Transcript Aviation Human Factors

AVIATION HUMAN FACTORS
LECTURE 4
Acceleration and G-Force
What is Acceleration
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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
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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 take-off, 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
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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
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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
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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 highperformance, aerobatic aircraft where the acceleration
forces may be as high as 9 Gs.
G-force
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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
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Typical examples of G-Force
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:
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Gx – Transverse G (chest to back)
Gy - Lateral G (side to side)
Gz – Vertical G (head to foot)
**Gz is the most dangerous
Gx-Force
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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
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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
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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.
Positive Acceleration (+Gz)
Negative Acceleration (-Gz)
Physiological Effects of High G Forces
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Circulatory System & Mental Function is greatly
affected by changes in G-Forces.
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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
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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”
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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.
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eyes are extremely sensitive to low blood flow &
the retina will not be supplied with adequate blood.
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At high +Gz force (5Gs), when no blood in brain pilot
will experience “Black out” and will completely loss
of vision.
“G-Loc”
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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 ...
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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.
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Other Effect of G-force
Breathing difficulties
 Heartbeat abnormalities
 Motion Sickness
 Fatigue
 Arm, Leg & Neck Pain
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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.
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G-forces treatment
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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.
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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….
Fatigue
 Alcohol
 Dehydration
 Illness
 Medication
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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.
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