Proficiency Level Three Combined Aviation Assessment Study Guide

Transcription

1 Proficiency Level Three Combined Aviation Assessment Study Guide Developed by: 533 St. Albert RCACS Last Revision: January 2014 Reference: A-CR-CCP-803/PG-001 Level Three Qualification Standard and Plan A-CR-CCP-803/PF-001 Level Three Instructional Guides

2 Table of Contents Performance Objective 331: Principles of Flight Describe Aircraft Stability... 2 Performance Objective 336: Meteorology Describe Properties of the Atmosphere Explain the Formations of Clouds Explain the Effects of Air Pressure on Weather Explain the Effects of Humidity and Temperature on Weather

3 Performance Objective 331 Principles of Flight: Describe Principles of Flight Describe Aircraft Stability Why do we need to know about aircraft stability? Knowledge of aircraft stability is crucial in understanding how aircraft will react when flying through turbulent weather, or perhaps when they are put through aggressive flight manoevres. It will also allow you to understand why aircraft are designed with certain features. What is stability? Stability is the tendency of an aircraft in flight to remain in straight, level, upright flight and to return to this attitude, if displaced, without corrective action by the pilot. What are the characteristics of stability? Static Stability The initial tendency of an aircraft to return to its original attitude, if displaced -VS- Dynamic Stability The overall tendency of an airraft to return to its original attitude Positive Stability The aircraft is able to return to its original attitude without any corrective measures -VS- Neutral Stability The aircraft will remain in the new attitude of flight after being displaced, neither returning to its original attitude, nor continuing to move away -VS- Negative Stability The aircraft will continue to move away from its original attitude after being displaced What are the axes of an aircraft? Longitudinal Axis (Axis of Roll) Runs the length of the aircraft, from the tip of the nose to the end of the empennage Lateral Axis (Axis of Pitch) Runs through the aircraft s wings, from wing tip to wing tip Vertical/Normal Axis (Axis of Yaw) Runs vertically through the aircraft from top to bottom All three axes intersect at an aircraft s centre of gravity 2

4 What is longitudinal stability? Stability around the lateral axis Known as pitch stability Achieved by designing the aircraft to be nose heavy if loaded correctly Influenced by the horizontal stabilizer and the centre of gravity What are the effects of the horizontal stabilizer? Located at the tail end of the aircraft, and functions as a counterweight Forces the tail down when the nose of an aircraft is pushed up When the stabilizer meets the airflow at a higher angle, it produces more lift which counters the initial disturbance What are the effects of the centre of gravity? Each aircraft s centre of gravity is naturally occuring and is dependent on its design When an aircraft is loaded, the centre of gravity can shift; drastic shifts in the centre of gravity can adversely affect the stability of an aircraft Too Far Forward! Produces a nose-down tendency Forces the pilot to use excessive back pressure on the controls Causes the aircraft to speed up and lose altitude Too Far Aft/Back! Produces a nose-up tendency Forces the pilot to use excessive forward pressure on the controls Causes the aircraft to slow down and eventually stall What is lateral stability? Stability around the longitudinal axis Known as roll stability Achieved by three design features built into an aircraft: dihedral, sweepback, and keel effect What is dihedral? When looking at an aircraft from the front, you will notice that the wings are angled so the wing tip is higher than the wing root this angle is the dihedral (or in the cases of a negative angle, the anhedral) What are the effects of dihedral? Assists the aircraft in maintaining lateral stability by changing the angle that the leading edge makes with the airflow Produces lift on a down-going wing when the aircraft is forced into a side-slipping motion What is sweepback? A design feature providing the same effects as dihedral, where the wings sweep back instead of protruding straight out from the fuselage What is keel effect? A form of built-in stability found in high-wing aircraft The bulk of the aircraft, which sits below the wings, acts as keel The fuselage acts like a pendulum and swings the aircraft back into position when the wing is forced up by a disturbance 3

5 What is directional stability? Stability around the vertical axis Influenced by the vertical tail surface, also known as the fin What are the effects of the fin? Weather vaning is an aircraft s tendency of always flying head-on into the relative airflow, and is a direct result of the fin If the aircraft yaws away from its course, the airflow strikes the fin from the side, forcing it back into position Will only work if the side area of the aircraft is greater aft of the centre of gravity than the area forward of the centre of gravity 4

6 What is the definition of aircraft stability? Describe dynamic and static stability. What are the factors influencing longitudinal stability? Directional stability is stability around which axis? 5

