Weather Effect On Aviation.pptx

Weather effect on aviation

Weather conditions Adverse weather phenomena are meteorological conditions that, if encountered during flight or ground operations, could reduce and even threaten the safety of those operations. Marginal weather conditions - are weather conditions somewhere between VFR and IFR such as low-level, layered clouds (associated or not associated with weather fronts) changing ceilings and visibilities with the advent of fog, dust, or haze conditions, even to the point of sky obscuration.

Adverse weather conditions These include, but not limited to: • Moderate to severe clear air turbulence; • Strong surface winds (exceeding 30 knots); • Low-level wind shear; • Thunderstorms; • Moderate or severe in-flight icing; • Icing which affects ground operations (including snow, freezing rain, drizzle, ice, fog, or sleet); • Meteorological conditions that contaminate a runway or takeoff surface and adversely affect aircraft performance; • Sandstorms and dust storms; • Cyclones, hurricanes, typhoons, and tropical storms; and • Natural hazards such as volcanic ash.

Thunderstorms Thunderstorms represent some of the worst dangers in aviation. The effects they have are most likely to be found in the form of:

• turbulence, • microburst, • tornadoes, • icing, • lightning, • hail, • heavy rain, • surface wind gusts, • runway contamination, • low status and • bad visibility.

Turbulence Turbulence is a chaotic air movement that normally cannot be seen. It can occur where air masses with different speed, direction or temperature meet

It can be created by:  Atmospheric pressure  Mountain waves  Jet streams  Cold or warm fronts  Thunderstorms Types of turbulence:  Light  Moderate  Severe  Extreme

Turbulence Turbulence can lead to:  Shaking  Loss of controllability  Stalling  Structural damage  Loosing altitude and attitude  Injuries among passengers  Crash In case of turbulence ‼ It is recommended for the pilots to avoid the changing the altitudes ‼ It is forbidden to land under severe turbulence

turbulence

by

Microburst Microbursts are small scale, very intense downdrafts which descend to the surface and upon contact with the surface, diverge outwards in all directions. All microbursts pose a significant threat to aviation. When a pilots receives a warning from Tower or onboard systems, aircraft that haven't started taking off (or are very early in the takeoff roll) stay on the ground, and aircraft on approach will discontinue the approach (go around).

Microburst

Windshear Wind shear is a rapid change in wind speed and/or direction over a short horizontal distance experienced by aircraft, conditions that can cause a rapid change in lift, and thus the altitude, of the aircraft. It can occur at any height, but is far more dangerous when encountered close the ground. As the aircraft passes into the region of the downdraft, the localized headwind diminishes, reducing the aircraft's airspeed and increasing its sink rate. Then, when the aircraft passes through the other side of the downdraft, the headwind becomes a tailwind, reducing lift generated by the wings, and leaving the aircraft in a low-power, low-speed descent. This can lead to an accident if the aircraft is too low to effect a recovery before ground contact.

Icing In aviation, icing conditions are those atmospheric conditions that can lead to the formation of water ice on the surfaces of an aircraft, or within the engine as carburetor icing. Inlet icing is another engine-related danger, often occurring in jet aircraft. Aircraft icing is one of the major weather hazards to aviation. It reduces aircraft efficiency by increasing weight, reducing lift, decreasing thrust, and increasing drag. Icing also seriously impairs aircraft engine performance. Other icing effects include false indications on flight instruments, loss of radio communications, and loss of operation of control surfaces, brakes, and landing gear.

Arrow Air Flight 1285 • Arrow Air Flight 1285 was a McDonnell Douglas DC-8 jetliner that  operated as an international charter flight carrying U.S. troops  from Cairo, Egypt, to their home base in Fort Campbell, Kentucky,  via Cologne, West Germany and Gander, Canada. • On the morning of Thursday, 12 December 1985, shortly after takeoff  from Gander en route to Fort Campbell, the aircraft stalled, crashed,  and burned about half a mile from the runway, killing all 248  passengers and 8 crew members on board. • The accident was investigated by the Canadian Aviation Safety  Board (CASB), which determined the probable cause of the crash was  the aircraft's unexpectedly high drag and reduced lift condition,  most likely due to ice contamination on the wings' leading edges and upper surfaces, as well as underestimated onboard weight.

Hail Hail is a form of solid precipitation.

It consists of balls or irregular lumps of ice, each of which is called a hailstone. Hailstones larger than one-half inch in diameter can significantly damage an aircraft in a few seconds.

Delta Airlines Flight 1889 from Boston,  Massachusetts, to Salt Lake City, Utah, made  emergency landing in Denver at 9pm , August 10,  2015 Pilots made landing with limited visibility because  of major cracks in the windshield -  after baseballsized hailstones wrecked the front of the plane.  The hail also destroyed the GPS navigation system  at the front of the aircraft, which was flying from  Boston to Salt Lake City on Friday night.  The pilots managed to land in Denver - where the  passengers could see the extent of the damage to  the Airbus 320's cone.  Pilots said they did not realize how bad the  damage was until they landed and saw the front  of plane.

