Safety Bulletin SB-09 Dic 2015 - special adverse convective wx & itcz by Evelop

Safety & Training Boletín de Seguridad Operacional para personal de EVELOP y ORBEST Safety & Training special bulletin for EVELOP & ORBEST staff

Núm. 09 Dic 2015

Adverse convective weather & the ITCZ (Intertropical Convergence Zone)

EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

NOTA: L a s s u ger en cia s , o p in io n es u o t r a s in f o r m a cio n es ex p r es a d a s en es t e boletín no son necesariamente las de Evelop Airlines S.L. y/u Orbest S.A. Los datos que se ofrecen en este boletín no sustituyen ni deben ser tomados como información oficial. Ningún artículo en este boletín pretende sustituir normativas, procedimientos publicados, ni recomendaciones del fabricante, el operador o el Estado. Este boletín está dirigido en exclusiva al personal de Evelop Airlines S.L. y Orbest S.A. NOTE: Suggestions, opinions and any other informations expressed in this bulletin are not necessarily those of Evelop Airlines S.L. and/or Orbest S.A. The information included in this bulletin neither substitutes nor must be taken as an official information. The content of this bulletin does not replace regulations, procedures or recommendations of the manufacturer, the operator or the State. This bulletin is exclusively addressed to Evelop Airlines S.L. and Orbest S.A. staff.

Dirección de Seguridad Operacional SMS Responsable: Joan Fiol joan.fiol@evelop.com 618 740499 Coordinador SMS: Luis Castaldo luis.castaldo@evelop.com 971 448034 Oficial Seguridad / FDM: Raúl Castiñeira raul.castineira@evelop.com Oficiales de Seguridad: Mantenimiento > MNT Javier Moragues TCPs > CAB Isabel Abela Ops Vuelo > FLT Carlos Magaz Raúl Castiñeira Oficina Técnica > OFT Tolo Font OCC > DSP Steve Nicoll Ops Tierra > GRH Rafael Rodríguez Entrenamiento > TNG Álvaro Sabater EVELOP Airlines, S.L. Avda. 16 de julio, 75 (Edif. Barceló) 07009 - Palma de Mallorca (Illes Balears) - España

Contenido elaborado por Gestión de Entrenamiento de Tripulaciones en colaboración con la Dirección de Seguridad Operacional

¿Tienes alguna sugerencia para mejorar este boletín? ¿Deseas que se trate algún asunto específico relacionado con la Seguridad? ¿Echas en falta alguna sección o quieres colaborar con algún artículo? safety@evelop.com EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

INTRODUCTION

onvective weather present a serious hazard to aviation. Aircraft entering a Cumulonimbus (Cb) cloud may experience severe turbulence, icing, lightning, precipitation, and strong winds (both vertical and horizontal).

These hazards, individually and collectively can lead to structural damage, injuries to crew and passengers, loss of separation/level bust as a result of an inability to maintain assigned height, and loss of control. Where possible, flight crews will wish to avoid passing with a margin of at least 20 nm of a cumulonimbus cloud. Particularly intense Cbs, often associated with squall lines, may also present related phenomena such as Tornados, Gust Fronts, and Microbursts, all of which can have an impact on air traffic management and airport infrastructure. Aircraft equipped with Weather Radar are able to identify the areas of cloud with the greatest vertical wind shear and navigate through (or if not possible around) areas of convective activity. Follow FCOM & FCTM: ⇒ PRO-SUP-30 Ice and Rain Protection ⇒ PRO-SUP-91 Adverse Weather ⇒ FCTM / SI-70 Use of Radar ⇒ FCTM / SI-10 Adverse Weather ⇒ Airbus FOBN Optimum use of Weather Radar ⇒ EVELOP Flying Around Weather Conditions Recommendations (Appendix 1) Reading Recommendations: ⇒ Reports on: (Available on Crew Web > Seguridad Operacional > 12-Accidents & Incidents) • Flight AF 447 • Flight Swiftair MD-83 Mali ⇒ “Airplane UpSet Recovery”, Airbus Training Aid. (Available on Crew Web > Training).

REFERENCE PUBLICATIONS ⇒ American Institute of Aeronautics and Astronautics (AIAA) P a p er No 2014-0612,

⇒

⇒ ⇒ ⇒

⇒ ⇒ ⇒ ⇒

NF1676L-16719 “Preliminary Analysis of Aircraft Loss of Control Accidents: Worst Case Precursor Combinations and Temporal Sequencing”. National Aeronautics and Space Administration (NASA) P ap er No NF1676L -11047 “Aircraft Loss-of-Control Accident Analysis” and Paper No 00299, NF1676L-11771 “Aircraft Loss-ofControl: Analysis and Requirements for Future Safety-Critical Systems and their Validation”. European Aviation Sa f et y P la n 2014-2017. European Commission Regulation (EU) No 965/2012 o n Air Op er a t ion s , P a r t -ORO – see European Flight Standards Implementing Rules. International Civil Aviation Organization (ICAO) An n ex 19 ” Saf et y Ma n a gem en t ” ; ICAO Doc 9859 “Safety Management Manual”; ICAO 2014 Safety Report; ICAO Doc 10011 ”Manual on Aeroplane Upset Prevention”; ICAO Doc 8335 “Manual of Procedures for Operations Inspection, Certification and Continued Surveillance”; ICAO Doc 7192 “Training Manual - Part F1 - Meteorology for Air Traffic Controllers and Pilots”; ICAO Doc 7192 “Training Manual - Part D3 - Flight Operations Officers/Flight Dispatchers”. Federal Aviation Administration (FAA) Ad v is o r y Cir cu la r No AC 00-24C ”Thunderstorms” and No AC 91-70A “Oceanic and International Operations”. European Authorities Coordination Group on Flight Data Monitoring (EAFDM) – “Developing standardised FDM-based indicators (Dec. 2013)”. United Kingdom Civil Aviation Authority Aer on au t ical In f o r m a t ion Cir cu la r AIC No . P 056/2010 “The Effect of Thunderstorms and Associated Turbulence on Aircraft”. International Air Transport Association (IATA) Saf et y R ep o r t 2014, 51 st Ed (April 2015).

