[TOC]
Definitions: wind - moving air mass in relation to fixed objects
relative wind - relative speed of an object traveling through air
drag - a force with the same orientation as the wind
Drag (measured in Newton, 10N = 1kg) Linear with:
- exposed surface area
- air density
- object shape (drag factor - linear in that factor)
Increases non linearly with:
- relative wind speed - drag increases proportionally to the square of the wind i.e. - 2x inc in speed -> 2^2 increase in drag.
Under the same conditions, object with drag coeff. 1.3 experiences 1.3x more drag
need to remember 1100, 2200, 3300, 4400 90, 81, 70, 60 i.e total for each = 100
Since air density / altitude is controlled by an ODE, the density decrease slower at higher altitudes - i.e. object moving upwards at lower levels of the atmosphere experiences faster reduction of drag.
Elongated and flat object (wing) is subjected to oblique wind two forces act on it:
- drag
- lift - perpendicular to the wind
Lift and drag are affected by the same four factors (air density, surface area, drag factor and wind speed)
Drag and lift coefficient depend on both the shape of the object and the inclination of the flat object relative to the wind - angle of attack.
Q50 - The lift depends on the angel of attack
Q56 - The lift depends on 4 factors: size of the wing, lift coefficient, air density, and wind speed.
Lift - broken down into many vector on both surfaces of the wing
Negative pressure (suction) on the upper surface
Positive pressure on the lower surface (assuming that the wing is a solid (in our case inflated solid))
The difference in pressure between the surfaces results in spiral air movement (vortices) along the wing tips
These vortices are caused by attempts to balance (compensate in original text) the air pressure difference
97 - Vortices cause increased drag, lower performance of the wing + turbulences in its wake
Q98 - The greatest turbulences generated by a glider are behind its trailing edge
Q54 - The negative pressure (suction) is about twice that of positive pressure experienced by the underside.
With an angle of attack of 10 degrees, the distribution of lift is 2/3 on the upper surface and 1/3 on the lower surface.
Q55 - 2/3 of the lift is distributed on the front of the wing, 1/3 is on the back of the wing.
Definition: the shape of the longitudinal section (front to back) of the wing
Current shape of glider wings: - asymmetric - quite thick - curved top surface, esp. on the anterior - lower surface slightly convex
Q47 - Wing profile is one of the most important factors that define the wing's characteristics, including flying and kiting performance
median chord of the profile, between (d) and (e) length of the profile, close to, but less than (a). thickness of the profile. trailing edge. leading edge.
Angle of attack (i): Angle between the direction of airflow (relative wind) and the median chord of the profile (a).
airflow will usually have some upward component in relation to the wing (because we lose 1.2m/s)
Point of stagnation or breakpoint (a): the point on the leading edge where the air streams divide between the upper and lower surfaces.
Center of thrust (b): the point where all the aerodynamic forces (lift and drag) effectively act. (i.e. like center of mass, close to the leading edge)
Stall point (c): the point on the upper surface where the airflow detaches from the surface of the wing and after which turbulence occurs and leads to a negative component of lift. This occurs mainly at large angles of attack.
The position of the significant aerodynamic points vary with the angel of attack.
Angle of attack is measured as the angel between the median chord and the wind direction at the trailing edge
Q069 and 070. See Figure A21. When the (already positive) angle of attack of a wing increases, the point of stagnation on the lower surface moves toward the leading edge.
Q70 - when the (already positive) angle of attack decreases (median is "more horizontal"), point of stagnation moves toward the trailing edge.
In (a), we find the optimum effect (10-15°), with a significant lift and reduced drag through low pressure on the upper and the lower surface pressure consistent and effective.
(b) significant impact. The lift is reduced and the drag increased. A stall point (X) (see also Figure A20) appears on the upper surface. Behind this point, turbulence results in a component of downward pressure downwards which replaces the negative pressure.
(c), the impact is detrimental. Airflow causes the lower surface to have negative pressure, and a positive pressure on the upper surface. With both effects acting downwards, the profile now has a negative lift.
(d) the angle of attack is zero. While a drag continues, the negative pressure persists on the upper surface, and to a lesser extent, the lower surface. These forces oppose each other and result in a very small lift.
Q61 - The relationship between lift and drag of a wing (profile) depends primarily on the angle of attack.
10 degrees - the ratio between lift and drag is at its maximum which corresponds to the maximum efficiency and the best glide angle.
Increasing the angle of attack -> increased lift, but also increased drag.
At 20 degrees, maximal lift, high drag. This corresponds to the minimum sink rate.
At 25 degrees, the lift disappears and the wing stalls (i.e. it is no longer flying).
