Transcript G-force

AHF 2203
AVIATION HUMAN FACTORS
Presentation 9:
G-Force and Accelerations
Presented by Mohd Amirul for AMC
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Recapitulate
• Lets recap what we have learnt last session:
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Orientation
Sensory input for orientation
Disorientation
Types of Disorientation
Visual Illusion
Prevention of Disorientation
Treatment of Disorientation
Motion Sickness
Cause of Motion Sickness
Symptom of Motion Sickness
Prevention and Treatment of Motion Sickness.
Learning Outcomes
• At the end of this session, student should be
able to:
– obtain causes of G-Force and it effects and also
able to identify necessary steps should be taken to
overcome it.
Presented by Mohd Amirul for AMC
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Presentation Outline
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Introduction
Acceleration
G-Force
Type of G-Force
Effect of G-Force
G-Force Treatment and Prevention
Conclusion
Presented by Mohd Amirul for AMC
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Introduction
What is Acceleration
• ACCELERATION is a change in VELOCITY per
unit of TIME.
• It is produced when either speed or direction
changes or both. (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 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
• 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 9.8m/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
• 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 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:
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.
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• +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 ...
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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.
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
Conclusion
• 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.
Key Points
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Acceleration
G-Force
Type of G-Force
Effect of G-Force
G-Force Treatment and Prevention
Presented by Mohd Amirul for AMC
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End of Presentation #9
5 Minutes for Q/A session
Presented by Mohd Amirul for AMC
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Practice
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State the main organs in our body systems and explain their function.
Hypoxic Hypoxia is the most common type of hypoxia in flight. Briefly explain
how it can occur during flight.
Briefly explain the concept of Effective Performance Time and state why this
is one of significance factor in flight.
Briefly explain how emotional problem might lead to hyperventilation
syndrome. Also explain the treatment of Hyperventilation.
How aircraft cabin pressurization works? Explain THREE major types of
decompression.
Relate Henry Law to the decompression Sickness Syndromes and Boyles Law
to Trapped Gas Syndromes.
Explain briefly how human could see using their eyes? Also describe THREE
types of vision and explain how to perform “space-eye movement
technique”?
What is Disorientation? How to recognize the person that faces motion
sickness syndromes?
Write the answers in the ESSAY form