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Boletín especial de Seguridad Operacional #9—Dic 2015

INDEX 1. Adverse Convective Weather 1.1 1.2 1.3 1.4 1.5

Cb – Cumulonimbus High Level Ice Crystal Icing Lightning Turbulence Wind Shear

2. THE ITCZ – Inter Tropical Convergence Zone 3. Weather Phenomenon associated to the ITCZ 3.1 Tropical Revolving Storm 3.2 Monsoons 4. Geographical Areas Climatology 4.1 4.2 4.3 4.4 4.5

Caribbean Western Africa South East Asia – Indonesia South East Asia – India Saudi Arabia

Appendix 1 A1.1 Adverse Weather Checklist A320 (OBS & EVE) A1.2 Adverse Weather Checklist A330-343 (CS-TRH MSN0833) A1.3 Adverse Weather Checklist A330-200 (CS-TRX MSN0802)

EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

1. ADVERSE CONVECTIVE WEATHER 1.1. Cb – Cumulonimbus

umulonimbus is a heavy and dense cloud of considerable vertical extent in the form of a mountain or huge tower, often associated with heavy precipitation, lightning and thunder. The mature Cumulonimbus cloud has a distinctive flat, anvil shaped top. The Cumulonimbus cloud (Cb) forms when three conditions are met: There must be a deep layer of unstable air. The air must be warm and moist. A trigger mechanism must cause the warm moist air to rise: Heating of the layer of air close to the surface. Rising ground forcing the air upwards (orographic uplift). A front forcing the air upwards.

Types of Cbs Convection. Ca u s ed b y h ea t in g of t h e lay er of a ir clo s e t o t h e s u r f a ce. Th is t y p e o f Cb commonly forms in the late afternoon after the peak diurnal heating. Thunderstorms of this type are a daily occurrence in many areas of the tropics. The storms are usually single Cb cells rather than clusters of cells and so can generally be avoided by flying around them. Orographic Uplift. Ca u s ed b y r is in g gr ou n d f or cin g t h e a ir u pw ar d s (Or o gr ap h ic L if t ). These storms form when a general flow of moist unstable air passes over higher terrain, such as a ridge line or mountain range. Such storms often form in a line along the ground feature and are therefore more challenging to avoid than single cells. Mass Ascent. Cau s ed w h en a w ea t h er f r on t f or ces t h e air u pw a r d s . As w it h o r o gr ap h ic lift, the Cb cells form in a line along the front, frequently embedded within wider frontal cloud, therefore presenting a challenge to aircraft trying to navigate through the front.

Effects Turbulence. V er t ical m o v em en t w it h in a Cb ca n b e a s m u ch as 50kt. The interaction between strong updrafts and strong downdrafts causes wind shear and severe turbulence within the cloud. Strong surface winds, variable in direction and strength, are common at surface level in the vicinity of the Cb. These can be particularly hazardous to aircraft on take-off or landing. In-Flight Icing. Mo d er a t e t o Sev er e icin g ca n b e ex p ect ed, es pecia lly in t h e h igh er lev els of the cloud. Electrical disturbance. Air cr af t fl y in g in t h e v icin it y o f Cb clo u ds m a y ex per ien ce elect r ical disturbances effecting communications and navigation systems. The electrical phenomenon known as St Elmo's Fire, while not a threat to safe flight, is an indication of nearby Cb activity. Aircraft in the vicinity of a Cb are at risk of being hit by Lightning. Precipitation. Hail can cause significant structural damage to an aircraft. Other precipitation, such as snow, sleet, or rain, can contaminate airfield and runway surfaces creating a hazard to aircraft attempting to take-off or land. Extreme weather. Sev er e d ow n dr af t s , microbursts and funnel clouds such as Tornados are also features of cumulonimbus clouds.

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Boletín especial de Seguridad Operacional #9—Dic 2015

Cb avoidance

light into a Cb is highly dangerous. The only sensible defense against the hazards associated with a Cb is therefore to avoid flying into one in the first place.

Planning. P r edict in g a n in d iv id u a l Cb cell is dif fi cu lt b u t it is po s s ib le t o p r ed ict t h e co n ditions which will trigger formation of a Cb. Forecasters are therefore able to advise flight crews and controllers of the likely timing, location, direction of movement, and height of cells and whether or not they may be embedded. Airport authorities can plan aircraft movements to take into account the disruption to operations caused by storms, and approach controllers can consider how they will manage en-route, departing, and arriving traffic when storms are in the vicinity. Flight crews can alter their routings to avoid forecast Cb activity or decide to carry extra contingency fuel in case they have to re-route in flight to avoid the storms or burn additional fuel because of the potential use of aircraft de/anti icing systems. Awareness. Aw a r en es s of t h e co n d it io n s w h ich lead t o t h e f o r m a t ion o f a Cb , r eco gn ition of a developing and mature Cb, and awareness of the signs which indicate the proximity of a Cb will help controllers and flight crews to plan operations to avoid the associated hazards. Weather Radar. In ad d it io n t o v is u a l r eco gn it io n , Weather Radar is a particularly valuable aid to avoiding Cb clouds. Airborne weather radar enables the flight crew to identify the areas of the storm cloud which hold the largest water droplets, which indicate the areas with strongest updrafts. The area of the cloud with the most severe turbulence is where the updrafts adjoin the downdrafts; therefore the pilot must avoid flying through the edge of the areas of cloud with the largest water droplets. It should be remembered that a large cloud will absorb a great deal of the radar pulse which may therefore not penetrate all of the way through the storm. This can give a false impression that there are no Cb cells beyond the cell immediately ahead of the aircraft. In flight avoidance. In cer t a in cir cu m s t a n ces , n a v iga t in g t h r ou gh a lin e of Cb cells m a y be the only option open to a pilot, either because his destination is beyond the line of cells or because he is unable to climb over them. In such circumstances, the aircraft may have to diverge from track by many, perhaps hundreds of miles, in order to find a gap in the wall of Cb clouds. The aircraft captain will need to judge the least hazardous track to follow through line of cells, something which will absorb the whole crew’s attention. The Weather Radar is invaluable in this situation. If the Cb cell is situated over the destination aerodrome, then the pilot would be well advised to hold off or divert rather than attempt a landing.

