AVIATION TECHNOLOGY GRADE 10 COURSEBOOK
ESSENCE STATEMENT
Aviation Technology explores the dynamic world of flight, equipping learners with the
fundamental knowledge and skills to understand aircraft construction, flight, and
airport operations. It is designed to align a learner to the Technical Studies track in
line with the Science Technology, Engineering and Mathematics (STEM) pathway.
Aviation technology is anchored on Kenya Vision 2030 and Sessional Papers No. 1 of
2015 and No. 1 of 2019, with the goal of equipping learners with the necessary skills
and knowledge to contribute to the growth and efficiency of the aviation industry.
This educational focus aims to foster economic development, enhance connectivity,
and support the tourism and trade sectors, which are vital to Kenya’s economic
growth. Through hands-on experiences, learners develop a comprehensive
understanding of the science and technology behind aviation.
This will enable them to analyze, design, and construct basic aircraft models,
comprehend the importance of aviation safety procedures, and appreciate aviation's
impact on society and the environment. The knowledge will promote the social,
economic, and industrial needs of the aviation industry. By engaging with real-world
applications and emerging technologies, learners gain the skills and knowledge
necessary to pursue diverse career opportunities, enhance the efficiency and safety of
the aviation industry and engage with a global community.
SUBJECT GENERAL LEARNING OUTCOMES
By the end of Senior School, the learner should be able to:
1. Develop understanding of Aviation Technology theories, concepts, principles, and
operations.
2. Acquire safety awareness and practices observed when working in the aviation
field.
3. Appreciate appropriate acceptable standards for weather, human and
environmental factors in flight operations.
4. Relate positively with members of the society when executing tasks related to
Aviation Technology.
5. Develop financial and consumer literacy skills in Aviation entrepreneurship.
6. Read, interpret, and apply aircraft related drawings.
7. Identify career opportunities available in the Aviation industry.
8. Understand and apply emerging technologies and environmentally sustainable
practices in the Aviation industry.
Ø
3. STRAND 4_METEOROLOGY 1
SPECIFIC OBJECTIVES.
• At the end of this strand, the learner should be able to:
a) Differentiate between International Standard Atmosphere (ISA) and Prevailing conditions.
b) Describe the characteristics of atmospheric layers.
c) Identify, read and interpret weather instruments.
Sub-STRANDS
v Introduction
v Atmospheric elements.
v Properties of the atmosphere.
v Atmospheric layers.
v International standard atmosphere (ISA) & prevailing conditions.
v Weather instruments
INTRODUCTION
• Meteorology refers to a branch of science concerned with the processes and facts of the atmosphere, including weather and climate.
• To enable safe and comfortable flights we must understand the behaviour of the atmosphere.
• The earth is wrapped by a protective blanket known as the atmosphere hence, Atmosphere is the gaseous envelope that surrounds the earth and rest upon it.
• The basic unit of each gas is a molecule, when three atoms of a molecule combine they form the ozone.
• The highest concentration of ozone is found in a 25km thick layer, 16-40km from the earth surface.
• The ozone layer absorbs harmful ultra-violet rays, thereby protecting the earth against its dangerous effects.
ATMOSPHERIC ELEMENTS
Parameters of air (pressure, density, temperature) vary considerably both in weight and geographic condition around the world.
In the lowest 65-80 km of the atmosphere, the relative proportion of each gas in the air mixture is almost constant.
Composition of the atmosphere
a)Nitrogen - 78%
b) Oxygen - 21%
c) Carbon (IV) oxide - 0.03%
d) Inert gases - 0.97%
In the atmosphere, we also have impurities due to the presence of dust, smoke and waste industrial gases.
PROPERTIES OF THE ATMOSPHERE
Temperature
Atmospheric Temperature Lapse rate
Temperature lapse rate can be defined as the changes in temperature with change in altitude.
There are three types of temperature lapse rate;
a) Positive Lapse Rate – This is where temperature decreases with increase in height/altitude.
a) Neutral Lapse Rate – This is where temperature remains constant with increase in height. The atmospheric layer with this type of lapse rate is referred to as Isothermal Layer.
c) Negative Lapse Rate – This is where the temperature increases with increase in height. The atmospheric layer with this type of lapse rate is referred to as Inversion Layer
Density
• Density is mass per unit volume of a substance hence, air density is the mass of air per a given volume.
