Turbulence

Question 1

Turbulence is dependant on the following criteria(4):

Answer 1

1. Speed of the wind
2. The amount friction offered by the surface
3. The size and shape of the obstacles
4. Thermal activity, being maximum at midday.

Question 2

The 7 types of turbulence:

Answer 2

1. Mechanical
2. Low level
3. Wake turbulence
4. Wind shear
5. Clear Air Turbulence
6. Mountain waves and standing waves

Question 3

Mechanical turbulence:

Principle -

Affective height -

Atmosphere stability’s effect -

Answer 3

Wind blowing over the earth’s surface being stirred into eddies by contact with hills, building or any other obstacles.

Within 3 000ft AGL

Instability will increase the height, and stability reduce the height.

Question 4

Explain Low level turbulence:

Principle -

Affected time of the day, and conditions -

Answer 4

Random eddies caused by convective currents from ground heating and wind over rough terrain.

Early morning, stratus cloud and with light winds.

Question 5

Wake turbulence:

In stable air, the vortices descend at -

to stabilise at -

If the air is unstable -

To avoid the turbulence, a following aircraft should always -

Answer 5

400 - 500fpm

1 000ft below the aircraft’s flight path remaining there for 4 minutes

The vortices will disperse quickly

Fly above the leading aircraft’s flight path

Question 6

Note: see radar separation minima in the radio licence notes

Answer 6

Note: see radar separation minima in the radio licence notes

Question 7

Wind shear may also be encountered when climbing or descending through a -

Answer 7

temperature inversion

Question 8

Where can Clear Air Turbulence be found?

Answer 8

Near jet stream, most severe on top of jet streams(polar and cold jet streams are worst). CAT can also be encountered crossing mountains and in the vicinity of thunderstorms

Question 9

How is a standing/mountain wave formed?

The effect is most severe(will rise above mountains) if the atmosphere is -

If not -

The the wind speed must be -

Answer 9

Strong wind blowing over across a range of hills or mountains.

Unstable.

The waves will not extend above mountain height

15kts for small mountains, and 30kts in the case of large mountains. Wind should increase with height.

Question 10

The mnemonic for wind shear operation effect:

Answer 10

Reduction(RUO) - working from right to left:

Under.
Over

Increase(IOU) - working from right to left:

Over
Under

Question 11

Micro bursts:

Principle -

The two type(and which one is more severe) -

A micro burst can be identified by -

Answer 11

A normal down-draught within a thunderstorms, which is created by falling rain and cooling due to evaporation, and since it is more dense it will accelerate towards the ground at speeds in excess of 60kts.

Wet and dry. Dry being more severe.

Virga, rain shafts and dust circles.