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Boletín especial de Seguridad Operacional #9—Dic 2015

1.2 High Level Ice Crystal Icing

or a number of years, it has been apparent that the detail design of some gas turbine engines has made them vulnerable to the risk of sudden loss of engine thrust if high densities of small ice crystals are encountered in very cold air. This Ice Crystal Icing (ICI) hazard has not usually resulted in complete engine failure (although there have been such instances) but more than one engine may be affected simultaneously. Satellite data has confirmed that areas of very small ice crystals in high concentrations exist within, and in the vicinity of, convective weather systems; whilst large scale convective systems are more likely to produce ICI this can also happen in smaller storms, just less regularly. The risk occurs outside of flight conditions which are currently defined by the regulatory authorities as "icing conditions" and therefore defined as such in the applicable AFM. In the light of evidence found during investigations of inservice occurrences of the phenomenon by engine manufacturers and the relative success of design modifications, which have resolved problems with particular engine types, the main regulatory agencies have been considering how to respond to this situation for a number of years now and have, at various points, issued interim operational guidance. This is most likely to occur in tropical latitudes where these systems are at their most extensive because warmer air can "hold" much more moisture, especially so when such convection occurs over the oceans where greater uptake of moisture is possible. Such strong convection produces cloud tops that, in some cases, can break through the Tropopause (Satellite evidence shows that even relatively small storms, in terms of spatial extent, can break through the tropopause). High altitude ice crystals may be present for some time after the active convection which produced them has begun to decay. They are extremely small, probably only about 40 microns in diameter and even at high concentrations, are unlikely to be evident visually even by day. With a radar reflectivity of only about 5% of that of average-sized raindrops, they will not appear on airborne weather radar displays because the temperatures which prevail at the altitudes where they are mostly found are too low for super-cooled liquid water to survive, so that what are now termed 'glaciated conditions' exist.

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At lower levels though, small ice crystals can occur in the presence of some super-cooled water droplets and this combination has been termed "mixed phase" conditions. The main risk of encountering high crystal concentrations appears to be downwind from the tops of large areas of convective cloud, the area where the visible anvil shape is seen when viewed from a distance. Overshooting tops (dome-like protrusions from the top of an anvil cloud) are an indicator that significant convection is occurring and that ICI may be a possibility. A clear distinction should be drawn between the high concentrations of very small ice crystals which have caused engine malfunction and the entirely different collections of larger crystals at lower densities that give rise to high level Cirrus, Cirrostratus and Cirrocumulus cloud, which are not hazardous.

Ice Crystals Effects

igh altitude ice crystals will not adhere to the external airframe, or protrusions from it, even though these are considerably warmer than the ambient temperature because of kinetic heating. Therefore, their presence will not activate conventional ice detectors. The microphysics which underlies the potential hazard, in respect of engine malfunction, is extremely complicated and has tended to manifest itself in slightly different ways in different incidents. This is because any undesirable effect caused by the ingestion of very small ice crystals at high densities has usually been shown to have been a function of details in engine design not originally foreseen as relevant. The common feature of most investigated incidents appears to be the initial accretion and aggregation of the ice crystals on relatively warm surfaces within the forward part of an engine followed by their subsequent detachment and partial melting as they progress through the engine core. Un-commanded thrust reduction may occur because of either direct or indirect effects of this passage and, even without any effect on engine function discernable to the flight crew, engine damage can result.

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The sign that a significant ICI encounter is in progress has usually been seen in a gradual reduction in engine rpm and a simultaneous rise in EGT. Thrust lever movement becomes ineffective and engine ‘rollback’ may continue until a sub-idle condition is reached. Other incidents attributed to ICI have arisen when a disrupted intake airflow has created an abnormal pressure gradient in the engine core which has led to a sudden airflow reversal. The majority of recorded events of engine malfunction attributed to this cause have occurred during the early stages of descent from high altitude with thrust reduced to Fight Idle. Recorded events in the cruise have usually followed a progressive build-up of ice during a much longer period of exposure to high crystal densities than has appeared to be required to cause effects in the flight idle/descent case. However, it has sometimes been challenging to identify where the ice accretion actually occurred since any effects will not necessarily occur whilst the accretion is still continuing and it appears that the glaciated conditions at an intensity to cause problems occur in relatively small 'pockets'. It is currently being suggested that such localized areas of high ice crystal density have up to 8 grams per cubic metre of Ice Water Content (IWC) compared to the current engine design standard for super cooled liquid water which is only 2 grams per cubic metre. In this respect, the effect which these ice encounters appear to have had on engine function represents a new challenge rather than a failure to meet existing reliability standards.