7 Performance Objective 336 Meteorology: Identify Meteorological Conditions Describe Properties of the Atmosphere Why do we need to know about the properties of the atmosphere? Being able to describe the properties of the atmosphere will allow you to better understand how weather conditions are created What is the atmosphere composed of? The atmosphere is composed of a mixture of invisible gases, as well as trace amounts of dust and debris in the lower levels What types of invisible gases make up the atmosphere? At altitudes of up to feet above sea level, the atmosphere is composed primarily of nitrogen (78%), oxygen (21%), and several other gases (1%) which include argon, carbon dioxide, hydrogen, and water vapour, among others. Why is water vapour important? Only found in the lower levels of the atmosphere Amount is never constant Most important gas in terms of weather Can change from gas into water droplets or ice crystals Responsible for the formation of clouds How is the atmosphere divided? The atmosphere is divided into four distinct layers, and extends for many miles from the surface of the earth. These layers are named troposphere, stratosphere, mesosphere, and thermosphere. The exosphere is not actually a layer of the atmosphere, but rather the start of outer space 6

8 Troposphere Lowest layer of the atmosphere Starts at ground level and extends to varying heights Air pressure, density, and temperature decrease with altitude Temperature will drop to a low of -56 C Most weather occurs here due to the presence of water vapour and strong vertical currents caused by terrestrial radiation Terrestrial radiation causes the troposphere to extend to varying altitudes there is more radiation at the equator than at the poles The jet stream exists in the upper parts of the troposphere The top of the troposphere is known as the tropopause, and is the boundary between the troposphere and the stratosphere Mesosphere Characterized by a decrease in temperature as low as -100 C at feet above sea level Meteorites usually burn up in this layer The top of the mesopshere is known as the mesopause, and is the boundary between the mesosphere and the thermosphere Stratosphere Extends feet upwards from the tropopause Pressure continues to decrease Temperature will gradually rise to 0 C Most of the ozone layer exists here, which prevents the more harmful solar radiation from reaching the earth s surface and explains the rise in temperature The top of the stratosphere is known as the stratopause, and is the boundary between the stratosphere and the mesosphere Thermosphere Highest of the four layers Named due to its intense temperatures First layer to be affected by solar radiation What little oxygen exists absorbs high amounts of the radiation Actual temperatures vary, but can exceed C What is meant by standard atmosphere? The decrease in temperature, pressure, and density with altitude is not consistant, but varies with local conditions. The International Civil Aviation Organization (ICAO) has set an international standard for the purposes of aviation, and different regions have different standards. What are the basis of ICAO standards in North America? Summer and winter averages 40 degrees north latitude Whare are the assumptions for standard atmosphere in North America? Air is a perfectly dry gas An average (mean) sea level pressure of of mercury An average (mean) sea level temperature of 15 C Temperature decreases with altitude at a rade of 1.98 C per feet 7

9 What are the principle properties of the atmosphere? Mobility Ability for air to move from one place to another Explains why air masses which form in the arctic can affect areas in the south Capacity for Expansion Most important property Air is forced to rise for various reasons As air pressure decreases, the air will expand and cool The cooling may cause condensation to occur and clouds to form, creating precipitation Capacity for Compression The opposite of expansion When the air cools, it becomes denser As the air sinks, it decreasese in volume and increases in temperature What are the factors affecting the properties of the atmosphere? Temperature Changes air density Density Creates the vertical movement of the air, causing expansion and compression (differences in pressure) Pressure Causes mobility across the surface as the air moves horizonally to fill gaps left by air that has moved vertically 8

10 Which gas composes 78% of the earth s atmosphere? What is the lowest layer of the atmosphere? The ozone layer can be found in which layer of the atmosphere? What are the assumptions for standard atmosphere in North America? How does mobility work as a property of the atmosphere? How does capacity for expansion work as a property of the atmosphere? 9

11 Explain the Formation of Clouds Why do we need to know about cloud formations? Understanding how clouds form will enhance your knowledge in meteorology and also your ability to predict weather How are clouds classified? Formation Height What are the types of cloud formations? Cumulus Formed by unstable air Cottony or puffy Seen mostly during warmer seasons May develop into storm clouds Stratus Formed by stable air Flat Seen year-round Associated with colder temperatures What are categories of cloud height? Clouds are classified into one of four categories based on their height above ground level Low Clouds Bases range from the surface to feet Composed of water droplets and sometimes ice crystals Use the word stratus as either a prefix (strato-) or a suffix (-stratus) High Clouds Bases range from feet to feet, with an average of feet in the temperate regions of the earth Composed of ice crystals Use the word cirrus as a prefix (cirro-) Middle Clouds Bases range from feet to feet Composed of ice crystals or water droplets, which may be at temperatures above 0 C Use the word alto as a prefix (alto-) Clouds of Vertical Development Base may be as low as feet and may rise as high as the lower reaches of the stratosphere May appear as isolated clouds or seen as embedded in layers of clouds Associated with thunderstorms and other summer phenomena 10

