The key to success in any investigation, in my opinion, is to be right, to be correct with your analysis of the facts and testimonies collected. You have to be correct and logical with your conclusions and you have to make recommendations, recommended corrective actions based solely on the conclusions. I would say that somewhere between 90-95% of the time that accident boards get the form of the investigation incorrect. They list conclusions without logically supported analysis, they come up with recommendations out of the clear blue sky with no support from the conclusions and they do not even collect all of the facts.
Case in point?
Take BEA’s investigation of AF447. I have not read a single fact, analysis or conclusion so far that leads me to believe that BEA considered the role of AF Dispatch Office in the mishap. It was AF Dispatch Office that had all of the latest and current metro satellite data that showed massive thunderstorms in the flight path of AF447, rising to altitudes well above the Airbus operating ceiling. Even while AF Dispatch had this data, they took no action to warn AF447 even though it was their specific requirement to do so since AF is a scheduled airline and AF447 was a dispatched flight.
Send any current airliner into a 60,000+ foot thunderstorm at night and I doubt any will escape the encounter unscathed. Plus passenger injuries are likely to be sustained even if the airframe makes it out the other side. Plus few passengers will speak well of the flight experience if they manage to live through being inside a 60,000+ ft thunderstorm.
In my opinion, political pressure on an investigation is not really so much an issue as is the poorly handled investigation, collection of the facts, poor analysis, poor conclusions and poor tie in of recommendations. Political and party pressures are a fact of life. They are afraid, under stress, and will do anything to survive. But the truth can not be hidden. If it is not found, the board wasn’t looking hard enough.