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ptrjong
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Project Tailhook

Wed Oct 24, 2012 10:47 pm

There was a short news item on Dutch TV tonight about the arrester hook for the naval JSF, which is being developed at Fokker Landing Gear in the Netherlands.

Employee: 'We've been working on the tailhook with a large team of engineers for many years now.'
Excellent Question: 'Don't your friends ask you what is taking you so long?'
Employee: 'Yeah, yeah. But we're working really hard on it.'

We've been bolting tailhooks on naval aircraft on jets since the 1940s, including heavier and much faster landing jets. Why not bolt the F-18's tailhook on? Unless they can make it 25 lbs lighter, what the hell is there to develop and why does it take so much time and money? Wouldn't old trial and error methods be much quicker and cheaper?

And isn't this exemplary for what is wrong in many sectors and in military aircraft production in particular, and what causes this?

A friend who is an engineer suggested that one of the problems is companies' desire to cut their overhead costs. Maintaining the knowledge how to bolt a tailhook on an aircraft costs a few bucks of company money whereas the millions to rediscover this will be funded by the government.

Thoughts?

Peter 
The only difference between me and a madman is that I am not mad (Salvador Dali)
 
BMI727
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RE: Project Tailhook

Wed Oct 24, 2012 11:19 pm

Quoting ptrjong (Thread starter):
Why not bolt the F-18's tailhook on?

I'm pretty sure it has to be integrated into the structure of the aircraft, so tailhooks will be aircraft specific. Not to mention making it interface with the hydraulics needed to raise and lower it.

Also, tailhooks see a strong but transient loading. For finite element analysis, that can drive up the necessary computational power, which often means adding time.
Why do Aerospace Engineering students have to turn things in on time?
 
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ptrjong
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RE: Project Tailhook

Wed Oct 24, 2012 11:25 pm

Quoting BMI727 (Reply 1):

Of course some work needs to be done. That's hardly my point.

How long do you think did it take to develop the F-4's tailhook?
The only difference between me and a madman is that I am not mad (Salvador Dali)
 
KELPkid
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RE: Project Tailhook

Thu Oct 25, 2012 12:22 am

I would imagine that the tailhook is an item that gets replaced a few times during the life of a typical naval fighter...   Especially since SOP for naval aviators is to apply full throttle the instant the wheels kiss (because if the tailhook doesn't catch a wire, you gotta go around!).
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tdscanuck
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RE: Project Tailhook

Thu Oct 25, 2012 3:36 am

Quoting ptrjong (Thread starter):
We've been bolting tailhooks on naval aircraft on jets since the 1940s, including heavier and much faster landing jets. Why not bolt the F-18's tailhook on?

Because the F-18 tailhook is almost certainly too heavy, and certainly doesn't fit.

Quoting ptrjong (Thread starter):
Unless they can make it 25 lbs lighter, what the hell is there to develop and why does it take so much time and money?

Because it's a really hard thing to develop, it's hyper aircraft specific, and I'll bet that the JSF is so far off weight targets that they'd kill their own grandmother to get 25 lbs.

Quoting ptrjong (Thread starter):
Wouldn't old trial and error methods be much quicker and cheaper?

Yes. And not meet the required performance.

Quoting ptrjong (Thread starter):
And isn't this exemplary for what is wrong in many sectors and in military aircraft production in particular, and what causes this?

Not really; there are many things wrong with military procurement but, above all others, the biggest causes are that the specs are always written to be right at the bleeding edge of what's technologically capable and the OEM's have no idea how they're going to meet all the requirements at the time the military awards the contracts.

Quoting ptrjong (Reply 2):
How long do you think did it take to develop the F-4's tailhook?

If the JSF was allowed to be anywhere close to as simple, as inefficient, or as (relatively) heavy as the F-4 they wouldn't have a problem.

Tom.
 
BMI727
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RE: Project Tailhook

Thu Oct 25, 2012 3:40 am

Quoting tdscanuck (Reply 4):
Because it's a really hard thing to develop, it's hyper aircraft specific, and I'll bet that the JSF is so far off weight targets that they'd kill their own grandmother to get 25 lbs.

Of course, if the F-35 is overweight that means the tailhook is going to have to cope with that much more force. Basically the opposite of simplifying and adding lightness.
Why do Aerospace Engineering students have to turn things in on time?
 
JETPILOT
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RE: Project Tailhook

Thu Oct 25, 2012 4:24 am

Quoting ptrjong (Thread starter):
There was a short news item on Dutch TV tonight about the arrester hook for the naval JSF, which is being developed at Fokker Landing Gear in the Netherlands.