• Density decreases with an increase in altitude within the atmosphere.
• Air density at sea level is assumed to be 1.225 kg/M^2.
Pressure
• Pressure is the mass per unit area.
• A column on air exerts pressure on the earth’s surface which decreases as the altitude increases.
• Pressure at sea level is assumed to be 1013.25mb or 101.3KN/M2, 760mmHg, 29.92inHg.
Wind
• Troposphere contains winds called jet streams.
• The strongest winds are encountered at the height of about 30,000 and above of winds moving from west to east at a speed of 150-350 miles per hour (mph).
Atmospheric layers
• The atmosphere is divided into four main layers namely:-
a) Troposphere – Ranges from 0 to 11Km, where we find the tropopause.
b) Stratosphere – Ranges from 11Km to 48Km, where we find the stratopause.
c) Mesosphere – Ranges from 48Km to 80Km, where we find the mesopause.
d) Thermosphere – Ranges from 80Km and above
A typical model showing THE ATMOSPHERic LAYERS
- Troposphere
• This is the lowest layer of the atmosphere and closest to the earth‘s surface with an altitude of 11Km (36,000ft) from the sea level.
• It is a layer with positive lapse rate where temperature decreases with increase in altitude at a rate of 6.5˚C per Km or 1.98˚C per 1000ft.
• It is a layer with most weather elements for example, cloud formation and precipitation.
• It contains 78% of all gases, dust and water vapour.
• There is a decrease in pressure with rise in altitude.
• There is a decrease in air density with rise in altitude.
• Wind velocity increases with increase in altitude.
• It is the only layer that supports life.
• It is separated from Stratosphere by a layer of discontinuity called tropopause.
- Stratosphere
• The altitude extends from 11km to 48km (56,000 ft-157,000ft).
• This is the second layer of the atmosphere extending above the tropopause
• It has an isothermal layer where temperature remains constant at -57°c from 11-15 km, and an inversion layer above this point, where the temperature increases up to 48 km.
• It contains the strongest winds called jet steams which are tubes of high speed winds moving from east to west. Airplanes take advantage of this wind to gain extra speed.
• Clouds are usually rear in this layer.
• This layer contains the ozone layer which keeps most of the infra- red radiation from the sun from reaching the earth’s surface, thus making the temperatures to rise in this layer.
Stratosphere is divided in to two layers:
a) Lower stratosphere
b) Upper stratosphere
a) Lower Stratosphere
• It extends from 36,000 feet to 82,000 feet (11-25km).
• The temperature in this region is almost constant at -57°c.
b) Upper Stratosphere
• It extends from 82,000 feet TO 157,000 feet (25-48 km).
• Temperature increases from -57°c to -2.5°c.
• At the end, there is a boundary layer called the stratopause.
3) Mesosphere
• It extends from 157,000 ft. to 262,000 ft.(48-80 km)
• This is the third layer of the atmosphere extending above the earth.
• The temperature falls rapidly hence it is the coldest temperature zone with an average temperature of -92°C
• At the top of mesosphere is the upper boundary layer called mesopause.
• It experiences very high velocities with a speed of about 300 km/h.
4) Thermosphere
• It extends from 262,000-1,312,355 ft. (80-400km).
• It’s the 4th layer extending from the mesosphere.
• There is no distinct temperature boundary to the top of this layer.
• The temperature increases rapidly due to the absorption of the solar energy.
• This zone is sometimes taken to include the ionosphere and exosphere.
• The ionosphere has the ability to reflect radio waves.
INTERNATIONAL STANDARD ATMOSPHERE (I.S.A) & PREVAILING CONDITIONS
• Prevailing Conditions refers to the atmospheric conditions that comprise of the existing state of the atmosphere in terms of temperature, wind and clouds.
• International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density &viscosity of the earth´s atmosphere changes over a wide range of altitude.
• It has been established to provide a common reference for temperature and pressure and consist of tables of various altitude.
• The international Standard Organization (ISO) published the ISA as an international standard.
