GRAVITATIONAL FORCES

“G” ß The measure of gravity acting on a object. ß The normal force which acts on all bodies is equal to 1 G. ß During freefall, an object will fall at 32.2 fps 2 terminal velocity is reached

ACCELERATION Change in velocity in either magnitude or direction ß The most common accelerative force is gravity DECELERATION Any reduction in the velocity of a moving body

INERTIAL FORCE ßThe resistance to a change in the state of rest or motion ßA body at rest tends to stay at rest, a body in motion tends to stay in motion

TRI-AXIAL REFERENCE SYSTEM

FACTORS AFFECTING ACCELERATIVE FORCES ßIntensity ßDuration ßRate of onset ßBody area and site ßImpact direction

PHYSIOLOGICAL EFFECTS OF LOW MAGNITUDE ACCELERATION

+Gz Forces Head to Foot

FACTORS MODIFYING +GZ

DECREMENTAL FACTORS Any factor that reduces overall efficiency of the body, especially the circulatory system ß Blood volume decrease - varicose veins - hemorrhage ß Blood pressure decrease - hypotension - fatigue/illness - alcohol abuse

INCREMENTAL FACTORS Any factor that increases overall efficiency of the body, especially the circulatory system ß Hypertension ß Fear & excitement ß Tensing of muscles ß Short stocky build ß L-1 Maneuver

L-1 MANEUVER Procedure: ßRemain upright ßTense muscles ßExhale against a closed glottis at 2 to 3 second intervals Note: Increases G-load tolerance by 4 Disadvantages: ßPhysically Exhausting

-Gz Forces Foot to Head

+/- Gx FORCES Mild transverse accelerations / decelerations during landing and taking off

TRANSVERSE “G” TOLERANCE ß+Gx 15 G’s 5 seconds ß-Gx 12 G’s 5 seconds

+/- Gy FORCES ßHuman body has minimal tolerance to right or left accelerations ßMost aircraft do not apply accelerative forces in the lateral direction

PHYSIOLOGICAL EFFECTS OF HIGH MAGNITUDE ACCELERATION AND DECELERATION

EFFECTS ßMinor discomfort ßIncapacitating ßMinor injury ßIrreversible injury ßLethal

SOURCES F Aircraft crashes F Ejection seats

G’s (Seconds)

AIRCREWMEMBER SURVIVABILITY DURING THE CRASH SEQUENCE

CRASH SURVIVABILITY CRITERIA ßAmount of decelerative forces transmitted to the body ßOccupiable living space

Human Tolerance Limits to Whole Body Impact +9 Gs +80 Gs -40 Gs -9 Gs +20 Gs - Gy -Gx +Gy + Gx +Gz -Gz -16 Gs (0.1 second duration)

AIRCRAFT DESIGN FEATURES (CREEP)! F Container F Restraint system F Environment F Energy absorption F Post crash protection

QUESTIONS?