Accident Investigation: Phases and Failure Types

To prevent future accidents.

Preparation/planning; Data collection; Analysis; Reporting.

A failure that occurs when a load exceeds the design limits.

Pilot-induced; Weather-induced; Wake turbulence-induced.

Aerobatics; Overreaction to turbulence; Improper recovery; Excessive landing loads; Operation outside the aircraft's envelope.

Gust loading and wind shear.

A failure that occurs below design stress limits and indicates an abnormal structural condition.

Poor design; Manufacturing defects; Improper repair or modification; Fatigue; Cracking; Wear; Corrosion; High temperature; Reduced capacity.

They reduce load-bearing capacity and increase failure risk.

A failure that occurs while adjacent or associated parts are still intact and subjected to high G loads.

A failure that occurs when the integrity of adjacent or associated parts is destroyed by the primary failure.

Ground impact.

A "smoking hole."

A deep crater; Fuselage follows the nose into the ground; Dirt rim; Random debris biased in the direction of travel.

A wide debris field; Fragmentation; Fan-shaped pattern; Engines may travel farthest due to mass.

A shallow crater; Largely intact aircraft; Tail continues forward, buckling the fuselage.

Multiple ground contacts or a bounce sequence; Possible partial structural failure; Aircraft remains recognizable.

A low-velocity, high-angle impact pattern with evidence of loss of control before impact.

What was the attitude of the aircraft at impact? What was the velocity of the aircraft at impact? Was the impact survivable?

A portion of the aircraft or its contents found a significant distance from the main wreckage probably came off in flight.

To predict the path of falling debris and estimate the point of separation.

Altitude; Speed; Wind; Mass; Drag.

Ensure a thorough investigation; Use resources efficiently; Avoid duplication or gaps.

Share findings; Monitor assignments; Coordinate progress.

Identify the Hazard; Assess the Hazard; Develop a Control; Implement the Control; Supervise and Evaluate the Control.

A condition or activity with the potential to cause damage, loss, or mission degradation.

The chance of a hazard resulting in bad consequences; risk level is expressed by hazard probability and severity.

Level A; Level B; Level C; Level D.

SCBA; Fully encapsulating gas-tight suit; Inner and outer gloves and boot covers; Hard hat.

The same as Level A, with slightly less skin protection.

Air-purifying respirator; Eye protection; Coveralls; Inner and outer gloves and boot covers; Hard hat.

Coveralls; Gloves; Hard hat; Eye protection.

Levels C and D.

Fuel; Hydraulic fluids; Liquid oxygen; Hydrazine; Pressure vessels; Mechanical hazards; Pyrotechnics; Batteries; Bloodborne pathogens; Radioactivity; Fumes; Dust; Vapors.

Evidence that can be lost, changed, or destroyed if not documented or collected promptly.

Initial photographs; Toxicology; Fuel samples; Oil or hydraulic samples; Loose papers; Icing; Skid marks; Switch positions; Instrument readings; Cockpit evidence; Control surfaces; FDR/CVR; Ground scars.

Aircraft Accident and Incident Investigation Standards and Recommended Practices (SARPs).

A mandatory standard.

A recommended practice.

Organization and Planning.

Procedures and Checklists.

Investigation.

Reporting.

Notification and reporting of aircraft accidents and incidents.

Investigation procedures.

An occurrence associated with aircraft operation involving a fatal or serious injury, substantial damage, or an aircraft that is missing or completely inaccessible, subject to applicable exceptions.

An occurrence other than an accident, associated with the operation of an aircraft, which affects or could affect the safety of operations.

An incident involving circumstances indicating that there was a high probability of an accident.

A system allowing organizations with technical expertise to participate in the investigation.

Aircraft manufacturers; Operators; FAA; Component manufacturers.

The NTSB.

The NTSB.

Gather additional factual information; Examine complex or high-interest accidents; Provide transparency to the public; Support findings and recommendations.

Internal NTSB technical review; Analysis of investigative findings; Review by NTSB Board members; Formal adoption of the final report.

Participants; Eyewitnesses; Background witnesses.

Crew, passengers, and controllers involved in the event.

People who directly observed the accident or events leading to it.

Not direct observers. Include mechanics, dispatchers, and acquaintances. Provide contextual information.

Non-questions; General questions; Directed questions; Specific questions; Summary questions; Leading questions.

Start broad and move toward specific. Leading questions should be avoided.

Who was flying, based on injury patterns correlated with cockpit evidence.

Injuries reflect force magnitude and direction and are correlated with aircraft structure and crash dynamics.

What human factors contributed? What caused injuries or fatalities? Was the accident survivable?

Sleep; Duty time; Nutrition; Stress.

It helps evaluate fatigue, workload, and physical condition and is critical for human performance assessment.

Drugs; Alcohol; Fatigue; Pre-existing conditions.

Design not optimal for the operator; may contribute to an accident but is not necessarily defective.

Delamination; Hidden internal damage; Damage that is not externally visible.

Damage may not be externally visible, and composites have limited "memory" of loading.

Connected metal fittings; Paint deformation; Honeycomb; Moisture.

Carbon fibers are hazardous to breathe and difficult to handle.

A failure that occurs while adjacent or associated parts are still intact and subjected to high G loads.

The wing bends upward and breaks off with an instantaneous overload signature.

The wing piece may strike the tail, leaving mutual indentations or smears; the tail may fail secondarily.

The tail bends downward and breaks off with an instantaneous overload signature.

A rapid pitch-down may cause the wings to fail downward secondarily.

To understand the equipment and techniques and be prepared to document the scene accurately.

"Keep everything relative to the story your photos must tell a stranger."

Flight path; Wreckage/scene; Technical; Flight depictions.

Aircraft manuals, system schematics, or seating charts overlaid with accident data.

Aircraft attitude and collision geometry.

Relative accuracy.

Thorough investigation; Efficient use of resources; Avoid duplication and gaps.

Operations; Structures; Powerplants; Systems; Human factors.

Lead and direct the investigation, coordinate participants, control evidence and information, secure the site, and brief personnel.

A team sent to conduct a major accident investigation.

The slides identify a major investigation as a Go Team investigation but do not provide a complete set of specific activation criteria.

The slides list Field Investigation and Desk (Administrative) Investigation as different investigation levels but do not provide a complete side-by-side definition.

Arrange transportation and establish initial meeting location; Secure wreckage if possible prior to arrival; Notify appropriate agencies; Initiate collection and preservation of documents and evidence; Assemble necessary investigation equipment.

The Field Investigations presentation includes a slide titled "Qualities of a Good Investigator," but the extracted slide text does not provide the individual qualities.

The slides describe final-report format and content and the processing of safety recommendations but do not provide a complete component-by-component list.

An explanation of the accident's primary causes, including contributing factors.

Review investigative findings before the NTSB formally adopts the final report.

The NTSB formally adopts the final report after internal technical review, analysis of findings, and review by NTSB Board members.

Support analysis of crash dynamics, survivability, fire patterns, structural failures, wreckage inventory, and correlation of radar, communications, and witness information.