Beyond the point of maximum efficiency, if the angle of attack is reduced or increased, then Cz (or lift) decreases or increases respectively. (not sure if I understood this)
Wing span - in meters. Length between the wing ends
Flat wingspan - wing span of the wing as measured while laid out on the floor
Projected wing span - projection of inflated wing on a flat surface
Flat wing span is greater than projected wing span
Area - meter ^2
Flat / actual surface area as measured on the floor Projected surface area - smaller or almost identical for a very flat wing
Take off weight (kg) - the sum of all of the weight carried by the wing:
- pilot
- glider!
- harness
Wing load = Take-off weight - weight of the wing
Wing loading: Average load / area unit (kg / m^2 ) Take off weight (total weight!) / area (usually projected)
Wing loading - min/max load + self weight / surface
For gliders - usual 2.5 - 4kg/m^2
Average Depth - average difference between the leading edge and trailing edge of the wing (m)
Average depth = surface area / wingspan
Wing torsion: changes in the angel of attack between different sections of the wing. Higher curvature - more stable wing, less stalls, less pilot intervention (i.e. along the wingspan axis)
Aspect Ratio: Ratio of wingspan to mean wing depth (mean aerodynamic chord) = wingspan^2 / area
wingspan ^ 2 / (wingspan * avg depth)
A long, narrow wing has a high aspect ratio, whereas a short, wide wing has a low aspect ratio.
Q78!!!!
High aspect ratio wing as having a modest elongation. The high aspect ratio wings therefore have a large wingspan and a small average depth. The wings are therefore a little longer with much smaller average depth
When the aspect ratio is large, the wing tip vortices are important and induced drag is large, which improves the performance of the wing in flight.
The aspect ratio of current paragliders is around 5 The aspect ration of current delta wings is typically 8.
A wing whose aspect ratio = 5 will have a major axis 5 times larger than its average depth
average depth of 5 times smaller than its area
Area 32 m2, 8 meter wingspan 64 / 32 = 2
Area 25 m2, 10 meter wingspan 100 / 25 = 4
Area 20, 10 m 100 / 20 = 5
d) Area 24 m2, 12 meter wingspan 144 / 24 = 6
a) Area 16 m2, 12 meter wingspan = 144/16 = ~8 b) Area 20 m2, 10 meter wingspan = 5 c) Area 12m2, 12 = 12 d) Area 12.5 m2, 10 meter wingspan = 100/12.5 = ~8
A glider which is not subject to acceleration (varying forces) will fly in a uniform linear motion (i.e. constant speed and direction)
Total weight in flight (take-off weight) acts vertically downward, is opposed by a counter force - resultant aerodynamic force
The resultant aerodynamic force can be separated into lift perpendicular to the trajectory and facing upwards, and drag , parallel to, and in the opposite direction of, the trajectory.
The component (force) of the take-off weight which is parallel to the trajectory (towards the leading edge and opposing the drag) has the same value as the drag and is called the thrust.
The trajectory is clearly identical to the direction of airflow. ???
The glide angle (α) is the angle between the trajectory and horizon.
Using geometry, we can easily prove that the glide angle (α) is identical to the angle (α’) formed by the lift and resultant aerodynamic force.
This latter observation is important to define the glide ratio (see below). It should not be confused with the
Glide angle (γ) formed by the angle between a chord line of the profile and trajectory.
The glide angle is identical to the angle formed between the FRA (resultant aerodynamic force) and the lift.
Typical glide ratio is about 8.
Glide angel depends on the angle of attach and varies with the lift and the drag.
Four way to calculate the glide ratio: - Horizontal distance traveled / vertical descent - Horizontal velocity / rate of fall - lift / drag = P / T - Cz / Cx = lift coefficient / drag coefficient
Glide ratio increases - glide angle decreases and vice verse
Drag of a glider decreases - the resultant aerodynamic force increases, the glide ratio decreases
Three principle axes:
-
Vertical axes - movement is called yaw Rotation movement forward/backward of the wing tips
-
Longitudinal axis - roll (R) - (around my Z axis) (i.e. parallel to the wings median chord)
-
Transverse axis - pitch - around the wingspan axis
Gliders are designed to fly straight uniform (balanced flight?)
It also recovers from temporary disturbances to normal flight.
A glider going from accelerated to normal flight without pilot intervention has stable flight characteristics.
A glider going from normal speed to accelerated speed without pilot intervention has unstable flight characteristics.
A glider which retains the flight behavior (flying condition) that is initiated by the pilot, but then released, is said to have indifferent flight characteristics.
The stability of the glider is defined by its behavior on its three principle axis.
A paraglider which, in calm air, either (i) rolls (ii) changes its angle of attack or (iii) yaws, without any pilot intervention, is said to be unstable with respect to, (i) the longitudinal axis, (ii) glide path, or (iii) vertical axis, respectively.
Note - learn axis and associated angels
Horizontal - airspeed Vertical speed - sink
They vary according to the angel of attack.
Decreasing the angel of attack by nose-diving the glider increases the speed.
When the angel of attack increases by pitching the wing the velocities decrease initially, then the horizontal velocity decreases and the sink rate increases.
