Doc 9756-AN/965Manual of Aircraft Accident andIncident InvestigationPart III — InvestigationNotice to UsersThis document is an unedited advance version of an ICAO publication as approved, in principle, by theSecretary General, which is rendered available to the public for convenience. The final edited versionmay still undergo alterations in the process of editing. Consequently, ICAO accepts no responsibility orliability of any kind should the final text of this publication be at variance from that appearing here.Advance edition (unedited)TABLE OF CONTENTSPageChapter 1.Introduction.................................................................................................................. III-1-1Chapter 2.Wreckage investigation .............................................................................................. III-2-1Appendix 1 to Chapter 2.Appendix 2 to Chapter 2.Appendix 3 to Chapter 2.Appendix 4 to Chapter 2.Accident investigator’s photography checklist ..................................Effect of fill flash ...............................................................................Depth of field and its relation to lens opening...................................Wreckage plotting methods .............................................................III-2-12III-2-13III-2-15III-2-17Chapter 3.Organizational investigation....................................................................................... III-3-1Chapter 4.Operations investigation ............................................................................................ III-4-1Chapter 5.Aircraft operating environment .................................................................................. III-5-1Chapter 6.Aircraft performance investigation ............................................................................ III-6-1Chapter 7.Flight recorders ........................................................................................................... III-7-1Chapter 8.Reconstruction of wreckage....................................................................................... III-8-1Chapter 9.Structures investigation ............................................................................................. III-9-1Chapter 10.Mid-air collision investigation ................................................................................Chapter 11.Fire pattern investigation.......................................................................................... III-11-1Chapter 12.Power plant investigation ......................................................................................... III-12-1Chapter 13.Systems investigation............................................................................................... III-13-1Chapter 14.Maintenance investigation........................................................................................ III-14-1Appendix 1 to Chapter 14.III-10-1Maintenance summary data sheets............................................... III-14-35Chapter 15.Helicopter investigation ............................................................................................ III-15-1Chapter 16.Investigating human factors..................................................................................... III-16-1Appendix A.Appendix B.Appendix CFailure modes....................................................................................................... III-16-37An integrated process for investigating human factors ......................................... III-16-42References ........................................................................................................... III-16-51Chapter 17.Survival, evacuation, search, rescue and fire fighting........................................... III-17-1Chapter 18.Pathology investigation ............................................................................................ III-18-1Chapter 19.Investigation of explosives sabotage ...................................................................... III-19-1Chapter 20.Investigating system design issues ........................................................................ III-20-1_____________________Chapter 1INTRODUCTION1.1INVESTIGATION PROCESSAccident investigation is a systematic process whereby all of the possible causes of an adverse event are evaluated andeliminated until the remaining causes are identified as applicable to that investigation. Furthermore, during theinvestigation, if other deficiencies are identified that were not part of this accident, the investigation team should notethem and provide this information to the applicable authority, even though it may not become part of the officialinvestigation report. Although many accidents appear to be similar to others, this may be misleading. Therefore, it isimperative that investigators keep an open mind so as not to focus on one aspect and thus overlook another. Becauseaccidents are infrequent, investigators must take every opportunity to obtain training with air carriers, military, aircraftmanufacturers and other accident investigators so as to retain currency and acquire the best methods for investigation.Many large air carriers and aircraft manufacturers have established accident investigation resources that should beconsulted in support of periodic training. Air carriers and aerodromes conduct periodic emergency exercises, and thesealso provide an opportunity for the accident investigators to utilize these scenarios for training. In the event of an actualaccident or serious incident, these relationships will be useful to the investigators in efficiently