Atmospheric Effects on Flight Review 1

ATC Chapter 7

Aim

To review atmospheric effect on flight

Objectives1. State the correct procedure for taxiing in strong

winds2. Define wind shear and state its effect on flight

characteristics3. Define the different types of turbulence and

state their effect on flight characteristics

TaxiingIncorrect 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

1. Taxiing

TaxiingWhen taxiing with a head wind the control column should be held backwards and into wind

1. Taxiing

TaxiingWhen taxiing with a tailwind the control column should be held forwards and away from wind

Remember “Climb into, Dive away from”

1. Taxiing

Wind ShearWind shear is a rapid change in wind speed or directionThe 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

2. Wind Shear

3. TurbulenceMechanical 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

Updrafts and DowndraftsOnce 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

3. Turbulence

ThermalsThermals are rising currents of air caused by uneven heating of the groundThey can result in very turbulent conditions and reach their peak around mid afternoonThe formation of fair weather cumulus clouds are an indication of thermal activity

3. Turbulence

Wake TurbulenceAs the wing produces lift trailing edge vortices are also produced, known as wake turbulenceThe larger the aircraft and the more lift being produced the larger the vorticesIf a light aircraft gets caught in the wake turbulence of a larger aircraft it can become uncontrollable

3. Turbulence

Helicopter DownwashHelicopter blades produce downwash in order to produce lift, the larger, heavier or slower the helicopter, the more downwash producedDownwash can be hazardous up to a radius three times the diameter of the rotor

3. Turbulence

Questions?