Speed range - the combination of velocity and sink that arise from the minimum to the maximum speed of the wing.
Polar curve of velocities - graphical representation of horizontal and vertical veclocities.
Examples of the angle of attack: these are typical orders of magnitude and not precise measures.
When the angle of attack is low (about 5°), the glider flies fast. This is at the right of the graph.
At 10-12°, the glider is has the best glide ratio (Fmax).
When the angle of attack is high (approx. 15-20°) the wing flies slowly
When the angle of attack of a glider flying at its best glide ratio is reduced by 2°, the airspeed is increases
When the impact of a glider flying at maximum glide ratio is increased by 2°, the airspeed decreases
Four main points on a polar curve:
- Airspeed at minimum sink rate - T_min - apex of the curve
- Airspeed at maximum glide ratio - F_max - the point which intersects the tangent of the polar curve which passes through the origin
- Maximum speed
- Stall speed
Wing loading slightly modified the polar curve for a wing.
Higher wing loading -> greater resultant aerodynamic force to equalize all of the other forces.
The range of speeds ( Tmax, Fmax, Vmax ) increase or decrease with the respective increase or decrease in the wing loading.
The ratio of the horizontal and vertical velocities (glide ratio) does not change with the loading for a given angle of attack (unless the loading deforms the wing)
The stall speed follows the same rules: it decreases or increases with respective decreasing or increasing wing loading.
!!! ? why? the relative velocity of the wing doesn't change. To fly at maximum glide ratio against the wind, a pilot must accelerate the wing. ok - it's because the glide ratio is defined by the horizontal distance covered.
In figure A34, the tangent to the polar curve which intersects the origin of the new axis corresponds to an air speed of 11m/s, or ground speed of 5m/s. This is the speed required to achieve the maximum glide ratio for this glider in a head wind of 6m/s.
As the head wind increases the glider must fly faster to achieve the maximum glide ratio. Question 143.
When flying with a tail wind, the same logic shows that the glider must fly at a speed closer to the horizontal speed at minimum sink rate to achieve the maximum glide ratio - i.e. break a bit?
Additional horizontal force is added to the take off weight - centrifugal force - directed towards the outer circumference of the turn (directed outside)
Effective weight - Take off weight + centrifugal force
Resultant force is the sum of the both of them, greater than P (take off weight)
Shaper turns - larger force
Load factor - R / P = effective weight / take off weight
Load factor is measured in G
In a stabilized turn, the resultant aerodynamic force (FRA) will be opposed exactly to the effective weight.
Sharper turn -> the greater centrifugal force -> greater and more horizontal effective load.
To maintain the equilibrium of forces, the resultant aerodynamic force will also be great and angled close to the horizontal.
Since; the wing loading = resultant aerodynamic force (FRA) / wing surface - and the surface of the wing remains the same; the wing loading also increases in proportion to the resultant aerodynamic force.
Relative wind speed (true airspeed of the wing through the air) increases -> the resultant aerodynamic force increases with the square of wind velocity. If the speed doubles, the resultant aerodynamic force is multiplied by 4.
In a stabilized turn, the resultant aerodynamic force should increase to balance (or “offset”) effective weight. To achieve this increase in the resultant aerodynamic force the glider itself will have increase speed, but to a lesser extent.
In other words, in a turn the whole speed range is increased, elavating the minimum speed.
Q156 - during a transition from a steady straight flight into a turn (also stabilized), the wing loading and minimum flight speed increases.
Chemical composition: 78% nitrogen, 21% oxygen, CO2 0.03%, water, etc.
Earth radius = 13,000km Atmosphere we care about - 10-15km
Troposphere - the layer directly in contact with the Earth, it is responsibly for weather and paragliding (LOL)
Stratosphere, ionsphere and mesosphere do not concern paragliders.
Troposphere is bound above by the tropopause, ca. 11km AMSL in nothern latitudes.
In winter the colder temperatures -> air more condensed -> troposphere is slightly smaller. (opposite effect in summer)
Air pressure and air temperature are the important properties of the troposphere.
Atmospheric pressuse units are hetraPascal (hPa) 1 atmosphere = 1000 hPa = pressure at sea level
Air is a compressible fluid - it is less dense at altitude, higher altitude -> lower pressure.
The decrease is not linear.
MSL - 1a 5500m - 0.5a 11,000 - 0.25a
If the pressure at sea level is 980hPa the pressure at 5500m will be half its value.
Boyle's law - pressure * 0.5 -> volume x 2
Air pressure decreases steadily and predictably with altitude, it can still vary locally.
Atmospheric pressure varies by redistribution of the air molecules around the earth by metrological effects.
Temperature decreases on average 0.65degrees / 100m This can change significantly.
Standard atmospheric pressure - average air pressure at mean sea level and temp of 15 celcius. 1013.2hPa, temp gradient 0.65
Air is warmed by convenction from the ground.