determining the causes.Investigation of accidents consists of three phases (see Figure 1.1):a)collection of data,b)analysis of data, andc)presentation of findings.Figure 1.11.2Investigation processCOLLECTION OF DATAThe initial phase of the investigation process should focus on defining and obtaining data relevant to the accident. Inparticular, highly perishable data should be given priority. Data collection will often develop into an on-going process asmore is learned about events surrounding the accident. Therefore, data collected early in the investigation may becombined with other data collected at later stages as a method of reaffirming and validating possible contributing factorsuncovered. Types of data to be collected include:a)accident particulars,b)meteorological,III-1-1III-1-2Manual of Aircraft Accident and Incident Investigationc)technical, andd)human factors.1.2.1Collection of accident particularsImportant reference data must be collected to facilitate collection of meteorological, aircraft performance and air trafficcontrol data. Primary sources of such data shall be obtained from flight plans, Air Traffic Services (ATS) radar data,navigation and topographical charts. Data collected should include:a)date (UTC and LMT),b)time (UTC and LMT),c)location,i)general locationii)grid referenceiii)elevation and topographyd)departure point,e)cruising altitude or flight level,f)destination and intermediate stops (with ETAs and ETDs), and RADAR tracks.1.2.2Collection of meteorological particularsThe forecast and local weather conditions may have significant importance on both the flight conditions and the aircraftperformance. This will include the atmospheric conditions, sun or moon locations, wind and any unusual considerationssuch as volcanic ash, smoke, windshear, visual illusions, icing, along with takeoff or destination considerations that mayhave impacted the takeoff or landing profile such as rushed departure or additional fuel reserve due to expected delaysor diversions.1.2.3Collection of technical particularsThis data is provided from the investigation at the accident or incident site along with maintenance and manufacturingrecords, onboard data collection devices and laboratory analysis of aircraft components. This information may alsoprovide a course for synthetic flight reconstruction and simulation. Other related indicators may be uncovered frommaintenance reports and review of similar incidents from accident and incident databases.1.2.4Collection of human factors particularsHuman factors information is sometimes the most difficult in fatal accidents because there are few witnesses to interviewto confirm what actions and conditions the flight crew were experiencing. Interviews with maintenance and co-workerscan be very emotional and challenging. Additionally, the results of autopsies and reconstruction of crew actions fromPart III. InvestigationChapter 1. IntroductionIII-1-3cockpit voice recordings and air traffic control tapes may provide indicators to the flight crew actions. Systems failuresmay also require interviews with maintenance and ground service personnel. These interviews should be conducted assoon as possible while their knowledge remains clear and is uncontaminated by conversations with other workers.1.3DATA ANALYSISData analysis is conducted in parallel with data collection. Often the analysis of data initiates additional questions thatrequire further data collection, simulation and consultation. Seldom are the results from an analysis an isolated causewith a specific resolution. Regular discussions between the various investigation team members is necessary so as tocollect and process all the necessary data.1.4PRESENTATION OF FINDINGSAccident reports should be provided in the format identified in ICAO Annex 13 for inclusion in the ADREP database.Often the investigation and presentation of information from incidents can be more useful and provide greater safetybenefits than accident investigations._____________________Chapter 2WRECKAGE INVESTIGATION2.1ACCIDENT LOCATIONThe location of the accident site must be determined and recorded. It is important to identify the point of impact and if notat the same location the position where most of the wreckage is located and the extent of the wreckage field. This canmost easily be done by the use of a Global Positioning Satellite (GPS) receiver and aeronautical charts or aerialphotographs. GPS receivers are available in several forms. Small, portable receivers are sufficiently accurate to identifythe accident site location and even general distances between objects in the debris pattern. See paragraph 2.3.3 of thischapter for detailed discussion of plotting with GPS receivers.Location can also be achieved by plotting the bearings and distances from known positions on a large-scale map or byusing aerial photography of the accident site in conjunction with a suitable map. The elevation of the site should bedetermined along with the consideration for any significant gradient in the accident area. In some circumstances andwhen terrain is deemed to be significant in the investigation, it may be desirable to have a profile of the terrain preparedby a surveyor. Maps of the local area and appropriate aeronautical charts should be used to establish the location of theaccident in relation to airways facilities and to airports. Airport lay-out charts and approach charts should be used inconnection with accidents occurring during the approach or take-off phase of flight.2.2ACCIDENT INVESTIGATION PHOTOGRAPHY2.2.1IntroductionPhotography is an important element of the investigation process. Clear, well composed