I have some sympathy for RHC
Guys, it may be a bit of a shock given my previous postings on the blade issue, but I actually have some sympathy for RHC.
The problem with these blades is related to degradation of the bond interface between the adhesive and the metal. The regulations (FARs) require demonstration of strength, fatigue resistance and damage tolerance, and I am sure that RHC would have complied with these requirements, otherwise they would not have received certification approval.
The real issue is that there is no specific requirement in the regs that stipulates demonstration that the bond will maintain strength throughout the life of the part. Understand that there are two component in adhesive bond which control strength; the bulk adhesive material and the interface between the adhesive and the metal.
Interfacial degradation is directly related to the methods for preparing the surfaces prior to bonding. The most probable mechanism of degradation is by hydration of the oxides on the bonding surface. For the oxides to hydrate the chemical bonds between the adhesive and the metal dissociate leading to disbonding. Now hydration takes time so if a test is undertaken at the time immediately after manufacture, then the strength would be adequate, but if the part is in service for a while the interface degrades and the strength of the bond progressively weakens.
This hydration is a direct result of environmental exposure, so you would expect that the regulations would address environmental effects and they do. However, the usual approach throughout almost all of the entire industry (NOT JUST RHC) to assessing environmental effects is to expose specimens for a short time until the moisture levels stablise and then test to generate design data. This approach will address the effects of moisture on the bulk adhesive properties.
The flaw with this approach is that the exposure time before testing is not long enough to enable hydration to occur. Therefore the results of the tests will provide sufficient confidence in the processes to convince the company and the FAA that the design is sound, even though the bond may experience interfacial degradation in later service. Yet testing of moisture conditioned specimens is standard practice throughout the industry.
The issue of hydration and bond degradation has only been known for a relatively short time and that knowledge came to light well after RHC started making -4 blades, so there is no reasonable expectation that RHC should have been aware of the additional needs for testing to assess resistance to environmental degradation and I am sure that almost all other manufacturers were equally unaware. Even if they eventually did become aware, the change of processes would require an entire and lengthy re-certification of the blade and hopefully that is what the -6 blades are.
I think the issue of product liability and warranty is a bit murky to say the least. If any company follows regs and adopts industry best practice to make a product are they liable if the regs are not explicit and industry best practice is deficient?
OK, I'm now going into my bomb shelter for a while....
Regards
Blakmax
PS I hope 13snoopy still is reading the thread even if he has stomped his feet and taken his bat and ball and gone away.