Corrosion within the laminate

[Colin]

Did you also get a quote from the factory next door?

[Charles]

No. Honestly, it didn't occur to me to call them as I didn't know they did any maintenance work. Do they?

[rwtucker]

This is a disturbing thread. I haven't seen any sign of corrosion yet but for those who have:

- Does there seems to be an association with coastal locations, high humidity, time in the soup, etc.
- Is there any indication that Diamond corrected the problem at some point or is a matter of time for all of us?
- For those who have looked at the strip, could Diamond have put a half micron of gold on nickle plated copper in the vulnerable area?

I don't suppose Diamond would see it this way but it is an airframe issue and that has a lifetime warranty.

[Charles]

Is that lifetime warranty transferable?

[Enrouk]

interesting, i will make inspection on my aircraft this week end

[Chris B]

an airframe issue and that has a lifetime warranty.

Hi Robert -

AFAIK there is no lifetime limit on the DA40 airframe (after implementing the recent spar SB). This is not universal among composite aircraft. But there is no "lifetime warranty" on the airframe. That would eventually bankrupt any aircraft manufacturer.

Chris

[rwtucker]

an airframe issue and that has a lifetime warranty.

Hi Robert - AFAIK there is no lifetime limit on the DA40 airframe (after implementing the recent spar SB). This is not universal among composite aircraft. But there is no "lifetime warranty" on the airframe. That would eventually bankrupt any aircraft manufacturer. Chris

I thought I had seen reference to that in other posts. Am I confusing "no hours limit" with "warranty?"

[Chris B]

I thought I had seen reference to that in other posts. Am I confusing "no hours limit" with "warranty?"

Hi Robert -

Yes, I believe so.

FWIW, Cirrus is currently quoting 12000 hr airframe life, with hope for extensions as the fleet ages and they get more real-world experience. Or possibly not.

Chris

[rwtucker]

Thanks Chris.

When you consider what we already know about the ways composite frames can deteriorate or turn out to be under-stressed in ways that only show up in time, these so-called "no limits" designations seem unwise. When you toss in what else we are likely to learn in the coming years, they may seem stupid.

On the other hand, Cirrus doesn't make Diamond look like the sharpest knife in the drawer. Objectively, it looks like we have the most vulnerable airframes and the most frequent and intrusive inspection schedules of the majors. Moreover, you could argue that our inspection requirements mean that the airframe lifetime is not unlimited. In a way, we have a 2,000 hour airframe with some 1,000 hour limitations.

Cirrus airplanes require only routine maintenance to the extent of their published useful life. An alternative is to develop major (or “heavy”) inspections at certain intervals to check the structure and replace suspect components. At Cirrus we chose to test for a useful life of 12,000 flight hours – about 60 years of average use. Most of our major structures, however, have been tested for twice this lifetime. At Cirrus we also chose to demonstrate that the structure is good for this design life without the need for any interim, heavy inspections – with their associated cost and inconvenience. At Cirrus we expect that, as real-life aircraft approach 12,000 hours, a further round of testing, analysis, and inspections will determine how to extend the useful life.

Other manufacturers use different combinations of life and inspections. For example:

Cessna (formerly Columbia) 350/400 have a lifetime of over 25,000 hours but with an extensive (bonded seams, checks for de-lamination, thirty wing bolt replacement, flight control removals, etc.) airframe inspection every 3,000 hours . . .

Diamond DA-40 training airplanes have no published useful life. Those airplanes are, somewhat similar to older designs, dependent upon regular “heavy” inspections to identify structural issues arising from routine use. These airplanes have an extensive “wings-off” inspection every 1,000 hours and even more intrusive structural inspection every 2,000 hours.

All of these approaches produce sound, strong airplanes – probably the best general aviation airplanes ever produced. Different engineering approaches, though, produce different trade-offs. At Cirrus we prefer the simple, uncomplicated approach – which we believe offers the highest level of convenience and economy for our customers.

Of course, you have to wonder what they mean when they imply they have tested airframes for 24,000 hours. You can simulate only limited aspects of sitting, flying, temperature changes, etc. for the equivalent of 120 years. I'm generally skeptical of MTBF testing.

[Lance Murray]

The root cause of this issue is that you should not bond carbon and aluminum together. This was an idiotic design failure.

"Fiber-reinforced plastics are corrosion resistant, but plastics reinforced with carbon fibers can induce galvanic corrosion in attached aluminum structure."

http://www.boeing.com/commercial/aeroma ... rrosn.html