Solar radiation enters the atmosphere, warms the ground which in turns warms the air.
Dry and dark ground is most efficient at warming up air.
Wet ground dissipates some of the solar energy by radiation, greatly reducing its effectiveness for warming up air.
A clear and smooth surface (rock face)
Dark ground is most efficient at warming air. Rock faces (clear and smooth surfaces) reflect some of radiation without absorbing it, also ineffective at warming the surrounding air.
At equivalent altitudes, warm air is less dense than cold air.
At ground level, sources of efficient generate flat, warm and light pockets of air. These pockets rise, and gradually warm the adjacent air up to tens to hundreds of meters above the ground. In addition, cool air descends to the ground and gets warmed up as well.
The vertical movement of (temp variable) air is convection.
This phenomenon takes place in the layer of troposphere called convection convective layer or convective boundary layer.
During sunny days, the thickness can vary from a couple of meters in winter to 2-3 km in summer.
During good weather, warm air mixes with pollution to create haze. This haze marks convective layer. Its upper limit is visible at altitude, as well as small cumulus clouds that develop in the updrafts.
Thicker convective layer -> stronger thermals available to paragliders.
The sun heats up the atmosphere in three phases:
- Radiation passes through the atmosphere without doing much
- The ground is heated up, heats up the air around it.
- Warm air rises, replaced by colder air - convection.
Adiabatic Transformation - the development of air mass moving vertically.
Air is a poor conductor of heat - a mass of air rising or falling will undergo changes of temperature with little energy exchange with the surrounding air.
A mass of descending air experiences inc. in pressure - according to Boyle's law there will be a corresponding decrease in volume.
Decreased volume -> more energy in smaller volume -> increase in temperature.
Air mass inc volume -> corresponding temperature drop.
Lapse rate / adiabatic gradient - the rate of decrease or increase in temperature of an air mass in vertical is the same whatever the temperature of the ambient air = 1 degree / 100m
Graph of temperature variation - measured temperature at different altitudes at a given time.
Snapshot of a potion of troposphere absent of significant vertical movement.
Pressure and adiabatic temperature vary with the altitude predictably along precise curves, emagrams are irregular, variable, unpredictable.
Obtained using radio sounding.
Incorporate balloon and measuring device. In CH - released from Payerne.
Temperature gradient - temperature drop / 100m
The average temperature decreases with altitude, but it can vary locally. These intermediate temperatures can vary irregularly.
Temperature inversion - when the temperature at higher air layers is warmer than below.
Isotherm layer - an air layer where the temperature remains constant.
For boring weather - we care about: night emagram day emagram
Clear nights - the ground emits infrared radiation back into space. This causes of cooling of the ground, cooling of adjacent air layers over tens of meters in above the ground
This causes inverted convention - air near the ground becomes colder than the air 500m above the ground. Forms a nighttime inversion air layer.
Overcast night: infrared radiation is reflected from the ground by the clouds -> less heat loss > smaller inversion
Windy - cooling air/ground will be disrupted at higher altitudes because of air circulation. Temperature gradient from the earth will persist weakly, ground inversion will be significantly reduced.
Sunrise - solar radiation quickly negates night time ground inversion.
During the afternoon, afternoon emagram will look higher Higher altitude - lower temp difference between night and day conditions.
Inversion and isotherm layers are effective at blocking thermals.
The layer above the convective layer is deep and better and with stronger thermals?
Deep convective layer - strong temp. difference between upper and lower atmosphere - i.e need that the general temperature gradient is large, no strong inversion or isotherm. The general temp. gradient is determined by the weather situation.
Temp gradient 0.3-0.5 degrees / 100m is low - modest convection.
0.6-0.8 - large, good thermals.
Swiss Plateau, Jura - gradient between 1000-3000m. Alps - 2000-4000m
Condensation - water vapor changing from vapor into liquid.
Dew point - the temp. where the air must be cooled so water vapor condences into a liquid.
Mist, frost - thin layers of liquid water and ice on a solid surface.
Air humidity - amount of invisible water vapor contained in the air. Unit - mass of water / volume - g/m^3 absolute humidity.
Warm air has greater capacity to retain water vapor before condensation.
State transformation - water needs to absorb energy to overcome intermolecular forces (solid -> liquid -> gas)
Gas -> liquid -> release of energy to the surrounding environment
Effect in thermals: dry air cools with normal rate of 1degree / 100m when it rises.
A mass of air saturated with water vapor will cool as it expands, generating further condensation. This condensation will heat the ambient air and release further energy.
Decrease of temp in the saturated air mass is less important than the adiabatic lapse rate of unsaturated air.
If saturated air descents it heats up - and could accommodate more water vapor. Evaporation of water into vapor requires heat.
The temperate of saturated gradient within a mass of air saturated with water vapor ascending depends on the amount of water vapor that evaporates??? Q41-43
Cloud is a portion of the atmosphere containing countless tiny droplets of liquid water suspended in the air.