12 What are some common cloud types? What is air stability? The normal flow of air is horizontal at the surface Vertical air currents develop when disturbances occur, normally caused by changes in temperature If the displaced air resists the change, it is said to be stable If the displaced air does not resist the change, it is said to be unstable When air rises, it expands and cools Stable Air If the rising air is cooler than the air it comes in contact with, it will sink back to its original position -VS- Unstable Air If the rising air is warmer than the air it comes in contact with, it will continue to rise 11

13 What are the effects of stable and unstable air on flight characteristics? Stable Air Poor low-level visibilty (fog may occur) Stratus type clouds Steady precipitation Steady winds, which can change greatly with height Smooth flying conditions Unstable Air Good visibility (except in precipitation) Cumulus type clouds Showery precipitation Gusty winds Moderate to severe turbulence What are lifting agents? Lifting agents are conditions which provide lift to initiate rising air currents, which in turn affect many weather conditions. The five lifting agents are described below. Convection Air is heated through contact with the earth s surface As the sun heats the earth s surface, the air in contact with the surface warms up, rises, and expands Orographic Lift Occurs when the sloping terrain forces the air upwards Process can be exaggerated if the air mass is already unstable Frontal Lift Warmer air is forced upwards by denser, colder air as two different air masses meet Process may be exaggerated if the warm air mass becomes unstable 12

14 Mechanical Turbulance Similar to orographic lift, except caused by smaller terrain such as forests, builidings, and large ditches This friction can cause eddies, which are usually confined to the first few thousand feet of the troposphere Process may be exaggerate if the air mass becomes or is already unstable Convergence In a low pressure system, wind blows towardsd the centre Excess air that collects in the centre is forced upwards to higher altitudes What are the two ways that clouds are formed? Temperature drops to the saturation point of the air Temperature remains constant but the amount of water in the air increases How do lifting agents relate to air stability? Each lifting agent either affects or is affected by air stability Convection, for example, is normally associated with unstable air since heat causes the convection, and is also a source of instability in the air Orographic lift, for example, is usually associated with stable air, as after the air has been forced up by the terrain it cools and becomes dense How does air stability relate to cloud formations? Air stability directly affects cloud formation Clouds created in stable air will form as stratus-type clouds Clouds created in unstable air will form as cumulus-type clouds 13

15 What are the two main types of cloud formations? What is unstable air? What are the effects of unstable air on flight characteristics? How does convection function as a lifting agent? 14

16 Explain the Effects of Air Pressure on Weather Why do we need to know about the effects of air pressure on weather? Knowing the effects of air pressure on weather will increase your understanding of how air moves and your ability to recognize weather patterns What is the Polar Front theory? The Polar Front theory, created by Norwegian meteorologists, claims that the interaction between high pressure areas over the poles and low pressure areas around the equator may provide force to the movement of air What is atmospheric pressure? Atmospheric pressure is the pressure of the atmosphere at any point due to the weight of the overlying air How do we measure pressure? Pressure at the surface of the earth is normally measured using a mercury barometer and is expressed in mm of mercury (mm Hg) or inches of mercury (" Hg) In meteorological work, it is common to use hectopascals (hpa) to measure pressure 1 hpa is dynes of force exerted on 1 cm 2 Average pressure at sea level is normally expressed as 760 mm Hg, or hpa Public weather broadcasts normally use kilopascals (kpa), displaying the average pressure as kpa What are pressure systems? Low Pressure Areas Normally move in an easterly direction at an average rate of 800 km per day in the summer and km per day in the winter Associated with thunderstorms and tornadoes Do not stay in one place for very long Air moves around a low pressure area in a counter-clockwise direction in the northern hemisphere High Pressure Areas Winds are usually light and variable Move very slowly, sometimes staying stationary for days at a time Air moves around a high pressure area in a clockwise direction in the northern hemisphere 15

