"Two-thirds of F-22 Raptor fleet suffering from corrosion"

October 25, 2007 (by Lieven Dewitte) - Even though it was known years ago that the composition of some mechanical access panels made the F-22 susceptible to corrosion and changes were made to fix the problem, the design flaw reappeared.

www.f-16.net...

Yep, the same problems just won’t go away. Raptor sure is stealthy, but with its already massive maintenance budget, now we’re just trying to keep them from rusting out.

Now, a decade later, about two-thirds of the military's fleet of Raptors are suffering from corrosion, prompting the Air Force to speed up the timeline for bringing the aircraft through Hill Air Force Base for depot-level maintenance.

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. Corrosively resistant replacement panels - which won't be ready to install for another six months - will cost millions more to produce and the jets will have to be brought back to Hill or another maintenance center for installation - at a cost of millions more.

Maintenance budget just keeps ballooning out of control on that bird.

Originally posted by iskander
Maintenance budget just keeps ballooning out of control on that bird.

Except that you provide no figures and leave out this part form the article... So one of the world most advanced aircraft has a few things to work out while still coming into service, shocking.

"...noting it would be absorbed by the "overall sustainment plan" budget - which he said exists to handle unforeseen problems with the jet."

reply to post by WestPoint23

"...noting it would be absorbed by the "overall sustainment plan" budget - which he said exists to handle unforeseen problems with the jet."

Rust all you want Raptor! We’ll just spend the maintenance reserve budget on panel/infrastructure replacement!

Stupid chinese metal. PTB dusted the unionised steel plants in America. You get what you pay for. Probably highly leaded throttles too. Hooya, lets disembowel America all the way. Dag, I scored ten on a single post, bless you my moderator sympatizers.

[edit on 2-11-2007 by jpm1602]

Wow. 2/3rds of them have corrosion. Point 1: Show me the plane that has been in service for any amount of time, including flying regularly in and around the salt environment of the ocean that DOESN'T have corrosion.

Point 2: How much corrosion is this talking about? According to this it's a whopping 17 panels. And they range in size from a few inches to several feet. So we're not talking a massive amount of corrosion here. We're talking a fairly negligible amount from the sound of things. The big thing here is that they're switching to titanium panels which is going to cost a bunch. They could have done it sooner, but it still would have cost them the same amount, or even more because of the development costs.

Point 1: Show me the plane that has been in service for any amount of time, including flying regularly in and around the salt environment of the ocean that DOESN'T have corrosion.

You are implying that all aircraft are suffering from corrosion which requires parts replacements?

Didn’t know F-22 is carrier launched. What ocean environment?

Point 2: How much corrosion is this talking about? According to this it's a whopping 17 panels. And they range in size from a few inches to several feet.

At whopping 350 million a pop, shouldn’t THO THIRDS of the entire fleet be free from corrosion of ANY kind?

Several feet of titanium verses several feet of aluminum does change RCS figures, so how will it affect the total radar signature of the “corrosion free” Raptor?

So we're not talking a massive amount of corrosion here. We're talking a fairly negligible amount from the sound of things. The big thing here is that they're switching to titanium panels which is going to cost a bunch.

So we are lowering our aircraft building standards even lower these days? Pilot killing F-16s wire chafing, F-111 fiasco, another pilot killer the Osprey, and now the most expensive fighter off all time is suffering “corrosion problems”?

They could have done it sooner, but it still would have cost them the same amount, or even more because of the development costs.

Well that’s all fine and dandy, but the Russians sure don’t seem to have a problem cranking out Flankers like they were pez, and their plants are so loaded with orders that all other model construction has been moved to other plats.

Sukhoi plant now builds Flankers exclusively, and their product does not appear to suffer from corrosion problems.

Corrosion problems with newly developed aircraft are pretty much universal. Every military aircraft, no matter how old or new, has ongoing corrosion control maintenance and prevention in place.
When I was a Crew Chief on F-15C/D's in the early 80's, we had certain points on the aircraft that were regularly checked for corrosion in their Annual Inspection, and even day to day operations. Ultrasonic inspections were quite common. Langley AFB is right on the backwaters of the Chesapeake Bay, and we even had local Technical Orders due to the salty air.
The F-22 is a fine aircraft. Its also a new aircraft. They aren't going to be able to address all the problems associated with "aging" at the beginning of the program. Just like the darn Processing Plant I work at now, maintenance is an ongoing issue (and corrosion control will always be a part of it)!