Employee: 'We've been working on the tailhook with a large team of engineers for many years now.'
Excellent Question: 'Don't your friends ask you what is taking you so long?'
Employee: 'Yeah, yeah. But we're working really hard on it.'

We've been bolting tailhooks on naval aircraft on jets since the 1940s, including heavier and much faster landing jets. Why not bolt the F-18's tailhook on? Unless they can make it 25 lbs lighter, what the hell is there to develop and why does it take so much time and money? Wouldn't old trial and error methods be much quicker and cheaper?

And isn't this exemplary for what is wrong in many sectors and in military aircraft production in particular, and what causes this?

A friend who is an engineer suggested that one of the problems is companies' desire to cut their overhead costs. Maintaining the knowledge how to bolt a tailhook on an aircraft costs a few bucks of company money whereas the millions to rediscover this will be funded by the government.

Thoughts?

Peter 

All you have to do is Google "tailhook JSF" and you can easily find what the issue is. The JSF is a cost cutting program to make one thing do everything. The JSF is a stupid compromise of an aircraft that does nothing particularly well including landing on carrIers using arresting gear. The arresting hook is located in the wrong place and they can't relocate it anywhere else. Welcome to economics meets modern warfare!
 
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ptrjong
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RE: Project Tailhook

Thu Oct 25, 2012 10:02 am

Quoting jetpilot (Reply 6):
All you have to do is Google "tailhook JSF" and you can easily find what the issue is.

I did not do this as this wasn't supposed to be a JSF rant.
Interesting.
http://3.bp.blogspot.com/-VqEq1NKQMT...W26Nwx3-9U/s1600/hooklocationC.png

However, it would seem that this has not (yet) changed the specifications for the tailhook itself and thus would not affect the people at Fokker Helmond.

My basic question is different. I understand that a carrier fighter tail hook is not a trivial item. However, shouldn't our experience and technical progress allow us to make a better and relatively lighter one than the F-4 tailhook in a timescale that is slightly similar, at least not tenfold?

The computational power we have now doesn't seem to help at all.
The only difference between me and a madman is that I am not mad (Salvador Dali)
 
aeroweanie
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RE: Project Tailhook

Thu Oct 25, 2012 6:41 pm

Things have changed a lot since the time that the F-4 was designed. Back then, engineers estimated the loads a component was likely to experience and then designed a structure that would (very) conservatively handle the loads. The result is a massive, heavy structure:

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Photo © Stephan T.



Further, in the past, loads were estimated for just a few conditions. I've been told that the wing of the DH-106 Comet was designed for just a few loading conditions. In contrast, Boeing considered thousands of loading conditions in the design of the 787 wing. The result is that the 787 wing has structure that is better matched to the loads it needs to handle and is far better optimized weight-wise.

Weight is a critical item on the F-35. As an example, after production of #1 had started, they redesigned the wing attach structure to save weight. As the hook has to handle high loads, a lot of effort has probably gone into optimizing its structure so that it is light but still can adequately handle the loads experienced in a wide range of conditions.
http://www.f-16.net/attachments/f_35chookgraphic_144.gif

All of this takes more time, but can result in what is termed "analysis paralysis", where project managers keep asking for more and more analysis, to make sure that the risk is absolutely minimized.
 
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ptrjong
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RE: Project Tailhook

Thu Oct 25, 2012 7:09 pm

Thanks, Aeroweanie, for a very interesting answer.

Wouldn't you agree that 'analysis paralysis' is a core problem in this industry today? What can be done to counter it?
The only difference between me and a madman is that I am not mad (Salvador Dali)
 
wingscrubber
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RE: Project Tailhook

Thu Oct 25, 2012 7:57 pm

Analysis paralysis is a good summary actually.

It does seem simple in principal to just go design and build a tailhook, or any other aircraft component for that matter, but the way modern aircraft programs are run, it's very easy to get bogged down in beuracracy which slows any real 'work' to a crawl.

Any component outsourced by an OEM to a supplier is going to necessitate the creation of a supplier-vendor relationship first, with program managers and buyers/agents on either side. Next there's going to be configuration management people, who get to dictate how documents and CAD files are sent and recieved. Then there'll be quality management folks involved from both sides as well.
So, before you ever get to an engineer, you've already built a team of 8 people just to buy a single component, each of whom will be charging their some if not all of their time to that project.

