Design flaw puts F-22 in shop for repairs

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Meathook

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Unread post22 Oct 2007, 15:37

Design Flaw Puts Fighter Jets in Shop for Repairs
October 21st, 2007 @ 3:13pm
SALT LAKE CITY (AP) -- The Air Force is speeding up its time line for bringing the F-22 Raptor to Hill Air Force Base for repairs after a design flaw that military officials have known about for years has reappeared.

The problem with the Air Force's newest fighter jet is that the composition of some mechanical access panels makes the Raptor susceptible to corrosion. Military officials changed the design to fix the problem, but it is back and about two-thirds of the military's fleet of the planes are suffering from corrosion.

"So the world's most expensive, most advanced aircraft is in the shop for repairs for something simple that someone figured out a long time ago?" said Nick Schwellenbach, national security investigator for the Project On Government Oversight.

"I'd like to say I was outraged, and it is outrageous," Schwellenbach said, "but it's all too common."

The Project on Government Oversight has exposed numerous other problems with the Raptor, which costs more than $130 million per plane. Those costs triple when research, development and other costs are factored in.

The plane is advertised as the world's most advanced fighter jet. It was intended to be ready for combat by 1997, but the Raptor has yet to fly a single combat mission because of cost overruns and delays.

It's unclear how much the corrosion issue will cost the Air Force to fix. Brig. Gen. C.D. Moore, who is leading production and sustainment efforts for the F-22 at Ohio's Wright-Patterson Air Force Base, said the "cleanup and mitigation" of already-identified corrosion problems could cost nearly a half-million dollars in labor costs alone.

But Schwellenbach and other defense experts are frustrated that this isn't a problem that was discovered during routine maintenance, but one that had been identified and addressed in the mid-1990s.

At the time, the Raptor's development was already years behind schedule and critics were beginning to complain that the Raptor was an expensive Cold War weapon in a post-Cold War world.

However, even as the Soviet threat diminished the Air Force continued to push to improve the plane's "low observable" qualities.

The Raptor was designed to have few exposed joints and edges to lower the aircraft's radar visibility. But techniques that made the plane more stealthy -- like filling the seams of the access panels with a soft, rubbery putty -- weren't always good for corrosion control.

Alerted to concerns that the metals, paint and other materials used in and around the panels would interact in a way that would cause severe corrosion, Col. Kenneth Merchant, now a brigadier general and vice commander at Hill's Ogden Air Logistics Center, oversaw a change in design. Merchant left his assignment in 1997 believing that the problem had been addressed by a change that included switching the metal used in the panels from aluminum to titanium. The change made the Raptor negligibly heavier. It also made the aircraft more vulnerable to radar.

Moore said the decision to overrule Merchant's change came over the course of several years as engineers sought to find "the right balance" between durability, performance and low radar visibility. "We thought we got it right," he said. "We understood there was a corrosion risk."

That irked Schwellenbach. "What's the point in it being more stealthy if it's in the shop?" he asked.

Souce: The Salt Lake Tribune
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elp

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Unread post22 Oct 2007, 16:58

You did want more work at the depot didn't you? :lol:


Pogo :lol:
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Meathook

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Unread post22 Oct 2007, 18:06

I hear ya, guess we will get very busy, very soon (more then we are already).

Thanks
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elp

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Unread post22 Oct 2007, 19:24

Looks like that may be the achilles heel for having lexus quality stealth... all those close fitting materials with the first goal being low observable above all else. Most likely once they get into a routine PDM cycle, someone will figure out fixes.

Hopefully the JSF ( goal affordable stealth ) will have less of these issues. Have fun. :D
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seruriermarshal

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Unread post23 Oct 2007, 03:20

Just political , how many F-104 crash ? It's cheaper . Now we talk about F-22 , new systems and stealthy , no fighter can do that . F-22A in RedFlag is best .
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Unread post31 Oct 2007, 14:52

The discovery of the flaw...which had been previously addressed in the program by the way...by the depot shows were getting our money's worth from those folks. I think its a good thing. Shows hard work and attention to detail by those folks who are servicing our new weapon system. If you really look at the whole F-22A program there have only been a few minor, non-critical issues found and only one airframe lost. Thats a pretty good track record for a new aircraft. Way to go depot team! Kudo's!
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snypa777

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Unread post31 Oct 2007, 19:56

I don`t think anybody should be playing the blame game on this. Flaws don`t show up sometimes for years, they tried a fix and it didn`t work. ok, now try something else. Chemical reaction tests can`t be hurried readily and sometimes we have to "wait and see". The issue is that the aircraft is in service and any degradation of the skin, even in a small way will compromise stealth at certain aspect angles.
I agree that the depot did it`s job even though corrosion shouldn`t have been too difficult to spot!
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checksixx

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Unread post31 Oct 2007, 20:10

snypa777...this isn't a slam on what you wrote...

The problem was discovered well prior to this and a change was implemented. It appears that somehow the manufacturer reverted back at some point along the way and now the problem has resurfaced. The only blame here is on the manufacturer.
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habu2

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Unread post01 Nov 2007, 19:00

Meathook wrote:
Alerted to concerns that the metals, paint and other materials used in and around the panels would interact in a way that would cause severe corrosion, Col. Kenneth Merchant, now a brigadier general and vice commander at Hill's Ogden Air Logistics Center, oversaw a change in design. Merchant left his assignment in 1997 believing that the problem had been addressed by a change that included switching the metal used in the panels from aluminum to titanium.


If I'm reading this right the problem is an electrolytic reaction between materials used in and around the putty and panels, resulting in galvanic corrosion. i.e. electrolysis.

http://en.wikipedia.org/wiki/Galvanic_corrosion
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Beagle79

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Unread post02 Nov 2007, 04:36

Murphy's Law: Whatever can go wrong, will [go wrong].... :? Such things, however unpleasant, are common when fielding a new design, let alone a revolutionary one like the Raptor. (Legacy airframes had their shares of such hiccups during their early days too.) Persist and we shall prevail :wink:
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Unread post02 Nov 2007, 23:28

I see it as Much Ado About Nothing.
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snypa777

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Unread post03 Nov 2007, 00:13

checksixx wrote:snypa777...this isn't a slam on what you wrote...

The problem was discovered well prior to this and a change was implemented. It appears that somehow the manufacturer reverted back at some point along the way and now the problem has resurfaced. The only blame here is on the manufacturer.


Thanks for the heads up Check`. I assume they reverted to the earlier process at the air forces request though? To do so under their own auspices would be negligent.

Habu 2, Galvanic corrosion would indicate a grounding issue to me or stray current....
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boff180

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Unread post04 Nov 2007, 00:00

Fair play to the guys for finding it and coming clean though.

There was/is a problem with the E-3 that was not discovered until the RAF received the E-3D and it was discovered.

Turbulence from the dish was causing cracking and damage to a specific area of the rudder with a risk of failure and decintegration in flight. The only fix at the time was to just regularly check and replace the panels. The solution found: vortext strakes close to the fin leading edge, removing the turbulence.

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habu2

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Unread post06 Nov 2007, 06:36

snypa777 wrote:
checksixx wrote:Habu 2, Galvanic corrosion would indicate a grounding issue to me or stray current....

Not necessarily, the materials can form what is essentially a battery, generating their own current. No external power required.

Did you read the link in my post?
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checksixx

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Unread post06 Nov 2007, 21:30

That wasn't my quote habu2...
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