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Learning Outcomes?
- • Describe factors that influence the body's tolerance to short duration accelerations.
- • Summarize the principles of crash-worthiness that increase crash survivability.
- • Describe the advantages and disadvantages of common types of restraint systems.
- • Demonstrate how to adopt an appropriate ‘brace position".
- • Describe ways to protect the head in an impact.
- • List the features and functions of the aircrew helmet.
- • Describe the effects of short duration acceleration on the body.
- • Describe the accident survivability potential of aviation platforms based on principles of crashworthiness and use of PPE.
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“Short Duration” Acceleration?
- • Acceleration acting upon the body for duration of less than half a second
- • collisions
- • ground impact
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Factors Affecting Human Tolerance?
- • Magnitude of force
- • Duration
- • 45G in 0.04s or
- • 25G in 0.2s
- • Rate of onset (Jolt)
- • Direction of applied force
- • +Gx>-Gx>+Gz>-Gz>Gy
- • Site of application
- • Back/buttocks > head/limbs
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‘CREEP’ factors?
- Container
- rigid protection of the occupants
- Restraint
- harnesses
- seat strength
- Environment
- the “flail zone”
- Energy attenuation
- breakup pattern
- size of the aircraft
- Post-crash factors & escape
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“C” is for?
- Container
- the “Roll Cage”
- Container
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“R” is for Restraint Systems?
- • The ideal restraint system is:
- • Comfortable
- • Efficient (it works as advertised)
- • Easy to use
- • Causes minimal restriction
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2 Point Harness (Lap Belt)?
- • Advantages:
- •Easy to use
- •Minimal restriction
- •Only 2 anchor points
- • Major disadvantages:
- Upper body restraint
- more serious injuries
- Submarining
- Brace Position
- Head down and hug knees
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3 Point Harness?
- • Advantages:
- • Better upper body
- • Disadvantages:
- • Minimal lateral restraint
- • Submarining
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4 Point Harness?
- • Advantages:
- •Good upper body restraint
- •Good lateral restraint
- • Disadvantages:
- •Submarining still
- • possible
- •Negative G
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5 Point Harness?
- • Advantages:
- • The best type of restraint
- • Negative G protection
- • No submarining
- • Disadvantages:
- • No head / limb restraint
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Problems with restraints?
- • Low takeoff point
- • tight
- • thoracic fractures possible
- • Dynamic overshoot
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Low take off point?
Compression Fracture
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Dynamic Overshoot?
- • Harnesses not securely tightened
- • Due to
- • air gap
- • elasticity of materials and body tissues
- • Exaggerated high-peak deceleration
- • Increased injury
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Delethalisation of the Flail Zone?
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“E” is for ?
- Energy Absorption
- Crumple Zones
- Energy Absorption in Seat Design
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“P” is for Post-Crash Factors?
- • Fire
- •fire retardant materials, fire extinguishing systems, smoke hoods
- • Exits
- number and location, exit signs, floor/ emergency lighting, structural damage to exits, fire in vicinity blocking exit, slides, proximity to ground
- • Orientation/location of aircraft
- •submersion, inverted attitude, darkness
- • Survival equipment
- •life jackets, rafts, beacons, first aid equipment
- •Water and food
- • Injuries
- •may prevent escape
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HELMETS & HEAD INJURY?
- Head Protection
- • Restraint system cannot fully protect from head injury
- • Therefore must rely on:
- • Rearward facing seats
- • Survival space
- • Helmets
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Head Injury?
- • 40 % of injuries
- • 20% of fatalities
- • Skull fractures
- • Primary brain injury
- • Secondary brain injury
- • Diffuse lesions
- •“Concussion”
- • Scalp/facial injuries
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Head Injury Prevents Escape?
- • Head injury & unconsciousness can cause death in an otherwise survivable crash from:
- • Fire
- • Drowning
- • Hypothermia
- • Unable to escape and evade
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• A dent of up to 12.5mm in the cranium does not cause fracture or permanent injury?
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Helmets do many things?
- • Protection from impact and penetration
- • Eye protection
- • Face/windblast protection
- • Hearing protection
- • Fire protection
- • Mounting ancillary items
- - Oxygen mask
- - Comms equipment
- - NVG, HMD, FLIR
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Helmets Prevent Head Injury?
- • Helmets designed using CREEP principles
- • Rigid container
- • Restraints
- • Energy attenuation
- • Limits force to the skull
- • Occupants remain conscious
- • Less serious injuries
- • Occupants remain conscious
- • Increases chance of escape and thus survival
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How does a helmet work?
- • Hard outer shell
- • Rigid container
- • Energy attenuation
- • Stiff foam liner
- • Spreads the load of impact
- • Shell and liner
- • Provides stopping distance
- • 15mm
- • Reduces 500G to 83G impact
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Effect of Stopping Distance?
- • Stopping distance determines peak acceleration
- • More distance reduces G to the head
- • No helmet;
- • distance = 3mm, G = 1700G FATAL
- • With helmet;
- • distance = 30mm,G = 170G SURVIVABLE
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Helmet Functions Impact Protection?
- • Attenuation of energy*
- • Resist rotary forces
- • Avoid dynamic overshoot
- • Protect against penetration*
- • Must stay on during impact*
- • MUST BE FITTED AND WORN CORRECTLY
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Helmet Functions Impact Protection?
- • Cracking of the shell absorbs impact energy
- • Deformable foam absorbs impact energy (& inc. s)
- • This helmet is not defective
- • it functioned as designed
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Visors down protect from?
- • Bird strike
- • Canopy fragmentation
- • Windblast on ejection
- • Glare and UV
- • Flash fire
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The Ideal Helmet?
- • Optimum weight, size, shape, C of G
- • Smooth
- • Comfort
- • Good fit
- • Ease of use
- • Good visibility
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ALPHA Series?
- • Advantages
- •High Impact Protection
- •HMD
- •Dual Visor
- •Good Stability & Retentivity
- • Disadvantages
- •Fit
- •NVGs - Visors
- •Weight
- •Oxygen Mask
- •No Ventilation
- •External Clutter
- •Difficult to Maintain
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HGU 56P
- • Advantages
- •Lightweight
- •Impact Protection
- •Comfort - Moulded liner
- •Stability
- • Disadvantages
- •Size
- •Weight
- HGU 55P
- • Advantages
- •Lightweight
- •Dual Visor
- •Moulded Liner
- •Good Stability and Retentivity
- •Comfortable
- •Easy to Maintain
- • Disadvantages
- •Limited Impact
- Protection
- •Lose visor during ejection
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Take home message…?
A helmet must be fitted and worn correctly to do its job !
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Quiz question 19:?
- The best negative G restraint is provide by which harness type:
- a. 2 point b. 3 point c. 4 point d. 5 point
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