Ok so next here come the engineers... you would think one man could design a tailhook? No... probably not.
First there's going to be the engineering managers (not necessarily the same as a project manager) then they'll assign a lead project engineer, and he may in turn be in charge of two or three more engineers. Next there'll need a stress analyst, and maybe a dedicated draftsman, and probably a maintenance engineer, and a manufacturing engineer. Ok so now we're up to a team of 18 people or so, before we ever get to the lab.

Also assume that if the vendor cannot make a part for the tailhook themselves, they themselves must go to a vendor for that part, and the above steps are repeated for the next tier.

Ok so imagine we've designed a tailhook and written our test plan and the first tailhook has been made, now we need to test the crap out of it. Suddenly we need a test lab manager, a test engineer and some lab technicians. If the project were civilian then a DER is needed too at this stage too.

Finally, imagine we've successfully passed testing, and not including the actual manufacturing people hired to make the things we now need even more people - logistics and shipping folks who then maybe, eventually will ship a part to actually be used on a prototype airplane, to go through yet more testing.

Finally, consider also the numerous team meetings that occur before, during and after development of the part - international business relationships are always expensive due to travel and hotel costs incurred by each side.

I think once upon a time, decades ago engineers had far more autonomy then they do now to actually research, design and build whatever it is that needs building. Because of this I think engineers with pencils and slide rules 40 years ago were far more capable than those of today, even with modern design tools at their disposal - so yes I do think that the guys who designed the F-4 phantom tailhook probably had a much easier time than the guys designing the F-35 tailhook!
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ptrjong
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RE: Project Tailhook

Fri Oct 26, 2012 11:21 am

Quoting wingscrubber (Reply 10):

Thanks for another good post.

I've learnt a few things from this thread. To make lighter aircraft, we need to do away with the conservative strength applied to old designs, and that means a lot more of knowledge is needed.

I still think, thought, that we could use Sydney Camm or Kelly Johnson around who would say: 'What, three years and three zillion to develop a tailhook? No way. We'll do with a less fancy design - see what you can do within six monhts.'
The only difference between me and a madman is that I am not mad (Salvador Dali)
 
tdscanuck
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RE: Project Tailhook

Fri Oct 26, 2012 1:02 pm

Quoting ptrjong (Reply 11):
I still think, thought, that we could use Sydney Camm or Kelly Johnson around who would say: 'What, three years and three zillion to develop a tailhook? No way. We'll do with a less fancy design - see what you can do within six monhts.'

That would work fine...if you didn't care about certification, budget, EAR/ITAR compliance, meeting spec, or complying with a full program procurement contract.

Tom.
 
BMI727
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RE: Project Tailhook

Fri Oct 26, 2012 5:42 pm

Quoting ptrjong (Reply 11):
I still think, thought, that we could use Sydney Camm or Kelly Johnson around who would say: 'What, three years and three zillion to develop a tailhook? No way. We'll do with a less fancy design - see what you can do within six monhts.'

They'd kill for the tools people have these days.
Why do Aerospace Engineering students have to turn things in on time?
 
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ptrjong
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RE: Project Tailhook

Sat Oct 27, 2012 12:08 pm

Quoting BMI727 (Reply 13):
They'd kill for the tools people have these days.

Of course they would.

So everything is just fine in this industry?
The only difference between me and a madman is that I am not mad (Salvador Dali)
 
citation501sp
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RE: Project Tailhook

Sat Oct 27, 2012 2:39 pm

Quoting tdscanuck (Reply 4):

Because it's a really hard thing to develop, it's hyper aircraft specific, and I'll bet that the JSF is so far off weight targets that they'd kill their own grandmother to get 25 lbs.

William Lear would have hired you in a second!
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tdscanuck
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RE: Project Tailhook

Sat Oct 27, 2012 5:37 pm

Quoting citation501sp (Reply 15):
William Lear would have hired you in a second!

I certainly would have said, "Yes!".

Tom.
 
scrubbsywg
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RE: Project Tailhook

Sun Oct 28, 2012 4:02 pm

what kind of materials or construction methods are we talking here?
 
tdscanuck
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RE: Project Tailhook

Sun Oct 28, 2012 8:28 pm

Quoting scrubbsywg (Reply 17):
what kind of materials or construction methods are we talking here?

Very very high point & shock loading, space constrained, needs to take impact well...it's basically the same requirement as landing gear struts. I'd bet on very high strength steel like 300M for the actual hook, and steel, titanium, or 3D-weave CFRP for the "stick" that connects the hook to the aircraft.

Tom.

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