Paragliding Manual - Espiral School PDF

PARAGLIDING MANUAL ESPIRAL ESCOLA DE VOO Espiral – Paragliding School offers the guarantee of the highest education and safety standards, enjoying the most modern equipment and extensive “Once you have tasted flight, you will experience. forever walk the earth with your eyes turned skyward, for there you have Our experience in free flight started been, and there you will always long to more than 30 years ago and we have 25 return.” Leonardo da Vinci years of participations on national and international championships. Paragliding changed many lives as the At the forefront of European schools experiences lived in the air showed the and far ahead on the national scene, we real importance of the day to day life. It have developed an innovative teaching was the door to new worlds of method that allows our students to be adventure, fascination and great accompanied from the first flight to the moments. We hope that the opportunity flight in distance. of flying can bring you pleasure, satisfaction, new friends and lasting memories. Man has always dreamed of flying in the air, spreading wings with his face in This is the main reason for this the wind, flying over mountains, rivers Paragliding Manual. and lakes. One of man's greatest dreams has always been to be free as a bird. It is everyone's desire to forget our Ricardo Diniz worries, to drop the world briefly and ascend to higher places where magic can still be found. In the universe of air, reality is behind us. This is the world of birds and here you can fly with them, look at the world from above and understand the insignificance of the human being. 2 This manual will help you feel comfortable with paragliding gear and with the necessary knowledge and skills to have a safe and pleasant flight. You must have a good physical health. You must have a strong mental attitude, good judgment skills and self-discipline. This manual is only the first step in all that paragliding has to offer. 3 INDEX Title Page Introduction 5 Equipment 8 Aerodynamic 28 Security 46 Meteorology 57 Aerology 72 Rules 84 Human Factors 94 First Aid 98 Paragliding Safety Practices Summary 114 Six stages to reach the sky 115 Bibliography / Acknowledgments 117 4 INTRODUCTION Man tried for many years to replicate the flight of the birds by building several types of flying machines. Along the history there are many written testimonials of these attempts. One of the man who gave a big contribution to the study of the flight was Leonardo da Vinci. He studied the insects and birds wings trying to understand how they worked. His drawings were an insight of the devices the future would bring. Leonardo da Vinci sketched a vision of flying machines in the 15th century in his manuscripts. His work consisted of several drawings of wings including an ornithopter moved by human strength; the name comes from the Greek word for "bird". Centuries later, when others began to experiment with his drawings, it became evident that the human body could not sustain flight by flapping artificial wings like birds. Man´s desire to fly was in the mind of the Portuguese people a long time ago. One man in particular has a particular role in history – João Torto. “João Almeida Torto was a nurse in Sto. António hospital in Viseu, he was also a barber with a bleeder license, astrologer and a master in writing. He publicly announced that on the 20th of June of 1540 he would fly with wings from the tower of the church of S. Mateus. On that day the crowd gathered in front of the church. João Torto climbed to the tower, pulled up with a rope his device and jumped. The flight went well to a certain point, but one of the wings stopped working untimely and the cap fell over his eyes. He described a descending bow, falling upright in the chapel of St. Louis, but soon fell there inanimate on the wings, looking in very poor condition. He came to himself two hours later, but died soon after. It was not yet in this way that man would conquer the air. ” Extracted text from História da Aviação Portuguesa, Museu do Ar 5 Sir George Cayley, in the century XIX, was the first man who studied flight theory in terms of mathematics and built a glider that launched from a hill, even glided satisfactorily. In Germany, between 1891 and 1896, Otto Lilienthal built a bat-winged glider. Throwing itself from the top of a hill, it maintained the stability of its glider by advancing or kicking its body or moving sideways. He planned to equip one of its gliders with engine. He failed to realize this plan because he died when one of his devices was destroyed in midair. Most flights from Lilienthal were done at 300 meters in height. In the early 1900s, the famous Wright brothers experienced glider flights in the hills of Kitty Hawk, North Carolina. The Wrights developed a series of gliders while experimenting with their aerodynamics. The difference between the Wrights and other enthusiasts was that they wanted to control the flight and become pilots, while the others just tried to stay in the air. By 1903, Orville and Wilbur Wright had achieved motorized flight of just over a minute by putting an engine in their best aerodynamic glider. In the fifties, the American engineer Francis Melvin Rogallo, recovered the idea of a flexible wing as a scientific instrument, full of possibilities. Rogallo, after the Second World War, began to investigate a wing shape that was not rigid. He was of the opinion that flexible surfaces provided greater stability than non-flexible ones. His first works are done at home with the help of his wife Gertrude, so he installed large fans in his living room and built his first wing with the kitchen curtains! He patented the flexible wing in 1951. 6 Paragliding is a word of French origin. Paragliding is the fusion of parachute + comb, ie slope parachute. Paragliding is a sport practiced on slopes and mountains, as we saw in the definition, gliding with a “parachute”. Paragliding is an air sport that emerged when climbers decided to shorten their descent faster and more comfortably after their ascension using parachutes. These parachutes are considered an American invention, patented in the 1960s by the Space Vehicle Recovery Agency. The main difference between this groundbreaking system and the top parachute (the most common) was that it could glide, enabling better performance and grounding at almost zero speed. In 1965, David Barish made wings that already surpassed finesse 4, made several past demonstrations on American television. It was considered the first paraglider of all time. It was not long before this new sport invaded Europe. Germany, Switzerland and France were the countries at the time that best welcomed this sport. Taking advantage of the same technical, meteorological and relief conditions as other types of gliding equipment, paragliding flies through a slower gliding flight ever devised by man. This youngest flight mode is also one of the most exciting. Paragliding has reached such a degree of refinement that today we are able to fly distances over 500 km by taking advantage of rising currents, thermal cycles and rising ascents. In Portugal, the paragliding arrived in 1987. The European record was set here in 1994 (204 Km). Since then the sport has been growing as we have excellent conditions for the practice of gliding. 7 EQUIPMENT EQUIPMENT PRESENTATION: The paragliding is generally composed of a fabric wing, sewn into cells, separated by ribs and joined by a set of harness suspensions where the pilot is installed. Wing: Usually made in 40g / m2 Nylon fabric, "zero" porosity. The coating is always made of polyurethanes or silicone. The wing has in general: Top surface - The entire upper surface of the wing. Bottom surface - The entire bottom surface of the wing. Leading Edge – The front stripe that first attacks the air and has a rounded shape. Trailing Edge - The back strip that last touches the air and has a tapered shape Stabilizer – Vertical appendage placed at each end of the wing, which can have varied shape and size. 8 Structurally the wing is also composed of: Ribs or interior panels – It is the interior elements of the wing, which by its shape give it the profile and that join the top to the bottom surface. They have several circular openings called internal valves, which allow air to circulate inside the wing. Cells – Inner part that divides the air and allows the internal pressure to remain stable. Cell openings – In all the leading edge there are holes that allow the air to enter the glider in order to build the internal pressure. Risers: Risers are linked at their upper end through small links or rings onto lines arranged into groups. There are usually 3 or 4 risers each left and right. They are called A, B, C and D risers, depending on where the lines extend from the wing. Lines – The rigging which connects the canopy to the harness is commonly known as lines. Their level of strength depends on their thickness and the properties of material used in their construction. They are usually covered with a protective sheath to guard against ground friction and are made from Dyneema, Kevlar, Spectra, Superaramid and so on. The lines extend from the wing's lower surface and cascade in thickness and number via a series of quick links. The lines are attached at one end to small loops sewn to the wing and at the other end to the risers via small carabiners. 9 Brakes – These are two sets of lines extending from the left and right trailing edge of the wing. Each one leads to the brake handle of the left and right side. If you pull the right brake you turn right. To turn smoothly, apply the brake while simultaneously shifting your body weight. Speed System: With an acceleration system on foot, the pilot, by pressing an accelerator connected to the risers A and B, can increase the speed. Usually the B lines are drawn and cause a flattening of the profile and a decrease in air resistance. Simultaneously the tendency to frontal closures increases. The speed system increases the maximum speed by lowering the angle of attack with a pulley guided, foot-operated system. The trimmer causes the same effect but operates by releasing Harness: the back risers. A harness is linked to the wing by the large carabiners at the lower end of the risers. Like canopies, harnesses also receive stamps of approval from certification agencies to ensure consumers. All certified harnesses are considered safe as tested. A back protector is made from soft foam of 10-20 cm and has polyester or kevlar support in addition to an airbag. Side protectors are similarly built. 