17 How do we display pressure systems on a map? Areas of like pressure are joined by lines called isobars. On a weather map, isobars will look similar to contour lines found on a topographical map. The isobars form roughly concentric circles, each circle being four hpa different than the circles before and after it. Groups of isobars will indicate areas of relatively high pressure, or relatively low pressure. What are the characteristics of air masses? Polar Regions Cold Dry -VS- Equatorial Regions Warm Moist What is the polar front? The polar front is the transition zone between the polar air and the equatorial air, and the movement of air within the polar front is thought to be the cause of air circulation in the troposphere What are the characteristics of the polar front? Many low pressure areas due to the differences in properties of the two air masses Cold air moves from north-east to south-west in the northern hemisphere, while warm air moves in the opposite direction Cold air bulges south and warm air bulges north, creating constant instability Cold air moves faster than the warm air and eventually envelopes it What is an air mass? An air mass is a large section of the troposphere with uniform properties of temperature and moisture along the horizontal plane How are the properties of air masses determined? An air mass will take on the properties of the surface over which it has formed How can air masses be described? By Temperature Arctic Cold (formed over the Arctic) Polar Cool (formed over the Polar region) Tropical Warm (formed over the Tropical region) By Moisture Continental Dry (formed over land) Maritime Moist (formed over water) 16

18 Normally these types of air masses are combined to describe the properties of temperature and moisture. In North America there are five air masses: Continental Arctic (ca) Maritime Arctic (ma) Continental Polar (cp) Maritime Polar (mp) Maritime Tropical (mt) What is wind? Wind is the horizontal movement of air within the atmosphere What are the characteristics of wind? Moves parallel to the isobars of a pressure system, meaning wind direction will vary at different locations along the pressure system because isobars are not straight lines Moves in different directions based on whether the pressure is a low or high system Why is wind important? Major factor in flight planning and flight characteristics Awareness of wind speed and direction is crucial in all parts of a flight, and especially during landing What is a pressure gradient? Rate of change of pressure over a give distance measured at right angles to the isobars When isobars are close together, the rate of change will steep and the wind speed will be strong When isobars are far apart, the rate of change will be shallow and the wind speed will be weak What causes land and sea breezes? Land and see breezes are caused by the differences in temperature over land and water 17

19 What is a sea breeze? Occurs during the day when the land heatsup more rapidly than the water Creates a lower pressure area over the land Pressure gradient caused by this change is usually steep enough to create a wind from the water What is a land breeze? Occurs at night when the land cools down faster than the water Creates a higher pressure area over the land Pressure gradient moves the air from the land to the water What is diurnal variation? Surface winds are generally stronger during the day than at night. This is due to the heating processes, which occur during the day, creating vertical currents and pressure gradients. At night, when the heating processes cease, the vertical currents diminish and the pressure gradients become shallower. What is Coriolis Force? As air moves from a high pressure system to a low pressure system, the air will not flow directly from one to the other. The rotation of the earth causes a deflection to the right (in the northern hemisphere). This force is known as the Coriolis Force. Coriolis Force also explains why air moves clockwise around a high, and counter-clockwise around a low pressure system. What is veering and backing? A change in wind direction clockwise relative to the cardinal points of a compass is known as veering A change in wind direction counter-clockwise relative to the cardinal points of a compass is known as backing Occur with changes in altitude; increases will cause veering and an increase in wind speed, while decreases will cause backing and a decrease in wind speed Changes are due to increases in friction with the surface of the earth at lower altitudes and decreases in friction at higher altitudes 18

20 What are areas of equal atmospheric pressure joined together by? What is a low pressure area? What is wind? 19

21 Explain the Effects of Humidity and Temperature on Weather Why do we need to know the effects of humidity and temperature on weather? Knowing the effects of humidity and temperature on weather will allow you to make informed decisions about activities in the field and in aviation like whether or not you need an umbrella! What is humidity? A representation of the moisture or water vapour present in an air mass What are some characteristics of water vapour? Makes up only a small percentage of the overall atmosphere Only gas which can change into a solid or a liquid in ordinary atmospheric conditions Causes most weather to develop How does moisture enter an air mass? Originates from a body of water, such as a pond or an ocean, over which the air mass forms or passes The size of the body of water will determine how much water is available for the air mass to collect The rate of evaporation will determine how much water is collected by the air mass In what forms can water exist in the atmosphere? Invisible Gaseous Visible Liquid Water Droplets Solid Ice Crystals What is condensation? Process by which a gas changes into a liquid by becoming denser Usually created by a cooling process What is sublimation? Process by which a gas changes into a solid without first becoming a liquid Usually occurs by freezing Occurs whenever snow, ice or hail fall from the sky Usuualy occurs in the winter or during exceptional summer storms What is dew point? The temperature to which unsaturated air must be cooled, at a constant pressure, to become saturated Temperature and dew point are responsible for the creation of clouds and precipitiation If the difference between temperature and dew point is smaill, the air is considered to be nearly saturated and a small drop in temperature will see the formation of clouds or precipitation What is relative humidity? The ratio of the actual amount of water present in the air compared to the amount of water which the same volume of air would hold if it were saturated Temperature and pressure must remain the same, otherwise relative humidity will change Saturated air will have a relative humidity of 100% Perfectly dry air will have a relative humidity of 0% 20

