1. Atmospheric Effects on Flight Review 1
ATC Chapter 7

2. Aim
To review atmospheric effect on flight

3. Objectives State the correct procedure for taxiing in strong winds
Define wind shear and state its effect on flight characteristics
Define the different types of turbulence and state their effect on flight characteristics

4. 1. Taxiing
Taxiing
Incorrect taxi technique in strong winds can lead to the aircraft becoming uncontrollable and in the worst case scenario flipping, spinning or skidding resulting in damage to the aircraft or passengers

5. 1. Taxiing
Taxiing
When taxiing with a head wind the control column should be held backwards and into wind

6. Remember “Climb into, Dive away from”
1. Taxiing
Taxiing
When taxiing with a tailwind the control column should be held forwards and away from wind
Remember “Climb into, Dive away from”

7. 2. Wind Shear
Wind Shear
Wind shear is a rapid change in wind speed or direction
The most dangerous phase of flight to encounter wind shear is during take-off or landing where the aircraft is low and slow
Incorrect recovery technique results in a number of incidents and accidents every year, generally speaking increasing your approach or take-off speed and the use of reduced flap settings will minimise the effects of wind shear

8. 3. Turbulence Mechanical Turbulence
When flying in close proximity to the ground it is important to have some understanding of the way in which local winds will interact with ground features
Upper level winds will often be different from the wind at low level. We need to keep an eye out for wind indications on the ground
Wind speeds below around 15 KTS are generally smooth and predictable
Wind speeds above 15 KTS are turbulent and harder to predict
At wind speeds above 20 KTS severe wind shear and turbulence can occur. Continued flight in these conditions is not advisable, consider climbing or alternate tracking

9. 3. Turbulence Updrafts and Downdrafts
Once you have some idea of the wind velocity you should be able to predict how the air is flowing over ground features and adjust your performance accordingly before it affects the aircraft
On the windward side of the obstacle we can expect an updraft. In order to counteract this we must:
Lower the nose
Decrease power
On the lee side of the obstacle we can expect a downdraft. In order to counteract this we must:
Raise the nose
Increase power
Strong updrafts and downdrafts are extremely hazardous. Vertical speeds of up to 3000ft/min can occur with strong winds. If in doubt do not continue the flight

10. 3. Turbulence
Thermals
Thermals are rising currents of air caused by uneven heating of the ground
They can result in very turbulent conditions and reach their peak around mid afternoon
The formation of fair weather cumulus clouds are an indication of thermal activity

11. 3. Turbulence Wake Turbulence
As the wing produces lift trailing edge vortices are also produced, known as wake turbulence
The larger the aircraft and the more lift being produced the larger the vortices
If a light aircraft gets caught in the wake turbulence of a larger aircraft it can become uncontrollable

12. 3. Turbulence Helicopter Downwash
Helicopter blades produce downwash in order to produce lift, the larger, heavier or slower the helicopter, the more downwash produced
Downwash can be hazardous up to a radius three times the diameter of the rotor

13. Questions?