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and independent of the Director of Civil Aviation. We have been informed of difficulties which have arisen, not only in formal Boards or Commissions of inquiry which have been appointed under the Regulations, but also in the preliminary investigation of accidents by the Inspector, in determining the proper functions of the Inspector of Accidents and those of the Director of Civil Aviation. There appears to us to have been a lack of co-operation, which would have eliminated some of these difficulties. 167. We understand that revised draft regulations governing the investigation of accidents are now under consideration, and we think it desirable to state certain principles which experience has shown should be applied in this matter. 168. In the interests of air safety, it is necessary to record and, in appropriate cases, investigate, not only " accidents " but also " incidents." The term " accidents " is used to indicate important happenings involving death of or injury to personnel, substantial structural damage, fires in the air, and the like ; the term " incidents " is used to include all events other than " accidents," the recording and possibly the investigation of which provide the essential background for safety regulation and the provision of aviation facilities. In what follows, these two terms are used only in these special senses. 169. There should be a legal obligation to report accidents ; there should be no legal obligation to report incidents ; instead, the need for reporting incidents in the long-term as well as the short-term interests of air safety should be brought home to all concerned through such media as Notices to Airmen and Notices to Aircraft Owners and Engineers. In our experience, the voluntary reporting of incidents achieves the end in view, and any attempt to impose a legal obligation, even if that were possible, would not be worth while. 170. It follows that the term " accident " must be defined in the Regulations with legal precision. This is a straight-forward problem of drafting, though careful judgment is needed to draw the best dividing line between accidents and incidents. 171. By contrast, it is neither possible nor desirable to define " incident " with legal precision. The need here is for a widespread realisation of the purpose served by the reporting of incidents. This will be far more effective than any academic definition. 172. The first essential in respect of major accidents is to safeguard the wreckage. Successful investigation usually depends on prompt action to record and preserve the oral and material evidence. Responsibility for this must rest, not only on the Inspector of Accidents, but also on other official personnel who will often be in a better position than the Inspector to take immediate action. Personnel likely to be in this position are the police, the Royal New Zealand Air Force, and officers