(EDIT)--changed "is" to "are"

[edit on 4-11-2007 by CreeWolf]

reply to post by CreeWolf

Corrosion problems with newly developed aircraft are pretty much universal. Every military aircraft, no matter how old or new, has ongoing corrosion control maintenance and prevention in place.

FOD, walk of shame, paved runways.

MiG-23/27/29, Su-25, etc, can take of and land from a potato field, and do so with out corrosion problems.

It’s an engineering factor, kind of like this one that got overlooked;

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 - particularly if moisture was to seep into the seams - 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 which included switching the metal used in the panels from aluminum to titanium.

www.f-16.net...

Somebody dropped the ball.

They aren't going to be able to address all the problems associated with "aging" at the beginning of the program.

“Aging” should not be a problem at the beginning of the program; it should be a service life extension question years down the road, not when the bird is being pushed out of the nest.

Kind of like with B-52s, should we use them for another 50 years? Sure, why not!

Iskander, you claim that the maintainence budget is ballooning out of control. You have no evidence to support this claim and respond to replies with drivel. I.E. Didn’t know F-22 is carrier launched. What ocean environment? Then you go on to claim that Russian planes don't have corrosion problems despite two people who actually are involved in modern planes telling you otherwise.

What's your point? Why are you here? Flame-bait? Trolling? Or what?

Umm... the main issue is that some of the seams between the access panels are filled with a filler to help reduce the stealth qualities of the aircraft. Naturally such a configuration combined with the operating environment does create the risk of corrosion. It's not that big a deal, once the routine PDM cycle is established someone will figure out fixes. In the mean time though it's just normal maintenance.

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.

Scientific Explanation

Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in contact with a different type of metal and both metals are in an electrolyte.

Source

As for Russian aircraft, I thought this was a discussion about F-22A Raptor corrosion? Producing simplistic aircraft which are cheap and durable is good, for some scenarios. However if they cannot survive first contact with the enemy your potato air fields will be useless.

Originally posted by JimmyCarterIsSmarter
I.E. Didn’t know F-22 is carrier launched. What ocean environment?

But it's not.

The F-22A Raptor is operated from a number of places which typically expose it to different environments. Raptors operating from Tyndall AFB and Eglin AFB, Florida, operate mainly over the restricted zone above the Gulf of Mexico. Raptors who operate from Langley AFB, Virginia, operate over and close to the Atlantic ocean. The location of these base exposes those Raptors, even when not flying, to the atmospheric conditions associated with the ocean environment. Furthermore the F-22 Raptor will be based in Hawaii, I trust I don't have to explain that one.

Westpoint;

First rule of material selection: Avoid galvanic pairs.

It should be imperative to take galvanic corrosion into account at the begining of the material selection process even in the simplistic machine desings. and when we are talking about multi billion dollar project i find it very disturbing that such elementary mistakes have been done.

Ps. I assume dome jackass forgot that certain komposites (mainly ones that contain graphite) can form galvanic pairs with metals...

What's your point? Why are you here? Flame-bait? Trolling? Or what?

My point is that the ball was dropped in spite of Col. Kenneth Merchant’s efforts.

He left his position believing that the corrosion problem which he foresaw was being addressed, while it was simply swept under the carpet.

In my book it’s called negligence on the part of the manufacturer, and the bill should be picked up by Boeing/Lockheed Martin/Pratt & Whitney, and not the American taxpayer.

First rule of material selection: Avoid galvanic pairs.

It should be imperative to take galvanic corrosion into account at the begining of the material selection process even in the simplistic machine desings. and when we are talking about multi billion dollar project i find it very disturbing that such elementary mistakes have been done

My point exactly, and that’s EXACTLY what Col. Kenneth Merchant made a point of, while it was simply forgotten about as a minor annoyance.

For the most expansive fighter in the history of aviation, such elementary problems should not only affect the units already in service, but they should not even be presents during design states.

It’s the Bradley all over again.

The problem we're having with a lot of newer ANYTHING is that composites are being pushed so hard and heavy that we're being coerced into using them in structures prematurely.

Not only is joining composites to metal a royal pain - it also causes a number of concerns. Graphite is something you NEVER want in contact with metal - period. Unless you just WANT it to corrode into nothing.