10 Helmet – It is intended to be light but effective with a rigid outer surface. They should be as light as possible, have openings that allow the pilot to hear and speak without difficulty and also enable the use of glasses (optional). This is one of the primary elements of our security. There are models without front protection (open) that are not recommended. Its use is mandatory. The helmet is ALWAYS the first piece to be placed and the last to be removed from all the flight equipment! Carabiners – Its purpose is to attach the harness to the wing. Each carabiner model has its characteristics so you should always check the individual locking system of each model, the breaking load can also vary. The life span of carabiners is around five years. Before we take off we should always check that the carabiners are closed and locked. Emergency Parachutes – It is used coupled to the harness for emergency use in case of loss of paragliding flight faculties. Its size must be proportional to the total weight in flight. Circular models are non-steerable and have a drop rate of approximately 4-5 meters per second. Wind sleeve – Transmit wind characteristics to ground or to in-flight pilot. 11 Boots – Its purpose is to protect the ankle and foot from uneven ground. Flight suit – Suit that acts as a thermal protector and windbreak. Gloves – Hand protection against cold and ground. Its use is mandatory. Flight instruments: There are a number of useful tools for harnessing ascenders and flight optimization, including: Variometer – measures the change in altitude or vertical velocity by varying atmospheric pressure, whistling in the event of rising or falling. 12 Anemometer – measures the wind speed. Radio VHF – Important for safety and facilitates communication between pilots and collection/picking teams. GPS – Device that provides global satellite positioning. It gives us with very little error our position, ground speed and altitude. It also allows navigation according to routes or intermediate points previously configured by the user. Today most pilots use GPS and variometer devices which allow a wider range of functions. EQUIPMENT PRECAUTIONS: The main enemies of our equipment are the sun, the ultraviolet rays that degrade and discolor the fabric, the thorns that easily damage or break up and the insects that can puncture or corrode with its gastric juice. Paragliding must not be left in the sun for longer than necessary, and care must be taken to ensure that it is not dragged on the ground. It should also be correctly folded at the end of use so that it will not crease or be damaged by the metal parts of the equipment. Suspension and control lines must not be damaged or broken and particular attention should be paid to areas of major wear. The small carabiners must always be tight and free of rust and those that make the connection between risers and harness must have resistance greater than 2000 kg closed and 500 kg open, and must have safety device that prevent accidental opening. The harness must be in perfect condition, with no break in the seams and belts and always properly tuned for the pilot. The emergency parachute must be properly folded, not damp and to be opened and dried every 6 months. 13 FOLDING TECHNIC After landing the brake handles should be attached to the risers. When there are other pilots landing the pilot should free the landing field in order to facilitate the landing of others. Choose a spot to fold the wing that is clean and away from the sun. There are 3 main methods of folding a wing (although there are small variations of these methods): Cell by cell The glider is folded from the tip of the wing to the center with a width wide enough to fit inside the inner bag. This method is good to control the wing in case of strong wind. 14 Half by half This method is the easiest way to fold the glider. Just start the same way as the previous method with all the lines on top of the glider. Pull the tip of the glider to the center making sure the leading edge cells stay on top of each other. Keep it wide enough to fit inside of the inner bag and fold it from the trailing to the leading edge. It´s very hard to fold the glider with this method in strong wind and it damages more the rigid structures on the leading edge. 15 Concertina This method is the best to keep the leading edge in its best shape. Pull all the plastic wires of the leading edge together and keep them vertical. Tie them up together and fold the trailing edge cell by cell. 16 There are many variations of this method. This is a popular one: All the methods require the wing to be laid flat on the ground over the upper surface with all the lines on top of the glider (over the inner part). The risers must be placed close to the trailing edge (attached or not to the harness). The wing is now folded and ready to be put on the backpack. Do not fold the glider if it´s wet or with sand and debris inside. All the gear should be kept in a dry storage place. Try and fold the glider with different technics from time to time so it doesn’t get wrinkles on the same spots. The sun light and high temperatures will shorten the life of the wing very fast. Don’t leave the wing inside of the car in the sun with high temperatures. 17 FLYING TECHNIC Basic control: The control of the paraglider is done with the 2 brakes, right and left, that are connect to the trailing edge. This control is done symmetrically or asymmetrically: Fly faster – Brakes up, horizontal and vertical speed increases Fly slower – Brakes down, horizontal and vertical speed decreases Rotate or turn – Lift the brake on one side and lower the opposite The faster and sharper we want the turn to be done the more amount of brake we should use. 18 GROUND HANDLING: The technique of ground handling is something you learn from the first lesson and it´s perhaps one of the most important lessons a pilot learns. Wing control on the ground and its effectiveness are essential for a safe take-off. There are 2 techniques for ground handling with small variations in style: Alpine - This technique is the most used one since the beginning of the sport, as the first paragliders required a great deal of thrust to rise above the pilot. Today's wings do not require a great deal of thrust and they go up easily. It is mainly used with low or no wind. Should not be used with moderate or strong wind. Reverse - Although it is a technique that requires more practice time before gaining greater control of the wing, it is undoubtedly much more precise and safer. The pilot observes the wing and lines before starting his race and can thus make a better check. It allows safer control on windy days. 19 FLIGHT METHOD: One of the factors that increases the safety of the flight in any kind of aeronautic sport, and most particularly in paragliding, is the approach the pilot does before flying. This approach should be done in a methodic and step by step way. The verification of the equipment, the evaluation of the weather conditions and the local environment should lead to a well-planned FLIGHT PLAN. THE FLIGHT PLAN should become, together with all the pre-checks, a routine that the pilot must do before each flight. It doesn’t matter how small the flight´s going to be the flight plan should be done in order to make sure he will have many more flights in his life… In each flight: Access the conditions – Annalise the shape of the terrain taking mental notes of the propitious and adverse areas for the flight. Check the wind direction, how far is the landing field, the obstacles around the take-off and any other specific points of the take-off area. Do not pass over with low altitude: forests, big water masses, electric cables, rotor areas, venturi areas and never fly in the lee side. Preview and analyze the take-off line – Locate the take-off corridor, the equipment check area, the point of no return and finally lay out the glider in a spot that allows enough space to go through it all. Lay out the flight plan – Plan the all flight, how and where to do the turns, decide the trajectories, the approach, the landing and anticipate eventual problems like strong wind or thermals. Note: Each time you arrive at a take-off access all the factors and...wait. I have as a rule from my 25 years on the free flight the 5 minutes rule: if the conditions are good then 5 minutes won’t make any difference; if the conditions are changing and I haven’t notice, then in 5 minutes I will have enough time to see if it all remains the same or not. I have seen changes in the wind within 5 minutes from 25 km/h a 60 km/h… 20 Flying in a paraglider demands a high concentration and lots of practice. The take-off and landing are the most sensitive moments of the flight of any aircraft. Lets annalise each detail. TAKE-OFF Before the pilot gears up he should be pay special attention to some important details:  Check the direction and intensity of the wind  Check if the take-off is free of obstacles  Check the number of pilots in the air and how they are flying (with speed bar, doing ears, etc)  Check how step is the take-off and the amount of space free  Check the shape of the cliff and possible rotors After checking all these items the pilot should prepare the gear. The wing should be stretched with the trailing edge towards the take-off and the upper part facing the ground. If the wind is weak the wing should be fully open, if the wing is strong the wingtips should be closed. After checking if the lines are clear and the wing is connected to the harness the pilot can gear up. The equipment should be inspected on a regular basis. Before each take-off is important to check the lines, brakes and small carabiners. There are 2 technics commonly used for take-off. The alpine and the reverse. The alpine is used when the wind is weak (bellow 15kmh). With stronger winds the reverse take-off should be used. 21 Run, imaginary line of the take-off, lift the feet of the ground With the glider fully extended and checked, keeping the wind on the face, let’s run and put the glider above the head. Control the pitch and the direction with the brakes, run towards the take-off until you reach maximum speed and the lift takes you off the ground. Immediately after take-off we should use a small amount of brake in order to keep the lift and to avoid any collapses. Pay special attention if you return to the ground!! In this case we should stop or, if there isn’t enough space, control the pitch and run. Do not seat! The pilot should only seat after being away from the cliff and with enough altitude. Before seating he should be sure that he´s heading into a safe direction without any pilots on his way. When sitting he must do it in a form that doesn’t compromise the stability of the flight. Errors and bad habits of take-off: 1. Run, run, run without using the brakes. 2. Use to much brake with the hands forward. 3. Pull the “As” down or push them forward. 4. Not releasing the “As”. 5. Not looking at the wing to check. 6. Not staying bellow the wing. 7. Letting the wing dive forward. 