RE Walter's 5406
If they were not carrying out such a trial as Walter suggests; then they were negligent for flying too fast and too close to high ground in weather conditions that can only be described as, at best, exceedingly marginal.
If they were using the equipment that Walter suggests for an approach to the HLS, then they were negligent for carrying out an unauthorised approach at high speed, in exceedingly marginal weather, to a landing site adjacent to high ground utilising equipment that had no CA Release and no R to S for the Chinook.