• At sea level, the International standard atmosphere(ISA) gives values as follows:-
• Temperature=15 °C /288k
• Pressure=1013.25mb/760mmHg/29.92inHg/14.7psi/101.3kNm-2
• Air Density=1.225kgm-3
• Speed of sound=340ms-2
• Acceleration due to Gravity=9.81ms-2
• I.S.A model divides the atmosphere in to linear temperature distribution.
Weather instruments
Windsock
• A windsock is an instrument used to measure the strength and direction of wind
• It is commonly found in airports. It is used to aid the air traffic controllers in selecting the runway depending on the wind direction.
Windvane
• It’s used for measuring wind direction.
• The pointer faces the wind while the tail faces the direction the wind is blowing to.
• It consist of a horizontally rotating arm with a pointer pivoted on the vertical shaft
Rain gauge
• The measurement of rainfall is done by a rain gauge when it rains, water from direct raindrops collects into the jar through the funnel.
Anemometer
• The speed of wind is measured using an anemometer in kmh or in nautical miles. When the wind blows, the cups rotate.
• The stronger the wind, the faster the rotation.
Thermometer
This is an instrument used to measure air temperature
Effects of weather to an aircraft in flight
- Turbulence
– This is caused by non-uniform wind flow. It leads to bumpy, rough and uncomfortable flight.
Factors leading to Turbulence
• Convectional vertical currents.
• Friction – The interaction of air with another surface i.e. with the ground or an obstruction and can cause mechanical turbulence.
• Wind Shear – Change in wind direction and speed over a short period.
• Aircraft cause wake turbulence behind their wings. This is particularly dangerous to other aircrafts during take-off and landing.
Precautions taken to avoid effects of turbulence on aircraft
• Aircraft must be properly separated.
• Aircraft must not fly above the other aircraft path, since vortices sink downwards.
• Avoid flying over areas of uneven terrains.
• Check weather forecast before planning a flight.
Keep heading and altitude change to minimum
2. Fog
• This reduces visibility.
• Very low visibility may lead to postponing of landings, taking off and other airport operations.
• Aircrafts may also be directed to other airports.
3. Rain
Rain affects the aircraft’s braking action during landing as the runway becomes slippery. This may limit take-off and landing weight
4. Temperatures
• The temperature is important in view of engine performance. High temperatures can lead to reduction in air density, which has a direct negative effect on engine performance. This can also lead to reduction of take-off weight.
- Crosswinds
• Crosswinds usually hit the aircraft from the sides during landing and taking off. This gives the aircraft unnecessary rolling which may be hazardous. The direction of wind is used in selecting runways.
6. Thunderstorm Hazards
• Flight through thunderstorms result to such hazards like hail, icing, lightning strikes and severe air turbulence.
• Since most low flying aircraft may not be equipped with weather radar, pilots must rely and have reliable and current weather data from the meteorological department.
• High wind speeds and severe down bursts are associated with thunder clouds.
• When a thunderstorm occurs near an airport, various operations like landing and takeoff and even refueling are suspended.
Effects of high altitude flights on aircraft
• Low temperatures at very high altitudes can cause aircraft icing which can lead to:-
a) Increase in drag hence loss of lift when it accumulates on the aircraft surface.
b) Decrease in propeller efficiency.
c) Blockage of the pitot heads and static vents hence introducing errors in pitot-static Instruments.
d) May affect radio antenna bringing the possibility of communication failure.
e) Carburation icing hence reduce engine efficiency.
Advantages of high altitude flight
HUMAN:-
a) Reduced noise levels.
b) Comfort i.e. less air bumps/ turbulence.
AIRCRAFT:-
a) Economical in fuel consumption-less drag is experienced.
b) Less buffeting/vibrations.
c) Reduced incidents of lightning strikes.
d) Low atmospheric pollution
Effects of high altitude flight on human beings
• Freezing
• Reduced humidity causes sore throat and cracking of skin.
• Anoxia which is caused by absence of oxygen supply to an organ or a tissue.
• Hypoxia which is caused by lack of sufficient oxygen in the brain, leading to blurred vision, impaired judgement and thinking, etc.
• Decompression sickness and vapour locks in the blood streams causing chest pains and sickness in breathing.
• The aircraft must be made from heavy structures to withstand high pressure differential hence more expensive.