1 Aviation Medicine CHAPTER 17 VIBRATION 181.study card

  1. Efects of Vibration?
    • -reduced visual acuity,
    • -interference with muscular control
    • -fatigue.
    • -Chronic backache -helicopter pilots
  2. PHYSICS OF VIBRATION?
    • - dampers that minimise the amplitude of vibration and lessen the time taken to return to the rest position.
    • - Damping reduce the amplitude of oscillations in an oscillatory system.
    • - Friction is one such damping effect.
    • - damping ratio determines the behaviour of the system
    • a) Overdamped-system returns (exponentially decays) to equilibrium without oscillating
    • b) Critically damped-system returns to equilibrium as quickly as possible without oscillating-desired for doors
    • c) Underdamped-system oscillates-amplitude gradually decreasing to zero.
  3. SOURCES OF VIBRATION?
    • -All machinery
    • -vehicles or the environment.
    • -frequency can be predicted by the rotational speed of the engine.
    • -fixed wing aircraft-higher frequencies.
    • -turbulence and occurs at lower frequencies-depends on atmospheric conditions-worse in high speed low-level flight.
    • -High G flight- vibration through an airframe-fighter manoeuvre ?flying on the buffet?
    • -firing of weapons
    • -failure of airframe components.
    • -helicopters-rotational speed of the rotor=4 Hz
  4. EFFECTS OF VIBRATION?
    • -undesirable effects on the human body
    • -1 to 100Hz
    • - motion sickness.
    • -Hyperventilation (resonance of the air in the trachea, tFreq of 3?4Hz.
    • -Abd pain (Joggers may be familiar with abdominal pain if running at their resonant frequency of 3?5Hz.
    • -Increased muscle activity - maintain body position and damp vibration.
    • -results in physical fatigue.
  5. Helicopter vibrations?
    • -12-15Hz (main rotor)
    • -23-25Hz (tail rotor)
  6. Lower Back Pain In Helicoptor pilots?
    • -posture and vibration (about 16Hz)- axial compressions of the spine
    • -reduced in recent years by improved seat design in newer aircraft.
  7. Visual Effect of Vibrations?
    • -60Hz making vision difficult
    • -instrument panel-inefficiency-eye?s pursuit reflex
    • -vestibulo-ocular reflex-Head moving or vibrating-able to fix on a distant target
  8. vestibulo-ocular reflex?
    • -very efficient nerve connection between the vestibular system and the eye muscles
    • -vision maintained- high frequencies of oscillation
    • -targeting mechanism on a ship rolling in heavy sea-maintain target despite heavy sea
  9. Vibrating Object and the eye?
    • -eyes try to track it
    • -requires a lot of processing by the brain
    • -tracking not efficient - rapidly vibrating objects such as a -vibrating instrument panel
  10. Resonant frequencies at about the heart rate?
    • -blood pressure fluctuations
    • -heart arrhythmias.
  11. Vibration of 20-100 Hz-muscle or tendons?
    • -tonic vibration reflex
    • -false perception of muscle stretch.
    • -Involuntary motions - degrade the accuracy of motor performance.
    • -proprioceptors can be fooled by vibration.
  12. EFFECTS OF VIBRATION?
    • -undesirable effects on the human body
    • -1 to 100Hz
    • - motion sickness.
    • -Hyperventilation (resonance of the air in the trachea, tFreq of 3?4Hz.
    • -Abd pain (Joggers may be familiar with abdominal pain if running at their resonant frequency of 3?5Hz.
    • -Increased muscle activity - maintain body position and damp vibration.
    • -physical fatigue.
  13. EFFECTS OF VIBRATION aeromedical evacuation of casualties?
    • - increased pain and bleeding,
    • - movement of fractures,
    • -risk of further injury
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david_hughm
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1 Aviation Medicine CHAPTER 17 VIBRATION 181.study card
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1 Aviation Medicine CHAPTER 17 VIBRATION 181.study card.txt
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