Ice Crystal Icing Avoidance

part from following guidance provided in AFM and / or the FCOM, the best way of way to avoid high concentrations of very small ice crystals is the effective use of the aircraft weather radar to ensure that significant convective activity at altitudes below typical jet aircraft cruise levels is detected and the assumption then made that at the levels above this should be avoided. When particular susceptibility to ICI is known, deviation by more margin than the typically-recommended 20 nm from all areas where large convective cells are present is advisable. Where particular engine types have been identified as at risk pending modification, a distance of 50 nm from such areas is usually recommended. This tactical strategy can be supported by considering the ICI risk when reviewing meteorological forecasts at the pre flight planning stage. Since there will not be any forecast of areas to avoid specifically because of an ICI risk, the probability that it is likely to be a feature of all large convective systems in tropical latitudes, especially those over oceanic or coastal areas, should be the assumption. Operationally, the best advice should be provided in the AFM and / or the FCOM. However, subject to any specifically applicable requirements or guidance, it is currently considered that the use of a thrust setting above Flight Idle during initial descent from high cruise altitudes in the tropics is a sensible precaution. A number of clues to the presence of ice crystals at densities with the potential to affect engine function have been deduced from past events and include: ∗ An air temperature significantly in excess of the corresponding ISA temperature ∗ The presence of some turbulence but rarely more than at light-to-moderate intensity ∗ Areas of heavy rain detected on weather radar below the freezing level ∗ The appearance of St Elmo's Fire on the flight deck windscreens. ∗ The appearance of small droplets of moisture on the flight deck windscreens - the result of impacting ice crystals being melted on contact with heated screens ∗ Transient failure of the TAT annunciation due to ice crystal accretion within the pitot probe / head which exceed the capacity of the heating system ∗ The absence of airframe icing. EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

1.3 Lightning

ightning is an atmospheric discharge of electricity. A lightning strike can be very distressing to passengers and crew but damage to an aircraft in flight which is sufficient to compromise the safety of the aircraft is rare. Lightning occurs as a result of a build up of static charges within a Cumulonimbus cloud, often associated with the vertical movement and collision of ice particles (Hail), which result in a negative charge at the base of the cloud and a positive charge at the top of the cloud. Beneath the cloud, a "shadow" positive charge is created on the ground and, as the charge builds, eventually a circuit is created and discharges takes place between the cloud and the ground, or between the cloud and another cloud. An aircraft passing close to an area of charge can initiate a discharge and this may occur some distance from a Thunderstorm. Lightning strikes on aircraft commonly occur within 5,000 feet of the freezing level. Lightning is accompanied by a brilliant flash of light and often by the smell of burning, as well as noise. A lightning strike can be very distressing to passengers and crew, but significant physical damage to an aircraft is rare and the safety of an aircraft in flight is not usually affected. Damage is usually confined to aerials, compasses, avionics, and the burning of small holes in the fuselage. Of greater concern is the potential for the transient airflow disturbance associated with lightning to cause engine shutdown on both FADEC and non-FADEC engines with close-spaced engine pairs. Lightning may also occur in Volcanic Ash clouds formed in the immediate vicinity of eruptions because the vertical movement and collision between solid particles within the cloud generates static charges. The Following map shows the uneven distribution of lightning strikes across the globe. The data is from space-based sensors.

Map showing the uneven distribution of lightning strikes across the globe. Image courtesy of NASA (NSSTC Lightning Team)

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Effects of lightning Aircraft Damage. Structural damage to aircraft from Lightning strikes is rare and even more rarely of a nature that threatens the safety of the aircraft. Nevertheless, there have been many incidents of lightning strikes leaving puncture holes in the radomes and tail fins of aircraft (entry and exit holes) and damage to control mechanisms and surfaces. Crew Incapacitation. Momentary blindness from the lightning flash, especially at night, is not uncommon. Interference with Avionics. A lightning strike can effect avionics systems, particularly compasses. Engine Shutdown. Transient airflow disturbance associated with lightning may cause engine shutdown on both FADEC and non-FADEC engines on aircraft with close-spaced engine pairs.

Avoidance of lightning

tandard advice to pilots is to remain at least 20 nautical miles displaced from any Cumulonimbus cloud. The dangers from Turbulence, Wind Shear, and Icing associated with Cumulonimbus clouds are far greater than the threat of Lightning.

1.4 Turbulence

urbulence is caused by the relative movement of disturbed air through which an aircraft is flying. Its origin may be thermal or mechanical and it may occur either within or clear of cloud. The absolute severity of turbulence depends directly upon the rate at which the speed or the direction of airflow (or both) is changing, although perception of the severity of turbulence which has been encountered will be affected by the mass of the aircraft involved. Significant mechanical turbulence will often result from the passage of strong winds over irregular terrain or obstacles. Less severe low level turbulence can also be the result of convection occasioned by surface heating. Turbulence may also arise from air movements associated with convective activity, especially in or near a thunderstorm or due to the presence of strong temperature gradients near to a Jet Stream. Jet Stream Turbulence, like turbulence caused by Mountain Waves, which can form downwind of ridges, occurs clear of cloud and in the form of Clear Air Turbulence (CAT).

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Very localized, but sometimes severe, Wake Vortex Turbulence may be encountered when following or crossing behind another aircraft. This turbulence is due to wing tip trailing vortices generated by the preceding aircraft; however, this phenomena is distinctively transient. Air moving over or around high ground may create turbulence in the lee of the terrain feature. This may produce violent and, for smaller aircraft, potentially uncontrollable effects resulting in pitch and / or roll to extreme positions. Relative air movements which involve rapid rates of change in wind velocity are described as wind shear and, when severe, they may be sufficient to displace an aircraft abruptly from its intended flight path such that substantial control input is required to compensate. The consequences of such encounters can be particularly dangerous at low altitude where any loss of control may occur sufficiently close to terrain to make recovery difficult. The extreme down-bursts which occur below the base of cumulonimbus clouds called Microbursts are a classic example of circumstances conducive to Low Level Wind Shear.

