrier qualification trials in September 1942 and March 1943 due to numerous shortcomings including poor stall characteristics, landing gear bounce, insufficient directional control at low-speed, high-power conditions and poor cockpit visibility on approach. After further development the F4U Corsair passed carrier qualification trials in April 1944. The bounce problems were really bad and led to changes in the oleo strut metering.

The biggest problem with the F4U when it came out was because of the rear placement of the seat in the F4U it gave the pilot poor visibility on approach when landing on an aircraft carrier. The Navy gave a bunch to the Marines to use on land, and through lend-lease the British Royal Navy to use off their own carriers. If I remember correctly, it was the British who then perfected the shallow left hand turn approach, only turning wings level just moments before the aircraft would touch down on the carrier deck. This way, it gave the pilot the visiblity they needed to make repeated, successful carrier landings in the F4U.

I'm sure the USN will get the F-35C figured out, and if all else fails the USMC and RN can just buy Super Hornets if push comes to shove!
 
ThePointblank
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RE: F35C Unable To Catch The Wire?

Tue Jan 17, 2012 3:25 am

Quoting spudh (Reply 10):
I found this:

http://3.bp.blogspot.com/-VqEq1NKQMT...W26Nwx3-9U/s1600/hooklocationC.png

Ouch!! that looks bad. I assume the wire isn't bouncing up fast enough after the wheel goes over it. That'll take a bit of fixing!!

The de Havilland Sea Vixen had a just short distance between the tail hook and the rear wheel. It managed just fine.
http://upload.wikimedia.org/wikipedia/commons/1/15/13_Sea_Vixen_landing_on_Eagle_Mediterranean_Jan1970.jpg
 
AAR90
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RE: F35C Unable To Catch The Wire?

Wed Jan 18, 2012 1:20 am

Quoting spudh (Reply 10):
Ouch!! that looks bad. I assume the wire isn't bouncing up fast enough after the wheel goes over it. That'll take a bit of fixing!!

Perhaps not. The CDP (cross-deck pennant) is normally lifted off the deck 2-3 inches by what are essentially leaf-springs. An acft tire rolling over the CDP would push the CDP forward and off the springs. The close positioning of the hook-point to main gear tires probably doesn't allow enough time for the CDP to re-position on the springs before the hook-point goes past. See this for a simplified explanation of arresting gear including a photo of what is probably happening for the F35C.

The real question is how NavAir allowed a tail hook-point design that will never grab a CDP that is resting on the deck to be put on a CV aircraft. The linked report shows exactly why the F35C is having "hook-skip" issues.

*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
spudh
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RE: F35C Unable To Catch The Wire?

Wed Jan 18, 2012 11:56 am

Quoting ThePointblank (Reply 17):
The de Havilland Sea Vixen had a just short distance between the tail hook and the rear wheel. It managed just fine

While it appears to have somewhat similar geometry a bit of measuring (albeit rough) appears to say otherwise. Dimensions are decimal feet. But again, its a short geometric length on a successful carrier fighter so will give confidence on a solution.

Quoting AAR90 (Reply 18):
The real question is how NavAir allowed a tail hook-point design that will never grab a CDP that is resting on the deck to be put on a CV aircraft. The linked report shows exactly why the F35C is having "hook-skip" issues.

Thanks for that great info. Hopefully there's enough Grumman boys with experience left in NG to bring a bit of sense to that situation. What would be very interesting/bad would be if the hook bounce amplitude corresponded with the hook to wheel length at landing speed in which case even a hook perfect for picking a wire off the deck wouldn't work as it would be in the air every time. The damping valve variations seem to reduce the effect but if the dynamics of the initial bounce are off then they'll have a real headache.
 
ThePointblank
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RE: F35C Unable To Catch The Wire?

Thu Jan 19, 2012 2:39 am

Quoting AAR90 (Reply 18):

The real question is how NavAir allowed a tail hook-point design that will never grab a CDP that is resting on the deck to be put on a CV aircraft. The linked report shows exactly why the F35C is having "hook-skip" issues.

Easy. They adapted the design of the hook from the Super Hornet, which has a blunt face to better provide cable shredding protection versus scooping. However, the F/A -18E/F's geometry places the distance of its main landing gear to tailhook point at 18.2 feet. Someone at NAVAIR didn't think about the geometry involved here.