22 What is temperature? A representation of the amount of heat in a given object Measured using a thermometer In aviation weather reports, normally expressed in degrees Celcius ( C ) What is the source of heat in the atmosphere? The sun is responsible for heating the earth and the atmosphere Solar radiation is absorbed by the earth s surface The earth radiates heat into the troposphere through terrestrial radiation This means the atmosphere is heated from below, not above What is diurnal variation? Causes the heating and cooling of the atmosphere During the day, the solar radiation exceeds the terrestrial radiation and the surface of the earth becomes warmer At night, there is no solar radiation and the terrestrial radiation cause the surface of the earth to cool What is seasonal variation? The axis around which the earth rotates is tilted This causes different amounts of solar radiation to strike the surface of the earth at different times of the year In the northern hemisphere, this results in the summer months being warmer, while the winter months are colder What are heating processes? Since air is a poor conductor of heat, there are four processes which assist in getting warm air into the higher levels of the atmosphere Convection Air over a warm surface becomes buoyant and rises Cooler air moves into the vacant location Vertical current of air distributes the heat to higher levels Turbulence Created as a result of friction with the surface of the earth Causes a mixing process Moves the heated air to other areas of the atmosphere Advection Cool air moves horizontally over a warm surface Air gets heated from below Compression Air masses are forced down Air pressure increases, compressing the air mass Compression forces the particles together, causing heat Also known as subsidence 21

23 What are cooling processes? Since the atmosphere is heated from below, temperature usually decreases as altitude increases The rate of temperature change is known as a lapse rate Lapse rate is only a guideline as there is a variation in air masses and the three main cooling processes Radiation Cooling Earth s temperature decreases at night with terrestrial radiation Air in contact with the ground cools Advection Cooling Air from a warm region moves over a cold region and cools Adiabatic Process As air warms it rises As air rises it expands and cools In a rising air current, temperature decreases at a rate independent of the surrounding air What are the effects of temperature on relative humidity? Temperature will affect the relative humidity of an air mass by changing the volume of the air mass Increasing the temperature of an air mass will cause it to expand, which will increase its volume Increasing the volume decreases the relative humidity, since the air mass will now have a higher capacity for water Decreasing the temperature of an air mass will cause it contract, which will decrease its volume Decreasing the volume increases the relative humidity, since the air mass will have less capacity for water How does temperature and humidity affect weather? Temperature & Dew Point Temperature changes during the heating and cooling processes As the temperature nears the dew point, the air becomes more saturated The increase in relative humidity allows clouds to form Relative Humidity As relative humidity increases, the weight of the air mass also increases When the dew point is reached, the air becomes saturated and clouds form Once an air mass reaches 100% relative humidity, any additional water or drop in temperature will cause precipitation What is precipitation? May be solid or liquid, depending on the temperature of the air mass Snow will occur when the air has a temperature below freezing Rain will occur when the air has a temperature above freezing Temperatures in an air mass change with altitude Water may freeze at higher levels of an air mass, causing snow or hail in summer months 22

24 What kinds of precipitation are there? The World Meteorological Organization (WMO) has listed seven main categories of precipitation, depending on temperature and cloud type Drizzle Small water droplets which appear to float In near freezing temperatures, water droplets may freeze on contact with objects (freezing drizzle) Rain Large water droplets Freezing rain occurs when liquid water droplets make contact with objects in near freezing conditions Ice Pellets Raindrops which are frozen before contact Generally rebound after hitting the ground Hail Formed in clouds which have strong vertical currents (like thunderstorms) Is a water droplet which has been prevented from leaving the cloud until reaches a certain mass Stronger vertical currents create larger hail stones Snow Pellets Formed in clouds over shallow water regions Water droplets do not form the hard shells of hail Pellets fall as soft snow pellets instead Snow Result of sublimation Flakes are a collection of ice crystals Usually in the shape of a hexagon or star Ice Prisms Created in stable air masses at very low temperatures Tiny ice crystals in the form of needles Can form with or without clouds Often confused with ice fog 23

25 What is relative humidity? What is dewpoint? 24