22 LANDING The final stage of the flight. It requires concentration and total control over the equipment. Many accidents occur at this stage. Before landing the pilot should make a careful and safe approach to the landing field. He must choose which technique is more suitable to the terrain and to the wind intensity. Choose the right trajectory and follow the traffic rules. There are 4 techniques: U,L,S,8 The technic used by the pilot to approach will depend on the configuration of the terrain and the pilot experience. The most commonly used is the S. When the pilot approaches the ground he should pay attention to the obstacles that surround the landing field, the space available to land, how steep is the ground and the obstacles within the landing field. After analyzing the direction and intensity of the wind he should avoid doing 360 turns and always keep the landing field within sight. Never do turns close to the ground and always keep in mind that may appear other obstacles at the last minute that where not visible from above. Approach to the door of the landing field – After the decision to land has been taken, always do the approach maneuvers with enough height. 23 "U" – Also known as Traffic Standard or Aeronautical Approach. This type of approach is composed of a descent area where we go for landing; start area of approach; tailwind segment; Base segment and End segment. Although it is the most used approach in aeronautics in the case of Paragliding it requires a very precise calculation of the glide. “L" – Although it is the maneuver normally used for the first flights from the cliff, it involves several problems. This type of approach forces the pilot to make an estimate of when he should turn, how high he should be and what the forward wind speed will be (without knowing at what speed he will move after completing the 90º turn). It does not allow a prior recognition of the terrain. 24 “S" – By making wide S-shaped turns the pilot can control the altitude he is losing and position himself at the correct entry point into the final. The inconvenience is that with each turn the pilot can get closer to the landing and even get in or over the landing. The S must be wide and the longer you fly straight to the final the better. “8" – In order to land without advancing on the ground, the 180º turns that are made when making S are extended to 270º. The 8 made must be wide and can open or close depending on the size of the field. This is the technique most used in Paragliding and the one that allows a better control. 25 "O" - Although it is by far the most technical and difficult approach, it has some advantages: check the slope of the terrain, check the presence of obstacles and know the wind direction and intensity. When completing each 360º turn we lose height and the wind makes us drift (if the wind is strong we can travel a great distance in a short time). This technique should be combined with another at the end so that the landing is simpler and safer. The final and touching down – The final is the time when the pilot should be more aware of the changes that may happen to the plan. He should be facing the wind, on the center of the field and with enough height. A few meters above the ground the brakes should be at 20 to 25%. When he gets lower he should brake progressively until it reaches 100% (that should be the moment he touches the ground). Landing with strong wind When the wind is too strong it’s necessary to have special attention to the landing approach. The back wind can take the glider too far away from the landing field that it cannot be possible to reach it when we to fly against the wind. The stronger the wind the shorter should be the leg of back wind (if necessary). 26 Airspeed / Groundspeed : When in flight we move inside the air mass that involves us. This air mass moves relative to the ground. Our speed is the sum or the difference between these two movements. Air mass mooves at 10 km/h Wing speed 35 km/h The wing has a ground speed of 35 km/h +10 km/h = 45 km/h Air mass moves at 10 km/h Wing speed 35 km/h The wing has a ground speed of 35 km/h -10 km/h = 25 km/h The airspeed is in both cases 35 km/h. If we fly against the wind we subtract the wind speed from our wing speed. If we fly with tail wind we add the wind speed to our wing speed. Never forget that the air speed is always determined by the position of our brakes. When near the ground never fly with tail wind. 27 AERODYNAMIC SAFETY 28 AERODYNAMIC Man could finally fly when he was able to generate enough energy to counteract the force that pulled him towards the earth center. Aerodynamic is the section of physic that studies the behavior of the bodies wrapped in a fluid, being in this case the fluid the air and the body the paraglider. Air is a compressive fluid- when the pressure increases the volume decreases. It is also sticky. It tends to keep itself glued to the bodies that pass through it. The compression phenomenon only happens at very high speed (usually above 200 m/s = 720 kmh) so the fluid we will consider will be a non-compressive given the fact we never fly that fast… An airfoil is the cross-sectional shape of a wing. An airfoil-shaped body moving through a fluid produces an aerodynamic force. SIDE VIEW DEFINITIONS Thickness Leading Edge Mean camber line Upper surface Trailing edge Chord Lower surface - Leading edge – The front part (where the air comes inside of the glider) - Trailing edge – The back part of the glider - Chord – A straight line that connects the leading edge to the trailing edge - Thickness – Where the lower surface is the furthest from the upper surface - Mean camber line – A line that is always at the same distance from the upper and lower surface 29 Attitude angle – Angle between the chord of the wing and the horizon. Angle of attack - Angle between the chord line of a wing and the relative wind (which is exactly opposite to the flight direction). Flight angle - Angle between the horizon and the flight direction or path. Relative wind - Produced by our wing during forward motion in the air. It has the same axis but opposite direction to the flight path. Angle of incidence - Angle formed between the chord and the longitudinal axis of the wing. Dihedral angle - Upward angle from horizontal of the wing. "Anhedral angle" is the name given to negative dihedral angle, that is, when there is a downward angle from horizontal of the wing. 30 STAGNATION POINT Point where the pressure is the highest. Stagnation points exist at the surface of objects in the flow field, where the fluid is brought to rest by the object. The Bernoulli equation shows that the static pressure is higher when the velocity is zero and hence static pressure is at its maximum value at stagnation points. The forces capable of counteracting our weight are called AERODINAMIC FORCES, and to know them, let's see a very simple example: Placing the hand in a horizontal position outside the window of a moving car, we see that there is a force that pushes it back, this force is called resistance to advance or simply resistance, if we place the hand in a vertical position we see that this resistance increases a lot. But if we finally place it in the oblique position, we see the emergence of a new force that pushes our hand upwards, which we call lift. In reality, what we feel is an oblique force called resultant of the aerodynamic forces, or RFA. DRAG The aerodynamic forces can be separated into those that work to offset gravity and those that impede forward progress. These later forces are called drag or resistance. The lift created by an airfoil depends on the shape. The drag also depends on the shape. The softer the contour of the object, the less drag it creates. 31 The drag of a wing with a given profile varies with 4 factors: Wing area - air density - profile shape - speed More speed - More resistance Lower density - lower resistance Larger area - higher resistance The drag we've been considering is total resistance. This total drag is the sum of the contribution of two types of drag Induced Drag Induced by lift. Due to the lower pressure in the upper surface, the air tends to circulate from the lower surface to the upper surface. The induced drag is generated as the wing passes through the air and it tries to compensate the difference in air pressures between the lower and the upper surface. As the higher pressure air at the lower surface of the paraglider curves around the wing end and fills the lower part of the lower pressure area at the upper surface, lift is lost, but the energy to produce the different pressures is still spent. The result is that it produces drag because it is wasted energy. The more energy the wing requires to fly, the higher the rate of descent needed to provide enough energy to be converted into thrust and thus overcome drag. 32 This flow of air combines with chord wise flowing air, causing a change in speed and direction, which twists the airflow and produces vortices. The purpose of paraglider design is to convert all the energy into useful lift and the necessary impulse. Any wasted energy translates into poorer performance. Designers try to reduce drag by increasing the length of the paraglider. The greater the wingspan of the wing, the lower the induced drag. There are several types of shapes that have been designed on the wing tips of different aircraft and although they work in different ways, the intended effect is always to reduce the aircraft's drag by altering the airflow near the wing tip. Such shapes increase the length of the wing without materially increasing the wingspan. Parasitic drag Parasitic drag is all the drag generated that does not depend on the lift, only depends on the speed. This is the drag that the air offers to any object passing through it. The surface of the paraglider deflects or interferes with the air flow around it. The parasitic drag increases with the square of the speed. Simply put, if the speed of the paraglider is doubled, the parasitic drag increases four times. There are 3 forms of parasitic drag:  Friction drag – This kind of drag is related with the friction created between the air and the object surface. The viscosity of the air causes a slowdown in the movement. Even though the surfaces may appear smooth, they can be quite rough when viewed under a microscope. This roughness allows a thin layer of air to cling to the surface and creates small areas of lower pressure that contribute to the drag. As the air flows through a wing, the friction causes the layer of air molecules directly in contact with the surface to stop. Air is a viscous fluid, hence the stationary air layer on the wing surface slows down the layer above it, but not as much as the layer above it. This layer then slows down the layer above but again not as much as the layer below, and this process is repeated. Therefore, the flow velocity increases with the 33 distance from the surface until the maximum flow velocity is reached. This decelerated air layer is called the limit layer. When the surface area is reduced, the amount of drag is reduced. The boundary layer can take two distinct forms: the laminar boundary layer and the turbulent boundary layer. - Laminar boundary layer - each layer of air molecules slides smoothly over the others. - Turbulent boundary layer - a layer of molecules with whirlpools and irregular airflow The roughness of a surface influences the transition point between these layers. As the roughness of a profile increases the transition point from laminar to turbulent runoff occurs earlier along the wing.  