Transcript Aviation Human Factors

Aviation Human
Factors
Lecture 9-Acceleration in
Aviation: G-Force
What is Acceleration
• ACCELERATION is a change in
VELOCITY per unit of TIME.
• It is produced when either speed or
direction changes. (moving car/aircraft,
falling objects)
Types of Acceleration
• There are three types of acceleration. These types
are Linear, Angular & Radial Acceleration.
• Linear Acceleration — change of speed in a straight
line. This type of acceleration occurs during takeoff, landing, or in level flight.
• Angular Acceleration — change in both speed and
direction, which happens in spins and climbing turns.
• Radial Acceleration —change in direction such as
when a pilot performs a sharp turn, dive
Acceleration in Aviation
• When we pilot an aircraft, all that we have
learned about gravity and have become
comfortable with sudden changes.
• Flight—in its purest definition—is overcoming
gravity to ascend through the air.
• Just as when we where learning to walk, a
primary goal of every flight should be to avoid
painful, gravity-induced incidents with the
ground.
• These encounters are called aircraft
accidents and mishaps, and they can be
destructive, even fatal.
Introduction
• Human beings are adapted
to live and survive within
the ever-present,
accelerative force of
gravity.
• While on earth, this is a
constant, and we live and
function with it from the
day we are born until the
day we die.
• As an baby learning to
walk, we learn very quickly
that misstep will
ultimately lead to a painful
gravity-induced incident
with the ground that we
call “a fall.”
What Goes Up Must Come
Down
• The force of gravity on earth causes a constant
acceleration of 9.8m/s²
• That means if you drop something it goes faster and
faster, increasing its speed downwards by 9.8 m/s in
each passing second.
• Acceleration is described in units of the force called
“G.”
• A pilot in a vertical turn may experience forces of
acceleration equivalent to many times the force of
gravity.
• This is especially true in military fighter jets and
high-performance, aerobatic aircraft where the
acceleration forces may be as high as 9 Gs.
G-force
• During positive Gs, the weight of the
body is increased in direct proportion to
the magnitude of the force.
• For example:
• On the ground, pilot weight = 200pound
• Under 3 Gs condition, pilot weight =
600pound
Typical examples of GForce
Activities
G-Force
•Weightless environment to train astronauts
0g
•Standing on the Earth at sea level
1g
•High-g roller coasters
3.5–6.3 g
•Formula One car, maximum under heavy
braking
5g
•Aerobatic plane or fighter jet, maximum
turn.
9-12 g
•Missile
100 g
Types of G-Forces
Three types of G-forces acted on the
body include:
1. Gx – Transverse G (chest to back)
2. Gy - Lateral G (side to side)
3. Gz – Vertical G (head to foot)
**Gz is the most dangerous
Gx-Force
• Gx—is described as force acting on the
body from chest to back (+Gx) or from back to
chest (–Gx)
• +Gx (positive) is experienced, for
example, during the take-off. This is the
force that pushes the pilot back into the
seat as the aircraft accelerates.
• –Gx (negative) is encountered during
landing This force pushes the pilot forward
into the shoulder strap.
Naval pilots flying from aircraft carriers feel the
extremes of Gx force. During take-off, the aircraft
accelerates to 160 mph in just under two seconds.
During landing, the aircraft will decelerate to a
complete stop in just a few feet.
Gy-Force
• Gy—occur when pilot expose to acceleration
from side to side. from right to left: +Gy, from left
to right: -Gy.
• Gy is encountered during aileron rolls, rudder
roll, vertical roll and uncontrolled aircraft.
• Aerobatic pilots routinely encounter this type
of G force and can still safely and precisely
maneuver their aircraft.
Gz-Force
• Gz - is a gravitational force that is applied to
the vertical axis of the body.
•
• +Gz (positive) - it is experienced from head to
foot. This happens when a pilot pulls into an
inside loop. pulls out of a dive or
• –Gz (negative) - it is experienced from foot
to head, and it is experienced when a pilot
pushes over into a dive.
Physiological Effects
of High G Forces
• Circulatory System & Mental Function is
greatly affected by changes in G-Forces.
– The heart and cardiovascular system unable to
keep blood flowing to the brain and maintain
consciousness.
• Other effects are motion sickness &
disorientation.
Effects of
High Gz Forces
• In aircraft, g-forces are often +Gz (positive) which
force blood towards the feet and away from the
head;
• This causes problems with the eyes and brain in
particular.
• As g-force is progressively increased the pilot may
experience:
– GREY-OUT, where the loss of color vision.
– BLACK-OUT, a loss of vision while consciousness is
maintained.
– G-LOC a loss of consciousness ("LOC" stands for "Loss Of
Consciousness").
– Death, if g-forces are not quickly reduced, death can occur.
“Grey Out”&“Black out”
• A “Grey Out”, occurs when the body
experiences a Positive (+Gz) force.
• Positive (+Gz) force causes blood flows from
the head to the lower parts of the body
• “Grey Out” makes a pilot loss of color vision.
– The eyes are extremely sensitive to low
blood flow & the retina will not be supplied
with adequate blood.
• At high +Gz force (5Gs), when no blood in
brain pilot will experience “Black out” and will
completely loss of vision.
“G-Loc”
• G-LOC, G-force induced Loss Of
Consciousness (LOC),
• G-LOC term is to describe a loss of
consciousness due to excessive g-forces
that causes blood away from the brain.
• The condition is most likely to affect
pilots of high performance fighter and
aerobatic aircraft.
If you GLOC you may ...
have some tingling or numbness
 have a pleasant dream
 not realize that you GLOCed!
 be a little confused or disoriented
 be aware that you have lost your
hearing

Pilot
was subjected to 15 g
for 0.6 second
“Red Out”
• A “Red Out” occurs when the body
experiences a negative (–Gz) force.
• –Gz force causes a blood flow from foot
to the head.
• When “Red Out” happen, pilot vision
turns red.
• This is probably because capillaries in
the eyes burst under the increased
blood pressure.
• “Red Out” are potentially dangerous and
can cause retinal damage.
Other Effect of G-force
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Breathing difficulties
Heartbeat abnormalities
Motion Sickness
Fatigue
Arm, Leg & Neck Pain
G-forces treatment
• Wearing the anti-G suites: this suite will
enhance the blood flow to the brain.
• Apply special breathing techniques,
called as “anti-G straining maneuver”.
This technique is to prevent the blood
from flow away from the brain.
G-forces treatment
• A well-rested, hydrated, and fit aviator will
physically be able to withstand higher G
forces can enhance aviator performance in
the high-G environment.
• When an aviator is well hydrated, there is
more circulating volume in the blood stream,
and it is easier for the heart to keep the
brain with oxygen blood.
Effect of G-force may
increase because of….
•
•
•
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Fatigue
Alcohol
Dehydration
Illness
Medication
Summary
• Any aircraft, civilian or military, can
expose the pilot, crew, and passenger to
forces in excess of 1 G.
• During steep turns and unusual attitude
recovery, civil aviation pilots can
experience high G forces that may take
them by surprise unless they are
prepared.
• Subsequently, all aviators need to
understand what makes their body more
resistant to the effects of G
acceleration.