Chapter 9 - Turbulence And Windshear Flashcards
What characteristics would an inversion have to be marked?
A temperature change of 10degC or more between surface and 1000ft.
What are the threats of a marked temperature inversion?
Lessened aircraft performance and marked wind shear.
How would you know about a marked temperature inversion when approaching or departing an airfield?
It will be broadcast on the air transport information service (ATIS)
How does a turbulence inversion form?
When turbulence causes mixing between the warmer air below and the colder air above a particular level.
Define turbulence.
Changing wind speed or direction over short distances.
Where can turbulence occur?
In cloud Near high ground The friction layer In thermals Near jet streams
When is turbulence reported?
When it is moderate to severe.
Where would you find the worst turbulence?
Cumulonimbus clouds Thunderstorms
What can be said about the turbulence related to thunderstorms?
It should be assumed severe.
What are some visual cues of turbulence?
CU clouds CB clouds Linticularis clouds Jet stream cirrus Obsticals
What defines light turbulence?
Accellerometer readings of less than 0.5g at CG.
What defines moderate turbulence and what is its affect on aircraft?
Accellerometer readings of between 0.5 and 1g. Aircraft effects: Deviation of aircraft attitude, but control remains Small variation in air speed Passengers have difficulty walking Occupants feel strain felt on seatbelts
What defines severe turbulence and what is its affect on aircraft?
Accellerometer readings of over 1g. Aircraft effects: Abrupt changes in attitude occur and may be out of control for a short time Large variation in airspeed Passengers will find it impossible to walk Occupants forced violently against seatbelts.
What is windshear?
Rapid change of direction and/or speed of wind.
Where do you find windshear?
Microbursts/gust fronts
Fronts
Inversions
Strong winds
Where do the worst wind shears occur?
Near the ground
Thunderstorms (no time to recover)
When is light wind shear reported?
Never only significant wind shear will be reported.
What happens to the section of wind that is close to land?
It backs by 30 degC, (Northern hemisphere), and halves in speed.
How does wind shear affect an aircraft?
It causes:
Abrupt attitude changes
Speed changes
Sudden bank
Flight path deviation
What is vertical wind shear and how is it measured?
The change of horizontal wind vector with height, measured in kts/100ft.
What is horizontal wind shear and how is it measured?
The change in horizontal wind vector with horizontal distance, measured in kts/1000ft.
What condition cause the worst wind shear?
Winds above 40kts
Variation of 10degC or more in inversions
What are mountain waves/standing waves/lee waves?
Turbulent undulating waves of air that form above and downwind of a mountain range.
What can the vertical and horizontal extent of mountain waves be?
50-100nm downwind and upwards to the tropopause.
How fast can the upwards and downwards movement of air within mountain waves be?
Can exceed 200fpm
What condition are required for mountain waves?
Stable air
Wind at 15kts or higher
Wind direction must be roughly constant and within 30deg of the perpendicular to the mountain range.
What can be an indicator for mountain waves?
lenticularis cloud. However the absense of them doesnt mean there are no waves.
If mountain waves occur, which side of the mountain is most dangerous?
The leeward side where the headwind is coming from mountain.
How would you reseive wind shear wanrings?
Met men
ATS - Air Traffic Service
Pilots
The on board pre-encounter equipment
What is the friction layer?
The layer of air in which the surface influences the air flow, also called the boundary layer.