Form or pressure drag – Arises because of the shape of the object. The general size and shape of the body are the most important factors in drag form; bodies with a larger presented cross-section will have a higher drag than thinner bodies; sleek ("streamlined") objects have lower form drag  Interference Drag - Drag that is generated by the mixing of airflow streamlines between the components such as the wing and the lines. It´s generated when the airflow across one component of a paraglider is forced to mix with the airflow across an adjacent or proximal component. Total drag - The total drag of a wing is the sum of the parasitic and induced drag. The total drag curve represents these combined forces and should be analyzed taking into account the air velocity. 34 Gliding is defined as the meters that a paraglider can move horizontally versus the meters in the vertical that has descended in the same time. If you have a glide of 10:1 it means that you have advanced 10 meters and descended 1. The maximum glide (L/D MAX) is the point at which the lift/drag ratio is greatest. At this speed, the total carrying capacity of the paraglider compared to the drag is the most favorable. In calm air, this is the speed used to obtain the maximum glide distance. The aerodynamic forces acting along the wing may be represented by a single force - Resulting Aerodynamic Forces (RFA), applied at a point called the Center of Pressure (CP). We have already seen how the drag, that is one of the components of the RFA, arises. Now let's see how the second force that composes it arises: the lift. LIFT 35 One big question that has been subject of discussion over the years is the origin of lift. Some theoretical explanation is widely proven although there are some authors that present alternate explanations. The problem is how to determine the percentage that each physical phenomenon contributes to the creation of lift. It is thanks to its aerodynamic shape that a paraglider is able to fly, and flying speed depends on the shape of the wing, which is specially designed and manufactured. During flight, the air that meets the leading edge (front edge) is forced to separate into two airflows. Due to its design, the wing is almost flat underneath whereas it is curved above. The principle of equal transit times tells us that the air dividing at the leading edge reaches the trailing edge at the same time. As the path to travel through the upper surface is longer, then the air velocity will be also greater. The lower portion of the separated airflow continues its course smoothly below, while the upper flow follows a larger course over the curved upper surface. The two flows meet simultaneously at the rear of the wing. Upper part: Less pressure => Force upwards! Lower part: Higher pressure According to Bernoulli's law of physics, accelerated air reduces the pressure the air exerts on a surface, thus there is less pressure on the upper wing side and more pressure on the lower side. Thus, due to this difference in pressure, the wing acquires lift, an upward force that enables the wing to fly. Pressure is force per unit area. It always acts perpendicular to the surface and decreases with altitude. 36 Total Pressure = Static Pressure + Dynamic Pressure Dynamic pressure depends on air velocity. Density decreases with: Pressure decrease / Temperature increase / Altitude The lift for a wing with a given profile varies with: 1. Wing area 2. Air density 3. Speed 4. Profile shape 5. Angle of attack The drag arises from the friction and impact of air particles on the surface of the profile, and the resultant of the sum of the previous ones. This set of forces is opposed by the weight of the pilot plus aircraft, applied in the so-called center of gravity, from the negative direction, that is, from top to bottom, and which constitutes our engine, the generating force of our movement, which, as in any glider, is always descending. In summary, we fly because we move forward and thus maintain a sufficient air speed for our paraglider profile to work contrary to our weight. GEOMETRICAL CHARACTERISTICS OF THE WING AND ITS ELEMENTS  Surface: is defined as the area occupied by a two-dimensional object (cm2, M2, km2, etc.). For paragliding, there are two types of surface: Actual area: is the value found if we extended the paragliding tissue in a flat surface and measure its full extent. Area (S) Wingspan (b) Aspect Ratio (AR) - AR = b2/ S  Wingspan - Maximum distance between edges.  Average chord - Average value of the distance between the leading edge and the trailing edge.  Aspect ratio – The ratio between the square of the wingspan and the surface. 37 S´- Projected span F´- Projected area To be able to maintain an identical internal pressure and wing load with heavy and light pilots, each paraglider model always has several sizes, generally between 24m2 and 30m2. Rotation Axes: In aviation there are 3 axes of maneuver to define all the movements of an aircraft: Longitudinal axis– Roll – which is an axis going forward and back. Example: Turning right, the right tip of the wing goes down and the left side goes up, thus we rotate about an axis through the center of the wing Lateral axis– Pitch– axis from side to side Example: When we apply brakes, the angle of attack increases and the paraglider noses up, thus we rotate about an axis drawn from wingtip to wingtip Vertical axis– Yaw– axis going up or down Example: The left wing moves forward and the right wing backwards. We have yawed right and rotated about an axis passing vertically through the wing. We call such rotation a change of heading. 38 Paragliding is one of the most stable aircraft on its 3 axes of rotation, largely because it has the center of pressure positioned far above the center of gravity, giving it a very balanced pendulum effect. Control and angle of attack: As we saw earlier, brakes are the only commands on our paraglider, through their symmetrical or asymmetrical movement. In glider aircraft the speed control is made by variating their angle of attack, as such, in paragliding this control is obtained with the symmetrical movement of the brakes: - Increase angle of attack= Pulling brakes = Slow down - Decrease angle of attack = Release brakes = Speed up Let´s see how speed and sinking varies towards brakes movement. Brakes released, the lift is moderate but the drag is as low as possible, so we fly at our top speed (trim speed). By pulling brakes, due to the impact and thrust of the air particles in the bottom part, we increase the supporting force (lift) and consequently also the resistance, which produces a reduction in the sinking and in the speed. There are optional systems that allow us to increase the performance of the paraglider in several aspects, namely at maximum speed, such as the accelerator that acts by pulling the risers A and B (accelerating), or the trimmer that acts by lifting the risers C and D (braking). Combined control: By shifting our weight, tilting the body towards the inside of the turn, we greatly improve the performance of the paraglider, reducing its sinking and reducing the radius of the turn. 39 But beware, if we pull the brakes deeply we deform so much the profile of our paraglider that we force the air to detach from its surface (detachment of the boundary layer), making the airflow become too turbulent, thus losing all the lift force and greatly increasing the drag, as in the example of the hand that we saw earlier. We go into STALL and we fall vertically. It is important to remember that a stall can occur at any flying speed and at any flying attitude. A stall occurs when the critical angle of attack (AT) is exceeded. The stall speed of a paraglider can be affected by many factors including weight, load factor due to maneuvering and environmental conditions. As the wing load increases, more AT is required to stay in flight at the same speed since more lift is required to support the additional weight. This is why paragliders with higher wing loads enter stall at higher speeds than paragliders with lower wing loads. Environmental factors can also affect the stall speed. Snow, ice, or the accumulation of rain (water) on the wing surface can increase the weight of the wing, as well as alter the shape of the wing and disrupt airflow, which increases stall speed. Turbulence is another environmental factor that can affect the stall speed. The unpredictable nature of turbulence can cause a paraglider to suddenly and abruptly stall at a faster rate than under stable conditions. Turbulence has a strong impact on the stall speed of a glider because gusts change the relative wind direction and can abruptly increase AT. When rain falls on the upper surface of a paraglider it can happen that many drops of water are glued along the entire fabric. Even when not wet it will cause the surface to become rough due to the presence of the drops and the air circulation on the top of the wing will separate from the surface. This phenomenon has been known for some time. With new wings the drops of water are absorbed more slowly by the fabric. Therefore, in new paragliders, the more drops are present in the upper surface and the larger they are, the greater the risk of the airflow detaching from the fabric. In both cases (more used and new wings) the available brake useable length decreases at first and then the wing stalls. The STALL is extremely dangerous in flight since its recovery needs several tens of meters, and if we fly at low altitude we can find the ground in the middle, hitting violently!  The stall always occurs at the same angle of attack, regardless of speed!!!! 