When you say "If people knew that whatever they wrote down in a postmortem would come back to haunt them, they would not be honest", it wold be the wrong lesson to conclude that postmortems should be blameless, because NASA and NTSB postmortems are definitely *not* blameless (rather they are not pre-determined to find blame at all cost, which is subtly different). To avoid this obvious conflict of interest, the lesson should be that the people involved must absolutely not be in charge of the investigation. Both engineers and pilots have a duty to follow procedures and professional standards, and if neglicence is found in the course of the investigation, those found guilty can and *will* have their licence suspended, temporarily or even for life.
When you say "If people knew that whatever they wrote down in a postmortem would come back to haunt them, they would not be honest", it wold be the wrong lesson to conclude that postmortems should be blameless, because NASA and NTSB postmortems are definitely *not* blameless (rather they are not pre-determined to find blame at all cost, which is subtly different). To avoid this obvious conflict of interest, the lesson should be that the people involved must absolutely not be in charge of the investigation. Both engineers and pilots have a duty to follow procedures and professional standards, and if neglicence is found in the course of the investigation, those found guilty can and *will* have their licence suspended, temporarily or even for life.