Detailed Aircraft Accident Investigation Study Guide
1. Introduction
• All aircraft accidents are unique, but share common elements in crash dynamics and wreckage
distribution.
• Key questions investigators must answer:
• - What was the aircraft’s attitude (pitch, bank, yaw) at impact?
• - Was the impact survivable based on forces and conditions?
2. Influence of Aircraft Velocity & Impact Angle
• Velocity determines the degree of breakup: higher velocity = more fragmentation.
• Impact angle determines distribution:
• - Steep angles concentrate debris near impact.
• - Shallow angles spread debris over larger areas.
3. Influence of Terrain
• Terrain type critically affects wreckage outcome.
• - Frozen field → aircraft may remain more intact.
• - Dense forest → greater breakup, irregular patterns.
• Upslope/downslope modifies calculations of impact forces and distribution.
• Accurate modeling of terrain’s retarding effect is nearly impossible.
4. Water Impacts
• High-velocity water impacts behave like solid ground → heavy breakup.
• Deliberate ditching can leave aircraft intact but sinking.
• Wave action complicates determining true impact angle.
• Distribution underwater depends on: depth, currents, buoyancy of parts.
• ‘Dispersed part rule’: Items far from main wreckage likely separated in-flight.
5. Land Impacts (5 Types)
• A. High Velocity, High Angle – ‘Smoking hole’, crater with rim, debris mostly in direction of travel.
• B. High Velocity, Low Angle – Widespread fan-shaped pattern, heavy items (engines) travel furthest.
• C. Low Velocity, High Angle – Shallow crater, largely intact wreckage, aft fuselage buckling from tail
momentum.
• D. Low Velocity, Low Angle – Aircraft may bounce several times, shedding parts but retaining overall
structure.
• E. Stall/Spin Impacts – Low velocity, high angle; may not hit nose first. Spin direction sometimes
identifiable.
6. Determining Impact Attitude
1. Introduction
• All aircraft accidents are unique, but share common elements in crash dynamics and wreckage
distribution.
• Key questions investigators must answer:
• - What was the aircraft’s attitude (pitch, bank, yaw) at impact?
• - Was the impact survivable based on forces and conditions?
2. Influence of Aircraft Velocity & Impact Angle
• Velocity determines the degree of breakup: higher velocity = more fragmentation.
• Impact angle determines distribution:
• - Steep angles concentrate debris near impact.
• - Shallow angles spread debris over larger areas.
3. Influence of Terrain
• Terrain type critically affects wreckage outcome.
• - Frozen field → aircraft may remain more intact.
• - Dense forest → greater breakup, irregular patterns.
• Upslope/downslope modifies calculations of impact forces and distribution.
• Accurate modeling of terrain’s retarding effect is nearly impossible.
4. Water Impacts
• High-velocity water impacts behave like solid ground → heavy breakup.
• Deliberate ditching can leave aircraft intact but sinking.
• Wave action complicates determining true impact angle.
• Distribution underwater depends on: depth, currents, buoyancy of parts.
• ‘Dispersed part rule’: Items far from main wreckage likely separated in-flight.
5. Land Impacts (5 Types)
• A. High Velocity, High Angle – ‘Smoking hole’, crater with rim, debris mostly in direction of travel.
• B. High Velocity, Low Angle – Widespread fan-shaped pattern, heavy items (engines) travel furthest.
• C. Low Velocity, High Angle – Shallow crater, largely intact wreckage, aft fuselage buckling from tail
momentum.
• D. Low Velocity, Low Angle – Aircraft may bounce several times, shedding parts but retaining overall
structure.
• E. Stall/Spin Impacts – Low velocity, high angle; may not hit nose first. Spin direction sometimes
identifiable.
6. Determining Impact Attitude