photographs allow theinvestigator to preserve perishable evidence, substantiate the information in the report, and illustrate the investigator’sconclusions. Every accident investigator needs a basic knowledge of photography. This allows the investigator to takequality photographs or to communicate effectively with a professional photographer in order to obtain photographs thatcontribute to a clearly written report.2.2.2EquipmentWhen selecting equipment, the investigator should keep in mind that aircraft accident sites are not always convenientlylocated. The investigator never knows how far the equipment has to be carried, what harsh conditions will beencountered during operation, if electrical power will be available, or telephone and internet access. Here are somedesirable attributes of an investigator’s equipment: It should be compact and light weight to make it easily portable. Itshould be easy to use under any conditions.2.2.2.1Cameras. The camera should be durable and reliable. It must have enough features to fulfill thephotographer needs. The controls should be conveniently located so that the operation is easy and the controls can beoperated while wearing gloves. The camera shutter should synchronize with an external electronic flash attachment. Itslens should have sufficient zoom range to accommodate most situations, and should provide macro capability — theIII-2-1III-2-2Manual of Aircraft Accident and Incident Investigationability to take close up photographs. If the camera depends on electrical power for its operation, extra batteries shouldbe available. There are a number of different types of cameras available to the investigator. Whatever the format of thecamera selected, it is essential that the person taking the photographs has experience taking outdoor photographsunder adverse and traumatic conditions.a)Disposable cameras are made by nearly every major manufacturer of photographic film in the world.They are simple to use. Many have built-in electronic flash. The camera is turned in to the processinglaboratory and is not returned to the user. The user gets the negatives and prints, and can have thephotographs scanned and stored digitally. These cameras take good, clear photographs as long asthey are used within their design parameters. The lenses on these cameras are fixed focus, andcannot be used for close-up photography. There is no provision for adjusting exposure to account fordifferent lighting conditions, other than activating the flash. The flash is powerful enough to be effectivefor working distances of 2-3 meters. These cameras are inexpensive, small and compact, very simpleto use, and make good photos. If the investigator has a more complex camera, a disposable cameramakes a good backup in case the primary camera becomes inoperative.b)Point and shoot cameras are more versatile than disposable cameras. The ones currently on themarket are usually fully automatic and therefore the camera makes focus and exposure adjustmentsitself. Many have zoom lenses. Some have macro capability. They use either film or digital medium.These cameras are versatile, compact, light weight, easy to use and available for harsh weatherconditions. They are an excellent choice for an investigator who is new to photography.c)Single lens reflex cameras are so called, because a mirror between the camera’s lens and the film orlight sensor directs the light coming through the lens to a focusing screen that is used by thephotographer to compose and focus the photograph. In essence, the photographer sees what thecamera sees. These are the most versatile cameras available to date and, with the properaccessories, can handle almost any photographic task in accident investigation. They require the mostknowledge of photography and experience in their use on the part of the investigator in order to beused effectively. Single lens reflex cameras are available that use either conventional film or digitalmedium.d)Video camcorders are extremely useful to investigators. Modern ones are light and compact, and thevideo digital medium can be edited on a computer using simple to use software. Investigators shoulduse video recorders to record fire fighting and rescue activities at the accident, to make notes duringthe accident site walkthrough, to record the steps in removal of wreckage, loading it on the vehicles,and unloading the vehicles into a hangar or other storage area. At least one video camera should beused to record the steps involved in component teardowns.2.2.2.2Accessories make the task of photographing wreckage easier and help the photographer improve thequality of the photographs. Here is a list of those accessories that are useful to accident investigators.a)Lenses. Accessory lenses may be auxiliary, which mount on the camera’s primary lens, orinterchangeable, in which case, the primary lens is removed, and another is installed. A zoom lenswith a range of 28mm to 135mm for a 35mm film camera, or its equivalent for a digital camera, thatalso has macro focusing capability, is ideal. Having all these features combined into one lens reducesthe need to carry heavy accessories.b)Flash. Flash is useful for filling shadows in bright sunlight. Most point and shoot and many single lensreflex cameras have a flash built into the camera. These provide supplementary illumination for use inmarginal lighting conditions, but usually are not powerful enough to fill shadows when photographingin bright sun. Since they are part of the camera, the photographer has no control over the angle of thelight when using one. The best flash attachment for an investigator is one that can be detached from