Cloud == fog.
Fog defined as visibility < 1km
Mist when 1km < visibility < 10km
Clouds form:
- During long nights (fall, winter) the Earth emits infrared radiation and gradually cools.
If the air layer around the earth cools down to the dew point, fog may form near the ground. called radiation fog.
Clouds form when a mass of air has upward movement - gradually cools until it reaches the dew point.
The three main phenomena that cause this: convention wind - air is forced to rise when it reaches a natural barrier meeting of two air masses of different temperature
The cloud base is the lower limit of these clouds and is the altitude at which water vapor in the rising air condences.
Higher humidity - more likely for clouds to form. Very high humidity - lots of low clouds.
Clouds have different shapes and heights depending on their formation: cirrus - very high clouds 6-10k meters. Generally not very thick
alto - thicker clouds at 3-6k
cumulus - ball shaped clouds
stratus - layered clouds that appear to be stretched
nimbus - clouds that generate precipitation (Q56)
lenticular clouds - lens shaped castellanus - castle with towers
Specific clouds:
Cumulonimbus (Cb): They respond to cumulus congestus that grow into huge thunderclouds, often mushroom-shaped, reaching very high altitudes (about 10,000m).
Currents (winds), ascending, descending and horizontal are very strong (much faster than the speed of paragliders), which makes these clouds very dangerous.
These clouds can generate hail but not always. (Q59,64)
There is precipitation and evaporation phenomena occuring at high altitude which cools the air locally, explaining the strong downdrafts during precipitation.
Stratocumulus (Sc): Cumulus closed and forming bands usually near the ground. They are common after rain.
Stratus (St): A layer of clouds often in close contact with the ground and for observers on the ground, fog. The clouds are typical of autumn and winter, especially during the night and the morning when there is a strong temperature inversion to 1000-1500m. ie a stable stratification in the lower atmosphere.
We can then observe a sunny day at altitude and ground fog.
Nimbostratus (Ns): very thick layer of closed clouds with its base is at about 1000m. altitude, and producing precipitation. Question 53. These clouds can grow to a very high altitude.
Castellanus Altocumulus (Ac cas) having the form of a castle with ramparts and towers. They are developed early in the morning and indicate humid, unstable and conducive conditions leading to the development of thunderstorms in the afternoon. Question 45.
Lenticular Altocumulus (Ac len): These clouds develop at altitudes above 3500m when winds are moderately high on a topographical feature that creates a wind ripple. Despite the wind, the clouds remain stationary because there is condensation on cooling the ascending, wind, and evaporation by warming the descending wind (see Figure M17). Questions 60 and 61.
A gray curtain of vertical stripes, slightly oblique, extending from the gray base of Cu cong. or Cb to the ground is a sign of precipitation, often visible from a distance.
Km/h to knot conversion - knots are almost x2 km/h km/h -> knots = *1.8 (x2 - 0.1)
Variation in the barometric pressure are due to warming and cooling of air in contact with the ground locally.
An area of high pressure might form on a land area which is cooler than its surroundings for a protracted period, such as the Arctic, Siberia or any continent in winter (low sun on the horizon), or an ocean during summer (North Atlantic), which is cooler compared to its neighboring continents.
A low pressure area (depression) may occur on an area which is warmer than its surroundings for a protracted period, such as the equator, the Sahara in summer, the Atlantic Ocean during the winter (cooler than continental Europe).
Low and high pressure zones are called centers of action because they are the cause of the general atmospheric circulation.
The average atmospheric pressure at sea level on land is 1015hPa.
When the air pressure is higher, it is referred to as a “high pressure zone” and where it is lower, a “low pressure zone”.
In the temperate regions, a pressure of 1035hPa would be typical of a strong winter anticyclone. Pressures higher than this are very rare.
In summer, the pressure of high pressure regions is generally lower than this, between 1020 and 1025hPa.
A pressure of 955hPa would be typical of an area of low pressure.
To simply illustrate the distribution of pressure on a map, lines are plotted following the areas of equal pressure (adjusted to sea level) called “isobars”.
All fluids (liquids and gases) move in an attempt to even out pressure differences.
If the pressure difference between an anticyclone and a cyclone (shown by many, tightly spaced isobars) is large, the surface winds will be strong.
In addition to this the winds are subject to the rotation of the earth. This interferes with the direct movement of air between centers of action, introduces a rotational element to the winds around the center of action. This is called the force, called the Coriolis force. The result is that the surface winds blow close to parallel to the isobars around the action center.
In the northern hemisphere, the air masses rise by turning anti-clockwise around the center of low pressure (cyclone), and clockwise around the center of the anticyclones
Memory aid: cyclone- anti-clockwise; clockwise-anti-cyclone
We can ascertain the main direction and speed of prevailing winds from the isobars, cyclones, anti-cyclones.
geostrophic wind - prevailing wind which links the centers of action.