This should also raise some more interesting concerns. Since a good chunk of the F-22 is of composite structuring, and very little metal.... for these panels to be corroding requires that two dissimilar metals be, at the minimum, connected by an electrolyte. Now, let's not forget what composites are. Typically, they are a metal, nonmetal, or metaloid that is formed into individual threads, usually laid out in a mesh pattern, and held in place by an epoxy/resin. The combined tensile strength of the threads/fiber and the rigidity of the epoxy/resin give the composite its properties.

.... so... what's happening to the composite if the carbon fibers are being corroded?

Composites aren't that easy to repair/replace. Add to this the low observable factor and how seemingly insignificant things can mean the difference between getting shot at - and not .... you're adding great risk in there.

While - yes, this can be 'remedied' through maintenance procedures - the fact remains that it's a rather dangerous design flaw that will end up costing even MORE money for an already golden bird.

And, if you really need to ask for verification that the F-22 is WAY over budget ..... then, what are you even doing in the aircraft forums? Seriously. Not only is it dang near a decade late - it is also worth its weight in gold.

Originally posted by Aim64C
Not only is joining composites to metal a royal pain - it also causes a number of concerns. Graphite is something you NEVER want in contact with metal - period. Unless you just WANT it to corrode into nothing.

Which may very well come back to bite Boeing in the balls with the 787 (same with Airbus on the 350)

And they (Boeing) don't have the US gov to fund them out of problems...

First off people are basing their opinion without even knowing the full facts, let's attempt to change that. The Raptor uses a soft, graphite composite filler in the spaces between the outside access panels to improve the stealth characteristics of the aircraft. These access panels are mostly made from aluminum, not a metal alloy which is sufficiently corrosive resistant. The design changes that Gen. Merchant mentions were ones he recommended (in the mid 90's) be made, such as switching the metal of the access panels from aluminum to titanium. However this would have made the aircraft slightly heavier, more expensive and it would slightly degrade the stealth characteristics of the aircraft. The decision was made to not adopt the recommended changes but to opt for less drastic measures as the former would slightly degrade the performance of the AC. So it's not that this "flaw" was not known of, nor that it was ignored, it just means the issue is more complicated. Those in charge wanted to make sure any design change would not negatively impact the aircraft.

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 - particularly if moisture was to seep into the seams - 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 which included switching the metal used in the panels from aluminum to titanium. The change made the Raptor, the twin engines of which produce a chest-rumbling 35,000 pounds of thrust each, negligibly heavier. It also made the aircraft slightly 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 observability. "We thought we got it right," he said. "We understood there was a corrosion risk."

Source

Current plans include sending the effected aircraft through a maintenance cycle to replace the corroded panels with more "corrosion resistant" ones until an acceptable long term fix is proposed.

And, if you really need to ask for verification that the F-22 is WAY over budget ..... then, what are you even doing in the aircraft forums? Seriously. Not only is it dang near a decade late - it is also worth its weight in gold.

"...noting it would be absorbed by the "overall sustainment plan" budget - which he said exists to handle unforeseen problems with the jet."

*notes that the "overall sustainment plan budget" does not HAVE to be spent* - Hmm....

And, why, pray tell, would you make the access panels out of metal when the rest of the plane immediately around it is made out of composites? All dissimilar metals are a potential for galvanic corrosion - especially with carbon/graphite - which is on the opposite end of the spectrum for metals.

Although what the graphite fibers are doing coming into contact with a joining metal is beyond me. That should be sealed off rather well. Titanium is rather corrosion resistant - but they should just make a dang composite access panel.

Just like they had problems with the F-18's vertical stabilizers wobbling around during maneuvers. They eventually added an additional spoiler ahead of the stabilizer root to keep this from happening. However, the F-18 wasn't made out of gold - and it actually has a place in the current arsenal.... things the F-22 doesn't have going for it.

Just tell Lockheed to quit before they hurt themselves, and let Northrop do some modifications to the F-23 to make it into a strike aircraft for the Navy (and maybe the Airforce - if they can stand not buying the most expensive thing they can find then go screaming back to the government "we have no money - and we need bombs for our planes!"). You know - something we need.

reply to post by iskander


So you're saying that only carrier based planes are affected by salt air? Well hell, we could have saved millions in washing off our planes after every flight! Corrosion is a common thing, and is generally found in almost every plane flying, yes, that's exactly what I'm saying.

And Flankers don't have the complexity, the composites, or the other challenges that are put into the Raptor. And don't even TRY to sit there and tell me that Russian aircraft designers have NEVER had problems with their designs, or that they don't have ongoing problems. Just because we don't hear about them doesn't mean they aren't happening.