Originally Posted by
Dave Therhino
If you look at the FAA's TARAM handbook, which contains internal guidelines for determining whether an unsafe condition exists on transport airplanes, it has a discussion of the fail safe design expectation for transport airplanes in section 6.1. It says, "If you determine that the condition violates the fail-safe philosophy, you should consider the condition unsafe regardless of the calculated TARAM uncorrected fleet or individual risk values." Here's a link to that document. Section 6.1 is on page 33.
https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/4e5ae8707164674a862579510061f96b/$FILE/PS-ANM-25-05%20TARAM%20Handbook.pdf
If the same type of stab trim wiring fault vulnerability as has been described for the Max exists on the NG, the FAA's own guidelines would classify that as an unsafe condition requiring corrective action via design change and an AD. However, it also would be an expensive change. In such cases, the decisions are often made by the leaders rather than via the normal process for more routine AD decisions. There's nothing necessarily wrong with that - as long as they make good decisions.
Vulnerability is not a failure condition.
if it were lots of military aircraft would never fly.
In my view currently flying aircraft come under "continued Airworthiness" standards which take into account in-service experience including maintenance
The issue at hand with the max is its original certification basis and whether the data used was valid..