It follows 3 main principles:
- Wind direction is parallel to the isobars.
- Rotation of the wind is clockwise around a high pressure and anti-clockwise around low pressure (for the northern hemisphere). For the southern hemisphere is the opposite.
- Wind strength is determined by the isobar spacing (= horizontal gradient pressure). Tight spacing (= high gradient pressure) and the wind is strong and vice versa.
abrupt pressure drop - crowded isobars - high winds expected.
flat distribution of pressure - nicely spaced isobars, light winds.
depression - in a depression (cyclone) air rises, cools and then increases in humidity?
- unstable
anticyclones - air falls, heats up and dries out. In Europe the high pressure region is often accompanied by a temperature inversion at 1500-2000m. anticyclonic weather is rather stable, convective layer of modest thickness.
between the CoAs there will be intermediate pressure zones (1010 - 1020 hpa) - barometric swamp
- Lower air density
- atmosphere is less dry and volatile than in an anticyclone
- wind speeds are low because the pressure gradient is small or zero
- this situation generates significant convection and is best for paragliding.
- potential for local thunderstorms
valley wind - a wind that blows from the main, wide valley section to its upper reaches with small side valleys and peaks that warm up faster.
mountain wind - is a wind that blows during the night from the small peaks and side valleys, which cool faster, towards the broader and deeper main valley, which cools more slowly.
Since the valley wind is denerated by the intensity of the sun and is enhanced by a soil surface without snow, it is greatest in July and August and least in December and January.
It is also greatest during mid-afternoon when the sky is clear.
In summer the valley wind starts in the late morning and the mountain wind usually in the evening (18-19:00h).
With altitude, the valley wind is stronger.
In wide valleys, the valley wind gradually disappears around 2000m and is overcome by the prevailing wind.
Each sunny slope contributes a small portion of ascending air a few tens of meters thick, adhering to the slope.
This should not be confused with the mountain thermals extending to the top of the convective layer which are generally separated from the valley walls (orange arrows).
Mountain thermals are more widely spaced, cylindrical and develop in areas that are particularly suited to heating of the ground by the sun (and thus protected from the winds of the main valley).
The updraft on the slope of the valley caused by the gentle thermal movement on the valley wall is the source of the breeze that allows paragliders to take off more easily.
During the night, each valley wall is cooled (nocturnal radiation) and causes the formation of a thin layer of down-slope wind. These winds come together and finally form the descending (mountain) wind at the bottom of the valley (large blue arrows).
Mountain thermals may be regarded as a variant of the slope wind (also convective in origin). However, unlike the slope wind, these detach from the wall and evolve independently in the free atmosphere.
Mountain thermals are stronger and more constant than the thermals from open plains (a rising column rather than a bubble).
Q001 - only the Confederation (the political institution that governs Switzerland) that has the authority to define the laws concerning the use of Swiss airspace.
Q2, 55 - The Confederation has delegated the implementation of laws and control the use of Swiss airspace to the OFAC/BAZL (French: Office Fédéral de l’Aviation Civile; German: Bundesamt für Zivilluftfahrt; English: Federal Office of Civil Aviation)
The Confederation has enacted an ordinance (law) on aircraft of special categories, which includes hang gliders and paragliders. This law is called OACS (French: Ordonnance sur les Aéronefs de Catégorie Spéciale) and became law on 24 November 1994.
Q3 - The OACS is the legal code that governs the activity of free flight in Switzerland.
The OACS gives a precise definition of a “slope glider”: flying machines, which use a slope to launch at running speed and are, immediately after the start, used for flights near slopes or gliding flights.
These aircraft do not need to be recorded in any federal register.
Although the use of an approved glider is recommended, the law does not require a review of the airworthiness of slope gliders.
There are no restrictions on the use of uncertified gliders wings. It should be noted however that there are few pilots using an unapproved wing. The pilot has the primary responsibility for the airworthiness of a glider.
A helmet and parachute are only mandatory for the pilot’s practical examination. Outside the exams, these are not required, but strongly recommended.
Only liability insurance specific for free flight is required by law (OACS).
This should cover a minimum of CHF1,000,000, providing for damages that might occur to uninvolved third parties on the ground
The party responsible for any damage must pay the difference if the amount of damage is greater than the guaranteed cover of the liability insurance.
Damages relating to any third party aircraft in flight are not covered by the mandatory liability insurance.
Any slope glider must have 2 sets of makings: (1) the identification number and (2) the plaque of the manufacturer.
The identification number is mandatory for any user of Swiss airspace.
The identification number is composed of 5 or more digits, must be easily recognizable and affixed to the underside (lower surface) of the wing. These figures, which are usually adhered to the fabric of the wing, each must measure 40 cm in height. The SHV/FSVL is responsible for managing and allocating these numbers to each pilot ??? is this still a thing?
The identification number is composed of 5 or more digits, must be easily recognizable and affixed to the underside (lower surface) of the wing.