Severity of Turbulence

or the purpose of reporting and forecasting of air turbulence, it is graded on a relative scale, according to its perceived or potential effect on a 'typical' aircraft, as Light, Moderate, Severe and Extreme. ⇒ Light turbulence is the least severe, with slight, erratic changes in attitude and/or altitude. ⇒ Moderate t u r bu len ce is s im ilar t o ligh t t u r b u len ce, bu t o f gr ea t er in t en s it y - vari-

ations in speed as well as altitude and attitude may occur but the aircraft remains in control all the time. ⇒ Severe t u r b u len ce is ch ar a ct er ized b y lar ge, ab r u p t ch a n ges in a t t it u d e an d altitude with large variations in airspeed. There may be brief periods where effective control of the aircraft is impossible. Loose objects may move around the cabin and damage to aircraft structures may occur. ⇒ Extreme t u r bu len ce is cap ab le of cau s in g s t r u ct u r a l d am a ge an d r es u lt in g d irectly in prolonged, possibly terminal, loss of control of the aircraft. In-flight turbulence assessment is essentially subjective. Routine encounters involve light or moderate turbulence, although to inexperienced passengers (or pilots), especially in small aircraft, these conditions may seem to be severe. The perception of turbulence severity experienced by an aircraft depends not only on the strength of the air disturbance but also on the size of the aircraft - moderate turbulence in a large aircraft may appear severe in a small aircraft. Therefore pilot reports of turbulence should mention the aircraft type to aid assessment of the relevance to other pilots in, or approaching, the same area. EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

1.5 Wind Shear

ind shear is defined as a sudden change of wind velocity and/or direction. It may be vertical or horizontal, or a mixture of both types. ICAO defines the vertical and horizontal components of wind shear as follows: ⇒ Vertical wind shear is defined as change of horizontal wind direction and/or speed with

height, as would be determined by means of two or more anemometers mounted at different heights on a single mast. ⇒ Horizontal wind shear is defined as change of horizontal wind direction and/or speed

with horizontal distance, as would be determined by two or more anemometers mounted at the same height along a runway.

Description

ow Level Turbulence which may be associated with a frontal surface, with thunderstorms or convective clouds, with microbursts, or with the surrounding terrain, is particularly hazardous to aircraft departing or arriving at an aerodrome. Wind shear is usually associated with one of the following weather phenomena:

• • • • •

Frontal surfaces; Jet streams; Thunderstorms or convective clouds especially cumulonimbus or towering cumulus; Mountain Waves; Microbursts.

Effects

he main effects of wind shear are:

• • • •

Turbulence Violent air movement (up- or down-draughts or swirling or rotating air patterns) Sudden increase or reduction of airspeed Sudden increase or decrease of groundspeed and/or drift.

Clear Air Turbulence (CAT), which may be very severe, is often associated with jet streams. Rotor action or down-draughts in the lee of mountain waves can create difficult flying conditions and may even lead to loss of control.

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Boletín especial de Seguridad Operacional #9—Dic 2015

2. THE ITCZ – INTER TROPICAL CONVERGENCE ZONE Description

he Inter Tropical Convergence Zone, or ITCZ, is a belt of low pressure which circles the Earth generally near the equator where the trade winds of the Northern and Southern Hemispheres come together. In the Northern Hemisphere, the trade winds move in a southwestern direction from the northeast, while in the Southern Hemisphere, they move northwestward from the southeast.

It is characterized by convective activity which generates often vigorous thunderstorms over large areas. It is most active over continental land masses by day and relatively less active over the oceans; the position of the ITCZ varies with the seasons. Over land, it moves back and forth across the equator following the sun's zenith point. Over the oceans, where the convergence zone is better defined, the seasonal cycle is more subtle, as the convection is constrained by the distribution of ocean temperatures. In July and August, over the Atlantic and Pacific, the ITCZ is between 5 and 15 degrees north of the Equator, but over the land masses of Africa and Asia it is located further north. In eastern Asia, the ITCZ may propagate up to 30 degrees north of the Equator. In January, over the Atlantic, the ITCZ is generally located no further south than the Equator, but it extends much further south over the land masses of South America, Southern Africa, and Australia. Over land, the ITCZ tends to follow the sun's zenith point. EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

The ITCZ is positioned north or south of the equator, this seasonal direction change is originated according to the Coriolis effect imparted by the rotation of the earth. For instance, when the ITCZ is situated north of the equator, the southeast trade wind changes to a southwest wind as it crosses the equator. The ITCZ is formed by vertical motion largely appearing as convective activity of thunderstorms driven by solar heating, which effectively draw air in; these are the trade winds. The ITCZ is effectively a tracer of the ascending branch of the Hadley cell, warm and moist air. The dry and cool descending branch is the horse latitudes. Where the trade winds are weak, the ITCZ is characterised by isolated Cumulus (Cu) and Cumulonimbus (Cb) cells. However, where the trade winds are stronger, the ITCZ can spawn a solid line of active Cb cells embedded with other cloud types developing as a result of instability at higher levels. Cb tops can reach and sometimes exceed an altitude of 55,000 feet, and the ITCZ can be as wide as 300 nautical miles in places presenting a formidable obstacle to aircraft transit.

Effects

ircraft flying through an active ITCZ (strong trade winds) will probably encounter some or all the hazards associated with Cb clouds such as icing, turbulence, lightning, and wind shear.

Within the ITCZ, convective breakthroughs of the tropopause often occur, with the majority occurring over land, especially in the second half of each day. Convective penetration of the tropopause is less common over oceanic areas where the phenomenon is more likely to occur in the early hours of each day, generating more isolated cells. Research sponsored by NASA has shown that 1% of tropical deep convective activity exceeds 46,000 ft altitude, with a small proportion of this reaching much greater heights.