There is a nice little history on the design of tail hooks for carrier based aircraft here:
http://thanlont.blogspot.com/2011/12...ef-history-of-tailhook-design.html

You can see that a lot of aircraft in the past had issues catching the wire when originally designed, and the proposed fix is comparatively simple; revise the shape of the hook point and modify the damping of the hook so that it is less likely to skip over all the wires.
 
checksixx
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RE: F35C Unable To Catch The Wire?

Thu Jan 19, 2012 7:40 am

I think this will be easily fixed. It will also be used for all the detractor's of the program to run wild with...I seem to remember the Super Hornet wing flutter problems early on...prompting cancellation cries and such...LoL
 
Powerslide
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RE: F35C Unable To Catch The Wire?

Thu Jan 19, 2012 4:41 pm

Quoting checksixx (Reply 21):

I think this will be easily fixed. It will also be used for all the detractor's of the program to run wild with...I seem to remember the Super Hornet wing flutter problems early on...prompting cancellation cries and such...LoL

but...but...the F35 must be absolutely perfect with no flaws from assembly day one.  
 
tommytoyz
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RE: F35C Unable To Catch The Wire?

Thu Jan 19, 2012 6:48 pm

Quoting ThePointblank (Reply 20):
Someone at NAVAIR didn't think about the geometry involved here.

I know it's pure speculation on your part, but I find that opinion highly unlikely. But if you a correct, that does not make the problem any less severe. Matter of fact, if NAVAIR was so sloppy, God know what else they overlooked.
 
rfields5421
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RE: F35C Unable To Catch The Wire?

Thu Jan 19, 2012 7:05 pm

Quoting ThePointblank (Reply 20):
Quoting AAR90 (Reply 18):
The real question is how NavAir allowed a tail hook-point design that will never grab a CDP that is resting on the deck to be put on a CV aircraft. The linked report shows exactly why the F35C is having "hook-skip" issues.

Easy. They adapted the design of the hook from the Super Hornet, which has a blunt face to better provide cable shredding protection versus scooping. However, the F/A -18E/F's geometry places the distance of its main landing gear to tailhook point at 18.2 feet. Someone at NAVAIR didn't think about the geometry involved here.

I made some calls, and you are off the mark.

NAVAIR did consider the geometry/ design. The problem is that how the tail hook responds to a deck strike, what happens when the tires cross over the wire and how the hook engages the wire is not yet something which can be computer modeled with 100% accuracy today.

They went what their experience told them was the best design. Experience of folks who have been doing this for close to 50 years. But since the first design is only right between 40-50% of the time, they expect to have to do a change/ redesign after these early tests. That's why they do these tests.

It is also possible that the design might have to be modified again when they get to carrier tests.

Look at the third chart in post 18.

The original bounce height was less than 1 and 1/2 inches. The modifications have it down to about 0.8 inches. That an adjustment of less than 3/4 of an inch on an aircraft traveling over 100 knots when it bounces. But it makes all the difference in the world in how the tail hook works/ doesn't work.
 
AAR90
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RE: F35C Unable To Catch The Wire?

Thu Jan 19, 2012 11:19 pm

Quoting ThePointblank (Reply 20):
Easy. They adapted the design of the hook from the Super Hornet, which has a blunt face to better provide cable shredding protection versus scooping. However, the F/A -18E/F's geometry places the distance of its main landing gear to tailhook point at 18.2 feet. Someone at NAVAIR didn't think about the geometry involved here.

Nothing about CV ops is ever that simple. With no knowledge of the F/A18 hook design beyond the included photos and your comment above, I suspect the F/A18 hook point [if it is truly "the same" as the F35 hook point in the photo] rests on the forward straight edge rather than the same edge as in the F35 photo. If true, that would lower the front "point" [red line in photo] so that it is below the midpoint of a CDP when said CDP is resting on the deck --not held up by the springs. The redesigned F35 hook point accomplishes the same thing... more likely to grab a CDP instead of skipping over it.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
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Faro
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RE: F35C Unable To Catch The Wire?

Fri Jan 20, 2012 10:57 am

Quoting XT6Wagon (Reply 9):
Thats right, the program evaluation found out that they are going to have to redesign the primary structure to relocate the hook.
Quoting ThePointblank (Reply 20):
You can see that a lot of aircraft in the past had issues catching the wire when originally designed, and the proposed fix is comparatively simple; revise the shape of the hook point and modify the damping of the hook so that it is less likely to skip over all the wires.

Agreed that a hook point redesign and damping modification is quite minor, no issue there. If I understand correctly, the problem would seem to be the supplemental redesign of primary structure to relocate the hook that also seems to be required.

Faro
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