40 The stall in a turn: When starting a turn we should progressively pull the brake without sudden movements, not forgetting to release proportionally the opposite brake, otherwise we will lower our air speed too much, running the risk of entering a stall on one of sides, which is extremely dangerous and produces a sharp vertical drop in auto rotation. Vortex effect: Consists of the turbulence belt caused by the pressure differential between the bottom and upper part, left by the marginal edges, which together with all the parasitic drag and respective trail turbulences, are responsible for the shaking of the paraglider when passing behind another. Aerodynamic stability/instability: A paraglider is in balance when all its forces are in balance. Stability is defined as the ability of the wing to maintain a uniform flight condition and return to that condition after being disturbed. Paragliders often encounter balance disorders during flight. These can occur in the form of vertical gusts, a sudden change in the CG, or movements in the brakes by the pilot. For example, a stable paraglider will show a tendency to return to balance after encountering a force that causes the leading edge to rise. 41 As a result of its specific characteristics, i.e. not having a rigid primary structure or real leading edge, keeping itself in shape by the action of internal air pressure, the paraglider is one of the aircraft with the greatest aerodynamic instability. This means that its profile and its general shape can be deformed whenever the angle of incidence of the air flow, partial or not, is negative, producing the so-called collapse. In a general way in turbulent situations to avoid the closing, the pilot should maintain a high angle of attack, avoiding collapses, and to recover it should force the profile to return to the correct angle, pumping in a wide way with the brake. THE POLAR CURVE On a graph or diagram where descent rate and flying speed are recorded, we can create a curve which will define the glide ratio for the entire range of speeds a paraglider can achieve. Measurements should be done in the absence of wind, lifting air or sinking air. The descent rate in vertical speed is measured in meters per second (m/s). 42 We can see that there are four important moments: - Maximum speed - Fly as fast as possible - 50/65Km/h. - Minimum speed - Point where the vertical speed is minimum. It indicates to us the horizontal speed at which we must fly to maximize an upward current - 21/24 km/h. - Stall speed - Stall speed can be identified as the point with the lowest horizontal speed. - Maximum glide speed - The point where the efficiency of our glider is maximized. Also known as best L/D (Lift and Drag). Flying as far as possible - 9 to 1. In the polar you can find the maximum glide by tracing a straight line from the origin of the graph. The tangent point to the curve identifies the best glide speed. The polar is obtained with calm air: Zero wind, no air going up or down When the air changes and we are in the presence of wind or air going up or down the best glide ratio may not be obtained with the same position of the hands!! The greater the wing loading, the greater the vertical and horizontal speed, Vmax and Vmin and of course, the faster the running start on launch. But the best glide ratio doesn't change. Although the descent rate and flying speed do differ, they increase by the same factor so their comparison remains the same producing the same best glide ratio. 43 The optimum glide ratio is the same for two pilots of different weights but is attained at different speeds An optimum glide ratio is one that allows us to cover the greatest distance. If however, on carrying out the very same measurements in either descending or ascending air current conditions or head wind, tail wind or any combination of these factors, then we will discover that the optimum glide ratio will no longer occur at the speed we described above. The speed will have to be adjusted to attain the optimum glide ratio over the ground for the prevailing conditions. An optimum glide ratio over the ground is attained: At a higher flying speed in headwind or descending current. At a lower speed in a tail wind or ascending air current. 44 Ground Effect It is a term used in aerodynamics that represents the effect of the proximity of a wing to the ground. In the wing of an aircraft, the proximity to the ground causes an increase in wing lift and a decrease in the drag. The air tends to circulate from below to above the wing. This causes an increase in resistance at the wing tip, which generates a circular airflow whose axis is a line coming out of the wing tips. The air circulates from below, where the pressure is higher, to above, where the pressure is much lower. The ground tends to "prevent" this circular movement of the air from bottom to top, increasing the lift, and decreasing the energy spent to generate these vortexes, and therefore reducing the drag enormously. The ground effect has its greatest effects up to approximately one half of the total length of the wing. The phenomenon is most easily observed when an aircraft is landing. At that stage the pilot often describes a feeling of "floating" or "walking on an air mattress" that forms between the wing and the ground. The consequence of this effect is increased lift and greater difficulty in landing. However, there is no air cushion that holds the plane. What actually happens is that the ground partially blocks the vortexes and decreases the amount of air to be directed down by the wing. This reduction increases the effective angle of attack of the wing as it creates more lift and less drag. This phenomenon is called Ground Effect as we can see in the images below. 45 SECURITY The basic types of paragliders and its certifications: The reactions of a wing to the different types of collapses and the speed of action necessary from the pilot, establish the level of security of the glider. The security rating is measured by a series of testes. These tests are done by organisms recognized worldwide like DHV in Germany or Air Turquoise. DHV The reactions of the wings on the tests divide the gliders into the following classes: - DHV 1 – Paragliders with simple and very forgiving flying characteristics - DHV 1-2 - Paragliders with good-natured flying characteristics - DHV2 - Paragliders with demanding flying characteristics and potentially dynamic reactions to turbulence and pilot errors. Recommended for regularly flying pilots - DHV 2-3 - Paragliders with very demanding flying characteristics and potentially violent reactions to turbulence and pilot errors. Recommended for experienced and regularly flying pilots. - DHV 3 – Paragliders with very demanding flying characteristics and potentially very violent reactions to turbulence and pilot errors, little scope for pilot errors. For expert pilots. 46 CEN The certification regulations have been changing through the years and almost all the paragliding manufactures use the CEN norm. The classification is called EN. DHV Class Flight characteristics Pilot profile equivalence Paragliders with a very high passive All pilots including school security and with very tolerant flight characteristics. Wings with very A 1 good resistance to colapses and turbulence. Paragliders with high passive Novice pilots security and with tolerant flight characteristics. Wings with good B 1-2 resistance to collapses and turbulence. Paragliders with moderate passive Recommended for pilots trained with the security and with dynamic reactions technics of wings collapses that fly many to turbulence or handling mistakes. hours and use active handling. C 2 Needs precise handling actions from the pilot. Paragliders with very demanding Recommended for expert pilots trained flight characteristics and with D with the technics of wings collapses that 2-3 violent reactions due to turbulence fly many hours and use active handling. or handling mistakes. Paragliders with very demanding flying characteristics and potentially Recommended for expert and CCC very violent reactions to turbulence competition pilots who fly for many 3 and pilot errors, little scope for pilot years and have a very good handling. errors. For expert pilots. There are other types of wing classifications. Some of these classifications are done by certifying organisms, some others are only indications of the use that the wing can have. Paramotor – Wings that are certified as for free flight and pass the wing loading tests for Paramotor. The weight range is usually longer ex. 80 – 120 kg 47 Tandem – Normal classification – the weight range is very big ex. 140 – 230 kg SpeedFlying / Mini wings – Some have normal certification (mini wings) others just have loading test. Very small areas for fast flights. Acro – No certification. Just load test. Almost all the wings that don’t have security certification go through the wing loading test which determines the max load it can withstand before it gets destroyed. Forms of flying: - Protective flying – If the pilot is novice he should fly in a protective form in order to ensure that the wing is always under control. He should not use to much weight shift and always keep a fair amount of brake to keep a higher angle of attack. - Active flying – It´s the way most of the experienced pilots fly and it consists on reacting fast with body and small hands movements before the wing can increase the problems. Usually they don’t use much brake. COLLAPSES and INCIDENTS USEFUL COLLAPSES EARS – This is the most common and safest maneuver. The total surface of the paraglider, after applying ears, is smaller and thus is under a higher load. The pilot performs ears in order to lose height and make the wing more stable in turbulent conditions. Keep your hands in the brake toggles, reach up and grasp the outer lines of riser A. Then pull down these lines slowly and symmetrically. 48 B´S – Here the aim is to fold the wing lengthwise with the result that partial stall produces a controlled, brisk loss of altitude. Ears with speed bar – Using the speed bar with ears will increase the vertical speed. It may be a safe and effective alternative to the use of B´s. With this system it´s possible to control both vertical and horizontal speed. Spiral Dive – A spiral dive consists of continuous tight 360º turns. It is the most effective maneuver for losing altitude. Begin turning, but if you sense a drop in speed, hold back slightly to resume the previous speed and then maintain greater brake pressure and weight shift. To make a recovery, gradually reduce the inner brake pressure and pull on the outside brake to slow the wing's rotation. 49 INCIDENTS Being dragged – With strong wind there is always the risk of dragging. To prevent it the pilot should pull both brakes, pull the C´s or release one of the brakes and pull the other to his limit. Control on the rear risers – If one of the break lines breaks it´s possible to control the direction pulling the rear risers. Use small inputs. Front Collapse – To recover normal flight, pull on both brakes symmetrically. Sometimes the front collapse is not symmetrical and the one side might require less or more braking. 