In-Flight Procedures Recommendations ⇒ Avoidance maneuvers should be performed as early as

possible, as weather radar information on nearby cells becomes partial, and possibly misleading, when the aeroplane gets closer to convective areas. Avoid convective weather with at least 20Nm separation margin. ⇒ No attempts to climb over the convective area should

be undertaken when buffet and performance margins are dangerously reduced and with a height margin difference of at least 5.000 ft. EVELOP Airlines

Boletín especial de Seguridad Operacional #9—Dic 2015

3. WEATHER PHENOMENON ASSOCIATED TO THE ITCZ 3.1 Tropical Revolving Storm Description

tropical revolving storm is an intense rotating depression which develops over tropical ocean areas, gaining strength as it is pushed west by the Trade Winds.

Tropical Revolving Storms are known by different names in different regions of the world. Tropical Revolving Storms are known as:

• • • •

Cyclones in the Indian Ocean, Bay of Bengal and Arabian Sea, Tropical Cyclones in the Southern Pacific, Typhoons in the China Seas, and Hurricanes in the Western Atlantic.

Characteristics The weather associated with these storms is violent; torrential rain accompanied by thunder and lightning, severe turbulence within active convective cloud and frictional turbulence generated by strong winds. Static electricity may make navigation aids unreliable. A Tropical Revolving Storm can cause significant damage to infrastructure and high loss of life. Areas affected by a significant storm can take months or even years to recover from the human, economic, and environmental damage. It is not uncommon for aircraft to be evacuated from an airport in advance of the landfall of a tropical storm. Damage and disruption to Airport and ATM infrastructure may render airports across a large area unusable. The diameter of a tropical storm is generally less than 500 nm and often only 100 nm in its early stages of development. With pressure frequently about 960 millibars, and often much less, the pressure gradient is such that winds regularly reach hurricane force. The circulatory velocity of these storms is so great that, once Typhoon Odessa, August 1985, Source: NASA formed, no frontal structure can persist and they become almost symmetrical circular depressions.

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Tropical revolving storms mainly form over the western parts of the tropical ocean areas. The factors which contribute to the intensity of a revolving storm are: ⇒ Instability. Tr op ical r ev o lv in g s t o r m s u s u a lly f or m clo s e t o t h e Inter Tropical Conver-

gence Zone (ITCZ) where there is marked instability. ⇒ Humidity. St or m s m a in ly o ccu r o v er t h e w es t er n p ar t s o f t h e t r o p ica l o cea n s where the air has had a long passage over the sea, or where air has crossed over from the other hemisphere, and has become saturated. ⇒ Latitude. Fo r a giv en pr es s u r e gr a dien t t h e s t r en gt h o f t h e w in d s in cr ea s es a s the storm approaches the Equator. ⇒ Temperature: Tr o pica l r ev o lv in g s t o r m s f o r m o v er w a t er s u r f a ces w it h a w a t er temperature of at least 27C.

A tropical storm can only maintain its power when it is located over the warmest parts of the oceans where surface waters are at 26°C or more. It will dissipate rapidly after crossing a coastline and moving inland, and it will lose energy more gradually if it strays into a region of cooler water. The number and severity of storms in a particular season are also influenced by other climatological factors including El Niño effect. Even when tropical storm has dissipated, there frequently remain extensive remnants of very warm and moist air in the upper atmosphere.

If this warm and humid air is absorbed into the circulation of a travelling Atlantic temperate-latitude depression it may provide sufficient added energy to cause a dramatic intensification of that depression, and this is undoubtedly the cause of some of the severe September Gales that have swept northwest Europe over the years.

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3.2 MONSOON Description

onsoon is traditionally defined as seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. The biggest temperature variations are found in the land masses of North America and Asia; however, because of the winds and weather usually associated with the monsoons in India and Southeast Asia, the word monsoon is often used to mean the prevailing wind and associated weather of these regions.

Monsoons are directly connected to the effect of the Intertropical Convergence Zone. Variation in the location of the ITCZ drastically affects rainfall in many equatorial nations, resulting in the wet and dry seasons of the tropics rather than the cold and warm seasons of higher latitudes. Longer term changes in the ITCZ can result in severe droughts or flooding in nearby areas. Monsoons are caused by the larger amplitude of the seasonal cycle of land temperature compared to that of nearby oceans. This differential warming happens because heat in the ocean is mixed vertically through a "mixed layer" that may be fifty meters deep, through the action of wind and buoyancy-generated turbulence, whereas the land surface conducts heat slowly, with the seasonal signal penetrating perhaps a metre or so. Additionally, the specific heat capacity of liquid water is significantly higher than that of most materials that make up land. Together, these factors mean that the heat capacity of the layer participating in the seasonal cycle is much larger over the oceans than over land, with the consequence that the air over the land warms faster and reaches a higher temperature than the air over the ocean. The hot air over the land tends to rise, creating an area of low pressure. This creates a steady wind blowing toward the land, bringing the moist near-surface air over the oceans with it. Rainfall is caused by the moist ocean air being lifted upwards by mountains (Orographic Lift), surface heating, convergence at the surface, divergence aloft, or from storm-produced outflows at the surface. However the lifting occurs, the air cools due to expansion in lower pressure, which in turn produces condensation and precipitation as the air becomes saturated. Monsoon is accompanied by: ⇒ Heavy Rains - significant reduction of friction on the runway, risk of take-off rejection or aquaplaning before touchdown and so risk of runway excursion ⇒ Strong Winds - depending on runway layout may create a significant crosswind component. ⇒ Severe Turbulence - impeding altitude/pitch/airspeed hold, increasing aircraft structure fatigue and passenger discomfort. ⇒ Reduced Visibility ⇒ Reduced ATM System Capacity

