Turbulence and windshear Flashcards
What is turbulence and how does it affect an aircraft
Disturbed air whose sudden changes in velocity cause air to move abruptly. Generally affects aircraft attitude but not altitude.
What is windshear
Substantial changes in wind direction or speed in vertical or horizontal plane.
What could windshear do to an aircraft
Displace aircraft from flight pack or put it straight into stall condition.
What are the types of turbulence
Mechanical e.g. physical objects. Thermal turbulence (air rising).
How is turbulence strength classified
Light, Moderate, Severe.
How can thermal turbulence be identified
Cumulus clouds. Within around and underneath moderate to severe turbulence
How does Low-level turbulence occur
Interaction between wind and earths surface. Layer of air influence is friction layer.
What results in a higher friction level layer
Hot days or areas of uneven surface. Surface friction slows surface winds causing a change in wind direction at the friction level.
What are mountain waves
Turbulent undulating waves of air.
Form above and downwind of a mountain range.
Extend 50-100NM and upwards to tropopause.
Where do mountain waves occur
Alps, Rockies.
Also known as lee waves or standing waves.
Conditions for mountain wave to occur
Wind speed must be 15-20kts.
Wind direction 30* perpendicular to range of mountains.
Must be a region of marked stability (inversion/isothermal) at mountain top height with less stable air above/below.
What are the visual warning signs of mountain waves
Lenticular clouds (ragged edges). Rotor/roll clouds.
Cap clouds.
Reported in SIGWX sometimes SIGMET.
What are the ways in which windshear can occur
Thunderstorms, Passage of a front, strong inversion, strong friction layer, topographical windshear.
What effect will a vertical current of air have
Airspeed changes,
Wings AOA changes.
Downdraft-Sink
Updraft-climb
What is CAT and where does it occur
Clear air turbulence. Greatest CAT occurs on the jet stream adjacent to the cold air.