. The Airbus 320's windshield and cone were severely damaged during a hail storm over eastern Colorado

Lightning strike A lightning strike is a sudden electrostatic discharge that occurs during an electrical storm. Types of lightning strike: cloud to ground (CG) lightning ground to cloud (GC) intra-cloud (IC) cloud to cloud (CC) A lightning strike may: puncture the skin of an aircraft can damage communication and electronic navigational equipment. ignite fuel vapors causing explosion; can blind the pilot rendering can also induce permanent errors in the magnetic compass. can disrupt radio communications on low and medium frequencies. However, serious accidents due to lightning strikes are extremely rare.

CAT – Clear Air Turbulence Clear Air Turbulence (CAT) is the turbulent movement of air masses in the absence of any visual cues such as clouds, it is invisible and it is very complicated to identify with conventional radar. The most susceptible altitudes for CAT are between 7000 and 12000 meters, in the regions where jet streams pass. At lower altitudes it may also occur near mountain ranges. Thin cirrus cloud can also indicate high probability of CAT

Jet streams Jet streams are strong westerly winds that blow in a narrow band in the Earth’s upper atmosphere – at the altitudes used by most aircraft. Where these packets of fast moving air form a tube, they are called jet streams. They can be faster than 200 knots By flying in a jet stream, aircraft travelling from west to east get carried along by the tailwind, saving them time – and/or fuel.

Winds effect • A headwind is a wind blowing directly against the course

of an aircraft. It will delay the arrival of flights and is to be avoided if it is possible. • A tailwind is a wind blowing in the same direction as the course of an aircraft. It increases the ground speed and results in a reduction in fuel consumption.

• A crosswind is a wind that blows at right angles to the

direction of travel. A crosswind is the component of wind that is blowing across the runway making landings and takeoffs more difficult than if the wind were blowing straight down the runway. If a crosswind is strong enough it may exceed an aircraft's crosswind limit and an attempt to land under such conditions could cause structural damage to the aircraft's undercarriage.

Fog, mist and haze Mist and fog are the terms used to describe low visibility caused by either water droplets or ice crystals suspended in the air.

Haze is associated with dry, and usually hot, conditions and reduces visibility, especially air to ground visibility The international definition of • fog is a visibility of less than 1 kilometer (3,300 ft); • mist is a visibility of between 1 kilometer (0.62 mi) and 2 kilometers (1.2 mi) • haze from 2 kilometers (1.2 mi) to 5 kilometers (3.1 mi). Fog is effectively surface cloud and has a significant impact on the conduct of flying operations particularly landing and take-off.

Volcanic ash Volcanic ash. Comprised of minerals unique to the volcanic eruption. Minerals common to most volcanic  ash are silica together with smaller amounts of the oxides of aluminum, iron, calcium and sodium. The  glassy silicate material is very hard and extremely abrasive. Its melting point is below jet engine burner  temperature which introduces additional hazards.  Volcanic ash may affect: a) the immediate safety of an aircraft:  • the malfunction or failure of one or more engines leading not only to reduction, or complete loss, of  thrust but also to failures of electrical, pneumatic and hydraulic systems. Volcanic ash contains particles  whose melting point is below modern turbine engine burner temperature; these particles then fuse in the  turbine section reducing the throat area and its efficiency leading to engine surge and possibly flame-out;  • the blockage of pitot and static sensors resulting in unreliable airspeed indications and erroneous  warnings;  • windscreens rendered partially or completely opaque; and  • contamination of cabin air requiring crew use of oxygen masks.. 

Volcanic ash Volcanic ash may affect: b) the longer term safety and costs affecting the operation of aircraft:  • erosion of external aircraft components;  • reduced electronic cooling efficiency and, since volcanic ash readily absorbs water,  potential short circuits leading to a wide range of aircraft system failures and/or  anomalous behaviour;  • flight crew manoeuvring for volcanic cloud avoidance which may potentially conflict  with other aircraft in the vicinity;  • deposits of volcanic ash on a runway resulting in a degradation of braking performance,  especially if the volcanic ash is wet; in extreme cases, this can lead to runway closure; and  • aircraft ventilation and pressurization systems becoming heavily contaminated. 

Contaminated runway A runway is considered to be contaminated when more than 25 % of the runway surface area (whether in isolated areas or not) within the required length and width being used is covered by the following: • surface water more than 3 mm (0,125 in) deep, or by slush, or loose snow, equivalent to more than 3 mm (0,125 in) of water; • compacted snow); or • ice, including wet ice.

Thank you for your kindest attention! May the skies be always clear for yo