These figures, which are usually adhered to the fabric of the wing, each must measure 40 cm in height.
The SHV/FSVL is responsible for managing and allocating these numbers to each pilot.
All wings flown by a particular pilot must have the same identification number, identical to that on the certificate of liability insurance which the pilot mush carry on each flight.
In practice, this number is usually identical to that of pilot license issued by the SHV/FSVL, but the law is only the number for the liability insurance and the identification on the wing must match.
The manufacturer’s plaque (a small piece of fabric sewn into an edge or a wingtip) must include the following information: name of manufacturer, type of wing, the year of manufacture, the minimum and maximum loads specified by the manufacturer.
Serial number is not mandatory
The minimum age for obtaining a license for free flight is 16 years.
A student may begin flight school at age 15.
There is no maximum age limit for having a pilot license, nor is a medical examination required, neither prior to, nor during a pilot’s flight career.
The validity of a glider pilot license is unrestricted, with respect to either the age of the pilot or minimum number of flights per year.
Once licensed, a pilot is not required to list his flights in a flight log.
Any pilots, domestic or foreign, domiciled in Switzerland must have a Swiss license for a gliding pilot to fly to Switzerland, even occasionally. Only foreign pilots domiciled abroad, who have an equivalent foreign license or international license (IPPI of the FAI - Federation Aeronautique Internationale) may occasionally fly in Swiss airspace.
The flight training or instruction of unqualified students is not permitted without the direct supervision of a person holding an instructor’s license that is recognized in Switzerland.
he program of tests for pilots shall be determined in the directives of the SHV/FSVL and approved by the OFAC/BAZL (Federal Office of Civil Aviation).
Flights with a passenger (tandem flight) can only be performed by pilots holding a relevant license (tandem license).
The flights with more than one passenger (e.g. 2 children) are not allowed.
There are 2 types of tandem patent: the license (A) and license (B). License (A) allows this pilot to take any passenger, including those without any license.
License B allows the pilot to take a passenger who holds a pilot certificate ("solo" license) in the same category.
For example a pilot with tandem paragliding B license, can not take a passenger who is a licensed delta pilot, but not a paraglider pilot
During his flight, a qualified pilot must carry 2 documents: certificate of insurance covering the identification number of the wing in which the flight is made and the paraglider pilot’s license.
Official who are able to ask for these documents are: OFAC/BAZL officials, representatives of public order (e.g. police), managers of aerodromes
The takeoffs and landings of slope gliders are not permitted on public roads, ski slopes and a distance of less than 5km from active military or civilian airport runways (which do not have control zone CTR) and 2.5km from a heliport.
The following may regulate or prohibit the takeoff or landing of slope gliders: the Confederation, cantons, municipalities and landowners
The chief of an airport may authorize, under certain conditions, landing on the (or beside) runway of the airport.
The following should be circumnavigated, or flown over at a safe distance: gatherings of people in the outdoors, buildings, highways and ski slopes, the public transportation facilities, overhead power lines and other overhead cables. There is no other requirement for these matters, and notably no specified minimum height
Provided that no goods are transported and that the pilot has the necessary documents when crossing the border, the pilots of slope gliders are allowed to enter and/or leave Swiss airspace. Foreign laws must be respected
The takeoffs and landings on public waters must be subject to prior authorization from the cantonal administration for navigation.
Towing of slope gliders with winches or vehicles (up to 150 meters above ground level) is allowed, subject to prior authorization by the Federal Office of Civil Aviation (OFAC/BAZL).
The training of persons to operate the winches to launch slope gliders is not subject to any regulation.
The radio frequencies reserved for the free flight, and without special training, is 130,925MHz for licensed pilots and 123,425MHz for pilot training !!!
- ICAO: International Civil Aviation Organization.
- VFR: Visual Flight Rules. These are the rules that apply to any aircraft which must fly "by sight". They define the minimum required visibility and the safe distance required in relation to clouds, the priorities to be adopted on convergence of aircraft, etc.
- All slope gliders should fly only in VFR conditions.
- IFR - Instrument Flight Rules. These do not apply to slope gliders. They are restricted to aircraft with the appropriate equipment needed to fly in poor visibility (“blind”)
- GND - Ground.
- AGL - altitude above ground level
- AMSL - (Altitude) Above Mean Sea Level
- FL - flight Level (altitude). The number following this abbreviation represents hundreds of feet.
Unfortunately the Americans, having commandeered international air law, never learned about meters. To find the number of meters, multiply the FL number by 30. For example, FL30 corresponds approximately 900m (30 x 30); FL100 is approximately 3000m (100 x 30); FL150 is approximately 4500m (150 x 30). FL 195 is approximately 5900m (195 x 30). (LOL)
The ICAO has legally defined 7 airspaces in the troposphere, designated by letters (A) to (G)
In Switzerland, only 4 of these types of spaces apply: (C),(D),(E) and (G). Memory aid: “Ceiling Defines Every Glide”. Questions 085 and 086. Figure L1 shows the distribution of these 4 spaces.