50 Asymmetric Front Deflation – The collapse of one side of our wing is a common problem when we fly in thermals – The wing will tend to turn since the part of the wing which remains inflated bears all the pilot's weight. To deal with this, pull down on the opposite brake and shift your weight to prevent turning too much and then pump the opposite brake. Full Stall – We have already seen that the stall happens when the air takes gets away from the wing, causing an abrupt fall in the lift. In paragliding, as we control the angle of attack through the deflection of the trailing edge, the wing will only tend to have a forward movement when we release the controls. In both cases the procedure to get out of the stall is to make the wing dive so that it gains speed again. In the paragliding the way the wing moves back is extremely violent because the paraglider does not have a rigid structure, so one must be very careful in the replacement of the hands on top in order to avoid an extremely violent movement. If the stall is done in slow movement it´s called a static loss, if it is caused after a large pitch movement it is called dynamic loss and its effects are very pronounced. Sustained stall is when you maintain it over a long period of time. 51 Parachutal stall – In a parachutal stall, the wing appears normal, but is in fact descending vertically like a parachute, hence the name. The wing is very calm when this happens. Airflow is not normal but it is smooth. A parachutal stall can be induced un-intentionally by the pilot by flying too close to the stall point or by flying slowly and going into wind shadow. Put both hands up or give a little push on the A´s. Spin – During the Spin one side of the glider turns backward (negative) whilst the other is still flying forward (positive) by keeping the negative side under stall point. Usually the glider oscillates, the pilot swings a bit forward and backward under it, and the negative side’s tip collapses to the front (not backwards as a normal collapse). 52 Twist – When the pilot rotates and the risers get twisted. Just un-twist by pulling the risers apart. Cravat – When a line goes over the top of the glider and doesn’t let it fly on that side. Pull the stabilizer line or pump the brake or do one ear. If it doesn´t work do a collapse. 53 Landing with back wind – Try and brake the wing very sharply in the last moment. If the speed is to high keep your feet inside the harness and don’t try to run. Landing in trees – When landing in a tree is unavoidable, both feet should be held together firmly and the eyes should be shielded with one hand from the branches. If possible, pull sharply on the brakes, before crashing. The most important thing is to grab the tree to avoid dropping down.. Water landing – Release the straps of the harness before touching the water, land with back wind and hands up. Swim to land. Don’t try and recover the wing until you are safe!!! 54 Reserve Parachute There are many types of reserve parachute but the most popular are Pull Down Apex (PDA). The parachute should be open and folded every 6 months so it is dry and to prevent a slow opening. Grasp the handle and pull smoothly, stretching your arm out in front. The reserve bag follows at a distance of about 30cm (12 inches). Throw out the entire bundle including the handle as vigorously as possible. The parachute will now open by coming overhead with a slight jolt It is mandatory to use reserve parachute in competition. Fly safely: As paragliding is an air sport, there is a need to begin by understanding the risk inherent in the practice of this sport. Safety deserves special attention so that we can fly with more pleasure and with awareness of the risks and difficulties. 55 There are two types of security: - Passive safety - helmet, dorsal protection, reserve parachutes, gloves, the careful choice of wing. - Active safety - measure, check, re-check, prepare, anticipate, know the rules and have knowledge of Aerology and Meteorology. To fly safely we must: - Use a safe glider - It consists of flying a glider corresponding to our level of piloting and experience. - Evaluate the level - We should never fly alone. We should choose places and conditions that we know well. - Analyzing conditions - Before each flight, take the necessary time to analyze conditions. Previous knowledge of the weather is completed by a long look at the sky, clouds, trees, birds, fumes, wind, or other paragliders.... - Adjusting the chair - The chair is fundamental in the behavior of the wing. Too tight it loses maneuverability in favor of greater stability. Too open it gains maneuverability to the detriment of stability. - Improve accuracy - Even with hundreds of flight hours we must never stop working and perfecting our gestures. We must always fight against small nervous and inaccurate gestures, learn to know the speed of the wing, train to dominate the ears and counteract the collapses. - Good physical and mental shape - Having good physical preparation is useful to be able to react calmly and correctly to a difficult situation. A good state of mind is also important, nothing is worse than flying tired, stressed, deconcentrated, without confidence or distracted. - To be airborne - To be airborne is to feel in harmony with the air in our gestures, in the way we observe, think, make decisions and fly. - Know the priorities - The rules are simple, but their respect is indispensable and must be automated by each pilot. - Use appropriate equipment - Choose the best equipment for the type of flight we practice, from helmet, dorsal protection, backup parachutes, radio, among many others. - Know how to give up - We must never start a flight that we do not want. We must never give in to environmental euphoria. We must never remain in the air when we do not feel well. We must always take a strictly firm and autonomous stance and sometimes know how to give up flying. 56 METEOROLOGY When Paragliding begun in Portugal in the early 90´s the weather forecast done by the pilots consisted on reading the surface pressure charts available on the daily newspapers. Mainly we just watched the wind from the window of our house and decided where to go flying… Today, with the multitude of information available, no pilot leaves home without knowing how strong the wind will be, at what time it will start to rain and how high the thermals will carry us! With all the internet tools we can increase the number of days we fly per year. We can also predict what is going to happen during the flight and what will be the best time to take-off. The air around the earth: The terrestrial globe is surrounded by a gaseous layer, called the atmosphere, which, due to its rotation movement, is thicker at the equator than at the poles. The atmosphere is divided into several layers, however, for the flight is only interesting to know the closest to the surface, which is composed of a gas mixture in permanent motion called Air, and for that reason is called Troposphere. 57 The air is composed by several types of gases and 2 of the main characteristics are pressure (atmospheric) and temperature. Both diminish with altitude. Pure air is a gas mixture consisting mainly of 21% oxygen and 78% nitrogen. Oxygen is a vital gas for breathing. Carbon dioxide (C02) lets the sunlight energy pass through but holds the heat reemitted by Earth (greenhouse effect). If there is too much C02 in the air, there will be a general warming of the Earth’s surface. This will involve long-term changes in climate. In addition, microscopic particles, called condensation nuclei shear, are suspended in the air. They come from the combustion residues, pollen and sea sprays. They play an important role in the condensation phenomenon that we will see later. The atmosphere that surrounds the earth has mass and so is pulled downward by gravity. The weight of air above and around us is felt as pressure on all earthly matter. This is called atmospheric pressure, and is measured in Hectopascals (hPa), or in Millibars (mb). Further standardization has been agreed upon with the establishment of one unit of atmosphere at sea level per 1013.25 hPa. 58 Atmospheric pressure is reduced in average by 100 mb per 1000 meters of altitude as we move upward. The temperature is reduced 6.5º per 1000 meters. Any variations in atmospheric pressure from place to place is accompanied by a tendency for air at greater atmospheric pressure to flow into the area of lower pressure. This horizontal displacement of air is commonly known as wind. Density Density is the mass per unit of volume, i.e., the number of air molecules per cubic meter. It depends mainly on temperature and pressure. Like almost all the materials, the air expands as it warms. Thus we have more particles in a cubic meter of cold air than in a warm one. This is the reason why the same volume of air is lighter if it is warm than if it’s cold. With a decrease in pressure, there is a decrease in density. Thus the density of air also decreases with altitude. At 6600 meters the density is only by half compared to that of sea level. Unit of measure: kg / m3 Average density at sea level (standard atmosphere): 1,225 kg / m3 Hot air Cold Air 59 The general circulation of the atmosphere: The variation of the angle of incidence of solar rays on the surface between the polar zones where it is tangential, and the equatorial zones where it is perpendicular, causes great differences in temperature and as such generates localized pressure ranges, responsible for the various climates of the globe: - High polar pressures - Low temperatures / Very dense air / High pressures of thermal origin. - Low subpolar pressures - Upward compensation movement / Light air / Low dynamic origin pressures. - High subtropical pressures - Declining compensation movement / Dense air / High dynamic origin pressures. - Low equatorial pressures - High temperatures / Very low air density / Low thermal pressures. The surface pressure variation is represented in the so-called "Weather Charts", through isobar lines that join points of equal pressure, defining fields and pressure cores. The pressure cores are called as it decreases or increases towards the center, respectively Low pressure or Depression, and High pressure or Anticyclone. 60 An isobar chart can inform us of many things. For example, in the earth's northern hemisphere: 1. The closer the isobars are to each other, the stronger the pressure gradient and thus the stronger the wind. 2. Winds invariably blow parallel to isobars because as the wind flows the earth turns below it. The result is an apparent turning to the right in the northern hemisphere. We call this the Coriolis effect: The Coriolis force acts when an air mass changes its latitude degree, meeting air masses that move faster or slower than it. This can be shown according to the following example: A passenger descending from a moving train has to run a few meters before stopping for he has stored the train speed (inertia). The same happens with the air particles moving from one point towards the poles, they carry with them a greater rotation speed and are ahead of the Earth’s rotation as the passenger who jumped from the moving train and, for a moment, goes faster than the train to stop afterwards. This gives the Northern Hemisphere winds the tendency to turn right and in the Southern Hemisphere the tendency to turn left. Similarly, the air particles that start from the pole towards the Equator have almost zero velocity at the start. The Earth turning from West towards the East follows exactly the same tendency to turn right. 