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Characteristics

onsoon climates have clearly marked seasons, each with a specific type of weather and wind from a certain direction. Monsoon climates are found in many parts of the world: West Africa, Ethiopia, northwest Australia, northwest corner of South Africa and the biggest areas of east and south Asia (including East Indies and Philippines). Over Asia the mountain ranges run mainly east to west and this, together with the fact that the land mass of Asia is the largest in the world, limits the transposition of warm and cold air masses and makes seasonal contrasts much greater. In winter, (January in the northern hemisphere) low temperatures over Asia give rise to an intense anticyclone (called Syberian high) which extends its influence over most of Europe and Asia. Because of the intense cold in the heart of Siberia in winter (average of minus 40 degress Celsius) the pressure in the anticyclone reaches very high values (sometimes even 1070 hPa). Air flows out from the high pressure region and gives rise to the winter monsoon, with north westerly winds in northern China. Further south the winds become northerly and finally north easterly as they take up the trade wind flow to become the northeast monsoon of Southeast Asia and Indonesia. India is cut off from the Siberian anticyclone by the barrier of the Himalayas, but it develops its own high pressure system, centered in northwest India (in the Thar desert) and northern Pakistan and, as a result, there is an eastward flow of air out along the Ganges valley area which eventually joins the northeast monsoon over the Bay of Bengal. Over China, Japan and eastern Asia, the air is generally very cold and warms up as it moves towards the equator. The flow from India is not as cold. Over the land the air remains dry, over the sea the monsoon becomes moist. The weather created by the monsoon depends on whether a land or sea track is followed and how much instability has developed. In summer, the pressure distribution is completely changed because the high land temperatures lead to low pressure systems over the areas of southern Asia which are subject to the most heating and high pressure over the oceans. The flow is then from the sea to the land and the air in many cases actually comes from the southern hemisphere as the southeast trade winds which are then turned by the coriolis force on crossing the equator to form the southwest monsoon. The southwest monsoon has its direction changed again as it reaches the land masses of Asia (for example being diverted to flow from the southeast up the Ganges valley towards the low pressure area over northwest India). Whilst the descriptions above have focused on the Asia monsoons, other parts of the world are subject to similar seasonal changes. The climatology of West Africa for example includes reference to the south west monsoon and that of Australia, the north west monsoon.

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4. GEOGRAPHICAL AREAS CLIMATOLOGY 4.1 Caribbean

he Caribbean climate is tropical, moderated to a certain extent by the prevailing northeast trade winds. Individual climatic conditions are strongly dependent on elevation. At sea level there is little variation in temperature, regardless of the time of the day or the season of the year. Temperatures range between 24°C and 32°C. In Kingston, Jamaica, the mean temperature is 26°C, whereas Mandeville, at a little over 600 meters high in the Carpenters Mountains of Manchester Parish, has recorded temperatures as low as 10°C. Daylight hours tend to be shorter during summer and slightly longer during winter than in the higher latitudes. The conventional division, rather than the four seasons, is between the long rainy season from May through October and the dry season, corresponding to winter in the northern hemisphere. Even during the rainy period, however, the precipitation range fluctuates greatly. Windward sides of islands with mountains receive much rain, whereas leeward sides can have very dry conditions. Flat islands receive slightly less rainfall, but its pattern is more consistent. For example, the Blue Mountains of eastern Jamaica record around 558 centimeters of rainfall per year, whereas Kingston, on the southeastern coast, receives only 399 centimeters. Bridgetown, the capital of Barbados, has an average annual rainfall of 127 centimeters, while Bathsheba on the central east coast receives 254 centimeters--despite the fact that Bathsheba is only about 27 kilometers away by road. Recording stations in the Northern Range in Trinidad measure some 302 centimeters of rainfall per year, while at Piarco Airport on the Caroni Plains the measurement is only 140 centimeters. Most of the rainfall occurs during short heavy outbursts during daylight hours. In Jamaica, about 80 percent of the rainfall occurs during the day. The period of heaviest rainfall usually occurs after the sun has passed directly overhead, which in the Caribbean islands would be sometime around the middle of May and again in early August. The rainy season also coincides with the disastrous summer hurricane season, although Barbados, too far east, and Trinidad and Tobago, too far south, seldom experience hurricanes. Hurricanes are a constant feature of most of the Caribbean, with a "season" of their own lasting from June to November. Hurricanes develop over the ocean (usually in the eastern Caribbean) during the summer months when the sea surface temperature is high (over 27°C) and the air pressure falls below 950 millibars. These conditions create an "eye" about 20 kilometers wide, around which a steep pressure gradient forms that generates wind speeds of 110 to 280 kilometers per hour. The diameter of hurricanes can extend as far as 500 to 800 kilometers and produce extremely heavy rainfalls as well as considerable destruction of property.