The spaces (E) and (G), called uncontrolled airspace, are the only places that paragliders may be used without permission and without radio contact with air control centers.
The spaces (C) and (D) are called controlled airspace, and should only be used after prior authorization and with radio contact with air control centers. The paragliders should not use these airspaces.
Space G "Golf" - all of CH, from grund to 600m AGL. Upper limit - 600m, lower limit - soil
Space E (above G) - "Echo"
On Jura + Plateau - FL100 (~3050 AMSL)
In the Alps, the upper limit of E varies according to the season and hours.
MIL ON - military flight times - Monday to Friday, 08-12, 13:30-17, E is generally FL130 - 3950m
MIL OFF - FL150 generally (4600 AMSL)
The diving line between Jura and alps is precisely represented on the gliding map and the AIP.
Knowledge of (C) and (D) airspace is less useful because paragliders can not use these.
In the Alps, (D) extends from the upper limit of (E) to FL195 (5950m AMSL). (C) extends from FL195 to FL600.
On the Plateau and the Jura, there is no airspace (D), and in this area (C) begins at FL100 extends to FL600.
- 600m AGL - Upper limit of (G) airspace
- FL100 (3050 m AMSL) - Upper limit of (E) airspace (Jura-Plateau)
- FL130 (3950 m AMSL) - Upper limit of (E) airspace (Alps, MIL ON)
- FL150 (4600 m AMSL) - Upper limit of (E) airspace (Alps, MIL OFF)
- FL195 (5950 m AMSL) - Lower limit of (C) airspace (Alps)
In many parts of the Swiss airspaces (E) and (G) there are areas only available to paragliders from 1st April to 31st October, and after military hours (MIL OFF).
We will see later that in normal gliding areas the legal separation distances from cloud are can be reduced.
Additional gliding areas, especially during times of military flights (MIL ON) can be locally and temporarily declared (e.g. in parts of the Alps and during certain periods in the summer period). These typically have upper limits at 3950m AMSL. These areas are defined in the AIP (see below)
There are additionally a number of local limitations to airspaces (E) and (G) for paragliders: Firstly all dangerous, prohibited and regulated areas in Switzerland are completely or partially restricted to paragliders. There are also many spaces around, and between, major airports, which are reserved for large aircraft and IFR flights.
A restricted area is where aviation activities can only be conducted according to certain rules (e.g. flight height is controlled by air traffic control). Nature reserves and the Swiss National Park are also restricted zones, although they are not defined as such in the aviation regulations, the guideline requires flight to be conducted at high altitudes, which is not possible for paragliders.
An exclusion zone is an area in which any unauthorized aircraft activity is prohibited. There are no such areas permanently defined in Switzerland. However an example is, in early June 2003, a restricted area of a 30km radius around Evian was defined for a few days due to the intergovernmental meeting of the G8. A similar exclusion zone was defined around Davos in 2009.
A danger zone is an area where an aviation activity can be dangerous.
There are three types of danger zones: - A gliding zone, in which the required separation distance from cloud is reduced for paragliders and sailplanes, and which may be dangerous for aircraft. - A flight zone in the clouds (only for suitably equipped and authorized gliders, and never for paragliders) which may pose a danger to any aircraft. - A military firing zone (DCA or artillery), only active during a period (often short). Examples are: (i) The area LS-D7, polygonal, about 7-8km radius around Grandvillard (between Moléson and Vanil Noir), extending from ground to an altitude of 2750m. See Figure L6.
These areas of flight through clouds are precisely defined and, together with the radio frequency to be used, are noted on gliding maps.
These zones can essentially cover almost all of the Swiss Alps and part of the Jura up to the canton of Neuchatel. And
(ii) The LS-D9 area in the valley of Conches, about 10km in radius, extending from ground to an altitude of 11,500m. See Figure L6.
These hazardous areas are not continuously active. In 2002, for example, these two dangerous areas were active only for a few days from January - March and September - December.
- The golden eagle nests in the spring from March to May in the Alps.
- The mating couple builds its nest in the cliffs below the upper limit of forest.
- Eagles are most disturbed when pilots fly near the nest in spring, which may scare the eagles and cause them to leave their eggs.
- The eagles mature at 5 years.
- They are monogamous for life.
- The mating couple lives in an area of approximately 100km2.
- Adolescent eagles roam vast distances in search of unoccupied territories.
- The undulating flight of the eagle is how it marks its territory
- Ibex give birth in June
- Chamois give birth in May
- Live on south facing slopes during winter spring
- In summer, after feeding on the slopes, these animals move to the shaded cliffs or breezy ridges to rest.
- These animals are most disturbed by the glider pilots when they fly near the slopes in the uninhabited regions above the upper limit of forest