3. Wind rotates anti-clockwise around depressions (lows) and clockwise around anticyclones (highs). In general, low pressure leads to unsettled weather conditions and high pressure leads to good weather conditions. In an anticyclone (high pressure) the winds tend to be light and blow in a clockwise direction (in the northern hemisphere). Also the air is descending, which reduces the formation of cloud and leads to light winds and good weather conditions. In a depression (low pressure), air is rising and blows in an anticlockwise direction around the low (in the northern hemisphere). As it rises and cools, water vapor condenses to form clouds and perhaps precipitation. This is why the weather in a depression is often unsettled - there are usually weather fronts associated with depressions. The air moves due to constant thermal imbalances. The atmosphere tries to equal the different pressures and temperatures that are caused by the differentiated heating of the different regions of our planet (this movement we call wind). There are also depressions that are caused by the overheating of an area. In the center of the Iberian Peninsula we usually have in summer this kind of depression. The instability of the lower layers of the atmosphere causes storms. This type of depression is favored by the entrance of cold air at altitude coming from the north. There are also areas that are called barometric swamps and are defined as areas where the isobars are far apart and the pressure is neither high nor low. 61 Weather fronts In its movement, the masses of air of different characteristics of temperature and humidity, rise and form to the so-called frontal system, which consists, in general, of a cold front, the engine of the system, and a hot front. Cold fronts are simply when a cold air mass replaces a warmer air mass. Northwest winds are common behind the front, and these winds help move cold air into the region. Precipitation in cold fronts is typically confined to the frontal zone, though there are exceptions. Showers and thunderstorms are generally the common precipitation types. The clouds that form are vertical. On a surface weather map, a cold front will be depicted by a thin blue line with blue triangles pointing in the direction the cold front is moving. 62 Cold Front Warm fronts occur when a warmer air mass replaces a colder air. The clouds that form are horizontal. Warm fronts on a surface weather map will be depicted by a thin red line with red semicircles extending in the direction the warm front is moving. Warm fronts tend to move slowly. Warm fronts are usually preceded by cirrus first (1000 km ahead), then altostratus or altocumulus (500 km ahead), then stratus and possibly fog. Warm front Because cold fronts move faster than warm fronts, they can catch up and overtake their related warm front. When they do, an occluded front is formed. The weather ahead of the cold occlusion is similar to that of a warm front while that along and behind the cold occlusion is similar to that of a cold front. 63 64 CLOUDS Clouds are made of water droplets or ice crystals that are so small and light they are able to stay in the air. The water or ice that the clouds are made off travels into the sky within air as water vapor, the gas form of water. Water vapor gets into air mainly by evaporation – some of the liquid water from the ocean, lakes, and rivers turns into water vapor and travels in the air. When air rises in the atmosphere it gets cooler and is under less pressure. When air cools, it’s not able to hold all of the water vapor it once was. Air also can’t hold as much water when air pressure drops. The vapor becomes small water droplets or ice crystals and a cloud is formed. As air rises it cools and decreases pressure, spreading out. Clouds form when the air cools below the dew point, and the air cannot hold as much water vapor. HIGH CLOUDS – 6000 to 12000 meters Cirrus (Ci) Cirrus clouds are short, detached, hair-like clouds found at high altitudes. Cirrus clouds form from the ascent of dry air, making the small quantity of water vapor in the air to sublime into Cirrus are made up completely of ice crystals. While the sun is setting or rising, they may take on the colors of the sunset. 65 Cirrocumulus (Cc) Cirrocumulus clouds are made up of lots of small white clouds called cloudlets, which are usually grouped together at high levels. Composed almost entirely from ice crystals, the little cloudlets are regularly spaced, often arranged as ripples in the sky. Cirrostratus (Cs) Cirrostratus are transparent high clouds, which cover large areas of the sky. They sometimes produce white or colored rings, spots or arcs of light around the sun or moon that are known as halo phenomena. 66 MEDIUM CLOUDS – 2000 to 6000 meters Altocumulus (Ac) Altocumulus are small mid-level layers or patches of clouds - called cloudlets - in the shape of rounded clumps. These are white or grey, and the sides away from the Sun are shaded. Mostly found in settled weather, altocumulus are usually composed of droplets, but may also contain ice crystals. Altostratus (As) Altostratus are large mid-level thin grey or blue colored clouds. Usually composed of a mixture of water droplets and ice crystals, they are thin enough in parts to allow you to see the sun weakly through the cloud. The sun cannot cast shadows when shining through altostratus clouds, which is how you can differentiate between altostratus and nimbostratus. 67 LOW CLOUDS – ground to 2000 meters Stratocumulus (Sc) Low-level clumps or patches of cloud varying in color from bright white to dark grey. They normally have well defined bases and some parts much darker than others. They can be joined together or have gaps between them. Stratus (St) A generally gray cloud layer with a uniform base which may, if thick enough, produce drizzle, ice prisms, or snow grains. When the sun is visible through this cloud, its outline is clearly discernible. 68 Nimbostratus (Ns) Nimbostratus clouds are dark grey or bluish grey featureless layers of clouds, thick enough to block out the sun. These clouds are often accompanied by continuous heavy rain or snow and cover most of the sky. VERTICAL CLOUDS – ground to 12000 meters Cumulus (Cu) - All cumulus clouds develop because of convection. As air heated at the surface is lifted, it cools and water vapor condenses to produce the cloud. Throughout the course of the day, if conditions allow, these can grow in height and size and can eventually form into cumulonimbus clouds. Mostly, cumulus indicate fair weather, often popping up on bright sunny days. Cumulus humilis These are wider than they are tall, often numerous in the sky and indicate fair weather conditions 69 Cumulus mediocris These are as wide as they are tall and are usually seen amongst a variety of other cumulus variations. Cumulus congestus These are taller than they are wide, looking like long chimneys capable of producing light showers 70 Cumulonimbus clouds Menacing looking multi-level clouds, extending high into the sky in towers or plumes. The base of the cloud is often flat with a very dark wall like feature hanging underneath, and may only lie a few hundred feet above the Earth's surface. Cumulonimbus clouds are born through convection, often growing from small cumulus clouds over a hot surface. They get taller and taller until they represent huge powerhouses, storing the same amount of energy as 10 Hiroshima-sized atom bombs. Cumulonimbus clouds are associated with extreme weather such as heavy torrential downpours, hail storms, lightning and even tornadoes. Lenticular clouds (Altocumulus lenticularis in Latin) are stationary clouds that form in the troposphere, typically in perpendicular alignment to the wind direction. Pilots tend to avoid flying near lenticular clouds because of the turbulence of the rotor systems that accompany them. 71 LOCAL WINDS All pilots have the obligation to analyze the flying spot before taking off. That analysis needs to be done no matter the number of times one has flown before on that specific spot. When we arrive at the take-off the intensity and direction of the wind should never be a surprise (it should be observed on the way from our house to the take-off). If there is a big difference in the speed or direction of the wind from what we observed on the way and what we see at the take-off, we should be extra careful before flying. 72 WIND: The geostrophic wind is the wind that blows out of the influence of ground friction. It is the wind influenced solely by pressure and the Coriolis effect. The geostrophic wind takes place over 700 m (2000 ft) and above all surface objects. We always use as a reference the direction the wind is blowing from: Local winds are represented by sea and land breezes, plus anabatic and katabatic flows. These winds do not appear individually on an isobar diagram or weather map. Due to their brief duration, they are affected very little by the earth's movement and Coriolis effect. They tend to prevail over light geostrophic winds and alter them. 73 Sea Breeze: The sea Breeze is a local wind with an onshore wind direction. As land heats up more rapidly than sea, and the warm air over land rises, the cool sea air will flow in from the water to replace it. Thus an onshore flow of air is formed during daytime which lasts until late afternoon or early evening. Land Breeze: A land breeze is a local wind which, opposite to sea breeze, implies an offshore wind direction (land to sea). It is formed at night when the sea cools less rapidly than land and the cold air flows out from the land to replace the warm air over the waters. It will increase its intensity when flowing along with the general prevailing wind. Mountain breeze: At sunrise on the valley the air is colder near the ground (night inversion) while on the slopes that are exposed to the sun light, the air heats and creates lift. This type of wind is called anabatic. 