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THE EJECTION SEQUENCE?
- - driven by a pneumatic control system.
- -the firing handle is pulled,
- - small explosive charge is detonated which sends a charge of hot expanding gases through pipe-work around the seat.
- -expanding gas first initiates the retraction of harnesses before a sear pin is removed from the top of the gun,
- -firing the primary cartridge.
- -The gun has a piston inside allowing the hot expanding gases to force the seat up the rails breaking the seat mounting shear bolts.
Canopy of the aircraft removed in three ways?
- a) Through canopy ejection-knife-like canopy breakers PC9
- b) Canopy detonation (Explodes and shatters the canopy)-BAe Hawk, Harrier.
- c) Canopy separation- F/A-18 Hornet.
human body can withstand about G?
+25Gz at an onset rate of 300G/sec before major vertebral damage is experienced.
EJECTION SEAT SCHEMATIC?
- - seat accelerates to about 50kts by 1 metre
- - reaches a peak of about 20G.
- -as the seat rises, the hot gases ignite secondary and tertiary cartridges.
- -as the seat leaves the aircraft, rockets (if fitted) are fired for additional acceleration.
- -at the same time,
- -the emergency oxygen bottle,
- -Barometric Time Release Unit (BTRU) and
- -drogue gun are fired.
- -as the seat goes up the rails, gravity swings the legs down with gas-driven restraints pulling the legs toward the seat and
- holding them firmly until the crew separates from the seat.
- -Once clear of the aircraft, the BTRU controls the rest of the ejection sequence.
Drogue parachute deployment?
- - deployed as the seat leaves the aircraft.
- -small drogue (60cm) pulls out the
- -main drogue (150cm) which decelerates and stabilises the seat until the following conditions are met:
- a) Altitude is less than 10,000 feet,
- b) Deceleration is less than about 4G (at about 250kt), and
- c) 1.25 sec has elapsed.
- - is a timer
- -controls the sequence of events following egress.
- -2.5 sec after egress and the altitude/G criteria are met,
- -open a scissor-shackle on top of the seat.
- -scissor shackle releases the harness
- -leg restraint then the drogue deploys the main parachute by pulling it from the head box of the seat.
- -separate from the seat
- -survival pack, beneath the seat, drops
- a) Separation from the aircraft,
- b) Descent and parachute opening, and
- c) Landing.
EJECTION INJURIES SEPARATION FROM THE AIRCRAFT?
- Back Injuries
- factors-seat geometry-force tend to push your body away from the seat-harness must tight
- -head, shoulders and back are pushed hard back into the seat.
- -Muscular tension at the time of firing is critical
- -neck flexed forward
- -fracture sternum.
- -most common area for these fractures is the middle (thoracic) to lower (lumbar) back area.
- Ejection seats
- -do not have very thick padding and it
- -must not be too compressible.
- -Sitting on a soft cushion greatly increases the risk of legs fractures and/or spinal damage due to dynamic overshoot.
- -if the thighs are not pressed flat on the seat pan, femoral fractures can occur due to dynamic overshoot as the seat rapidly accelerates and closes the air gap under the thighs.
-bruising and abrasions.
- -Chin and sternum injuries
- -helmet weigh 14-16 times their normal weight due to the acceleration forces.
- -flailing of limbs
- -result in multiple fractures or dislocations.
- -barotrauma -air forced into lungs + stomach
Barotrauma is minimised?
- if the helmet and oxygen mask are retained during the ejection sequence
Essential of doning a helmet ?
- -fitted properly
- -both visors down,
- -chinstrap securely fastened and
- -the oxygen mask on with the ?toggle? (if fitted) down.
- -nape strap is critical in helmet retention
- -prevents the helmet rolling forward
- -must be done up ?comfortably tight?.
DESCENT AND PARACHUTE DEPLOYMENT?
- -exposure to the elements
- -wind blast
- -The aerodynamic ?flat plate? load at 600kts is 1200lb per square foot.
- -Drag will rapidly decelerate the pilot,
- -wind blast may dislodge protective equipment as well as cause physical injury.
- -Tumbling and flailing may cause limb injuries such as dislocations.
Shortly after the seat leaves the aircraft ?
- -drogue gun fire a metal rod upwards.
- -small drogue chute deployed-stabilise the seat, prevent flail, prepare for main chute deployment
- so that the main chute is not fouled by the seat.
- ?Opening shock?
- -deceleration force experienced by the ejectee as the main chute opens.
- -the higher the altitude, the greater the opening shock
- - 25,000 feet-as high as 16G,
- -10,000 feet it is only about 8G.
- -BTRU delays parachute opening until 10,000 feet.
entanglement in parachute risers may also be a cause for injuries?
physiological effects of altitude?
- -hypoxia and
- decompression illness
- - phase of ejection which is most likely to cause injury.
- -depend upon whether the person adopts a good landing posture,
- -what injuries have already been sustained,
- -the landing surface,
- -the condition of the parachute,
- - the weight of the person,
- -whether it is day or night,
- -the presence of hazards (such as power lines, trees, etc.),
- the weather conditions (eg. haze, fog, rain, wind) and
- -where the aircraft lands, with the possibility of fire.
parachute landing technique?
- -spread the force of impact over as large an area as possible.
- -bending the knees on landing
- -then dropping on to the side of the body and
- -rolling to dissipate as much energy as possible.
- - 30% chance # vertebra
- - always assume that fractures are present and minimise movement after landing.
FACTORS AFFECTING SURVIVAL?
- Delayed Decision: ejecting outside the ejection envelope
- -being a lack of ejection awareness and
- -temporal distortion.
- Ejection Awareness:
- -mental preparedness to eject.
- Temporal Distortion:
- -under stress, perception of time alters.
- EJECTION VECTORS
- CORRECT EJECTION POSTURE
- MINIMUM SAFE EJECTION ALTITUDE
- ABSOLUTE MINIMUM EJECTION ALTITUDE
- -rated as a Zero/60 seat.
- -absolute minimum ejection altitude is ground level, wings level, sink rate zero and a speed greater than 60KIAS.
- - Zero/0 seat, as fitted to most modern high performance aircraft,
- -is capable of removing the occupant from the aircraft even when stationary.
- -relies purely on a ballistic trajectory whereas the Zero/0 seat,