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4.2 Western Africa

est Africa lies between latitudes 4°N and 28°N and longitudes 15°E and 16°W. The Gulf of Guinea is the southern boundary, while that to the north is the northern boundary of Mauritania, Mali and Niger; the Mount Cameroon/Adamawa Highlands and the Atlantic Ocean form the eastern and western limits. West Africa includes 16 countries: Benin, Cape Verde, Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, Togo and Upper Volta. West Africa has wet and dry seasons resulting from the interaction of two migrating air masses. The first, is the hot, dry tropical continental air mass of the northern high pressure system, which gives rise to the dry, dusty, Harmattan winds which blow from the Sahara over most of West Africa from November to February; the maximum southern extension of this air mass occurs in January between latitudes 5° and 7°N. The second, is the moisture-laden, tropical maritime or equatorial air mass which produces southwest winds. The maximum northern penetration of this wet air mass is in July between latitudes 18° and 21°N. These two air masses meet in the Intertropical Convergence Zone (ITCZ). The north and south migration of this ITCZ, which follows the apparent movement of the sun, controls the climate of the region. The ITCZ migrates latitudinally on a seasonal basis. In July, when the sun is over the Tropic of Cancer, the ITCZ reaches its northernmost position at about 15°N; in January it reaches ~5° S when the sun is over the Tropic of Capricorn. The most important consequence of this shifting is the annual alteration of wet and dry seasons in tropical Africa. Areas near the equator in western and southern Africa have a single intense rainy season from July to September. The ITCZ moves northward over this region between February and May, and southward again between October and December. Since the distance covered by the ITCZ is quite large in this part of the continent, the rainy seasons are less intense than those of western Africa. The arid and semi-arid regions of Africa (Sahara and Sahel) lie north of about 10°N, near the northern limit of the ITCZ, and receive one rainy season with very little precipitation. Farther to the north, along the Mediterranean Sea coast, the climate is not affected directly by the ITCZ and rain falls in the winter.

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4.3 South East Asia - INDONESIA

he main variable of Indonesia's climate is not temperature or air pressure, but rainfall. Split by the equator, Indonesia has an almost entirely tropical climate, with the coastal plains averaging 28°C, the inland and mountain areas averaging 26°C, and the higher mountain regions, 23°C. The area's relative humidity is quite high, and ranges between 70 and 90 percent. The extreme variations in rainfall are linked with the monsoons. Generally speaking, there is a dry season (June to September), and a rainy season (December to March). Western and northern parts of Indonesia experience the most precipitation, since the north- and westward-moving monsoon clouds are heavy with moisture by the time they reach these more distant regions. Western Sumatra, Java, Bali, the interiors of Kalimantan, Sulawesi, and Irian Jaya are the most predictably damp regions of Indonesia, with rainfall measuring more than 2,000 millimeters per year. Typhoons can hit the Islands of the Indonesia between September and December, and can cause rainstorms and heavy winds. However, not every Typhoon that hits Indonesia is a strong one, and in some years only a few Typhoons occur during the tropical storm season.

4.4 South East Asia - INDIA

ndias climate can be classified as a hot tropical country, except the northern states of Himachal Pradesh and Jammu & Kashmir in the north and Sikkim in the northeastern hills, which have a cooler, more continental influenced climate. In most of India summer is very hot. It begins in April and continues till the beginning of October, when the monsoon rains start to fall. The heat peaks in June with temperatures in the northern plains and the west reach 45° C and more. The monsoons hit the country during this period too, beginning 1st of June when they are supposed to find the Kerala coast, moving further inland from day to day. Moisture laden trade windssweep the country bringing heavy rains and thunderstorms; sometimes these monsoon rains can be very heavy, causing floodings and damage, especially along the big Rivers of India, Bramaputhra and Ganges. The plains in the north and even the barren countryside of Rajasthan have a cold wave every year in December-January. Minimum temperatures could dip below 5°C but maximum temperatures usually do not fall lower than 12°C. In the northern high altitude areas of the northern mountains it snows through the winter and even summer months are only mildly warm. Typhoons are usually not a danger, these tropical storms are quite seldom in India. The Typhoon Season is from August to November; the East coast of India has the highest Typhoon risk.

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Boletín especial de Seguridad Operacional #9—Dic 2015

4.5 Saudi Arabia

ith the exception of the province of Asir on the western coast, Saudi Arabia has a desert climate characterized by extreme heat during the day, an abrupt drop in temperature at night, and very low annual rainfall. Because of the influence of a subtropical high-pressure system, there is considerable variation in temperature and humidity. The two main differences in the climate of Saudi-Arabia can be felt between the coastal areas and the interior. The average summer temperature is about 45° C, but readings of up to 54° C are not unusual. The heat becomes intense shortly after sunrise and lasts until sunset, followed by surprisingly cool nights. In the winter, the temperature seldom drops below 0° C, but the almost total absence of humidity and the high wind-chill factor make a quite cold atmosphere. In the spring and autumn the heat is temperated, temperatures average around 29° C. The region of Asir along the Western coast is influenced by the Indian Ocean monsoons, usually occurring between October and March. An average of 300 millimeters of rainfall occurs during this period, that is about 60 percent of the annual precipitation. For the rest of the country, rainfall is very low and erratic. The entire year's rainfall may consist of one or two local, heavy cloudbursts or Thunderstorms.

An enormous dust cloud approaches the Saudi capital Riyadh. The Telegraph

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Boletín especial de Seguridad Operacional #9—Dic 2015

APPENDIX 1 (The documents in next pages are not updated. FOR INFO ONLY) A1.1 Adverse Weather Checklist A320 (OBS & EVE)

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Boletín especial de Seguridad Operacional #9—Dic 2015

(Cntd.) A1.1 Adverse Weather Checklist A320 (OBS & EVE)

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Boletín especial de Seguridad Operacional #9—Dic 2015

A1.2 Adverse Weather Checklist A330-343 (CS-TRH MSN0833)

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Boletín especial de Seguridad Operacional #9—Dic 2015

(Cntd.) A1.2 Adverse Weather Checklist A330-343 (CS-TRH MSN0833)

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Boletín especial de Seguridad Operacional #9—Dic 2015

A1.3 Adverse Weather Checklist A330-200 (CS-TRX MSN0802)

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(Cntd.) A1.3 Adverse Weather Checklist A330-200 (CS-TRX MSN0802)

https://drive.google.com/open? id=0BxqkWXoaUJRYOEdKSUYzU0 1IV2s

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NOTAS

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Boletín especial de Seguridad Operacional #9—Dic 2015

NOTAS

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