74 By midday the heat is distributed evenly by all the slopes generating vertical movements of the air and descending movements in the middle of the valley. At the end of the day the shady slopes cool down and create descending movements of the air, the slopes illuminated by the sun and the center of the valley generate lift (thermal restitution). During the night, the temperature drops and the air flows down towards the valley. This wind is called katabatic wind. 75 Foehn Wind Foehn is described as a wind but actually includes a local phenomenon. Foehn winds are warm, dry and down slope that occurs on the leeward/downside of a hill or mountain where rising air mass causes precipitation. The diagram pictures a 2000 m mountain with the wind on the left. Air temperature at ground level is 14 ºC. On ascending, it forms a cloud at 5 ºC (it dropped 0,98º per 100m – Dry Adiabatic Lapse Rate) and by reaching the summit at 0 ºC (Saturated Adiabatic Lapse Rate – it drops at 0,6º per 100m), rain and snow fall on the facing side and the cloud loses much of its initial humidity. As a result, the cloud evaporates toward leeward at 1 ºC. As it descends temperature rises to 18 ºC due to compression. It is clear that by now the dry air temperature after the process has risen by 4 ºC. The Foehn can blow extremely strong because gravity helps accelerate the flow on the downslope side. Wind-Gradient Wind-gradient is the gradual reduction in wind speed as we approach the surface due to the friction of the ground. This is a matter of concern to us in flight. On the landing approach, especially in the final few meters, you should prepare yourself for a sudden drop in wind speed, provided that there is wind. Your paraglide may lose airspeed in a strong gradient and approach a stall speed. It is important to offset the effects of wind-gradient by carrying more airspeed on final approach before you reach the gradient level. 76 OROGRAPHIC LIFT: When the wind flows against a hill it is forced to go up. As it goes up generates a mass of rising air on the slope that is exposed to the wind. That mass of air is called orographic lift. Depending on the shape of the cliff and the intensity of the wind it will generate different ways and intensities of lift. The higher the wind or the steeper the cliff, the higher the rotors and the turbulence on the leeward. The best wind is created when the air mass hits the slope perpendicularly. The wider the slope, the more the air masses must avoid it perpendicularly over a large area and the easier it is to use this slope for soaring practice. At the top, because it is being compressed, the air flow accelerates producing a stronger wind zone. On the opposite side, behind the slope, the wind descends and enters in turbulent flow of rotor, generating a range of great turbulence and descent, quite dangerous - leeward. At the foot of the slope, where the wind speed is low, the upward surface is too little usable. With the altitude of the slope, the rising wind increases its speed and volume. The greater the verticality of the slope, its irregularity or the intensity of the wind, the greater should be the rotors and the associated turbulence, but also the greater should be the lift in the front of the slope, within our limits of course... 77 NEVER FLY WITH WINDS ABOVE 30 KM/H OR WITH OSCILLATIONS ABOVE 15 KM/H Types of slopes: - Progressive and regular (Hill) - Vertical (Cliff) 78 - Uneven (Rocky) The top of the hill and irregularities on the slope are zones where the wind will speed up, we should be careful in days of strong wind as it might cause a loss in our ground speed. Flight in dynamic lift: When flying in dynamic lift we should fly in front of the cliff and never behind the edge. If we fly inside of the cliff we could be in zones of rotors, descending air and acceleration. We should fly in "8´s" along the cliff, never turning our back to the wind, always doing the turns facing the wind. The turns should be done with easy and slow movements, trying to maintain the wing stable. 79 The correct speed to fly is at minimum sink – brakes at chest level – using a trajectory parallel to the cliff adjusting whenever necessary. When in-flight the pilot should always keep in mind to observe the indicators of the wind such as smoke, clouds or birds in order to avoid being caught in a situation of false head wind. THERMAL LIFT A thermal is an updraft that is created by the difference of temperature and it contains one or more lift centers. These centers are surrounded by descendent movements of air that compensate the lift. This type of lift has its origin on the heating of certain zones of the soil that heat up by contact making the air less dense. As it heats the air rises up to the point when the temperature inside of the thermal equals the temperature of the air that surrounds it and it stops. In order to get the most out of this current of hot air, one should turn in 360º staying inside the column climbing until it´s possible. To fly in these type of conditions the pilot should have enough experience in controlling the wing in turbulence and analyzing the air. 80 TURBULENCE Irregular and abrupt movements in the atmosphere caused by the displacement of small swirls in the air stream. Atmospheric turbulence is caused by random fluctuations in wind flow. It can be caused by thermal or convective currents, differences in relief, variation in wind speed across a front zone, or changes in temperature and pressure. Types of TURBULENCE: In general terms turbulence is defined by radical and abrupt variations in the direction and intensity of air flow, which can be of different types: - Obstacle turbulence - Rotors generated at the rear of all obstacles that the wind encounters. It is also known as mechanical turbulence. - Thermal turbulence - When an air bubble is rising, it disrupts the flow of air of the prevailing wind. Moreover, it creates a depression above the ground which tends to balance itself by sucking the surrounding air. 81 - Downwind situation - Rotors are created on the leeward side of objects such as houses, trees, etc.... it may even be hills or the whole mountains. The rotors increase in size and strength in proportion to the wind speed increase. These rotors can reach several hundred meters in length. The shape of the downwind ground also plays a role on the rotors strength. The steeper the downwind ground, the stronger is the turbulence. The strongest turbulences are generated when the windward and leeward slopes are steep. - Trail Turbulence - It originates from the vortex effect of paragliders, which in their passage leave behind them a conveyor belt of small rotors. Wind situations: A windward side, exposed to wind, can also create critical rotors as those found in the leeward side. They are due to topographic changes, including: - The foot of the cliff - Depressions 82 - Terrace Wind-shear situation: Vertical: it is a change in the wind direction and strength when catching altitude (wind gradient). In the lower layers up to 300 meters above areas with high terrain roughness, there may be differences of more or less 20 knots per 100 meters. In general, we can say that in a plain surface the wind is weaker but more turbulent, given the ground obstacles, than the one reigning 300 meters above. Horizontal: when two valleys meet, or when two winds, one local and one dominant, meet, turbulence is generated. 83 FLIGHT RULES The organization that controls and regulates our sport at national level, is the Portuguese Free Flight Federation (FPVL), whose activity depends on the National Civil Aviation Authority (ANAC). Our activity as 2 sides: sportive and legal. At a sportive level, our governing authority is the International Aeronautical Federation (FAI - Fédération Aéronautique Internationale). Within the FAI there are several committees that draw up the sports regulations for each sport. The one that manages the paragliding is the CIVL - Commision Internationale de Vol Libre. FPVL is responsible for writing and controlling the sports regulations in Portugal (which must be drawn up in accordance with FAI international regulations). However, since our activity is also dependent on ANAC's on the legal side, FPVL's regulations must also obey the Portuguese legislation whose laws are elaborated by ANAC. One of the international organizations that establishes the legislation through which national civil aviation legislation is drawn up is the International Civil Aviation Organization (ICAO) whose headquarters are in Montreal - Canada. 84 The European Union Aviation Safety Agency (EASA) is an agency of the European Union with responsibility for civil aviation safety. It carries out certification, regulation and standardisation and also performs investigation and monitoring. It collects and analyses safety data, drafts and advises on safety legislation and co-ordinates with similar organisations in other parts of the world. The idea of a European-level aviation safety authority goes back to 1996, but the agency was legally established only in 2002. Its based in Cologne, Germany. FPVL is a federation that has, at the moment, the status of public sport utility (it has objectives that serve the general interests of the community) and is partially financed by the Portuguese government. Given that it is a federation, its statutes (rules that dictate its constitution and functioning) and general rules of operation are drawn up and voted on at general meetings of associates. These statutes can only be changed in a general assembly through the proposal of any of any delegate. The general assembly is the highest decision-making body and is composed of the delegates representing the clubs, pilots, instructors and judges of each sport. Within the FPVL, in addition to its governing bodies (direction, supervisory board, general assembly board, jurisdictional council and discipline council) there are several other departments: DIT - Department of Instruction and Titulations - Technical body responsible for all areas related to the instruction or titling of pilots and instruction or titling of pilots and students. This is an organ in which its members are nominated by the by the Board of Directors. CAC - Competition and Arbitration Council - Responsible for all areas related to competition and judges. This is an organ in which its members are elected by direct vote of the delegates. The REGULATION OF INSTRUCTION AND TITULATION establishes the norms and rules for the teaching and practice of our modality, and frames the national system of flight permits. It regulates all teaching activity and establishes the levels and qualifications of pilots and instructors. This, like all technical regulations (e.g. Competition Regulations), can be altered by the General Assembly or by the by the General Assembly or by the Board. There are other regulations that establish the rules for competition, dual flight, etc. The learning licence is issued by FPVL to the student through a registered school with a valid operating license for the year in question. To issue this licence the student will have to present a certificate (medical certificate) that proves his physical and mental fitness for flight practice. He will also have to subscribe an insurance covering personal accidents and civil liability. This licence is valid until the end of the calendar year and can only be reval

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